INTERNATIONAL ATOMIC WEIGHTS FOR 1913* = 16 Name. Symbol. Atomic Weight. Name. Symbol. Atomic Weight. Aluminium Antimony Al Sb 27.1 120 2 Molybdenum. . Transferring Steel Drillings, is useful in transferring small par- ticles of steel to or from the bal- ance to complete the weighing. Dissolving. After the sample has been weighed, it is dissolved in order that the element or ion may be freed THE OPERATIONS OF ANALYSIS 19 and subsequently converted into a form in which its quantity may be conveniently measured. Most metallurgical materials are soluble in acids, and those that are not may be converted into soluble form by fusing them with suitable fluxes. After weighing the sample it should be transferred, with the aid of a small camel's hair brush, from the watch glass directly to the beaker, casserole, flask, crucible, or other receptacle in which the analysis is to begin. When the acid or other solvent is added, if solution does not take place without heat, the beaker should be placed on the hot-plate or over a low burner under the hood. The quantity of the solvent to be added is usually given in the method. The solvent is measured approximately in a graduated cylinder (Fig. 19) and if its volume is considerably FlG 19 _ reduced by evaporation before the sample is dis- Graduated solved, more of the solvent should be added. A Cylinder, hot-plate with the heat applied under the center is convenient; for, by moving the determination towards the center or away from it, any desired degree of heat may be found. Reagents. All reagents should be tested as to their purity, especially for the quantities of those impurities which would interfere with the action of the reagent, or would in any way introduce error into the result.* The quantity of a reagent used in a determination is measured accurately only when the reagent serves as a measure, either directly or indirectly, of the element sought. In other cases when only an excess of the reagent is desired to insure the com- pletion of a reaction, the quantity used may be measured only approximately. In the description of the methods as given in this book, it is assumed that the following reagents are at hand: distilled water; hydrochloric acid, specific gravity 1.20; nitric acid, specific * "The Testing of Chemical Reagents," Van Nostrand & Co. 20 METALLURGICAL ANALYSIS gravity 1.42; sulphuric acid, specific gravity 1.84; and ammonia, specific gravity 0.90. Where these reagents are mentioned with- out qualification, the above concentrations are meant. If other concentrations are desired, the strength is indicated either by specific gravity, or in the ratio by volume of the concentrated reagent to water. By the latter method the ratio is indicated by a colon (:), which stands between the two volumes, the volume after the colon always referring to water. Tables on pages 332 to 334 show how to make the acids to any desired density by giving directly the volume of the concentrated acid and the volume of water necessary for each concentration. Precipitation. It should be kept in mind that electrolytes are the more completely ionized the more dilute the solution, and that precipitates come down cleaner from a dilute solution, that is, freer from substances adsorbed from the solution.* It should also be remembered that no substance is absolutely insoluble in aqueous solution; and necessarily the larger the volume of solution, the greater quantity of the precipitate will be required for its saturation. If the solubility of the precipitate is not so small as to be negible, precautions must be taken to reduce the solubility to a minimum. This may be done by adding a liquid in which the precipitate is less soluble than in the original solution, or, in the case of an electrolyte, by adding an excess of the precipitant, or of a soluble salt containing one of the ions of the precipitate. For instance, if we wish to pre- cipitate SO4 from solution as BaSO4, we add an excess of BaC^. The solution is saturated with Ba ions from the BaCb, which reduces to a minimum the solution and dissociation of BaSCU.f Precipitates are more easily filtered and washed if they are granular or crystalline. They should, therefore, be left in the mother liquor at a moderate temperature but not boiling as long as circumstances permit. By this treatment the fine *Ostwald: "Foundations of Analytical Chemistry," p. 18. f Ibid., p. 73. THE OPERATIONS OF ANALYSIS 21 crystals are dissolved and redeposited upon the coarse ones. This enlargement of the crystals, as explained by Ostwald, is due to surface tension on the boundary surfaces between solids and liquids, which tends to reduce the surface, thereby enlarg- ing the individual grains.* Filtration. The filters used should have been washed with hydrochloric and hydrofluroic acids, and, if for gravimetric work, the average weight of ash should have been determined. Very finely divided precipitates like BaSO4will often run through ordinary filter paper. If a paper is selected whose pores are smaller than the particles of precipitate, the trouble of refiltration may be avoided. The size of the filter selected should be determined by the bulk of the pre- cipitate, rather than by the volume of the solution to be filtered, and the paper should be folded to fit the funnel snugly. The clear super- natant solution should be decanted first and allowed to run down a glass rod into the filter while the precipitate remains undisturbed in the bottom of the beaker. (Fig. 20.) The clear solution runs through readily, after which the precipi- tate may be washed by decantation or transferred to the filter and washed on the filter. The 1 - ~II,,,,^JL filter paper should not be filled FIG. 21. " Policeman." w * tn s l u ti n nearer to the top than 5 mm. If the precipitate sticks to the beaker, it may be rubbed loose with a " police- man " (Fig. 21; a bit of small rubber tubing on the end of a * Ostwald: "Foundations of Analytical Chemistry," p. 22. FIG. 20. Filtering. 22 METALLURGICAL ANALYSIS glass rod) and then washed into the filter by inclining the beaker at a high angle, with a glass rod held with the left hand across the top of the beaker and resting in its lip, so that when a jet of water is directed up into the beaker with the right hand, it will flow back down the sides, carrying the precipitate with it to the lip and down the glass rod directly into the filter. In this way the last traces of precipitate are transferred to the filter. (Fig. 22.) FIG. 22. Completing the Transfer of a Precipitate to the Filter. If filtering is to be done by gravity, the funnels should have long stems, which are kept full of solution while filtering. In laboratories where routine work is done and the same determina- tion must be made on many samples, much time is saved by the use of multiple stirring and filtering devices such as are described by Keller and shown in Figs. 23 and 24.* Metallurgical laboratories should be provided with apparatus for filtering by suction. Since compressed air is also needed, * Trans. Amer. Inst. Min. Eng., 36, 3. THE OPERATIONS OF ANALYSIS 23 it is convenient to have a pump which exhausts the air on one side of the piston and compresses it on the other, suitable equaliz- ing tanks being provided for the compressed air and for partial vacuum. Before entering the pump the air should pass through a scrubber containing a solution of sodium hydroxide for the removal of acid fumes. In small laboratories, the Richards pump may be used for this purpose (Fig. 25), and, in connection with a Woulf bottle, the air may be compressed for a blast FIG. 23. Stirring Machine in Position for Rinsing. FIG. 24. Decanting and Filtering Apparatus. Position at End of Filtration. lamp. The stem of the funnel is put through a rubber stopper into a filter-flask which is connected with the exhaust. A per- forated platinum cone (Fig. 26) should be put in the funnel under the filter to support it when the suction is turned on. To save the trouble of transferring the filtrate from the filter- flask to a beaker, by the use of a bell-jar, the filtrate may be delivered to the beaker directly. The stem of a funnel is intro- duced through a rubber stopper in the top of the bell-jar, under which is placed the beaker to receive the filtrate. The bell-jar 24 METALLURGICAL ANALYSIS (Fig. 27) rests on a smooth plate and the joint between them is sealed with vaseline or grease. If the bell-jar has no side Water from Main Richards Pump Waste Pipe FIG. 25. Richards Pump and Woulf Bottle Combined to Obtain Both Blast and Suction. FIG. 26. Perforated Platinum Cone. FIG. 27. Bell Jar Arranged for Filtering by Suction Directly into a Beaker. tubulure, the air may be exhausted from a tube introduced through the stopper. THE OPERATIONS OF ANALYSIS 25 Use of the Gooch Crucible. Precipitates which require only drying or heating to moderate temperatures before weighing may be filtered in a Gooch crucible (Fig. 28), dried, and weighed directly. The Gooch crucible is attached to a carbon filter with a short, soft rubber tube (Fig. 29), and may be connected with suction if desired. An asbestos felt is made in the crucible, either by shaking up asbestos in distilled water and pouring into the crucible until the felt is of the desired thickness, or the asbestos Rubber ' Tubing -Carbon filter FIG. 28. Gooch Crucible. FIG. 29. Gooch Crucible Attached to Filter Flask for Filtering by Suction. fibers may be put in dry and pressed down with a glass rod. The felt is then washed with water to carry away small fibers that will pass through the perforations of the crucible. The crucible with felt is then dried for an hour in an air bath at a little above 100 C., cooled in a desiccator and weighed. It is again attached to the carbon filter, and when the filtration and washing are completed, it is dried, cooled, and weighed as before. When filtering in a Gooch crucible, very strong suction should not be applied, since it causes the asbestos felt to pack, which greatly retards the speed of filtering. 26 METALLURGICAL ANALYSIS Washing of Precipitates. Precipitates that settle readily are best washed by decantation. Let the precipitate settle, carefully decant the clear solution through the filter, leaving the precipitate in the beaker, add wash water, digest over the heat as long as desired and again decant. Repeat this treatment as often as necessary and finally transfer the precipitate to the filter. After the precipitate has been trans- ferred to the filter, it should be washed by directing the jet of wash water down against the inside of the funnel, a little above the filter paper, carrying the jet around just above the edge of the filter and then down spirally into the filter. The wash bottle may be used, but it is simpler and more agreeable, where much work is done, to wash from a tank by gravity. This is effected by placing a tank for distilled water, which is provided with heat by gas or electricity, about three feet above the working table, from which, with a suitable rubber tube, the water is conducted to the funnels. This FIG. 30. An Elevated Tin-lined tube (Fig. 30) is provided at the lower end with a wash-bottle nozzle and a spring clamp for shutting off the water. By opening the clamp and directing the nozzle with the same hand the washing proceeds rapidly from one funnel to the next. The rubber tube should be long enough to permit the operator to carry the nozzle from one end of the line of funnels to the other. The washing of precipitates would be a comparatively simple Copper Tank in which Dis- tilled Water is Heated for Washing Precipitates by Gravity. THE OPERATIONS OF ANALYSIS 27 matter if the contaminating substances would freely leave the surface of the precipitate and diffuse evenly throughout the wash water. In this case four or five washings would ordinarily be sufficient, but, as explained by Ostwald, owing to adsorption, that is, the greater concentration of dissolved substances at the surface of the precipitated particles, the number of washings must be greatly increased, and the washing should be continued until it is found by testing the wash water as it comes through, that it no longer contains the contaminating substances. In some cases twenty or thirty washes are required. Richards con- siders the difficulty of freeing precipitates of contamination by washing, due to occlusion, or the enclosing of solutes in the pre- cipitate as it is formed. Burning Precipitates. When the washing is complete, if the precipitate is one that is to be burnt and weighed, and can be burnt in contact with the paper without danger of re- duction, it can be put in the crucible and burnt without previous drying, if the heat is applied carefully at the be- ginning. If, on the other hand, the precipitate is a compound of lead, tin, or other FIG. 31. Transferring a Dried Pre- cipitate from the Filter Paper to a Platinum Crucible. metal easily reduced when in contact with hot carbon, the precipitate must be dried and transferred from the paper to the crucible (Fig. 31), where it is burnt out of contact with the paper. The paper is then held over the crucible on a platinum wire and burnt in a Bunsen flame, the ash being allowed to fall into the crucible. When a wet precipitate is transferred from the funnel to the crucible to be burnt at once, the cover should be put on the crucible and kept there until all volatile matter has been driven 28 METALLURGICAL ANALYSIS out. Great care should be taken that the heat is increased so gradually that the precipitate is not thrown out by the escaping steam. When all volatile matter has been driven off, the cover is removed from the crucible and the temperature raised to oxidize the carbon of the filter, after which the cover is replaced and the heat of the blast-lamp applied if necessary. In burning a filter, it should be remembered that oxygen is needed as well as heat; the flame, therefore, should not envelop the crucible, but the FIG. 32. Arrangement of Crucible and Cover for Burning a Precipitate, FIG. 33. Method of Using Oxygen in Burning a Precipitate. crucible should be inclined and partially uncovered (Fig. 32), with the Bunsen flame applied only near the bottom. The cover should be so adjusted that the hot gases from the crucible can escape upward while fresh air is drawn in on each side of the cover. The carbon should be burned off at as low a tempera- ture as possible to avoid reduction of the precipitate. When rapid work is necessary, time may be saved by burn- ing precipitates in oxygen. The oxygen may be introduced into the crucible through a clean clay tobacco-pipe (Fig. 33). Before the pipe is lowered into the crucible, the flow of oxygen THE OPERATIONS OF ANALYSIS 29 must be so regulated that it will not blow the precipitate away. The Care of Platinum. Platinum is attacked by chlorine, and, therefore, by any combination of substances that yields chlorine, as aqua regia, etc.; by mixtures of hydrobromic and nitric acids; by hydriodic acid slowly; and by boiling ferric chloride solution. Mercury will adhere to platinum, forming a plate on the surface, but it may be driven off by heat. At high temperatures, platinum is attacked by the hydrates, nitrates, and cyanides of the alkalies and the alkaline earths; by a mixture of sulphur or sulphides with alkaline salts ; by phos- phorus and arsenic, and the metals that form alloys with platinum, such as lead, tin, antimony, gold, etc. Substances that contain these elements in easily reducible form should not be heated in contact with platinum. When charcoal is burned in contact with platinum, silicon is reduced from the charcoal and combines with the platinum, making it brittle. The reducing flame gives to platinum a dull gray appearance, and repeated heating and cooling promotes the growth of crystals which increase in size until they give the surface of the metal a spotted appearance. To prevent the growth of such crystals and the final cracking of the platinum, rub with sea-sand held on the moistened finger until the surface of the metal is bright. To Clean Platinum. If it is known what substance pro- duces the stain or discoloration on the platinum, use the best solvent known for that substance, which at the same time will not attack the platinum. For obstinate cases, fuse a little sodium carbonate on the stain, cool, and dissolve by boiling with hydro- chloric acid, and then rub the platinum bright with sea-sand. A sand-soap may be used, but the sharp sand of the soap wears the platinum away faster than the round grains of sea-sand. Hold the sand on the moistened finger or on a damp cloth when 30 METALLURGICAL ANALYSIS rubbing the platinum. Do not rub the platinum against a solid lump of sand-soap. The Desiccator. When the precipitate has been sufficiently heated in the crucible to bring it to the definite form in which it is to be weighed, the crucible is placed in a desiccator (Fig. 34) while it is still hot, but not glowing, to be left to cool before it is weighed. The desiccator may con- tain any good absorbent of moisture. Either concentrated sulphuric acid or calcium chloride serves the purpose well, and the desiccator should be occasionally replenished with a fresh supply of the desiccating agent to maintain its efficiency. If sulphuric acid is the dryer used FIG 34 Desic- m tne desiccator, glass beads should be put in cator. with the acid to prevent its flowing too easily and being thrown against the crucible when the desiccator is handled. The contact between the desiccator and its cover should be made air-tight by applying occasionally a mixture of vaseline and paraffine. Objects weighed when warm, weigh less than when cold, owing to upward currents produced in the air about them, which buoy them up; and the rate at which moisture is deposited upon them from the air depends upon the temperature; there- fore, they should always be cooled in a desiccator and weighed at room temperature, or all weighings made at as nearly the same temperature as possible. Weighing Precipitates. After the crucible has cooled in the desiccator, usually from fifteen to twenty minutes, it is care- fully taken from the desiccator with a pair of clean forceps or tongs and placed upon the balance for weighing. Care should be taken not to touch the crucible with the hands until the final weighing has been made. Weigh as quickly as possible and record the weight in the weight-book. Return the crucible with its contents to the desiccator with the forceps, carry it back to the THE OPERATIONS OF ANALYSIS 31 working table and heat it again for ten minutes, cool and weigh again as before, and if the weight does not agree with the former weight, repeat this treatment until the weight is constant. If a very large crucible or other large object is weighed it should be counterbalanced by a similar object on the other balance pan to neutralize the effect of deposition of moisture from the atmos- phere. Calculating Results. The results of analyses are usually expressed in parts per hundred, or per cent. If the precipitate finally weighed is in the' form in which it is to be reported, it is only necessary to divide its weight by the weight of the sample taken for analysis and multiply the result by 100. For example, if the CaO from 0.5 gm. of limestone weighs 0.1931 gm., to find the percentage of lime in the limestone, the question may be simply stated thus: If in 0.5 gm. of limestone there are 0.1931 gm. of lime, in 100 parts of limestone there are how many parts of lime? 0. 5:0. 1931 = 100 :x It is evident in cases pf this kind that the calculation is simplified by taking a definite weight of the sample that is simply expressed, as 1 gm., 0.5 gm., or 0.2 gm., because that number must be used as divisor. When the precipitate weighed is not in the form in which it is to be reported, the quantity in the desired form must be calculated from the weight of the precipitate. For example, if the precipitate of BaSO4 from 5 grams of steel weighs 0.0232 gm., what is the percentage of S in the steel? We first find the weight of S in 0.0232 gm. BaSO 4 , and with that weight proceed as in the last example. To find the weight of S in 0.0232 gm. of BaS0 4 , we multiply by the factor for S in BaSO 4 . The 32 METALLURGICAL ANALYSIS factor is the number which expresses the weight of S in one part of BaS0 4 , and is obtained as follows: The molecular weight of BaSCU is 233.44, being composed of 1 atom of Ba, atomic weight 137.37 1 atom of S, atomic weight 32 . 07 4 atoms of O, atomic weight 16= 64. 233.44 Then, if in 233.44 parts of BaSO 4 , there are 32.07 parts of 32 07 S, there is in one part of BaSO 4 =0.13738 part of S. 2oo.4 1 The factor, then, for S in BaS04 being determined once for all as 0.13738, we proceed as follows: if one part (or gram) of BaS0 4 has 0.13738 part (or gram) of S, 0.0232 gm. of BaSO 4 will contain 0.0232X0.13738 = 0.003187 gm. of S. Then, pro- ceeding as in the first example above, we find the percentage of S as follows : 0.003187X100 7j The whole operation may be expressed in one equation: 0.0232X0.13738X100 _ n nr/17 " p U.Uu~r/. O Factor Weights. In the above example, if we had weighed not 5 gms. of steel, but 0.13738 gm., or better, 0.1374 gm., this latter number would become the denominator in the above equation and the solution would be simplified, for the denominator would then be the same as the factor for S in the numerator and the two would cancel. We would then only have to multiply VOLUMETRIC ANALYSIS 33 the weight of BaS0 4 by 100, or move the decimal point two places to the right. A weight of this kind is called a factor weight and is used to simplify the calculation of the result. In the case above, the weight 0.1374 gm. is too small a quantity of steel for the sample, for the yield of BaSC>4 from that quan- tity of this steel (0.000637 gm.) is so small that errors in manipu- lation would be greatly magnified; a simple multiple as 20 or 50 times this factor weight, can be used and still the calculation remain extremely simple. Such factor weights are much used in routine gravimetric work in which the form weighed must be converted by calculation into another form before the percentage is estimated. VOLUMETRIC ANALYSIS Volumetric Apparatus. Volumetric analysis demands the use of graduated flasks, pipettes, and burettes. The chemist should test such apparatus to see if it is correctly graduated, and, if it is not, he should determine the errors and make the necessary corrections. This is done by weighing the distilled water contained by the apparatus, at the temperature at which it was graduated usually marked on the apparatus or by comparing the volume contained with that which is held by similar specially standardized apparatus sold by dealers. Measuring flasks (Fig. 35) are usually graduated to hold the quantity indicated at the temperature marked on the flask, but some flasks have a second graduation higher up on the stem to which they should be filled to deliver the indicated quantity. Pipettes (Fig. 36) and burettes (Figs. 37, 38) deliver the quan- tities indicated, and should be given half a minute to drain. * Titration methods and colorimetric methods are, strictly speaking, not volumetric methods in the sense that gas analysis is; for in the former we must still use the balance for weighing the sample and for standardizing the solutions, but the determination of the weight of the substance sought is accomplished through volumetric operations, 34 METALLURGICAL ANALYSIS The point of the pipette should touch the side of the receiv- ing vessel to deliver the last drop; do not blow out the last drop. To fill a pipette, place the upper end in the mouth and draw the solution in until the meniscus stands somewhat above the graduation of the pipette. Withdraw the pipette from the /I FIG. 35. FIG. 36. FIG. 37. FIG. 38. FIG. 35. Graduated Flask. FIG. 36. Pipette. FIG. 37. Burette. FIG. 38. Burette that Fills to Zero Automatically with Overflow Cup and Side Tube for Filling from Reservoir. mouth and quickly place the index finger of the right hand over the upper end to hold the solution in the pipette. Then turn the pipette with the left hand, admitting the air slowly until the meniscus falls to the graduation. Press firmly again with the index finger to prevent further admission of air until the pipette is brought in position to be discharged. Poisonous liquids and those giving off unpleasant gases should be drawn into the pipette by attaching the upper end of the pipette with a rubber tube to VOLUMETRIC ANALYSIS 35 the exhaust tap on the work table. The suction can be con- trolled by operating the tap or by pressure on the rubber tube. For the accurate reading of the burette, some chemists prefer a burette float, but for regular routine work it is sufficiently accurate to read the bottom of the meniscus, especially if a strip of white paper be held just back of the burette. To read the burette when it contains very dark-colored solutions, such as potassium permanganate solution, it is necessary to hold a light just behind the burette to render the meniscus visible. A light may be supplied by a simple jet attached with a rubber tube to the gas tap on the table. Cleaning Solution. All apparatus must be kept scrupulously clean. This applies especially to volumetric apparatus, which must be free from grease and all other foreign matter so that solutions will flow out evenly and not leave drops adhering to the sides. An excellent cleaning solution is made by adding 10 gms. of potassium dichromate to a liter of commercial sulphuric acid. After using the cleaning solution it should not be thrown away, but returned to the bottle for future use. The apparatus to be cleaned should be left full of the cleaning solu- tion for several hours, and thoroughly washed with distilled water after the cleaning solution has been returned to its bottle. Titration. Instead of precipitating, filtering out, and weigh- ing a substance, it is better in many cases to measure it while in solution by the method of titration. For carrying out the process of titration it is necessary to prepare a solution of a reagent which will react in a definite way with the substance to be determined. This solution must have a certain deter- mined strength and is called a standard solution. It is also necessary to provide means for determining when the reac- tion is complete. A reagent used for this purpose is called an indicator. To make an analysis by titration, then, we put the sample in solution in such form that the ion sought will react 36 METALLURGICAL ANALYSIS in a definite way with the standard solution. The standard solution is run in from a burette until the indicator shows that the reaction is complete; by noting the volume of the standard solution that has been used, and knowing its value per cubic centimeter in the substance being determined, it is easy to calculate the amount of that substance present. Standard Solutions. Standard solutions are made to con- tain a definite amount of the active agent in every cubic centi- meter. Two kinds of standard solutions are in general use normal solutions, and empirical standard solutions. Normal Solutions. A normal solution is a standard solution which has in a liter that quantity of reagent which contains 1.008 gms. (the atomic weight) of replaceable hydrogen, or the equivalent of that amount of hydrogen in some other active agent, as 35.46 gms. chlorine or 8.0 gms. of oxygen. A normal solution of hydrochloric acid will, therefore, contain 36.468 gms, of HC1 per liter, and such a solution of sulphuric acid, 49.043 gms. H 2 SO4 per liter. A normal solution of potassium permanganate should con- tain 31.606 gms. of the salt per liter, since the weight of K 2 Mn 2 Os which contains, in available oxygen, the equivalent of 1.008 Q -j r* f\* gms. hydrogen is ' , =31.606 gms. (In K 2 Mn 2 O8 there are 5 atoms of available oxygen. K2Mn2Og = K2O-f 2MnO+50.) In like manner a normal solution of K 2 Cr 2 O7 will contain 49.03 gms. of the salt (K 2 Cr 2 O 7 = K 2 0+Cr203-r-3O. = 49.03); JXo and such a solution of iodine will contain 126.92 gms. of iodine (I 2 +H 2 = 2HI+O). If the normal solution is not a convenient strength, any suitable multiple as the half, fifth, tenth, hundredth, or the twice normal way be used. A normal standard solution is convenient if the one solution is to be used for different purposes and on different substances, but if the standard solution is to be used for one particular process, as is usually the case in metal- VOLUMETRIC ANALYSIS 37 lurgical analysis, the empirical standard solution is the more useful and convenient. Empirical Standard Solutions. An empirical standard solu- tion is made so that 1 cc. of it will be equivalent to a simple definite value of the substance to be determined, as 0.01 gm. or 0.005 gm. ; 1 per cent or 0.5 per cent when a sample of definite weight is worked upon. Empirical standard solutions are made by calculating, from the reaction involved, the amount of the titrating reagent required to react with 0.01 gm., 0.005 gm., or any other desired amount of the substance to be determined, and then weighing out as many times this amount as there are cubic centimeters in the whole volume of solution to be made. Preparation of an Empirical Standard Solution. A standard solution of potassium permanganate of such value, for example, that 1 cc. will oxidize 0.01 gm. of iron from the ferrous to the ferric form is made as follows. The reaction which takes place between KMn(>4 and ferrous iron in the presence of [2864 is as follows: 10FeS04+2KMnO4+8H 2 S0 4 = 5Fe 2 (S04)3+K2S04+2MnS04+8H 2 0. If 10 atoms of Fe" are oxidized by the available oxygen from 2 molecules of KMnCU, 0.01 gm. of Fe" will require for its oxidi- zation 0.0056601 gm. of KMnO4, as shown by the following proportion: 10(55.84) : 2(158.03) =0.01 : 0.0056601, 55.84 being the atomic weight of iron and 158.03 the molecular weight of KMnO4. Having determined the amount of KMnCU required in 1 cc., if we wish to make a liter of such a solution, we weigh out 1000 times 0.0056601 gm., or 5.6601 gm., dissolve it in distilled water, and dilute the solution to 1 liter in a graduated flask. 38 METALLURGICAL ANALYSIS Standardizing Solutions. In order that a standard solu- tion have the strength intended, it must be made with great care. The purity of the reagent must be known, and any impurity allowed for, the weighing must be accurate, there must be no loss after weighing, the reagent must not be subjected to con- ditions that will change its form before or after it is put in solu- tion, and the temperature of the solution should be the same when it is used for titration as when it was made. As a safe- guard against errors from these sources, a solution that is to be used for titration should be standardized against a reagent of known purity to determine its actual strength per cubic centi- meter, that is, an exact quantity of such reagent is weighed out, put in solution and titrated under as nearly as possible the same conditions as exist when determinations are made on unknown materials. There should be the same impurities present and in the same amounts, and the volume to be titrated should be the same when standardizing as when making regular determinations. See that the burette is perfectly clean, and if it is wet with distilled water, rinse it out with some of the solution that is to be standardized before filling for the test. Place the burette in a vertical position in a burette clamp attached to a stand. Nearly fill the burette with the solution to be standardized. Open the tap and let a little of the solution run out, in order to fill the point of the burette below the tap, and to bring the meniscus down to the graduations. See that a bubble of air is not held just below the tap. Now read the burette at the bottom of the meniscus and record the reading. Let the solution run from the burette into the solution to be titrated, stirring or shaking, until the reaction is complete as shown by the indicator. Care must be taken to stop the titration at the exact end-point, therefore, as the end-point is approached, the solution must be run in very slowly drop by drop. When the end-point is reached, close the tap of the burette, and after waiting half a minute for the solution to VOLUMETRIC ANALYSIS 39 run down the sides, read the burette and record the reading. The difference between the two readings of the burette indi- cates the volume used in the titration. After some practice the burette can be read to the second decimal place. The record should stand thus: Second reading of the burette 37 . 58 cc. First reading of the burette 1 . 24 Volume used in titration 36 . 34 To find the value of 1 cc. of the solution in the burette, divide the weight of the substance acted upon, after correcting for impurities, by the volume used in the titration. Correcting a Standard Solution. If a solution is tested with a .view to correcting what remains, to the exact strength desired, a definite portion, as 100 cc., should be taken out for the test, so that the remaining volume, which is to be corrected, may be known. To indicate the method of correcting a standard solution, we will suppose that the potassium permanganate solution in the example above, when tested against a known weight of iron, is found not to have the value, 0.01 gm. of Fe per cubic centimeter, but 1 cc. proves to be equivalent to only 0.0096 gm. of Fe. If we have 900 cc. of the solution left, we may correct it as follows. If 1 cc. of the solution is equivalent to only 0.0096 gm. of iron, it does not contain 0.0056601 gm. of KMnO 4 , but only 0.0054337 gm. 0.01 : 0.0056601 = 0.0096 : 0.0054337 There must be added, then, to each of the 900 cc. remaining (0.0056601 -.0054337) 0.0002264 gm. of the salt, or to the total volume (0.0002264x900) 0.0238 gm. The calculation is simplified by reducing to this form: /1-.0096\ 40 METALLURGICAL ANALYSIS On the other hand, if the solution is too strong, it may be corrected as follows: let us suppose that 1 cc. is equivalent to 0.0107 gm. of Fe instead of 0.01 gm., then each cubic centimeter of the solution has in it, not 0.0056601 gm. of the salt, but 0.006056307 gm. 0.01 : 0.0107 = 0.0056601 : 0.0060563. There is, therefore, in each cubic centimeter of the solution too much KMnO 4 by 0.0003962 gm., and in the 900 cc. remaining there are 0.35658 gm. (0.0003962X900) too much of the salt. This is a sufficient quantity of the salt to make 63 cc. of the correct strength (0.35658 -=-0.0056601 = 63). We have then only to add 63 cc. of distilled water to the solution to dilute it to the correct value. This problem stated in one equation may be reduced to the form: (1.07-1)900 = 63. Factor Weights for Standard Solutions. It is not always easy to make a standard solution of an exact predetermined value, nor is it easy to keep it at an exact value. The object of making the standard solution so that 1 cc. will be equivalent to a simple definite value, as 0.01 gm. of the substance to be determined, is, of course, to simplify the arithemtical calcula- tion of the result after titration. If we have a standard perman- ganate solution of the value of 0.01 gm. of Fe per cubic centi- meter, and use 1 gm. of iron-ore for analysis, the number of cubic centimeters of solution used in the titration will represent directly the percentage of iron in the ore. Suppose, for example, it is observed after titration in such a case that 62 cc. of the standard solution had been used in titration, then the calculation would be as follows: VOLUMETRIC ANALYSIS 41 It is evident from this equation that the calculation would remain equally simple if the weight of the ore taken is always just 100 times the value of the solution. If the KMnCU solu- tion should have the value 0.0096 instead of 0.01, we would only have to weigh out 0.96 gm. of ore instead of 1 gm. to preserve the simplicity of calculation. It is simpler then, instead of try- ing to make and keep a solution at an exact definite value, to standardize it as often as necessary, and, as its value changes, change the weight of ore taken to correspond with it. Indicators. In all titrations there must be a means pro- vided for detecting when the reaction is complete, that is, when the substance being measured has all been acted upon. This l-p&int is detected in a variety of ways, for example, by the Formation of a precipitate, as in titrating cyanide with silver nitrate; by the failure of a precipitate to form, as in the Gay- Lussac method for silver; by the standard solution giving its color to the solution titrated, when the action is complete, as in the permanganate titration; by the change or disappearance of the color of the solution titrated, as in the cyanide method for copper; by a change of color in drops of a test solution, to which drops of the solution being titrated are added from time to time, as the titratien proceeds, or by the change of color due to the presence of a test solution, or indicator, added to the solution titrated. The last method is the one employed when the end-point is marked by a change in the solution titrated from the alkaline to the acid condition, or vice versa. Several indicators are in use for detecting this change. They vary in their sensitivity and in their suitability for different uses. For convenience the more common ones are given below with their adaptability to different uses. Phenolphthalein, colorless with acids and pink with alkalis, is good for hydrochloric, nitric, sulphuric, and the organic acids; and also for the alkalis NaOH, KOH, Ba(OH)2 and Ca(OH) 2 . It is not good for ammonia, nor in the presence 42 METALLURGICAL ANALYSIS of C02, but may be applied after expelling the CC>2 by boiling. Methyl Orange, pink with acid and yellow with alkalis, is good for hydrochloric, nitric, and sulphuric acids; the hydrates, carbonates, and bicarbonates of the alkalis, and also for am- monia. Cochineal, purple red with acids, and blue with alkalis, is good with ordinary mineral acids and alkalis, including ammonia. It is also reliable in the presence of CO2, but not with the organic acids. The reagent used for detecting the end-point will be described under each titration method. COLORIMETRY Many substances regularly determined in metallurgical anal- ysis, when in solution and in certain definite forms give to the solutions characteristic colors, which may be used as a basis for the quantitative determination of these substances. The intensity of the color of a solution depends upon three elements, or factors. They are : the quantity of coloring matter used, the volume of the solvent in which it is held, and the thick- ness of the solution through which the light passes before enter- ing the eye. It is well known that if we keep two of these quan- tities constant and vary the third in a determinate way until two solutions are alike in color, we can estimate the quantity of coloring matter in one, if the quantity in the other is known. These three variables form the basis of three classes of methods in colorimetry, and of three types of colorimeters. When two solutions are brought to agreement in color by the addition of coloring matter to one, the amount added is the measure of that in the other. If the agreement is effected by dilution, the color- ing matter is then proportional to the volumes. If they are brought to equality by changing the thickness of the sections COLORIMETRY 43 observed, the quantity of coloring matter is then inversely proportional to the measurements of these sections.* In laboratories where the first method is used, a series of solutions is prepared (Fig. 39) with varying amounts of the standard, representing the percentages from the lowest to the highest demanded in that laboratory. For instance, the first may contain 0.01 gm. of the color-producing substance, the FIG. 39. Series of Standard FIG. 40. FIG. 41. Camera for Eggertz Solutions for Colorimetry. Eggertz Tubes. Tubes. second, 0.03 gm., the third, 0.05 gm., etc. Then, if the sample is dissolved and diluted to the same volume as the standards, in a similar tube, its place in the series is easily found and its value determined at once. Theoretically, this is the best colori- metric method known, but it is not so practical as some others, on account of the large number of standards required, and the necessity for frequent renewals due to their lack of permanency. *C. H. White, Jour. Am. Chem. Soc., 34, 639. 44 METALLURGICAL ANALYSIS The second method, proposed by Eggertz,* is usually carried out in two graduated tubes of equal bore (Figs. 40, 41). The two solutions, the standard and the unknown, are diluted until the colors are the same when the tubes are held between the observer and a uniform light. The ratio existing between the quantities of coloring matter in the two tubes is then equal to FIG. 42. FIG. 43. FIG. 42. Colorimeter in which Hollow Glass Wedges are used to Vary the Depth of Solution Examined. FIG. 43. Colorimeter in which Solid Glass Plungers Lowered into the Solutions Change the Thickness of the Sections Compared. the ratio between the volumes of the two solutions. Since three of these quantities are known the fourth is readily estimated. In the third method, equal quantities of the standard and the unknown are dissolved in equal volumes of the solvent, and the thickness, or depth, of the solutions under examination * Chemical News, 44, 173, Fern Kontorets Analer, 1862, p. 54. IRON ORES SAMPLING 45 is varied until the colors are the same. The percentages of coloring matter are then inversely proportional to the thickness of the sections. Several colorimeters (Figs. 42, 43) have been devised for varying and measuring the thickness of solutions under examination. These instruments are usually constructed and graduated in such a manner that the desired percentage may be read off at once. With these instruments, comparisons can be quickly made, and any number of readings may be taken and averaged without changing the volumes of the solutions. The solutions are not diluted by guess as in the Eggertz method, and preconceived notions of the value of the material cannot influence the operator, since he cannot see the graduations until the colors are matched. METHODS OF ANALYSIS IN THE METALLURGY OF IRON AND STEEL ANALYSIS OF ORES Sampling Iron Ore. For the general principles- of sampling see page 8, and for the quantity to be taken, and the size to FIG. 44. Sampling Trowel FIG. 45. Sampling Pick for Drawing for Friable Ore. Ore from well below the Surface. which the lumps should be crushed before quartering down the sample, see the table on page 11. For the applica- tion of the table, ordinary iron ores would be classed as very uniform, low-grade material. Sampling Ore in Cars. Soft ores may be sampled with a garden' trowel (Fig, 44) or the sampling pick (Fig. 45). Before 46 METALLURGICAL ANALYSIS taking the sample, remove three inches of the surface at the point where the sample is to be taken and then dig into the ore with the trowel or sampling pick, take up the sample, and deposit it in an iron pail. Since it is not practicable to mix ore in cars previous to sampling, it should be kept in mind that the accuracy of the sample increases as the number of points from which it is taken is increased. The U. S. Steel Corporation takes at least 15 samples from 50-ton and 12 from 25-ton cars (Fig. 46),* of 2 to 3 ozs. each; that is, the total sample contains not less than 1J Ibs. from each small car and 2 Ibs. from each large car. Samples from ten cars may 6 o o o :O c FIG. 46. Parallel System of Sampling Ores. be combined into one. The fact that this very small sample is representative indicates that the ore is extremely uniform in character. The points from which the samples are taken should be as evenly spaced as possible over the surface of the ore. If a lump is found at a point from which a sample is to be taken, a small piece is broken from the lump for the sample; the size of this piece will depend upon the size of the lump; if the lump is average ore in the space represented by that sample, the chip taken off for the sample will be as large as the usual sample. The rope-net system in use at some of the hard-ore mines in the Lake Superior district is best for the even spacing of points * J. M. Camp, J. Ind. Eng. Chem., 1, 107-15. Also Electrochem. Met. Ind., 7, 65-72. IRON ORES SAMPLING 47 from which samples are to be taken. A rope net of 18-in. mesh (Fig. 47) is placed over the car, the knots or the squares indi- cating the points at which samples are to be taken. Moisture Sample. If the regular sample is taken from well below the surface, a portion of it 2000 grams or so may be put in a tin box or jar with tightly fitting cover for a moisture sample. If a special sample is taken for moisture, it is taken from well below the surface, and three samples, equally spaced, are taken from each car. Sampling a Cargo. A cargo may be sampled by taking a few ounces from each grab as it is unloaded, by means of a scoop LJL , I _J FIG. 47. Rope Net System of Sampling for Hard Ores. attached to a suitable handle. This method, however, is more expensive than taking samples from the surface while unloading is going on. The latter method is adopted by the U. S. Steel Corporation. Before unloading begins, samples are taken from the cone of ore under each hatch; then after unloading has pro- ceeded far enough at a hatch to expose the bottom of the vessel, the sloping faces of ore exposed are then carefully sampled. The total sample of the cargo should be made up of at least nine- tenths from the faces, and not more than one-tenth from the surface of the cones. A cone is sampled by taking samples a foot apart along two lines which cross at the apex of the cone and end directly under the edge of the hatch midway between the center and the side of the boat as shown in Fig; 48. 48 METALLURGICAL ANALYSIS A face is sampled by climbing up the face, using a ladder, if necessary, and taking samples from points a foot apart (Fig. 49) along lines equally spaced 4 ft. apart. Preparation of the Sample. The sample is dried, if necessary, at 100 and crushed to pass a half-inch mesh screen, or finer (see table on p. 11). Thoroughly mix the ore and quarter it alter- nately until only one-quarter of the original sample remains. Crush this to one-quarter inch, mix and sample it down as before until about 2 Ibs remain. Grind this to pass a 20-mesh screen or finer, roll well and take out about 3 ozs., dry at 100, grind on FIG. 48. Cargo Sampling The Cone. FIG. 49. Cargo Sampling The Face. a bucking board to 100 mesh, or finer in an agate mortar (see p. 14) and place in a stoppered bottle and reserve for analysis. MOISTURE The moisture sample should contain not less than 2000 gms.> and should be carefully protected from loss of moisture until weighed (see Moisture Sample, p. 47). It is evenly spread out not more than 1 in. deep in a pan, and dried at 100 to a constant weight (4 to 6 hours, or over night) . The loss in weight is moist- ure. Sometimes a weight of 2 Ibs. is used for the moisture sample, in which case the loss in weight multiplied by 1000 gives the moisture in 1 ton. IRON ORES COMBINED WATER HYGROSCOPIC WATER To reduce the results of an analysis to the basis of dry ore, it is necessary to determine the moisture or hygroscopic water in the powdered sample when it is analyzed. Heat a clean platinum crucible to drive off the moisture, cool it in a desiccator, weigh it, and then weigh and transfer to it about 1 gm. of the ore. Heat it about an hour on a toluene bath or in an air bath held at 105 C. to 110 C. (See p. 70.) Cool in a desiccator and weigh. The loss in weight is hygroscopic water. COMBINED WATER * Blow a small bulb at one end of a hard glass tube (Fig. 50) which is about 20 cm. long and 6 mm. internal diameter and another near the middle. Warm the tube to dry it thoroughly; the drying is hastened by drawing the air from it at the same time by introducing into the bulb-tube a smaller glass tube attached to the suction tap by a rubber tube. Cool and weigh the tube. Intro- duce into the bulb at the end, about half a gram of ore through a thistle tube, not letting the ore touch the sides of the weighed tube. Weigh the tube containing the ore. The weight of the empty tube deducted leaves the weight of the ore introduced. Hold the tube in a horizontal position and gradually heat the bulb containing the ore in the Bunsen flame, keeping the tube cool from the middle to the open end by wrap- ping it with cloth or filter paper wet with cold water. Do not use so much water that drops run down to the hot part of the tube. Turn the tube in the flame so that the bulb does not * Method of S. L. Penfield, Am. Jour. Sci., Third Series, 48, 31, 1894- FIG. 50. Bulb Tube for De- termining Com- bined Water. 50 METALLURGICAL ANALYSIS become soft enough to flow. The heating should be continued at least fifteen minutes, and the blast lamp should be used if minerals are known to be present that give up water with difficulty. When the water has all been driven out of the sample and has been condensed in the middle of the tube and while the bulb is still hot, grasp it with forceps or tongs and pull it away, sealing up the end of the tube with the flame. Dry the outside of the tube, cool, and weigh it. Then warm the tube to drive out the water, sucking out the moisture as before the first weighing, and then cool and weigh it again. The difference between the last two weights represents the total water. From the total water deduct moisture which has been previously determined, to find the weight of combined water. Reduce the weight to per cent in the usual way. (See p. 31.) LOSS ON IGNITION The sample is weighed in the same manner as for hygroscopic water and heated at the highest temperature of the blast lamp for thirty minutes. The hygroscopic water, the combined water, carbon dioxide, and other volatile substances, if present, will be driven out; carbonaceous matter burned; and ferrous com- pounds oxidized to ferric compounds. It serves as a rough guide to the water and C0 2 in limestone, and to the water, in materials free from other volatile substances and from elements subject to oxidation. IRON IN ORES POTASSIUM PERMANGANATE MARGUERITTE METHOD Outline. The iron is dissolved from the ore in hydrochloric acid. It is then reduced to the ferrous condition with zinc, sulphuric acid added, and the quantity of the iron is measured by titrating it with a standard solution of potassium permanganate. IRON IN ORES PERMANGANATE METHOD 51 Reagents. Potassium chlorate, KClOa, Pure Zinc, Zn.* Standard Potassium Permanganate Solution. Make the per- manganate solution in the manner described on page 37, using 2.83 gm. of KMnCU per liter. This solution should be equiv- alent to 0.005 gm. of Fe per cubic centimeter, and if it is carefully prepared with chemically pure KMnCU and distilled water that has been previously boiled with a little KMnCU, the error should not be greater than one-half of 1 per cent. Freshly prepared solutions of permanganate usually contain small amounts of Mn(>2, either originally in the salt as an impur- ity, or reduced from it by dust or other impurities in the water or in the bottle in which it is kept, and this induces the formation of more MnC>2 with a corresponding weakening of the solution. After dissolving the KMnO4, the MnC>2 should be filtered on asbestos or the solution decanted from it, before diluting to the final volume. Filter paper should not be substituted for asbestos, as it would reduce the KMnCU. The container for the permanganate solution should have been previously cleansed with the cleaning solution (p. 35) and then with pure water. If, before standardiz- ing, the solution is allowed to age for several days, the clear solution decanted into a clean bottle, and kept away from dust and sunlight, it should keep indefinitely with very little change in strength. Standardization of Permanganate Solution. Weigh about 1 gm. of ferrous ammonium sulphate FeSO^NH^SCU-GH^O. Dissolve it in 20 cc. of water to which has been added 5 cc. of hydrochloric acid. Add about 3 gm. of granulated zinc and then add 10 cc. of sulphuric acid mixed with 20 cc. of water. * Zinc should not be used as a reducing agent for iron in ores carrying titanium, since part of the titanium is also reduced and is subsequently oxidized with the Fe by titration, vitiating the result. For titaniferous ores use either the method on p. 59 or that on p. 62. 52 METALLURGICAL ANALYSIS When the zinc is all dissolved, dilute with distilled water to 500 cc. and titrate at once before the iron becomes partially oxidized by exposure to the air. So large a quantity as 3 gms. of zinc is not necessary for the reduction of the iron for it is already in the ferrous condition except a small amount which may have become oxidized by exposure of the solution to the air, but the zinc is added to produce, as nearly as possible, the conditions which exist when the ore-solution is titrated. Multiply the weight of ferrous ammonium sulphate taken, by its factor for iron (14.24 if it is known that the salt conforms exactly to the formula), and divide this weight of iron by the number of cubic centimeters required for the titration. This gives the value of 1 cc. of the permanganate solution in iron. Make three or four such tests that do not vary more than 0.0001 gm. from each other and average the results. In order that the same conditions may exist when standardizing a solution as when regular titrations are made of unknown ores, iron ores in which the iron has been accurately determined are often used for standardizing, but it is evident that we must have an accurately standardized solution before we can prepare such a standard ore. It is therefore necessary to have recourse finally to a standard whose composition has been determined gravimetrically. Ferrous ammonium sulphate made and kept with ordinary care does not usually vary much from the theoretical composition, yet a quantity that is to be used for standardizing should be carefully analyzed for iron gravimetrically. The method for this determination follows. IRON IN FERROUS AMMONIUM SULPHATE GRAVIMETRIC METHOD Weigh accurately about 0.5 gm. of ferrous ammonium sulphate, FeS04(NH 4 )2SO 4 -6H 2 O. Transfer it to a No. 4 beaker and dissolve in 50 cc. of water to which has been added 10 drops of hydrochloric acid. If water alone were used for the solvent, basic salt would be pre- cipitated by hydrolysis. HC1 readily dissociates, saturating the solu- IRON IN ORES PERMANGANATE METHOD 53 tion with H ions, which prevents dissociation of the water into H and OPI. There are therefore no OH ions available for the formation of basic salt. Heat to boiling. Add nitric acid drop by drop until the solution turns yellow or red, through brown. Not more than 8 or 10 drops are required if the solution is kept at the boiling-point. 3FeCl 2 +HN0 3 +3HC.l=3FeCl 3 +NO+2H 2 0. Oxidation is necessary, since NH 4 OH does not completely precipitate iron in the ferrous form. Dilute with hot water to 500 cc. Add while stirring 5 cc. ammonia. FeCl 3 +3NH 4 OH =Fe(OH) 3 +3NH 4 Cl. Basic ferric sulphate is precipitated in neutral solution, therefore, the ammonia should be stirred in quickly to render all portions of the solution alkaline as soon as possible. Heat to boiling. Remove from the heat and let the ferric hydroxide settle. Decant the clear solution through a 9 cm. filter, leaving the precipitate in the beaker. Wash twice by decantation with 100 cc. hot water (see p. 21) transfer the pre- cipitate to the filter and wash on the filter with hot water, never letting the precipitate get cold until the washing is complete. The washing is complete when the wash water comes through free from chlorides. Collect 2 or 3 cc. of the wash water on a watch glass as it runs from the funnel, add a drop of nitric acid and then test for chlorides with a solution of silver nitrate. Nitric acid is added to neutralize ammonia, which if present would dissolve the silver chloride. If the chlorides are not washed out, the high temperature at which the precipitate is burnt will form ferric chloride which is easily volatilized and lost. 54 METALLURGICAL ANALYSIS The precipitate of ferric hydroxide should be filtered as soon as it settles; long contact of the ammoniacal solution with the glass may contaminate the precipitate with silica dissolved from the glass. Place the moist filter with its contents in a platinum or porcelain crucible (see note below) that has been cooled in a desiccator and weighed, cover the crucible, and carefully drive off the moisture and volatile part of the filter paper at so low a temperature that the escaping gases are not ignited. When the volatile matter is all out, uncover the crucible and carefully burn the carbon at as low a temperature as possible with free access of air to prevent the reduction of ferric to magnetic oxide. When the carbon is all burnt, heat the precipitate to a high temperature for a few minutes with a small blast flame directed against the bottom of the crucible, and away from the top. 2Fe(OH) 3 =Fe 2 3 +3H 2 0. A high temperature is required to drive off the last traces of water- on the other hand it induces the formation of Fe 3 4 , especially if reduc- ing gases are allowed to enter the crucible. In " Methods for the Analysis of Iron and Steel Used in the Laboratories of the American Rolling Mill Co.," page 26, it is pointed out that the ignition of ferric oxide in platinum induces the formation of Fe 3 4 , and it is suggested that the precipitate be ignited and weighed in a porcelain crucible placed inside a platinum crucible. Cool in a desiccator and weigh. Heat again at a high tem- perature for a few minutes, cool and weigh. Repeat this treat- ment until the weight is constant. Calculate the weight of Fe in the Fe 2 O 3 (Factor 0.6994) and the percentage in the salt. Additional Methods of Standardization. Iron wire in which the iron has been carefully determined may be used for standard- izing permanganate solutions. The wire is carefully cleaned, wound into a coil (on a pencil or glass rod), weighed, and treated by the method below for the determination of iron in ore. Blair* recommends the use of a solution of ferric chloride * " The Chemical Analysis of Iron," seventh edition, p. 236. IRON IN ORES PERMANGANATE METHOD 55 made from wrought iron free from manganese and arsenic, and in which the iron and phosphorus have been accurately determined. The oxidizing power of permanganate solution may be measured by oxalic acid, but the solution must be hot when titrated, and the other conditions under which the titration is made are not the same as when solutions of ore are titrated. 5H 2 C 2 4 2H 2 O + 2KMnO 4 + 3H 2 SO 4 = K 2 S0 4 +2MiiS0 4 +10CO 2 +10H 2 0. This latter objection applies also to Lunge's method of standardiz- ing the solution. By this method a measured volume of the solution is decomposed with hydrogen peroxide and sulphuric acid, the available oxygen liberated, collected and measured in a gas burette.* Fe in Ore. Weigh 0.5 gm. of ore or a factor weight (see p. 40). Transfer it to a 300 cc. beaker or casserole. Add 10 cc. of hydrochloric acid, cover with a watch glass, and raise the temperature but do not boil. Fe 2 3 +6HCl=2FeCl 3 -{-3H 2 0. According to this reaction, 0.108 gm. HC1 will dissolve .5 gm. Fe 2 3 . In 10 cc. of hydrochloric acid 1.20 sp.gr. at 15 there are 4.68 gm. of HC1; however, HC1 is driven off by heat, and if the ore does not dissolve readily it may be necessary to add more acid. If a solution of ferric chloride boils, iron is carried away by the vapor mechanically. Add a few crystals of KClOs to destroy carbonaceous matter. In the titration some permanganate would be reduced by the car- bonaceous matter if it were not destroyed, and it would also give the solution a color that would persist after the iron had been reduced, making it impossible to detect by the loss of color when reduction is complete. *Chem. Ind., 1885, 168; Olsen, "Quantitative Analysis," p. 298. 56 METALLURGICAL ANALYSIS When the solution of the iron is complete and the residue is white, or if the acid appears to have no further action, evaporate off most of the free acid (to about 5 cc.) at a low heat; do not boil. There should be only a little HC1 left, for in titration a somewhat concentrated solution of hydrochloric acid, or a weak solution if hot, reacts with KMn0 4 as follows: 2KMn0 4 +16HCl=2KCl+2MnCl 2 +8H 2 0+5Cl 2 . This reaction may be prevented, however, by the addition of a few grams of manganous sulphate before titration. If it is suspected that iron remains undissolved in the residue, as will be the case if the ore has not been finely ground or if it contains a silicate or titanate of iron, dilute with 15 cc. of hot water, filter, wash once or twice with hot water, place the filter with the residue in a platinum crucible, burn the paper, cool, add 1 cc. each of sulphuric acid and hydrofluoric acid, evaporate until sulphuric acid fumes begin to come off, and transfer the solution from the crucible to the filtrate containing the greater part of the iron. Instead of treating the residue with sulphuric and hydrofluoric acids, the iron may be extracted from it as follows: after burning the filter paper and cooling, add 2 or 3 gms. of sodium carbonate and fuse, digest the fusion with hot water, which leaves the ferric oxide as a precipi- tate, filter out the ferric oxide, dissolve it in a little hydrochloric acid and add it to the main solution of iron. When the iron is all in solution and only a little free hydro- chloric acid remains, add about 3 gm. of granulated zinc to reduce the ferric to ferrous chloride. Zn+2HCl=ZnCl 2 +H 2 , 2FeCl 3 +H 2 =2FeCl 2 +2HCl. When the brown color of ferric chloride has disappeared and the solution is clear, or if the action on the zinc ceases, add 10 cc. of sulphuric acid which has been mixed with 20 cc. of water. When the iron is all reduced (the solution becoming color- less) and the zinc is all dissolved, transfer the solution to a large IRON IN ORES PERMANGANATE METHOD 57 beaker or white dish, being careful to wash out all of the iron solution from the original beaker, dilute with cold distilled water to about 500 cc. and titrate with standard permanganate solu- tion, stirring, until a faint permanent pink pervades the whole solution. For the method of titrating, reading the burette, and calculating the result, see pages 35 and 39. REDUCTION OF THE IRON BY MEANS OF THE JONES REDUCTOR If many reductions are to be made with zinc, the process is much more quickly carried out by the use of the reductor. This re- ductor * in its simplest form (Fig. 51) consists of a glass tube about 60 cm. in length, the upper half of which has an internal diameter of 25 mm. with a funnel top, and the lower half is drawn down to a diameter of 6 mm. The tube is provided with a glass tap at the point where the diameter is reduced. Glass wool is placed in the tube above the tap to a depth of 10 to 15 mm. to support the column of zinc. The large part of the tube is then filled to the funnel with amalgamated zinc. The zinc is amal- gamated to prevent its rapid con- sumption. To prepare amalgamated zinc, put into a beaker enough granulated zinc (through 20- on 30- Suction FIG. 51. Reductor. * Blair, "Chemical Analysis of Iron," seventh edition, p. 94. 58 METALLURGICAL ANALYSIS mesh screen) to fill the tube, cover it with distilled water, add about 5 gm. of mercury and 5 cc. sulphuric acid, and stir vigor- ously with a glass rod. In a few minutes the zinc is amalga- mated and ready to be transferred to the reductor. Use of the Reductor. Attach a filter flask to the reductor with a perforated rubber stopper and connect the filter flask to the suction. Prepare a dilute solution of sulphuric acid (25 cc. of sulphuric acid in a liter of water) and pass 200 cc. of it through the reductor, keeping the zinc always covered with solution. If air comes in contact with the zinc, hydrogen peroxide is formed, which, after being absorbed by the iron solution, reacts later with the permanganate when the iron solution is titrated, vitiating the result. Discard this wash solution, reconnect the flask and run a blank, in the manner following, to see how much permanganate solution is required, owing to traces of iron in the zinc, to produce the pink end-point. Pass 300 cc. of the dilute sulphuric acid solution through, never letting the surface of the solution in the funnel of the reductor fall down to the zinc, disconnect the filter flask and titrate directly into the flask. The quantity required to produce the end-point must be deducted from all titrations made on solutions passed through the reductor. When the insoluble residue has been filtered from the solu- tion of ore and most of the hydrochloric acid has been driven out by evaporation, dilute the solution to about 100 cc. with the dilute sulphuric acid solution (25 cc. acid to a liter) and pass it through the reductor into a clean filter flask. Wash all the iron solution from the beaker, with the very dilute sulphuric acid and pour it through the reductor. Follow this with more of the dilute sulphuric acid solution until 200 cc. of this solu- tion have passed through, then follow this with 100 cc. of dis- tilled water, never letting the air come in contact with the zinc, and finally leaving the funnel partially filled with water. IRON IN ORES PERMANGANATE METHOD 59 Disconnect the filter flask and titrate directly into it with the standard permanganate solution, deduct the quantity required for the blank and calculate the result. Additional Reducing Agents. As noted on page 51, zinc should not be used for reducing iron in titaniferous ores. For such ores, stannous chloride, sulphurous acid, ammonium bisul- phite, hydrogen sulphide, or some other reducing agent should be used. The method of reduction by stannous chloride is very rapid and satisfactory, and is applicable with either the potassium dichromate method or the potassium permanganate method, if, before titrating with the latter, manganous sulphate and phosphoric acid are added. POTASSIUM PERMANGANATE METHOD FOR IRON REDUCTION WITH STANNOUS CHLORIDE ZIMMERMAN-REINHARDT METHOD Reagents. Stannous Chloride Solution. Dissolve 250 gms. SnCb in 100 cc. hydrochloric acid (1.2), dilute with water to 1 liter. Mercuric chloride solution. A saturated solution of pure HgCb in water. ' Titrating Mixture " Manganous sulphate and phosphoric acid solution. Dissolve 90 gms. MnSCU in 650 cc. of water, add 175 cc. sulphuric acid (1.84), and then 175 cc. phosphoric acid (1.75 sp. gr.). Standard permanganate solution. (See p. 51.) Fe in Ore. Weigh .5 gm. of ore and transfer it to a small porcelain crucible. Heat over a Bunsen burner for a few minutes at low redness to destroy carbonaceous matter. A high heat makes the ore more difficult to dissolve. Place the crucible with the ore in a 400 cc. beaker. Add 10 cc. of hydrochloric acid and 4 cc. of stannous chloride solution. 60 METALLUKGICAL ANALYSIS Stannous chloride hastens solution by reducing the iron, but care must be taken that too much stannous chloride is not added. Stop the addition when the solution clears.* Heat to dissolve the iron. When the solution begins to turn yellow add stannous chloride solution drop by drop to reduce the iron. Finally, when all the iron is dissolved from the ore and the volume of solution has been reduced by evaporation to about 10 cc., add stannous chloride solution drop by drop until the color just disappears, then add one drop more. 2FeCl 3 +SnCl 2 =2FeCl 2 +SnCl 4 . Reduction by stannous chloride is effected best in a concentrated hot solution. If the solution is cool or dilute the reduction is slow and too much stannous chloride will be added before the color disappears. If iron is suspected in the residue, before the final addition of stannous chloride, filter, wash twice with hot water, burn the filter in a platinum crucible, add 2 or 3 gms. of Na 2 C0 3 and fuse. Cool and dissolve out the soluble salts with hot water, leaving the ferric oxide precipitated. Filter out the ferric oxide, wash it from the filter paper with a jet of hot water f (Fig. 52), dissolve it in hydrochloric acid and add to the main solution. Then proceed with the final reduction with stannous chloride. If any platinum should be dissolved and should pass into the iron solution, it produces when stannous chloride is added a yellow color which persists after the iron is all reduced. The complete reduction of the iron can then be detected only by testing drops of the solution with a reagent such as potassium sulphocyanate. Dilute to the capacity of the beaker with cold water and add, quickly, 5 cc. of mercuric chloride solution; stir vigorously. SnCl 2 +2HgCl 2 =SnCl 4 +2HgCl. The excess of stannous chloride must be oxidized before titration. If too much stannous chloride has been added, or if the solution is warm when the mercuric chloride is added, or if it is added slowly, part of the * Mixer and Dubois. Jour. Am. Chem. Soc., 17, 405. f Eng. and Min. Jour., 96, p. 695. IKON IN ORES PERMANGANATE METHOD 61 mercuric chloride will be reduced to metallic mercury, giving a gray color to the precipitate instead of the pure white of mercurous chloride. 2HgCl+SnCl 2 =SnCl 4 +Hg 2 . The presence of mercury spoils the determination, as it causes a reduction of the standard solution. The determination must therefore be discarded. Add 10 cc. of the manganous sulphate and phosphoric acid FIG. 52. Washing a Precipitate from the Filter Paper to a Beaker. solution. Stir and titrate with standard permanganate solu- tion. The formation of brown ferric chloride on titration would render the detection of the end-point difficult, therefore, phosphoric acid is added in sufficient quantity to prevent the formation of ferric chloride. Manganese sulphate prevents the reduction of the permanganate by the hydrochloric acid.* * For suggested reasons for this action see Tread well-Hall, "Analytical Chemistry," 2, 482-3. 62 METALLUKGICAL ANALYSIS POTASSIUM BICHROMATE (PENNY'S) METHOD FOR IRON IN ORES Outline. The iron is dissolved from the ore in hydrochloric acid. It is reduced to the ferrous condition with stannous chloride, the excess of stannous chloride oxidized with mer- curic chloride and the quantity of the iron is then measured by titrating it with a standard solution of potassium dichromate. Reagents. Stannous chloride solution. (See p. 59.) Mercuric chloride solution. (See p. 59.) Potassium ferricyanide solution. Dissolve a small crystal, not more than 10 mgm., of KsFe(CN)6 in 25 cc. of water. This must be made fresh just before using. Standard solution of potassium dichromate. Dissolve 4.4 gm. K2Cr20r in 1 liter of water. One cubic centimeter should be equivalent to about 0.005 gm. of Fe. Standardize this solu- tion against an ore, iron wire, or ferrous ammonium sulphate in which the iron has been accurately determined. If ore is used for standardizing, take 0.5 gm., or if iron wire, weigh about 0.25 gm. and treat it by the process for ore (p. 63). If ferrous ammonium sulphate is used, treat it as follows: Standardization of Potassium Dichromate Solution. Weigh accurately about 0.5 gm. of FeSO 4 (NH 4 )2SO 4 6H 2 O. Dissolve it in 10 cc. of water and 5 cc. of hydrochloric acid. (See note, bot- tom of p. 52.) Heat to boiling and add 1 drop of stannous chloride solution. Cool and dilute to 200 cc. with cold water. Add 5 cc. of mercuric chloride solution. Stir, and titrate with the potassium dichromate solution until a blue color ceases to form when a drop of the iron solution is added to a drop of potas- sium ferricyanide solution on. a white tile. Before beginning the titration, place several drops of the potassium ferricyanide solution on a white tile or plate, then as titration proceeds, take out a drop of the iron solution on a glass rod and add it to a drop of the ferricyanide solution; a blue IRON IN ORES BICHROMATE METHOD 63 color is produced as long as any iron remains unoxidized in the solution. The first test that fails to give a blue color indicates that all the iron is oxidized and this point is therefore the end-point. Read the burette and divide the weight of iron in the salt taken by the number of cubic centimeters used in the titration to find the value of 1 cc. of the solution in Fe. Fe in Ore. Weigh .5 gm. of ore and transfer it to a small porcelain crucible. Heat over a Bunsen burner for a few minutes at low redness to destroy carbonaceous matter. (See notes on p. 59.) Place the crucible with the ore in a 400-cc. beaker. Add 10 cc. of hydrochloric acid and 4 cc. of stannous chloride solution. Heat to dissolve the iron. When the solution begins to turn yellow add stannous chloride solution drop by drop to reduce the iron. Finally, when all the iron is dissolved from the ore and the volume of solution has been reduced by evaporation to about 10 cc., add stannous chloride solution drop by drop until the color just disappears, then add one drop more. If iron is suspected in the residue, before the final addition of stan- nous chloride, filter, wash twice with hot water, burn the filter in a platinum crucible, add 2 or 3 gms. of sodium carbonate and fuse. Cool and dissolve out the soluble salts with hot water, leaving the ferric oxide precipitated. Filter off the ferric oxide, wash it from the filter paper with a jet of hot water (Fig. 52) dissolve it in hydrochloric acid and add to the main solution. Then proceed with the final reduction with stan- nous chloride. If any platinum should be dissolved and should pass into the iron solution, it produces when stannous chloride is added a yellow color which persists after the iron is all reduced. The complete reduction of the iron can then be detected only by testing drops of the solution with a reagent such as potassium sulphocyanate. Dilute to 200 cc. with cold water and add quickly 5 cc. of mercuric chloride solution. Stir vigorously and titrate at 64 METALLURGICAL ANALYSIS once with standard potassium dichromate solution, testing a drop of the iron solution occasionally on a white tile with a drop of potassium ferricyanide solution, in the manner described above under the standardization of the dichromate solution, until the blue color is no longer produced. Read the burette and calculate the percentage of iron in the ore. 6FeCl 2 +K 2 Cr 2 7 +14HCl=6FeCl3+2CrCl3+2KCH-7H 2 0. The iron solution becomes green as titration proceeds, owing to the formation of chromic chloride. When ferrous iron is added to a solution of potassium ferricyanide, Prussian, or Turnbull's, blue is formed, and the color of the tests becomes fainter as the amount of ferrous iron diminishes. Fe' / Cl 2 +K 3 Fe' // (CN) 6 +2H 2 O=Fe"(CN) 6 KH 2 Fe /// (OH),-h2KCL* DETERMINATION OF FERROUS IRON By the foregoing methods the total iron in an ore is deter- mined. It is sometimes necessary to determine the amount of iron present in the ferrous condition. This is done by dissolving the material under con- ditions that are neither oxidizing nor reducing, and titrating the ferrous iron at once. Reagents. Carbon dioxide. This may be generated in a Kipp appa- ratus, or in a flask (Fig. 53) provided with a separating funnel and delivery tube. Place calcium carbonate (mar- ble or limestone fragments) in the flask and let dilute hydrochloric acid (1 : 3) drop from the funnel to produce the gas at the desired rate. * Treadwell-Hall, " Analytical Chemistry," Vol. 1, p. 95. Hofman, Heine, and Hochtlen, Annalen, 337 (1904), p. 1. FIG. 53. Carbon Dioxide Generator. DETERMINATION OF FERROUS IRON 65 Hydrochloric acid (1.2) diluted with an equal volume of water. " Titrating solution " of manganese sulphate and phosphoric acid. (See p. 59.) A standard solution of potassium permanganate. (See p. 51.) Fe in the Ferrous Condition. Weigh 0.5 gm. of ore and transfer it to a 250-cc. Florence flask. Close the flask with a two-hole stopper provided with intake and delivery tubes of glass. Let the delivery tube dip under water in a beaker. Attach the intake to the C02 generator and pass the gas ten minutes to displace the air. Disconnect the gas generator and attach to the intake a funnel, through which introduce 30 cc. of dilute hydrochloric acid (1 : 1). Disconnect the funnel and re-attach the gas generator to the intake and pass carbon dioxide through the flask. While the gas passes through, gently warm the flask with a Bunsen burner until the ore is dissolved and the volume has been reduced by evaporation to 15 cc. Cool, add 20 cc. of the " titrating solution," and 100 cc. of water, and titrate with standard permanganate solu- tion. For FeO and Fe2Os. If the iron is to be reported as oxides, subtract the weight of ferrous iron from the total iron, the remain- der will, of course, be the weight of trivalent, or ferric iron, in the ore. Multiply the weight of ferrous iron by the factor 1.2865 to obtain the corresponding weight of ferrous oxide, and the weight of ferric iron by 1.4298 for the weight of ferric oxide. Then divide the weight of each of these oxides by the weight of ore taken to find the percentage of each present. Materials which will not completely decompose in hydrochloric acid may be treated according to Cooke's Method.* Weigh 0.5 gm. of the ore and place it in a large (80 cc.) plat- inum crucible, add a little water that has been recently boiled and about 10 cc. of dilute sulphuric acid (1 : 3). Place the * Bull. 422, U. S. Geolog. Survey, p. 168. 66 METALLURGICAL ANALYSIS crucible under the funnel on the water bath (Fig. 54). Start the flow of CO2 and of water through the bath. When the air under the funnel has been re- placed by CC>2 raise the funnel and quickly add to the crucible about 6 cc. of strong hydro- fluoric acid and replace the fun- nel. When steam issues freely from the funnel cut off the sup- ply of C02 and continue the boiling for one hour or until the ore is all decomposed. Turn off the heat and turn on the COs and the water. Place in the beaker in which the titration is to be made 300 cc. of cold freshly boiled water and 10 cc. of sulphuric acid. Now wash the contents of the crucible into the beaker and titrate with standard perman- ganate solution, letting the solu- tion run in as rapidly as possible with continuous stirring until the first pink blush pervades the whole solution and persists at least two seconds. If much iron or much hydrofluoric acid is present the color fades rapidly. DETERMINATION OF FREE METALLIC IRON In the investigation of furnace products it is sometimes necessary to determine the quantity of iron that has been reduced to the metallic, or elementary condition. This determination may be made by dissolving the iron in a neutral solution of FIG. 54. Cooke's Apparatus for Ferrous Iron Determination. The water bath has a specially made cover with circular trough in which water is kept to make an air-tight joint with the funnel which is turned over the crucible. DETERMINATION OF FREE METALLIC IRON 67 mercuric chloride under an atmosphere of carbon dioxide, and titrating with potassium permanganate solution; or by dissolving in dilute hydrochloric acid, collecting the evolved hydrogen and measuring it in a gas apparatus, estimating its weight and its equivalent in iron. In case iron sulphide is present, the latter method must be used, and the hydrogen sulphide generated must be absorbed by passing the gas through a solution of potassium hydroxide or other absorbent before measuring the volume of hydrogen.* Reagents. Neutral saturated solution of mercuric chloride. Solution of manganous sulphate and phosphoric acid (titrat- ing mixture). (See p. 59.) Carbon dioxide. (See p. 64.) Standard solution of potassium permanganate. (See p. 51.) Free Metallic Fe. Weigh 0.5 gm. of the sample. Transfer it to a 300-cc. flask. Add 75 cc. neutral saturated mercuric chloride solution and close the flask with a two-hole rubber stopper pro- vided with intake and delivery tubes of glass. Let the delivery tube dip under water in a beaker as a seal. Pass carbon dioxide to displace air in the flask. (See p. 64 for method of generating carbon dioxide.) Heat to just below boiling and hold at this temperature for half an hour or until the metallic iron is all dissolved. Cool the flask, maintaining within it an atmosphere of C0 2 . Fe-f 2HgCl 2 = Hg 2 Cl 2 +FeCl 2 . When cold, filter the solution through asbestos into 30 cc. of " titrating mixture," wash with cold water, and titrate with standard permanganate solution. Ferrous iron may be determined in this material by return- ing the asbestos with residue to the flask and proceeding accord- ing to the method given on page 64. * These methods were contributed by D. A. Lyon, metallurgist of the U. S. Bureau of Mines, in whose investigations they were used by J. F. Cullen and G. A. Reinhardt. 68 METALLURGICAL ANALYSIS Free Metallic Iron in the Presence of Titanium. If metallic titanium or iron sulphide is present it is advisable to determine the metallic iron by dissolving the sample in dilute hydrochloric acid and measuring the hydrogen evolved. This is carried out in the apparatus shown in Fig. 55. From the reservoir R, acid is delivered to the test-tube B through the tube E. At C the glass tubing is connected by a rubber tube on which is a clamp. The tube E passes through a two-hole stopper to the lowest point in the bottom of the test- tube B, and is here drawn to a fine capillary opening. The test- tube B is connected by a capillary glass tube to the burette at D. The leveling tube F contains a solution of sodium hydroxide (250 gms. per liter) to absorb the hydrogen sulphide which is evolved with the hydrogen. Nearly fill the acid reservoir with dilute hydrochloric acid (1 : 1). Remove the test-tube B from its stopper and, by blowing at A, force the acid over to fill the tube E. Close the clamp C and wipe dry the point of the tube E. Weigh 0.5 gm. of the material to be analyzed and transfer it to the dry test-tube. Fit the test-tube to its stopper. Read the burette. Lower the leveling tube F, release the clamp at C, and draw in the necessary volume of acid (2 ins. or so in depth), and close the clamp at C. Collect the evolved hydrogen in the burette. When evolution has ceased, warm the acid in the test- tube with a very small flame for a few minutes. The acid will attack metallic titanium if the heating is continued. Pass the gas back and forth from the burette by means of the leveling tube until the absorption of hydrogen sulphide is complete and the FIG. 55, Apparatus Assembled for the Determination of Free Me- tallic Iron. DETERMINATION OF SILICA IN ORE 69 hydrogen is at room temperature. Finally, force the acid in the test-tube back, by raising the leveling tube, until it just stands at the fine point of the tube E (its initial position), and read the burette. The increase in volume is due to the hydro- gen; calculate its weight from the barometer and thermometer readings. Fe+2HCl=FeCl 2 +H 2 . One gram of hydrogen is equivalent to 27.6488 gms. of iron. 1 cc. of hydrogen at C. and 760 mm. mercury weighs 0.00008987 gm. Suppose the volume of hydrogen is 24.5 cc. at a temperature of 18 C. and a pressure of 740 mm. At C. and 760 mm. this volume would become 273X740X24.5 000 ^ (273+18)760 = .00008987X22.37 = .00201041 gm.=wt. of the hydrogen. 27.6488 X. 0020104 = .055585 gm.= equivalent in iron. .055585X100 r = 11.11 per cent Fe in the material. DETERMINATION OF SILICA IN ORE HYDROFLUORIC ACID, BERZELIUS METHOD Outline. The ore is dissolved in hydrochloric acid, the solution taken to dryness and the residue heated to dehydrate the silica. The residue is treated with hydrochloric acid, filtered and weighed. The silica is volatilized with hydrofluoric acid, the residue weighed and deducted from the weight of impure silica. Reagent. Hydrofluoric acid, HF. SiO 2 in Ore. Weigh 1 gm. of ore (or 0.5 gm., if high in silica) 70 METALLURGICAL ANALYSIS and transfer it to a casserole or beaker. Add 20 cc. of hydrochloric acid, cover with a watch glass, and heat to dissolve. M 2 Si0 3 +2HCl = 2MCl+H 2 Si0 3 . M represents bases of soluble silicates. Evaporate the solution to dry ness and hold the residue at a temperature of about 120 C. for one hour. H 2 Si0 3 =Si0 2 +H 2 0. Do not heat above 130; some SiO may recombine with bases, forming FIG. 56. Freas Electric Oven. FIG. 57. Control of the Temperature of an Air Bath. soluble silicates. A Freas electric oven (Fig. 56) is excellent for main- taining a constant temperature, but it is not difficult to adjust the heat under the air-bath, if a thermometer is fixed with its bulb opposite the bottom of the beaker (Fig. 57). Cool and add 10 cc. of hydrochloric acid and 10 cc. of hot water. Heat to dissolve soluble salts, dilute with a little hot water, filter, and wash (four or five times) with hot dilute hydrochloric acid (1:3) until the 8162 is free from iron, and then wash with hot water to remove the hydrochloric acid. SILICA IN ORE 71 If washed with hot water before all the iron is out, basic salts of iron may be precipitated in the filter when the free acid has been removed. (See note p. 52.) Place the filter with the 8162 in a weighed platinum crucible, carefully raise the temperature with a Bunsen burner and burn off the filter paper. Then heat with a blast lamp five minutes. A high heat is necessary to drive off the last traces of combined water. Cool in a desiccator and weigh. Add to the crucible enough hydrofluoric acid to dissolve the Si02 (5 cc.) and two drops of sulphuric acid. Take care not to breathe the fumes of hydrofluoric acid, as they are extremely irritating; neither should the acid be allowed to touch the skin. Evaporate carefully to dryness in a hood with a good draft. Ignite with the blast lamp, cool in the desiccator and weigh. The loss in weight represents the SiC>2. With high silica ores it may be necessary to repeat the treatment with hydrofluoric and sulphuric acids until the weight' of the residue is constant. Silicon tetrafluoride being volatile is lost on evaporation. Titanium fluoride is also volatile; therefore, sulphuric acid is added to retain titanium in the crucible as sulphate in case titanium is present. The sulphates of iron, aluminum, and titanium are broken up at a high temperature, liberating S0 3 , the oxides remaining in the crucible. SILICA IN ORE FUSION WITH SODIUM CARBONATE Outline. The ore is fused with a flux, dissolved in dilute hydrochloric acid, and the silica is dehydrated by evaporating the solution to dryness. The residue is treated with hydro- 72 METALLURGICAL ANALYSIS chloric acid, and the silica is filtered from the solution and weighed. Reagents. Sodium carbonate, Na2COs. Potassium carbonate, K^COa. SiO2 in Ore. Weigh 0.5 gm. of ore and transfer it to a platinum crucible. Add about 5 gms. of fused sodium carbonate. Put on the cover and fuse with the blast lamp. Direct the flame against the side of the crucible so that melting will begin at the top. If heated rapidly at the bottom, the sudden expulsion of C0 2 may throw some of the charge from the crucible. Si0 2 +Na 2 C0 3 = Na 2 Si0 3 +C0 2 . The fusion should be complete within fifteen or twenty minutes. Take the crucible in the tongs and turn it so that the fusion will run well up on the side. Continue turning it until the fusion freezes in a thin layer, covering as much of the inside of the crucible as possible. When the crucible is cool, place it on its side in a casserole which contains nearly enough water to cover the crucible, also put the crucible cover in the casserole. Cover with a watch glass and pour down the lip of the casserole hydrochloric acid to make the solution acid. Warm to hasten solution, and as the fusion dissolves add more hydrochloric acid to keep the solution always distinctly acid. Na,SiO,+2HCl =2NaCl+H 2 Si0 3 . Take out the crucible and cover, carefully wash them off, and let the washings run into the casserole. Evaporate the solution in the casserole to dryness, and hold at a temperature of about 120 for an hour. Add 20 cc. of dilute hydrochloric acid (1 : 1), warm to dissolve the soluble salts, dilute with 20 cc. of hot water and filter. Wash several times with warm DETERMINATION OF SULPHUR IN ORE 73 dilute hydrochloric acid (1:3) and finally wiih hot water to remove all hydrochloric acid. Burn carefully in a weighed platinum crucible over a Bunsen burner, ignite at the highest temperature of the blast lamp five minutes, cool in a desiccator and weigh. Calculate the percentage of SiC>2. A small amount of silica is carried through with the filtrate. For very accurate work this must be recovered by dehydration a second time. Evaporate the filtrate to dryness, take up the residue with very dilute hydrochloric acid, filter and burn the two filters together before weighing. For other notes see the method for silica pages 70 and 71. DETERMINATION OF SULPHUR IN ORE Outline. The ore is fused with a flux, the fusion treated with hot water to dissolve sulphates, the residue filtered off, the filtrate acidified with hydrochloric acid, evaporated to dry- ness and the silica dehydrated. The residue is treated with dilute hydrochloric acid and the silica is filtered out. The sulphur is precipitated from the filtrate with barium chloride, filtered and weighed. Reagents. Sodium carbonate, Na2COs. Sodium nitrate, NaNOs. Alcohol, C 2 H 6 0. Barium chloride, BaCfe, 10 per cent solution. S in Ore. Fuse 1 gm. (or 1.3738 gms., ten times the factor) of ore with 8-10 gms. of sodium carbonate and about 0.5 gm. of sodium nitrate in a platinum crucible. Sodium nitrate is added to oxidize sulphur to S0 3 and is preferred to potassium nitrate, for if potassium salts are present, the precipitate of barium sulphate will contain potassium sulphate. Only a small amount of the nitrate should be added, since it attacks platinum. (See p. 29.) If the fusion is made with a gas flame, the products of combustion which contain sulphur must not be permitted to enter the crucible. This may be prevented by inclining the crucible and allowing the lower 74 METALLURGICAL ANALYSIS part to project through a hole in a sheet of asbestos, as shown in the figure (Fig. 58),* or a spirit lamp may be used. Cool the fusion. Treat it with hot water to dissolve soluble silicates, sulphates, etc., and to precipitate the iron as oxide. Barium sulphate when precipitated has a tendency to carry down impurities with it, some of which cannot be removed by washing. If iron is present, ferric sulphate comes down with the barium sulphate, and on ignition breaks up into ferric oxide and S0 3 , the latter escaping. Other trivalent metals also, as far as possible, should be removed. If the ore contains manganese its presence will be indicated by the green color of the fusion, and it should be removed by the addi- tion of a few drops of alcohol, which precipitates it from the sodium manganate, as manganese dioxide. Sodium hydroxide and aldehyde are also produced by the reaction. Mn0 2 +Na 2 C0 3 +0 =C0 2 +Na 2 Mn0 4 , Na 2 MnO 4 +C 2 H 6 =2NaOH+Mn0 2 +C 2 H 4 0. Decant the solution through a filter and wash twice by decantation. Acidify the ni- trate with hydrochloric acid and evaporate the solution to dryness. FIG. 58. Arrangement of Crucible to Pre- vent the Products of Combustion of the Gas from Contami- nating the Fusion. If nitric or chloric acid is present, the barium salts of these acids will be precipitated with the sulphate, and cannot be washed out. These acids are broken up by evaporating with hydrochloric acid. Silica, also, would contaminate the precipitate if it were not dehydrated and removed. Cool; add a few drops of hydrochloric acid and 200 cc. of hot water. Lowe, Zeit. f. Anal. Chem., 20 (1881), p. 224. DETERMINATION OF PHOSPHORUS IN ORE 75 Only a very little hydrochloric acid should be used, as barium sulphate is slightly soluble in hydrochloric acid. Filter and wash well with hot water. Heat the filtrate to boiling and add boiling barium chloride solution, drop by drop, stirring until the precipitation of barium sulphate is complete. Then add 10 cc. more of barium chloride solution and let the determination stand hot (not boiling) half an hour or more. If barium chloride solution is added rapidly, barium chloride comes down with the sulphate. (See Precipitation, p. 20.) Filter and wash four times by decantation. Transfer the precipitate to the filter and wash until the washings are free from barium. (Test with sulphuric acid.) Burn carefully at a low heat with a Bunsen burner. Burn- ing filter paper reduces some barium sulphate to the sulphide; but, if air is admitted and the heating continued, the sulphide is reoxidized. Cool in a desiccator and weigh the BaSCU. Calculate the percentage of sulphur according to the method given on page 31. If the factor weight of ore was used, the weight of BaSO4 multiplied by 10 gives the percentage of sulphur in the ore. DETERMINATION OF PHOSPHORUS IN ORE MOLT BD ATE METHOD, WEIGHING THE YELLOW PRE- CIPITATE Outline. The ore is dissolved in hydrochloric acid, by pre- vious fusion if necessary; the silica dehydrated and filtered off; the hydrochloric acid in the filtrate is replaced by nitric acid by evaporation; ammonia is added, and the phosphorus is precipitated by ammonium molybdate, filtered in a Gooch crucible and weighed. Reagents. Sodium carbonate, Na2COa, fused. Dilute nitric acid, HNO 3 (2:3). Alcohol, C2HeO (95 per cent). 76 METALLURGICAL ANALYSIS Molybdate solution. Dissolve 10 gms. MoOs in 40 cc. of cold water and 8 cc. of ammonia. Filter, and pour this solution slowly into dilute nitric acid (40 cc. nitric acid (1.42) +60 cc. water). Stir and keep the solution cool to prevent the precipitation of molybdic acid. If a precipitate begins to form, stop the addition of the ammoniacal solution, cool by placing the beaker in cold water, and continue agitation until the precipitate dis- solves. Add about 0.05 gm. of microcosmic salt to clear the solution of suspended impurities. Shake, let the solution stand twenty-four hours, and filter or decant the clear solution for use. Wash solution of ammonium nitrate. Add to 10 cc. of nitric acid (sp.gr. 1.42), 200 gms. ammonium nitrate, and water to make one liter. P in Ore. Weigh 1.63 gms. of ore (100 times the factor) and transfer it to a casserole. A large precipitate of ammonium phosphomolybdate is not easy to wash and dry for weighing. A sufficient quantity of ore should be taken to yield from 0.2 gm. to 0.4 gm. of the precipitate. Therefore 1.63 gms., 100 times the factor weight, is a convenient quantity to take of ores containing from 0.2 to 0.3 per cent phosphorus. Of ores higher in phosphorus, 1 gm., or better, 50 times the factor weight, 0.815 gm., should be taken; of ores lower in phosphorus, 200 or 300 times the factor weight, that is, 3.26 gms. or 4.89 gms., would be required. Add 30 cc. of hydrochloric acid. Digest over a moderate heat until there is no further action on the ore. Dilute with an equal volume of water and filter into a casserole. Evaporate the filtrate to dryness, and while the evaporation is going on, burn the filter paper with the residue in a platinum crucible, cool, and add sodium carbonate, in quantity about six times the weight of the residue. Fuse, place the crucible in the casserole in which the ore was dissolved, and dissolve the fusion in hot water acidulated with hydrochloric acid. If it has been previously determined that all the phosphorus in the ore under examination is soluble, the residue need not be fused, DETERMINATION OF PHOSPHORUS IN ORE 77 but may be discarded after filtering and washing. In this case, before filtering, the solution should be taken to dryness, the residue baked to oxidize phosphorus, dissolved in a little hydrochloric acid, and then diluted with water. Evaporate this solution to dryness and heat the residue as well as that from the filtrate, at about 200 C. for half an hour, or until they no longer yield an odor of hydrochloric acid. Baking of these residues should be continued until the carbonaceous matter is destroyed and the phosphorus is oxidized to P0 4 ; otherwise, all the phosphorus will not be precipitated. Cool and treat each of the residues with a little hydrochloric acid to dissolve the iron. Dilute with an equal volume of hot water, and filter both into a small Erlenmeyer flask. Wash well with hot water. Evaporate the combined filtrate until it has a syrupy consistency, or until ferric chloride begins to separate. The washed precipitate may be burnt and weighed in the usual manner for the determination of Si0 2 . Hydrochloric acid dissolves the yellow precipitate and therefore must be removed by evaporating with nitric acid. Add 30 cc. of nitric acid (sp.gr. 1.42) and evaporate to 15 cc. Dilute to 50 cc. with water. Add ammonia until all the iron is precipitated and there is a slight excess indicated by the odor. Add dilute nitric acid (2:3), a few drops at a time, shaking until the precipitate is just dissolved, then add about 5 cc. more, or enough to give the solution an amber color. These proportions of nitric acid and ammonium nitrate in the solu- tion are the best for the precipitation of the phosphomolybdate. Heat the solution to 80 C. and add 60 cc. of molybdate solu- tion. FeP0 4 +12(NH 4 ) 2 Mo0 4 +24HNO 3 = (NH 4 ) 3 P0 4 .12Mo03+21NH 4 N03+Fe(N0 3 )3+12H 2 78 METALLURGICAL ANALYSIS A high temperature hastens the precipitation, but if heated higher than 80 C. there is danger of bringing down molybdic acid with the yellow precipitate. Shake five minutes, let settle one hour, and filter in a Gooch crucible; or shake ten minutes and filter at once. The solution should be shaken violently, by hand, shaking machine (Fig. 59), mechanical stirrer (see Fig. 23, p. 22, and Fig. 60, p. 98), or by a jet of compressed air. Wash five times with the wash solution of ammonium nitrate; then wash twice with alcohol. Dry one hour in an air bath at about 130 C., cool in a desic- cator, and weigh. If 100 times the factor weight (1.63 gms.) has been used, the weight of the yellow precipitate will represent the percentage of phosphorus in the ore: if any multiple of that weight is used, divide the weight of the yellow precipitate by the multiple. (See p. 32.) The compound (NH 4 )sP0 4 -12Mo03 contains theoretically 1.653 per cent phosphorus, but the precipitate formed according to this method has been found by repeated tests to contain 1.63 per cent phosphorus. Phosphorus from the Filtrate from SiO?. Phosphorus and silica may be determined in the same sample. Weigh the sample of ore and proceed with the determination of silica (p. 71) until the silica has been filtered from the solution. Evaporate the filtrate until solids begin to separate. Add 30 cc. of nitric acid (1.42), evaporate to 15 cc. and complete the determination in the manner described in the preceding method (p. 77) If the FIG. 59. Camp's Shaking Machine. PHOSPHORUS IN ORE 79 weight of ore used was not a factor weight for phosphorus, calculate the percentage of phosphorus in the manner described on page 31. PHOSPHORUS IN ORE WEIGHING AS If the yellow precipitate is always formed under the same con- ditions, its composition is constant and the method in which the yellow precipitate is weighed is a very exact one for the determination of phosphorus; but, since the conditions of pre- cipitation are not always uniform, it is better, for very exact work, to dissolve the yellow precipitate, reprecipitate the phos- phorus with magnesia mixture, and weigh as Mg2P207. Reagents. Magnesia mixture: Dissolve 55 gms. MgC^ GEbO and 70 gms. NH 4 C1 in 650 cc. of water and dilute the solution to one liter with ammonia (sp.gr. .96). Also the reagents required for the method on page 75. P in Ore, Weigh 2.7873 gms. ore (10 times the factor) and proceed according to the method on page 76 until the yellow precipitate is ready to be filtered. Filter on a 9-cm. filter paper and wash five times with the ammonium nitrate wash solution. Place a clean beaker under the funnel, pierce the filter paper and wash the precipitate through with a fine jet of hot water. Drop a little ammonia on the filter and wash with hot water. If any precipitate sticks to the flask in which it was formed, dissolve it out with a few drops of ammonia mixed with a little water and add the solution to that in the beaker. Keep the volume small (not greater than 50 cc.). Stir and, if the precipitate does not all dissolve, add a little more ammonia. (NH 4 )3PO 4 - 12Mo0 3 +24NH 4 OH = 12(NH4)2Mo0 4 H-(NH 4 ) 3 P04+12H 2 0. Add hydrochloric acid to neutralize the solution and if the yellow precipitate begins to form, add ammonia to dissolve it. 80 METALLURGICAL ANALYSIS If a white precipitate remains insoluble in ammonia, filter it out. Add hydrochloric acid to slight acidity and then 10 cc. of magnesia mixture. Add ammonia drop by drop, stirring constantly, until the solution is neutral. Note the depth of the solution in the beaker and add ammonia until the volume is increased by one-third. Stir and let the solution stand four hours. Filter and wash with dilute ammonia. Dry the precipitate. Separate the precipitate from the filter paper. (See Fig. 31.) Burn the paper on a platinum wire, letting the ash fall into a crucible; add the precipitate to the crucible and heat to low redness over a Bunsen burner until the precipitate is white. Then heat with a blast lamp ten minutes. 2MgNH 4 P0 4 = Mg 2 P 2 7 +2NH 3 +H 2 O. The temperature must not be raised until the precipitate is white. If the filter paper is burned in contact with the precipitate some phos- phorus may be reduced and attack the platinum. Cool in a desiccator and weigh. The weight of Mg2?2O7 multiplied by 10 expresses the percentage of P in the ore. PHOSPHORUS IN ORE EMMERTON'S VOLUMETRIC METHOD Outline. The ore is dissolved, the phosphorus precipitated as ammonium phosphomolybdate and filtered. The precipitate is dissolved in ammonium hydrate, the molybdic acid reduced with zinc and titrated with standard potassium permanganate solution, the quantity of phosphorus being measured indirectly. Reagents. Sodium carbonate. Na2COs; Dilute nitric acid (2:3); Dilute sulphuric acid', 25 cc. of sulphuric acid (1.84) diluted to one liter with water. PHOSPHORUS IN ORE 81 Standard solution of KMnO 4 ; 2.83 gms. of KMn0 4 dissolved in water and the solution diluted to one liter. This solution may be standardized by taking a definite weight of a phosphate in which the percentage of phosphorus is known, dissolving and precipitating the phosphorus as ammonium phosphomolyb- date, filtering and dissolving the yellow precipitate in ammonia, reducing and titrating exactly as given below in the method for ore; or the permanganate solution may be standardized against iron as directed on page 51. When the value in iron has been determined multiply the value by 0.88163, the ratio of molybdic acid to iron, and the product by 0.01794, the ratio of phosphorus to molybdic acid; the result will be the value of 1 cc. of the permanganate solution in terms of phosphorus. Since the ratio of phosphorus to molybdic acid in the yellow precipitate is not constant under varying conditions of formation, great care should always be taken to produce the yellow precipitate under as nearly the same conditions as possible. Molybdate solution. (See p. 76.) Wash solution of acid ammonium sulphate: to one liter of water add 16 cc. of ammonia (sp.gr. 0.90) and 25 cc. sulphuric acid (sp.gr. 1.84). A reductor charged with amalgamated zinc. (See pp. 57 and 58.) P in Ore. Weigh 3 gms. of ore (or a factor weight) and proceed according to the method on page 76 until the yellow precipitate has been formed. Filter on a 9-cm. filter paper and wash with acid ammonium sulphate solution until 2 or 3 cc. of the wash water do not give a brown color on the addition of a drop of ammonium sulphide. The precipitate must be washed free from molybdic acid because the phosphorus is measured indirectly by titrating back to molybdic acid the molybdenum oxide which has been reduced from the yellow precipitate. Pour 5 cc. of ammonia and 20 cc. of water into the flask in 82 METALLURGICAL ANALYSIS which the precipitate was formed to dissolve any adhering precipitate, and then pour this solution on the precipitate in the filter, letting the filtrate to run into a 250-cc. beaker. (NH 4 ) 3 P0 4 - 12Mo0 3 +24NH 4 OH = 12(NH 4 ) 2 MoO 4 +(NH4)3P04+12H 2 0. Rinse the flask into the beaker and wash the filter with water until the solution in the beaker measures about 60 cc. Add 10 cc. of sulphuric acid (1.84) and pass the solution through the reductor, after having passed through 100 cc. of warm dilute sulphuric acid (25 cc. sulphuric acid (1.84) in 1 liter). The equation 2Mo0 3 +3H 2 =Mo 2 3 +3H 2 expresses the complete reduction of MoOa to molybdic oxide, but reduction is not complete when the solution passes through the reductor in the manner here described. Emmerton gives Moi 2 0i 9 as the form he obtained, and Blair and Whitfield give Mo 24 37 as the product of the method as carried out by them. It is evident, therefore, that the operator must always carry on the reduction in the same manner and under the same con- ditions. Then follow with 200 cc. of the same dilute sulphuric acid in the manner described on page 58, being careful to keep the end of the small tube of the reductor below the surface of the solu- tion in the flask to prevent reoxidation. Remove the flask from the reductor, washing into it from the reductor any adhering solution. Titrate with standard permanganate solution. The solution, after passing through the reductor, should be bright green in color; if brown it is not sufficiently reduced and must be discarded. In titrating with permanganate, the solution of the yellow precipitate changes in color from green through brown and pinkish yellow to colorless. When the solution becomes colorless, add the permanganate solution, drop by drop shaking until a pink color is produced, which lasts for one minute. Subtract from the reading of the burette the amount given by a blank determination in which the same quantities of reagents are used as in the regular process. (See p. 58.) Multiply the value of 1 cc. in phosphorus by the number of cubic centimeters thus PHOSPHORUS IN ORE 83 obtained. Divide this product by the weight of ore taken and multiply the result by 100. (See p. 31.) Reduction with Powdered Zinc. Instead of reducing the molybdic acid by means of the reductor, reduction may be effected by adding powdered zinc to the solution of yellow precipitate. This operation is best carried out by returning the solution of the yellow precipitate to the flask in which the precipitate was formed and washing the filter until the volume of solution is about 75 cc. Then add 5 gms. of powdered zinc (through 100- mesh) and 15 cc. of sulphuric acid (sp.gr. 1.84). Close the flask at once with a rubber stopper carrying a delivery tube which dips into a beaker containing a saturated solution of sodium bicarbonate. After standing thirty minutes the zinc should be in solution and the molydbic acid reduced, when it is ready to be titrated with standard permanganate solution. A blank should be run at the same time and the necessary correction made for all determinations. When this method of reduction is used, the factor express- ing the ratio of molybdic acid to iron is 0.85714 instead of 0.88163, there being this difference in the degree of reduction of the molybdic acid by the two methods. PHOSPHORUS IN ORE PEMBERTON'S ALKALI-METRIC METHOD Outline. By this method the ore is treated in the manner described on page 76 to the formation of the yellow precipitate. After the yellow precipitate is filtered off it is washed to free it from acids, and its phosphorus content measured indirectly by titrating with an alkali. Reagents. Wash solution of riMc add; 13 cc. nitric acid (sp.gr. 1.42) in 1 liter of water. Wash solution of potassium nitrate. Dissolve 1 gin. KNOs in 1 liter of water. 84 METALLURGICAL ANALYSIS Phenolphthalein solution. Dissolve 1 gm. of C2oHi404 in 500 cc. alcohol, C 2 H 6 O (95 per cent). Standard solution of sodium hydroxide. Add to 100 gm. of pure NaOH an amount of water just insufficient to dissolve it completely. Let it settle in a tall, covered vessel. Most of the sodium carbonate which is present as an impurity remains undissolved. Add one drop of a solution of barium hydroxide to precipitate CO2. If a precipitate forms add another drop and repeat until a precipitate ceases to form. Withdraw 17 cc. of the solution with pipette and dilute to 1 liter. This solu- tion must be protected from the C02 of the air. Standard nitric acid. Twenty-one cubic centimeters of nitric acid (sp.gr. 1.42) diluted to 1 liter. These standard solutions must be tested against each other and the stronger one diluted until they are of equal strength, as follows: With the pipette take out 20 cc. of the sodium hydroxide solution, dilute it with 60 cc. of water, add 3 drops of phenol- phthalein solution and titrate with the standard nitric acid until the pink color just disappears. Phenolphthalein is red with alkalies and colorless with acids. It is a weak acid and is very slightly dissociated in acid solutions. Accord- ing to Ostwald's theory it is colorless when undissociated, but when combined with alkali hydroxide, the salt is dissociated, revealing the red color of the cation.* If the solutions are not of equal strength dilute the stronger and test again. Suppose 19.4 cc. of nitric acid solution were required to neutralize 20 cc. of sodium hydroxide solution; then the volume * Ostwald, " Foundations of Analytical Chemistry," 124. For another explanation of this reaction see Stieglitz, Jour. Amer. Chem. Soc., 25, 1112. Kober and Marshall, Eighth International Congress of Applied Chemistry, 6, 157. PHOSPHORUS IN ORE 85 of nitric acid solution remaining must be increased according to the ratio 19.4 : 20. 19.4 : 20 = vol. nitric acid remaining to be diluted: final vol. nitric acid. The difference between the third and fourth terms repre- sents the amount of water to be added. Standardization of the Sodium Hydroxide Solution. When the solutions are of equal strength the sodium hydroxide solu- tion is standardized by weighing 2 gms. of an ore in which the phosphorus has been previously determined, and carrying it through the process as given below. The weight of phos- phorus being known and the number of cubic centimeters of sodium hydroxide solution required to complete the reaction below having been determined, the value of 1 cc. of the solution is given by dividing the weight of phosphorus by the number of cubic centimeters of sodium hydroxide solution required for the reaction. 2(NH 4 ) S P0 4 12MoO,+46NaOH = 2(NH 4 ) 2 HP04+(NH 4 ) 2 Mo04+23Na 2 Mo04+22H 2 0. Instead of using a standard ore, yellow precipitate may be used. This is prepared from a phosphate in the manner described for its precipitation from a solution of an ore, and carefully dried at 150 C. Weigh about 0.2 gm. of yellow precipitate, add standard sodium hydroxide solution, 10 cc. at a time, until the precipitate is dissolved. Dilute with 50 cc. of water. Add 3 drops of phenolphthalein solution and titrate with the standard nitric acid. The volume of nitric acid used, deducted from the volume of sodium hydroxide solution, leaves the number of cubic centimeters of sodium hydroxide solution required to neutralize the yellow precipitate. Multiply the weight of yellow precipitate by the factor for phosphorus, 0.0163, and divide this by the number of cubic centimeters of sodium hydroxide solution used. 86 METALLURGICAL ANALYSIS P in Ore. Weigh 2 gms. of ore and proceed exactly in the manner described on page 76 until the yellow precipitate has formed and settled. Filter on a 9-cm. filter paper and wash 5 times with 1 per cent solution of nitric acid, then wash with potassium nitrate solution until the acid has all been removed. Place the filter paper and its contents in the flask in which the precipitate was made and add to the flask standard sodium hydroxide solution, 20 cc. at a time, with the pipette, shaking to disintegrate the filter, until the yellow precipitate is all dissolved. Dilute with 50 cc. of water, add 3 drops of phenol- phthalein solution, and titrate the excess of alkali with the standard nitric acid. Take the difference between the number of cubic centimeters of nitric acid used in the titration and the total volume of sodium hydroxide solution added and multiply the result by the value of 1 cc. in phosphorus. PHOSPHORUS IN THE PRESENCE OF TITANIUM Weigh 2 gms. (or a factor weight) of ore, add 30 cc. of hydrochloric acid and heat to dissolve as much of the ore as possible. Evaporate the solution to dryness and bake. (See p. 70.) Add 25 cc. of hydrochloric acid and 25 cc. of water. Heat to dissolve the iron, and filter. If titanium is present, when the residue is washed with water, the filtrate often runs through turbid. This can be avoided by washing with dilute nitric acid, or better, with an acid solution of ammonium nitrate (p. 76). The filtrate contains the greater part of the phos- phoric acid, but a considerable part may remain with the residue. Treatment of the Residue. Fuse the residue with sodium car- bonate and extract with water. Sodium phosphate and silicate go into solution and sodium titanate remains insoluble. Filter, acidify the filtrate with nitric acid, evaporate the solution to dryness, and bake at 120 C. Cool, moisten the residue ALUMINA IN ORE 87 with nitric acid, and add water to dissolve all except silica. Filter from the silica. Concentrate the nitrate to small bulk by evaporation, nearly neutralize with ammonia, and precipitate the phosphorus with ammonium molybdate. Treatment of the Filtrate. Evaporate the filtrate until solids begin to separate; then add nitric acid and proceed according to the method on page 77, until the yellow precipitate is filtered and washed. This yellow precipitate, and that obtained from the insoluble residue, are dissolved in ammonia according to the method on page 81. If the solution runs through turbid, and a gelatinous residue remains on the filter, heat the 'solution for some time and filter. Treat both these residues with nitric acid and precipitate the phosphorus from the result- ing solution with ammonium molybdate. Filter out this yellow precipitate, dissolve it in ammonia, and add it to the main solution. The phosphorus may now be determined by either precipitating with magnesia mixture (p. 79), or by adding sulphuric acid, reducing and titrating by Emmerton's method (p. 80). ALUMINA IN ORE PHOSPHATE METHOD Reagents. Ammonium phosphate solution. Dissolve 100 gms. of (NH4) 3 PO4 in 1 liter of water. Sodium thiosulphate solution. Dissolve 200 gms. Na2S20s in water and dilute to 1 liter. Acetic acid, CH 3 CO-OH, 80 per cent. Ammonium acetate. Dissolve 200 gms. CHsCO-ONH^ in water and dilute to 1 liter. AkOs in Ore. Weigh 1 gm. of ore and proceed according to the method for silica (p. 71) until the silica has been filtered off and washed. Cool the filtrate and dilute it to about 400 cc.; add 30 cc. of ammonium phosphate solution, and then add ammo- nia until a faint permanent precipitate is formed. Add 1.5 cc. 88 METALLURGICAL ANALYSIS of strong hydrochloric acid. Stir until the precipitate is dis- solved and add 50 cc. of sodium thiosulphate solution. 2FeCl3+2Na 2 S 2 03=2NaCl+2FeCl 2 +Na 2 S 4 6 . The aluminum is precipitated as the neutral phosphate from a boil- ing solution faintly acid with acetic acid, and it comes down free from iron, if the iron has been reduced with sodium thiosulphate. Heat just to the boiling-point and add 8 cc. of acetic acid mixed with 15 cc. of ammonium acetate solution and boil ten minutes. Let the precipitate settle a few minutes, filter as rapidly as possible, and wash ten times with hot water. Ignite the filter and its contents at a low temperature until the carbon is destroyed, and then at the highest temperature of the muffle furnace or the blast lamp. Cool and weigh as A1PO4, multiply by 0.4184, the factor for A1 2 O 3 . MANGANESE IN ORE VOLHARD'S METHOD Outline. The ore is dissolved in hydrochloric and nitric acids. These acids are replaced with sulphuric. The solution is diluted and nearly neutralized with sodium carbonate. An excess of zinc oxide is added and the solution is titrated hot with standard potassium permanganate solution. Reagents. Emulsion of pure zinc oxide. ZnO shaken with a sufficient amount of water to form an emulsion. Saturated solution of crystallized sodium carbonate, Na 2 C0 3 -10H 2 0. Standard potassium permanganate solution. (See p. 51.) This solution may be made of such strength that 1 cc. equals 0.1 per cent manganese for the quantity of ore taken. It is standardized against an iron ore in which' the percentage of manganese is known. Or it may be standardized against iron MANGANESE IN ORE 89 in the usual way and its value in manganese calculated from the following reactions. 6MnS0 4 +4KMn0 4 +5ZnS0 4 + 14H 2 =4KHS04+7H 2 S0 4 +5Zn(HMn03) 2 . 10FeS04+2KMn0 4 +8H 2 S0 4 = 5Fe(S0 4 )3+2MnS0 4 +K 2 S0 4 +8H 2 0. The first reaction is that upon which this method depends; the second is the familiar reaction of potassium permanganate with iron. It will be observed that two molecules of potassium perman- ganate oxidize 10 atoms of iron in the one case, and 3 atoms of manganese in the other. The value of the solution in man- ganese, therefore, may be calculated from its value in iron by 3(54 93) multiplying the value in iron by the factor ,! . =0.2951. lU^tDO.OTry Mn in Ore. Treat 1 gm. of ore in a casserole with 15 cc. of hydrochloric acid. Add 5 cc. of nitric acid to oxidize the iron. Heat to complete the decomposition. Add 25 cc. of water and 5 cc. of sulphuric acid. Evaporate until the sul- phuric acid begins to fume. Cool, dilute to 150 cc. with water and heat to dissolve sulphates. If it is suspected that any manganese remains undissolved, filter and burn the residue in a platinum crucible. Treat the residue with a little hydrofluoric acid (1 cc.) and a few drops of sulphuric acid and evaporate to sulphuric acid fumes. Dilute the solution in the crucible and add it to the main solution. Nearly neutralize the sulphate solution with a solution of sodium carbonate. Transfer it to a 500-cc. graduated flask and dilute with water to the graduation. Mix well, take out 50 cc. with the pipette and let it run into a small Erlenmeyer flask. Add 50 cc. (an excess) of zinc oxide and titrate with potassium permanganate solution. A sufficient quantity of zinc oxide is added to neutralize the solution, precipitate the iron, and provide an excess which will keep the solu- 90 METALLURGICAL ANALYSIS tion neutral as titration goes on. Sulphuric acid is formed by the reac- tion, and the solution should be kept neutral for the reaction to proceed according to the equation given above. Keep the solution hot while titrating, but do not let it boil. After each addition of permanganate, shake vigorously and let the precipitate settle. If kept hot it settles readily and the pink end-point can be detected in the layer of clear solution above the precipitate. The result obtained by this titration must be multiplied by 10, since only 0.1 of the whole was titrated. MANGANESE IN ORE TITRATION WITH SODIUM ARSENITE Outline. The hydrochloric acid in which the ore is dissolved is displaced by sulphuric. The solution is then diluted and the manganese is oxidized to permanganic acid by adding ammonium persulphate and silver nitrate. The silver is then precipitated with sodium chloride and the solution titrated with a standard solution of sodium arsenite. Reagents. Dilute sulphuric acid (1 : 1). Ammonium persulphate, (NH^H^Og. Solution of silver nitrate. Dissolve 66.66 gms. AgNOs in one liter of water. Dilute 20 cc. of this solution to 1 liter for use. Each 15 cc. contains 0.02 gm. AgN0 3 . Standard solution of sodium arsenite. A stock solution is made by dissolving 30 gms. sodium carbonate in water, adding 10 gms. of arsenious acid, boiling until the acid is in solution, and diluting to 1 liter. Dilute about 125 cc. of the stock solution to 2000 cc. and standardize this solution against a steel or an ore in which the manganese has been previously determined. Sodium chloride, 0.2 per cent solution. Dissolve 2 gms. NaCl in water and dilute the solution to 1 liter. Mn in Ore. Weigh 1 gm. of ore and transfer it to a casserole MANGANESE IN ORE 91 or beaker. Add 25 cc. of hydrochloric acid and 5 cc. of sulphuric acid. Heat until the sulphuric acid fumes. Cool, add 25 cc. of water and heat until the salts are dissolved. If the insoluble residue is suspected of containing manganese, filter and burn the residue in a platinum crucible. Add 2 or 3 drops of dilute sulphuric acid (1:1) and about 5 cc. of hydrofluoric acid. Evapo- rate until the sulphuric acid fumes. Add 5 cc. of the dilute sulphuric acid (1 : 1). Warm until the residue is in solution and add it to the main solution. Transfer the solution to a 50-cc. graduated flask. Dilute to the mark and mix. With a pipette transfer 10 cc. of the solu- tion to a 1 50-cc. Erlenmeyer flask. Add 15 cc. of the silver nitrate solution and about 1 gm. of moist ammonium persulphate; heat over -a flame or water bath until the pink color of per- manganic acid appears. 2MnS0 4 4-4(NH4) 2 S 2 8 +8H z O=2H 2 Mn04+4(NH4) 2 S04H-6H 2 S0 4 . The silver nitrate is a catalytic agent and hastens the above reaction.* The reaction takes place equally well in nitric acid or sulphuric acid or a mixture of the two. It is essential to have a sufficient amount of silver nitrate present. While the permanganic acid is forming remove the flask from the heat and place it in a cold water bath. When cool, dilute to about 100 cc., add 7 cc. of sodium chloride solution, and titrate with sodium arsenite solution until the pink color is discharged. If the silver is not precipitated with sodium chloride, the manganese is reoxidized, and the end-point is not permanent. Since a standard solution of sodium arsenite sometimes changes in strength suddenly and unexpectedly, some chemists prefer to titrate with a standard solution of ammonium ferrous sulphate instead. See sodium bismuthate method, p. 92. * Marshall, Proc., Royal Soc. Edin., 1900, p. 225. 92 METALLURGICAL ANALYSIS MANGANESE IN ORE COLOR METHOD Treat 1 gm. of ore in the manner described in the preceding method until it is dissolved and the solution is diluted to 50 cc. in a graduated flask. Mix and pour the solution through a dry filter paper. With the pipette transfer 10 cc. to an 8-in. test-tube, 1 in. in diameter. Add 15 cc. of silver nitrate solution and about 1 gm. of ammonium persulphate. Heat in a water bath and when the color of permanganic acid appears, remove the test-tube from the heat and place it in a cold water bath. Compare this solution in a colorimeter (see p. 44) with a similar solution prepared in exactly the same way from a standard ore in which the manganese is known. Instead of a standard ore a standard steel may be used, in which case dissolve 0.2 gm. of the steel in 10 cc. of nitric acid (sp.gr. 1.2), add 15 cc. of the silver nitrate solution, and 1 gm. of ammonium persul- phate, and proceed according to the method given above. MANGANESE IN ORE SODIUM BISMUTHATE METHOD Outline. The ore is decomposed with hydrofluric and sul- phuric acids. After the hydrofluoric acid has been removed by evaporation, dilute nitric acid is added, the solution cooled and the manganese oxidized to permanganic acid with sodium bismuthate. The excess of sodium bismuthate is filtered off, a measured volume of standard ferrous sulphate solution added to the filtrate and the excess of ferrous sulphate titrated with standard potassium permanganate solution. Reagents. Hydrofluoric add, HF. Dilute nitric add, (1 : 3) (sp.gr. 1.135). Dilute nitric add, dilute 30 cc. HNO 3 (sp.gr. 1.42) to 1 liter with water. MANGANESE IN ORE 93 Sodium bismuthate, NaBiOs. Standard potassium permanganate solution, 1 gm. KMn04 to the liter. After this solution has been made according to the method given on page 51, determine the exact amount of manganese it contains per cc. by standardizing it against iron in the usual way. From its iron value calculate the weight of manganese in each cubic centimeter of the permanganate solution using the following equation: 10 Fe : 2Mn = value in Fe per cubic centi- meter : weight of Mn per cubic centimeter. Ferrous sulphate, 25.5 gms. FeS0 4 -7H 2 O to the liter. It is. convenient to have this solution of such strength that 1 cc. is equivalent to 0.1 per cent manganese. The value of the ferrous sulphate solution in terms of the permanganate solution is determined as follows: Measure into a 250-cc. Erlenmeyer flask 50 cc. of cold nitric acid (sp.gr. 1.13). Add about 0.5 gm. of sodium bismuthate. Agitate and filter through asbestos. Wash the filter with 50 cc. of cold 3 per cent solution of nitric acid. Add 50 cc. of ferrous sulphate solution and titrate with potassium permanganate solu- tion to a pink color. Mn in Ore. Treat 1 gm. of ore (if the ore contains more than 2 per cent manganese use 0.5 gm.) in a platinum crucible with 4 cc. of strong sulphuric acid, 10 cc. of water, and 10-20 cc. of hydrofluoric acid. Evaporate until the sulphuric acid fumes freely. Cool and dissolve in 25 cc. of dilute nitric acid (1:3). Transfer the solution to a 200-cc. Erlenmeyer flask, using 25 cc. of nitric acid (1 : 3) to rinse the crucible. Cool and add 2 or 3 gms. of sodium bismuthate, and agitate the con- tents of the flask for several minutes. Sodium bismuthate in the presence of an excess of nitric acid oxidizes the manganese to permanganic acid. The permanganic acid is stable in 94 METALLURGICAL ANALYSIS nitric acid of 1.135 sp.gr. if the solution is cold; if hot the excess of the bismuth salt is decomposed and tha nitric acid then reacts with the per- manganic acid. Dilute the solution with 50 cc. of 3 per cent nitric acid and filter through asbestos into a 300-cc. Erlenmeyer flask. Wash the asbestos with 50 to 100 cc. of cold 3 per cent nitric acid. Run into the solution in the Erlenmeyer flask 50 cc. of standard ferrous sulphate solution from a pipette. If the permanganate color is not discharged, add more ferrous sulphate solution, accurately measured, until the color is discharged. Then titrate back to pink color with standard permanganate solution. Having thus determined the number of cubic centimeters of ferrous sulphate solution required to react with the manganese in the sample, and knowing its value per cubic centimeter in man- ganese, calculate the percentage of manganese in the sample. For example, suppose 24 cc. of ferrous sulphate solution are equivalent to 100 cc. of potassium permanganate solution, and in the determination 50 cc. of ferrous sulphate solution are added to the solution and the excess titrated back with 25 cc. of potassium permanganate solution; 44 cc. of the ferrous sul- phate solution were, therefore, required to react with the man- ganese in the sample, and this number is to be multiplied by its value in manganese. In addition to the method of standardizing given above under reagents, after the solutions have been tested against each other, the ferrous sulphate solution may be standardized by taking an ore in which the manganese has been previously determined, and running it according to the above process. Instead of titrating with ferrous sulphate, a standard solution of arsenious acid may be used. (See p. 90.) MANGANESE IN ORE 95 MANGANESE IN ORE JULIAN'S METHOD Outline. The ore is decomposed with hydrochloric acid and the solution taken nearly to dryness. Nitric acid is added, the solution boiled and the manganese is oxidized to manganese dioxide by adding potassium chlorate. After the solution is cooled and diluted a measured volume of standard solution of hydrogen peroxide is added and the excess of peroxide is titrated with standard potassium permanganate solution. Reagents. Hydrofluoric add, HF. Potassium chlorate, KClOa. Standard potassium permanganate solution, 1.7375 gms. KMnCU per liter. Hydrogen peroxide. Dilute 1 Ib. of hydrogen peroxide with about 500 cc. of water, add 200 cc. of sulphuric acid (sp.gr. 1.84), and dilute the solution to 9000 cc. with water. Determine the relative values of these two solutions as follows : Boil 60 cc. of strong nitric acid for about five minutes. Cool and dilute it to about 300 cc. with cold water. Add to the cold solution 50 cc. of the hydrogen peroxide solution and titrate it with the standard permanganate solution. The hydrogen peroxide solution is standardized by weighing a sample of ore in which the manganese has been previously determined and treating it according to the method given below. Mn in Ore. Weigh 1 gm. of ore and transfer it to a beaker. Add 20 to 30 cc. of strong hydrochloric acid and heat to dissolve the manganese. If the insoluble residue is suspected of contain- ing manganese, add a few drops of hydrofluoric acid and evaporate the solution almost to dryness. Manganese-free glass must be used if hydrofluoric acid is em- ployed. 96 METALLURGICAL ANALYSIS Add 75 cc. of strong nitric acid. Boil until clear. Add potassium chlorate, a little at a time, until green chlorine fumes cease to come off. Then add another crystal of potassium chlor- ate and boil five minutes. 5Mn(N0 3 ) 2 +2KC10 3 +4H 2 0=5Mn0 2 +2KN0 3 +8HN0 3 +Cl 2 .* Cool the solution, dilute it to about 300 cc. with cold water and add with the pipette 50 cc. of hydrogen peroxide solution. Mn0 2 +H 2 2 +2HN0 3 =Mn(N0 3 ) 2 -f2H 2 0+0 2 . After the manganese dioxide has dissolved determine the excess of hydrogen peroxide by titrating with standard permanganate solution. 5H 2 2 +2KMn0 4 +6HN0 3 =2KN03+2Mn(N0 3 ) 2 +8H 2 0+50 2 . The equivalent in hydrogen peroxide solution of potassium permanganate used in titration is deducted from the total volume of hydrogen peroxide solution added and the remainder which represents the quantity of hydrogen peroxide that reacted with manganese dioxide is multiplied by its value per cubic centimeter in manganese. LIME IN ORE Outline. The ore is decomposed by fusion with a flux. After dissolving the fusion in hydrochloric acid, the silica is dehy- drated and filtered from the solution. The iron and aluminum are then precipitated from the filtrate with ammonia, and filtered. The calcium is then precipitated from the filtrate with ammonium oxalate, filtered, burnt to CaO and weighed. Reagent. Ammonium oxalate solution. Dissolve 40 gms. (NH4)2C2O 4 +H 2 O in a liter of water. CaO in Ore. Weigh 1 gm. of ore, transfer it to a platinum * Julian, " Quantitative Analysis," 236. MAGNESIA IN ORE 97 crucible, and proceed according to the method for silica (p. 71) until the silica has been filtered from the solution. Make the nitrate alkaline with ammonia to precipitate the hydrates of iron and aluminum. Boil off the excess of ammonia. Aluminum hydrate is somewhat soluble in ammonia. Let the precipitate settle, filter, and wash. The precipitate may be used for the determination of iron or aluminum. Acidulate the filtrate with hydrochloric acid and evaporate it down to 150 cc. Add 10 cc. of ammonia and 5 cc. of ammonium oxalate solution. Boil until the calcium oxalate precipitate is formed. Let the beaker stand in a warm place until the precipitate settles. Filter and wash with hot water. Before filtering add a few drops of the precipitant to the clear supernatant solution to test for unprecipitated calcium. See also the method of precipitation given on page 162. Retain the filtrate for the determination of magnesia. Burn the precipitate in a platinum crucible, cool, and weigh as CaO. For the method of titrating calcium oxalate and for the reac- tions see the method for lime in limestone, pages 163 and 164. MAGNESIA IN ORE Reagent. Solution of ammonium phosphate. Dissolve 100 gms. (NH 4 )2HPO 4 in 1 liter of water. MgO in Ores. Acidulate with hydrochloric acid the filtrate from the calcium oxalate; see the method above for lime. Add 5 cc. of ammonium phosphate solution and reduce the volume by evaporation to 200 cc. Cool the solution, stir the cool solution with a stirring machine (Fig. 60), and add 25 cc. of 98 METALLURGICAL ANALYSIS ammonia, drop by drop. FIG. 60. Mechanical Stirrer Driven by a Jet of Com- pressed Air. Stir continuously for one hour, let settle, and filter; or, if possible, let stand over night before filtering. Wash the precipitate thoroughly with dilute ammonia (1 : 4). Dry, and separate the precipitate from the filter paper. (See Fig. 31.) Heat the precipitate in a crucible with a Bunsen burner at a low red heat until the precipi- tate is white. Burn the filter paper on a platinum wire and let the ash fall into the crucible. After the car- bon has all been burnt and the precipi- tate is white, heat for a few minutes at a high temperature with the blast lamp. Cool in the desiccator and weigh the Mg 2 P2O7. The factor for MgO is 0.3621. For notes and precautions, see the method for magnesia in limestone page 165. TITANIUM IN ORE Outline. The ore is decomposed with potassium pyrosulphate and sulphuric acid, v the solution diluted, and the silica filtered from it. The filtrate is nearly neutralized with ammonia, sodium sulphite added to reduce the iron, and the titanium precipitated by boiling after adding acetic acid and sodium acetate. The impure metatitanic acid is filtered and purified by decompos- ing it and repeating the process.* Reagents. Potassium pyrosulphate, K2S207. Sodium sulphite. Dissolve 20 gms. Na 2 S0 3 -f 7H 2 O in 100 * Gooch, Chem. News, p, 55. Drown, Trans. Amer. Inst. of Min. Eng., 10, p. 137. TITANIUM IN ORE 99 cc. of water and add sulphuric acid to render the solution dis- tinctly acid. Acetic acid, C2-H4O2. Sodium acetate, NaC2H 3 02+3H 2 O. Sodium carbonate, fused Na2COs. TiO2 in Ore. Weigh 1 gm. of very finely pulverized ore and mix it with 15 gms. of potassium pyrosulphate in a large platinum crucible. Heat gently to melt, and raise the temperature grad- ually to a low red heat and keep the mass in quiet fusion thirty minutes. Too high a temperature drives off sulphuric acid and spoils the fusion. Cool and add about 20 cc. of strong sulphuric acid. Heat until the contents of the crucible are perfectly liquid; then cool. If a sufficient amount of acid was added the fusion remains liquid after cooling. Pour the solution into 400 cc. of cold water in a 600-cc. beaker. Rinse off the crucible and stir the solution until only silica remains undissolved. Filter, and to the filtrate add ammonia carefully, until the precipitate dissolves slowly on stirring. Warm and add sodium sulphite solution slowly, a little at a time, until the color, at first produced, entirely disappears. Fe 2 (S04)3+Na 2 S03+H 2 0=2FeS0 4 +Na 2 S0 4 +H 2 S04. Do not heat to boiling, as titanium oxide in that case would sep- ite as a milky precipitate and render it difficult to determine when the luction is complete. If the precipitate forms and the solution becomes turbid, add a few drops of hydrochloric acid to clear it and continue the addition )f the sulphite solution, giving plenty of time for the reaction to take 100 METALLURGICAL ANALYSIS After the addition of about 50 cc. of the sulphite solution the titanium solution should be colorless and have a strong odor of sulphur dioxide. If the color persists, the ferric salts are not all reduced. Continue the addition of the sulphite solution and warm until the color disappears. Add 50 cc. of acetic acid and 20 gms. of sodium acetate and boil vigorously three minutes. Ti(S0 4 ) 2 +4NaC 2 H30 2 +3H 2 0=2Na 2 S04-h4HC 2 H 3 2 +TiO(OH) 2 . Let the precipitate of impure metatitanic acid settle, filter, and wash with hot water. Place the filter with residue in a platinum crucible, burn off the filter paper, and weigh the impure titanium oxide. Add to the titanium oxide ten times its weight of sodium carbonate and fuse. Boil the fusion with water until it is dis- integrated. Filter and wash. Wash the residue off the filter into a beaker. Let the precipitate settle and decant the clear liquid back through the filter. Dissolve the remaining titanium precipitate adhering to the filter paper with a little hydrochloric acid, letting it run through the paper to the residue in the beaker. Burn the filter paper at a low heat and add the ash to the beaker. Dissolve the contents of the beaker in hydro- chloric acid, then add 10 cc. of dilute sulphuric acid and evap- orate until the sulphuric acid just begins to fume. Cool and dilute with 25 cc. of water. Boil, filter, and wash. Dilute the filtrate to 250 cc., nearly neutralize it with ammonia, and add to it about 20 cc. of sodium sulphite solution to reduce the remaining traces of iron. Add 30 cc. of acetic acid and 10 gms. of sodium acetate. Stir and let the precipitate of meta- titanic acid settle, filter, wash with hot water, burn, and weigh as Ti0 2 . TITANIUM IN ORE WELLER'S METHOD Outline. The ore is fused with potassium pyrosulphate, treated with sulphuric acid and dissolved in water. The solu- tion is filtered and diluted to a definite volume in a graduated TITANIUM IN ORE , ' 101 flask; an aliquot part is taken out and treated with hydrogen peroxide, which gives it a yellow color, the intensity of which depends upon the quantity of titanium present. This is com- pared with a standard solution in which the titanium is known.* Reagents. Hydrogen peroxide, 3 per* cent solution free from hydrofluoric acid. Potassium pyrosulphate, K^^O?. Dilute sulphuric acid, (3 : 100). Standard solution of titanium sulphate. Weigh 0.6 gm. of potassium titanic fluoride which has been recrystallized several times in a platinum crucible with a little water and concentrated sulphuric acid, the excess of acid having been expelled by gentle ignition. Dissolve in a little concentrated sulphuric acid and add dilute sulphuric acid (3 : 100) to make the volume 100 cc. One cubic centimeter of this solution corresponds to 0.002 gm. of TiO 2 . This solution may also be prepared by igniting pure Ti02 at a dull red heat to a constant weight, melting cautiously with potassium bisulphate until Ti(>2 dissolves and the fusion becomes clear. Cool and dilute the solution to a definite vol- ume with dilute sulphuric acid (3 : 100). Then, with the pipette, take out 20 cc. and determine the Ti02 by the gravimetric method given on page 99 and dilute the remaining solution with weak sulphuric acid solution (3 : 100) until 1 cc. contains 1 mg. of Ti0 2 . Standard solution of ferric sulphate. Prepare a dilute solu- tion of Fe2 (804)3 in dilute sulphuric acid and determine its value per cubic centimeter in iron by means of standard permanganate solution. The ferric sulphate solution may be prepared from ferrous sulphate by dissolving the ferrous sulphate in dilute sulphuric acid and oxidizing it at the boiling-point with nitric acid according to the method given on page 53, evaporating * Berichte, 15, p. 2593. Hillebrand, Jour. Amer. Chem. Soc., 1895, p. 718. 102 METALLURGICAL ANALYSIS the solution until sulphuric acid fumes are evolved and diluting with water. TiO2 in Ore. Weigh 0.5 gm. of ore and fuse it with 5 gms. of potassium pyrosulphate in a platinum crucible at a red heat for at least ten minutes. Cool, add 5 cc. of sulphuric acid, melt again, cool, and put the crucible with its contents in a beaker containing 200 cc. of water and 5 cc. of sulphuric acid. Warm to about 90 C. and stir to dissolve all that is soluble. Filter into a 250-cc. graduated flask and dilute the solution to the graduation with sulphuric acid solution (3 : 100). Measure with a pipette 50 cc. of the titanium solution and transfer it to one of a pair of Nessler or other colorimetric tubes. In the other tube place that quantity of ferric sulphate solution which contains as much iron as there is in the solution of ore in the first tube. Since the iron gives a slight color to the solution it is necessary to have an equal quantity in each tube. Dilute the ferric sulphate solution in the second tube to 50 cc. with dilute sulphuric acid (3 : 100). Add to each tube 5 cc. of hydrogen peroxide. Hydrogen peroxide added to a sulphuric acid solution of titanium produces a strong yellow color, the intensity of which depends on the amount of titanium present, and is independent of the excess of hydro- gen peroxide. The change of color is much more sensitive with small amounts of titanium. Therefore the method is suitable only for materials low in titanium. If the titanium is high, the gravimetric method may be used; or the sulphate solution of titanium may be diluted to a large volume in a graduated flask and a suitably small portion withdrawn for the colorimetric determination. Now run into the second tube from a burette, standard titanium solution until the color produced is the same as that in the first tube. The quantity of titanium in the volume of standard solution added to the second tube is equal to that in the solution of ore in the first tube, which represents one-fifth of the sample. ANALYSIS OF IRON AND STEEL 103 Instead of Nessler tubes, Eggertz tubes or a colorimeter may be used. If the determination is to be made with a colorimeter of the third type described on page 44, make the solutions to the same volume in the following manner. Prepare the solutions in two large test-tubes, each with a graduation to indicate a volume of 50 cc. From the 250-cc. flask containing the solution of ore transfer 50 cc. to one of the tubes; to the other, add a sufficient quantity of ferric sulphate solution to contain the same amount of iron that is contained in 50 cc. of the solution of ore. Add to this 5 cc. of the standard titanium solution (or more if necessary, accurately measured) and make up to the graduation with dilute sulphuric acid (3 : 100). Then add to each tube 5 cc. of solution of hydrogen peroxide, mix, and transfer to the color- imeter for comparison. Rare Elements in Iron Ore. Methods for determining other elements in ores may be found by referring to the index. ANALYSIS OF IRON AND STEEL Sampling. Sampling is best done, as explained on page 9, while the metal is still molten. The samples are taken with an iron hand-ladle while the metal is being poured. If the metal is poured into large ladles for transfer to another part of the plant, one sample is taken from each ladle, and the drillings from these are mixed for the final sample. In the case of cast-iron, the molten metal is poured from the sampling ladle, either upon an iron plate or into a mold. If the sample is to be crushed after cooling it is best to let it cool in a thin layer. If it is to be drilled, the mold should be an inch or so in depth. A very convenient mold (Fig. 61) described by Camp * consists of two sections, which gives a casting 6 ins. long and 1J ins. thick, to which is attached at one end a section J in. thick. The latter is * Met. and Chem. Eng., 10, p. 668. 104 METALLURGICAL ANALYSIS FIG. 61. A Sample of Cast-iron and Mold in which the Sample is Cast. broken off and crushed for analysis and the large section is used for physical tests. . As shown by Howe * and others t, the impurities in steel tend to segregate on cooling in those parts which freeze last. Therefore, to obtain a represen- tative sample of the metal in solid form, it is necessary to drill well into the metal; and to be sure that the material comes within the specifications axial drillings should be taken, and these should be analyzed as a separate sample. Steel drillings should be well mixed, and since the fine and the coarse differ in composition, the weight taken for analysis should consist of both fine and coarse in the same ratio that exists between them in the sample as a whole. See weighing for analysis, page 18. If the sample of cast-iron is crushed, it should be made to pass through an 80-mesh sieve, and all that will not pass through such a sieve should be rejected. DETECTION OF SEGREGATIONS OF SULPHUR Sulphur occurs in steel as MnS, but if there is not enough manganese present to combine thus with all the sulphur, the excess of sulphur combines with iron as FeS. Therefore, to detect segregations of sulphur on the surface, spread a piece of white silk cloth moistened with a solution of lead acetate on the surface of the metal, and then drop dilute hydrochloric acid on the silk. The dilute hydrochloric acid liberates hydrogen * Trans. Amer. Inst. Min. Eng., 38, 104. f Sauveur, " The Metallography of Iron and Steel," 6, 10. SILICON IN IRON AND STEEL 105 sulphide from the metallic sulphide and this precipitates black lead sulphide on the silk directly over the segregations. Photo- graphic printing paper moistened with dilute sulphuric acid and pressed against the surface of the polished metal serves this pur- pose well. SILICON IN IRON AND STEEL * Reagent. Nitric acid, HNOs (sp.gr. 1.2). To make 1 liter mix 391 cc. HN0 3 (1.42) with 646 cc. H 2 O. Si in Steel. Weigh 4.693 gms., transfer it to a beaker, add 40 cc. of dilute nitric acid, and warm to dissolve. FeSi+6HNOa=Fe(NO,),+H,SiOa+2H,0+N,Oa+NO. Low carbon steels dissolve very readily. If the action becomes too violent, and there is danger of loss, place the beaker in a dish of cold water. When the metal is dissolved, evaporate the solution to dry ness and raise the temperature until ferric nitrate is decomposed. Cool, add 30 cc. of hydrochloric acid and heat until the ferric oxide is dissolved. Evaporate the solution to dryness. Redis- solve in 30 cc. of hydrochloric acid and dilute to 150 cc. Filter, wash with hot dilute hydrochloric acid and cold water alter- nately until the precipitate is free from iron. If washed with hot water, there is danger of precipitating basic salts of iron in the filter in the absence of an excess of acid. (See p. 52.) Burn off the carbon of the filter paper in a platinum crucible with a Bunsen burner and then drive off the last traces of water with the highest heat of the blast lamp. Cool in a desiccator and weigh the silica. The weight multiplied by 10 gives the percentage of silicon in the steel. If the silica weighed is not pure, it may be treated with hydro- fluoric acid and sulphuric acid, according to the method given on page 71, and the impurity weighed and deducted. * Camp. Met. and Chem. Eng., 10, p. 669. 106 METALLURGICAL ANALYSIS SILICON IN STEEL BROWN'S METHOD * Reagents. Silicon mixture. Dilute 300 cc. HN0 3 (1.42) with 600 cc. of water and add to it 125 cc. H 2 SO 4 (1.84). Hydrochloric acid, HC1, dilute, (1 : 1). Si in Steel. Weigh 4.693 gms. of steel and transfer it to casserole. Add 60 cc. of the silicon mixture. Warm to dis- solve the steel, and evaporate the solution until the sulphuric acid fumes freely. The determination should be covered with an inverted funnel to pre- vent loss by spattering. Cool, add 10 cc. of dilute hydrochloric acid and 50 cc. of hot water. Warm until the soluble salts are in solution. Filter and wash, alternately, with hot dilute hydrochloric acid and cold water until the iron salts are removed, and then complete the washing with hot water. Burn the filter and residue in a plati- num crucible and proceed according to the method described on page 105. SILICON IN IRON DROWN'S METHOD Weigh 0.4693 gm. (twice the factor weight, 0.9386, may be taken if the iron is low in silicon), transfer it to a porcelain casserole, add 20 cc. of the silicon mixture, and proceed accord- ing to Drown's method for Si in steel. The weight of SiC>2 multiplied by 100 gives the percentage of silicon in the iron: or, if twice the factor weight was used, after multiplying by 100, divide the result by 2. * Trans. Amer. Inst. Min. Eng., 7, p. 346. SILICON IN IRON 107 SILICON IN IRON FORD'S METHOD Weigh 0.4693 gm. of the finely pulverized sample and transfer it to a platinum dish or porcelain casserole. Add 20 cc. of con- centrated hydrochloric acid, cover with a watch glass, and boil rapidly to complete dryness. Without cooling (if the deter- mination is in platinum), add 20 cc. of dilute hydrochloric acid (1:1). Heat a few minutes, add 50 cc. of hot water, and continue heating to dissolve the iron. Filter, and proceed according to Brown's method. This method is not so accurate as Brown's method, but it is rapid, and the rapidity may be increased by filtering with suction, using a perforated platinum cone to support the filter paper, and finally by burning the precipitate in an atmosphere of oxygen. (See Fig. 31.) SILICON IN FERRO-SILICON The silicon in ferro-silicon and other high silicon products may be determined in the same way as silicon in iron, if the mate- rial is soluble in acids. If very high in silicon the powder must be fused with an alkali or an alkaline salt and the fusion dis- solved and treated according to the method for SiO2 in ores, page 72. Since the material is high in silicon, only a small por- tion is necessary for the sample. Si in Ferro-silicon. Weigh 0.4693 gm. Fuse with a mixture of 20 gms. of sodium carbonate and 4 gms. of potassium nitrate.* Blair recommends that the material be fused with sodium per- oxide,! and Preuss prefers 10 gms. of KOH in a nickel crucible. t When the fusion is complete, cool it and dissolve it in water and hydrochloric acid and evaporate the solution to dryness. * Johnson, " Chem. Anal, of Special Steels," p. 120. t Chem. Anal, of Iron and Steel, p. 224. j Z. Angew. Chem., 23, p. 201. 108 METALLURGICAL ANALYSIS Dissolve the residue in hydrochloric acid and water, filter, and evaporate the filtrate to dryness, dissolve this residue in a little hydrochloric acid and water, and filter a second time. Burn the precipitates together in a platinum crucible and weigh. The silicon is then purified with hydrofluoric acid and sul- phuric acid in the usual way. If the precipitate of silica is large, a second treatment with the acids will be necessary to remove all the silica. The loss in weight (SiCb) multiplied by 100 gives the percentage of Si sought. SULPHUR IN STEEL OXIDATION WITH NITRIC ACID Reagents. Dilute hydrochloric acid (1 : 10). Sodium carbonate, Na2COs. Barium chloride solution. Dissolve 10 gms. BaCb in 100 cc. of water. S in Steel. Weigh 4.579 gms. of steel (one-third the factor multiplied by 100), transfer it to a 500-cc. beaker, and add 40 cc. of strong nitric acid. 3MnS+12HNO,=Mn,(S0 4 )i+Mn(NOa)i+9NO+6H,0. Low-carbon steels dissolve freely in strong nitric acid. If the action is too violent, place the beaker in cold water. High-carbon steels dissolve in strong nitric acid with great difficulty and strong hydrochloric acid should be added, a few drops at a time, to hasten the solution. If too much hydrochloric acid is added, there is danger of loss of sulphur by the formation of H 2 S. If dilute nitric acid were used, the sulphur would be liberated, but not oxidized to the sulphate. In dissolving high carbon steels, if the acid is reduced by evaporation to a small volume before solution takes place, more acid should be added. When the steel is in solution add about "0.5 gm. of sodium carbonate and evaporate the solution to dryness in an air bath. Silica must be dehydrated and filtered from the solution and the nitric acid replaced by hydrochloric, before precipitation of the sulphur. SULPHUR IN STEEL 109 Cooi the residue and add 30 cc. of strong hydrochloric acid. When in solution add about 0.5 gm. of sodium carbonate and evaporate the solution to dryness in an air-bath. If the temperature should be raised high enough to break up man- ganic or ferric sulphate, the sulphuric acid would be retained as sodium sulphate, which is stable at a high temperature. Nitric acid must be removed, since it interferes with the precipita- tion of barium sulphate. Redissolve the residue in hydrochloric acid and evaporate the solution until ferric chloride begins to separate, to expel the free hydrochloric acid. Add 2 cc. of hydrochloric acid. An excess of hydrochloric acid is necessary for the formation of the- precipitate, but the excess should be small, since barium sulphate is. slightly soluble in hydrochloric acid. Dilute the solution with an equal volume of water. Filter and wash with cold water. The nitrate and washings should not exceed 100 cc., since the pre- cipitation is better in a moderately concentrated solution; if too dilute, the iron may separate and be carried down with the barium sulphate. Heat the filtrate to boiling and add, drop by drop, 10 cc. of hot barium chloride solution. Then add 10 cc. more of barium chloride solution, boil a few minutes, let the precipitate settle for half an hour, or longer if con- venient, in a warm place, filter and wash alternately with warm dilute hydrochloric acid and cold water, and finally wash with water until the washings are free from barium. (See p. 75.) Burn the filter and its contents in a weighed platinum crucible, cool, and weigh the BaSCU. The factor for sulphur in barium sulphate is 0.13738. If the weight of steel specified at the beginning of this method was used, to obtain the percentage of sulphur, multiply the weight of barium sulphate by 3, 110 METALLURGICAL ANALYSIS SULPHUR IN IRON AMERICAN FOUNDRYMEN'S ASSOCIATION METHOD * Outline. The iron is dissolved in concentrated nitric acid, potassium nitrate added to oxidize the sulphur, the solution evaporated to dryness and heated to drive out nitric acid, the potassium retaining the sulphur as sulphate. The residue is treated with sodium carbonate solution to dissolve sulphates, filtered, the filtrate acidified, and taken to dryness. The residue is taken up with dilute hydrochloric acid, the silica filtered from the solution and the sulphur precipitated from the filtrate with barium chloride. Reagents. Potassium nitrate, KNOs. Solution of sodium carbonate. Dissolve 10 gms. Na2COs lOH^O in 1 liter of water. Barium chloride solution. Dissolve 10 gms. BaCl2 in 100 cc. of water. S in Iron. Weigh 3 gms. of drillings for the sample and trans- fer it to a platinum dish. Cover the dish with a watch glass and dissolve the sample slowly in concentrated nitric acid. When the iron is completely dissolved add 2 gms. of potassium nitrate. (See note on sodium nitrate, p. 73.) Evaporate the solution to dryness and ignite the residue over an alcohol lamp at a red heat. Cool, add 50 cc. of the 1 per cent solu- tion of sodium carbonate. Boil a few minutes. The sulphate is taken into solution as alkaline sulphate and the iron left as ferric oxide. Filter, wash the precipitate with hot 1 per cent solution of sodium carbonate, acidify the filtrate with hydrochloric acid, evaporate the solution to dryness, and dissolve the residue in 50 cc. of water and 2 cc. of hydrochloric acid. Filter and wash the Si02. Dilute the filtrate to 100 cc., heat it to boiling, * Chem. Eng., 4, p. 213. SULPHUR IN IRON OR STEEL 111 and add barium chloride solution in the manner described in the preceding method. Filter, wash the precipitate well with hot water, ignite, and weigh. Multiply the weight of BaSCU by the factor for S, 0.13738, divide the result by 3, and multiply by 100. SULPHUR IN IRON OR STEEL EVOLUTION METHOD * Outline. The steel is dissolved in hydrochloric acid in a flask and the H2$ formed is absorbed in an alkaline solution of cadmium chloride, the H2$ is liberated in the solution with hydrochloric acid and is titrated with standard iodine solution. Reagents. Standard iodine solution. Place 3.958 gms. of pure iodine in a liter flask with about 6 gms. of potassium iodide and 10 cc. of water. Let the flask stand without heating until all the iodine has been dissolved, then dilute with water to the graduation. One cubic centimeter of this solution should be equivalent to 0.0005 gm. of sulphur. If 5 gms. of material are taken for analysis, 1 cc. of this solution will then be equiv- alent to 0.01 per cent sulphur. The solution should be stand- ardized against a steel in which the sulphur has been previously determined, and either corrected to the above value, or a factor- weight of steel taken so that 1 cc. of the solution will be equiv- alent to 0.01 per cent S. (See Factor Weights for Standard Solutions, p. 40.) Starch solution. Make an emulsion of about 1 gm. of starch in 4 cc. of cold water. Pour this slowly into about 200 cc. of boiling water and boil five minutes after the starch has been added. Cool to room temperature and add 1 gm. of zinc chloride dissolved in 10 cc. of cold water. Mix well and let it stand twenty-four hours or more, shaking it occasionally. Decant the *Camp, Met. and Chem. Eng., 10, p. 669. Philips, Stahl u. Eisen, 16, p. 633. 112 METALLURGICAL ANALYSIS clear solution for use. The zinc chloride is added as a pre- servative, since it prevents the growth of vegetable molds. The starch solution gives a much more delicate end-point if the starch, of which it is made, has been soaked twenty-four hours in very dilute hydrochloric acid, and then washed, dried, and heated three hours in an oven at 100 C.* Cadmium chloride solution. Dissolve 5 gm. CdCU in 375 cc. of water mixed with 625 cc. of ammonia. Apparatus. The steel is dissolved in a Florence or Erlen- meyer flask, fitted with a 2-hole stopper, through which pass a FIG. 62. Apparatus for Determination of Sulphur. Evolution Method. thistle tube or separatory funnel and a delivery tube. The delivery tube above the flask should lead upward from the flask a few inches, and should be enlarged so that the condensation will return to the flask. Beyond the enlargement the delivery tube passes down through a 2-hole stopper to the bottom of a small Erlenmeyer flask or a large test-tube, containing cadmium chloride solution, in 'which the H^S is absorbed. From the other hole in the stopper of the absorbent flask, a delivery tube of glass or fused quartz passes horizontally through a Bunsen flame, and then, with a right-angle bend, passes vertically * Chem. Abs., 4, 2617. SULPHUR IN IRON OR STEEL 113 downward to the bottom of another similar absorbent flask or test-tube containing cadmium chloride solution. (Fig. 62.) S in Steel. Weigh 5 gms. (or a factor weight) of steel p transfer it to the solution flask described above. Place in each of the small absorbent flasks or test-tubes 15 cc. of cad- mium chloride solution diluted to 60 cc. with water. Heat the quartz tube between the two absorbent flasks to redness. When steel, especially high-carbon steel, is dissolved in hydrochloric acid, all the sulphur is not liberated in the form of H 2 S, but a considerable part is combined with hydrocarbons, one of which, (CH 3 )S 2 , has been identified by Phillips. These mercaptans are not very volatile, and when they pass over with the H^S they are not completely absorbed by the cadmium chloride solution. These difficulties may in a measure be obviated by dissolving the steel in strong hydrochloric acid, by boiling briskly at the end of the operation, and by passing the unabsorbed gas from the first cadmium chloride flask through a red-hot tube before it enters the second flask. The sulphur in the unabsorbed com- pounds is changed by heat into H 2 S, which is absorbed in the second cadmium chloride flask. From the separatory funnel run into the solution flask 50 cc. of hydrochloric acid and close the tap of the funnel. Warm the flask so that the steel will dissolve briskly. MnS+2HCl = MnCl 2 +H 2 S/ Dilute hydrochloric acid (1 : 1) is often used in this method, but the difficulties, owing to the formation of mercaptans, as mentioned above, are lessened by the use of strong acid. After the steel is dissolved boil the solution until the vapor has carried over into the absorbent all the sulphur producfs that are volatile. H 2 S+CdCl 2 =CdS+2HCl, HC1+NH 4 OH =NH 4 C1+ H 2 O. Before allowing the solution-flask to cool, open the tap of the separatory funnel to prevent the formation of a partial vacuum 114 METALLURGICAL ANALYSIS in the flask, which would draw in the cadmium chloride solu- tion. Disconnect the two absorbent flasks and empty them into a 500-cc. beaker, being careful to wash all of the cadmium sulphide from the delivery tubes and flasks into the beaker. Dilute the solution to 400 cc. with cold water, add 10 cc. of starch solution, and enough hydrochloric acid to dissolve the cadmium sulphide and to render the solution acid. CdS+2HCl = H 2 S+CdCl 2 , Stir gently to mix the solution well and titrate at once with standard iodine solution to a strong blue color. H 2 S+I 2 =2HI+S. The solution should be mixed so that no part of it will be ammoniacal when titration begins. To prevent the escape of H 2 S the solution should not be stirred briskly. There should be sufficient volume to hold the H 2 S in solution; it should be cool and the titration should begin promptly, before there is time for H 2 S to escape. The end- point is the familiar blue color produced by the combination of starch and free iodine. When accuracy must be sacrificed for the sake of speed, this method may be simplified by dispensing with the quartz tube and the second absorption flask. For rapid work the apparatus usually consists of an Erlenmeyer flask , fitted with a 2-hole stopper which carries JIG. 63. Apparatus for Sul- ,, . ,, , , ,, ..." , .. phur. Rapid Method. a tmstle tube for the introduction of acid and a delivery tube, terminating in a large test-tube which contains the absorbent. (Fig. 63.) CARBON IN STEEL 115 CARBON IN STEEL SOLUTION AND COMBUSTION Outline. The steel is dissolved in an acid solution of the double chloride of copper and potassium, which leaves all the carbon as a residue. The carbon is filtered from the solution and burnt to CO2 in a combustion furnace. The CO2 is absorbed in a solution of potassium hydroxide and weighed. Reagents. Solvents. Solution of copper and potassium chlor- ide. Dissolve 140 gms. CuCl 2 -2KCl-2H 2 in 400 cc. of water and 60 cc. of hydrochloric acid (sp.gr. 1.2). A solution of copper and ammonium chloride may be used as a solvent, but the potassium salt is usually freer from carbona- ceous impurities. If steel is dissolved in the ordinary acids, some of the carbon escapes in gaseous form.* The copper and potassium chloride solution dissolves the iron and leaves the carbon in solid form. Absorbent of CO2- Solution of potassium hydroxide (sp.gr. 1.2). Dissolve 300 gm. of KOH in 1 liter of water. Owing to possible impurities in the solution, which will absorb oxygen while the combustion is going on, the solution should have oxygen passed through it while it is hot, or it may be titrated while hot to a faint green with potassium permanganate solution. The potash bulbs should be filled to about two-thirds of their capacity with this solution. The bulbs should be refilled with fresh solution after they have absorbed about 0.5 gm. of CO2. After a bulb is filled, dry off the outside and the inside of the entrance tube. The inside may be dried with a small roll of filter paper. If the inside is not dried, a deposit of potassium carbonate may choke the tube. Absorbents of Moisture. Calcium chloride; dehydrated * For the forms of carbon in steel, see Sauveur, " Metallography of Iron and Steel," 14, 8. 116 METALLURGICAL ANALYSIS Fused calcium chloride should not be used, since it con- tains some CaO, which would absorb CCb- Soda-lime, a mixture of sodium hydroxide and lime, is a drying agent, and is also a better absorbent of C02 than potas- sium hydroxide solution. It is not used alone, since it is soon saturated, but follows the bulb containing potassium hydroxide solution to take out the last traces of C02. These drying agents should be in granular form with grains only a few millimeters in diameter and free from dust. All that will pass through a 20-mesh sieve should be discarded. Potassium hydroxide broken up quickly and placed in a tube may be used as a drying agent. It also absorbs C02. Absorbents of Hydrochloric Acid. Anhydrous copper sul- phate. Saturate small pieces of pumice with a strong solution of CuS04 and heat in a dish to drive off all the water. This is also an absorbent of water. A saturated solution of Ag2S04 in sulphuric acid (sp.gr. 1.4). Oxidizing Agents. Copper oxide. Make a square of cop- per gauze 15 cm. on the edge into a roll about 2 cm. in diameter and enclose this in a sheet of asbestos to protect the silica tube from the copper oxide formed. Place it in the combustion tube and heat it in a current of oxygen or air- until the copper is converted to CuO. If a silica tube is heated in contact with copper oxide, the copper oxide combines with the silica and the tube is destroyed. Hot copper oxide converts CO to CO2. Platinized asbestos may be used for this purpose instead of copper oxide. Absorbents of Chlorine. A roll of silver foil is placed in the cooler part of the combustion tube beyond the copper oxide. The silver foil should be taken from the combustion tube occasionally and heated in a current of hydrogen to free it from chlorine. A bulb containing the following mixture may be used for this purpose : CAKIiuN IN STEEL 117 0.2 gm. pyrogallic acid ( 3 gms. neutral oxalate of potassium (K2C2O4+H2O). 4 drops concentrated sulphuric acid. Add water to make 20 cc. Apparatus. Combustion may be carried out in a fused silica combustion tube heated in either an ordinary gas combustion furnace or in an electric furnace. The silica tube should have an inside diameter of about 22 mm. and a length of 50 to 60 cm. Combustion tubes are also made of platinum, porcelain, and hard glass. The electric furnace (Fig. 64 C) consists essentially FIG. 64. Apparatus for the Determination of Carbon in Steel. of an alundum tube, about 30 mm. inside diameter (just large enough to receive the silica combustion tube) wound with nichrome or other resistance wire and imbedded in a non-conducting refractory ma- terial (magnesia and asbestos). The oxygen or air, before being admitted to the combustion tube, is passed first through a bulb A, containing potassium hydroxide solution, and then through the U-tube B, the first limb of which contains soda lime, and the second, dried calcium chloride. The rubber stoppers in the combustion tube must be protected from the heat. The ends of the tube are kept cool by strips of asbestos cloth, which dip in water, and asbestos plugs held in 118 METALLURGICAL ANALYSIS platinum gauze are placed just inside the stoppers to protect them from radiant heat. In the combustion tube, a little beyond its middle point, toward the exit end, is placed the roll of copper oxide enclosed in a sheet of asbestos, and beyond that, in the cooler part of the tube, a roll of silver foil to absorb chlorine. If silver is not used, the chlorine may be absorbed by passing the gases, after they leave the combustion tube, through a bulb contain- ing potassium oxalate solution (see Reagents). The gases then pass through the U-tube E, which contains in the first limb dehydrated copper sulphate, and in the second, dry cal- cium chloride. From this tube the gas passes into the weighed potash bulb F, and from that to the tube G, which is also weighed, and which contains in the first half soda-lime, and in the second, dry calcium chloride. A larger calcium chloride tube H follows, which serves as a protection to G from moisture, in case air should be drawn in from that end of the train. When the bulb F and the tube G are detached from the train to be weighed, they should be closed with stoppers made of small pieces of rubber tubing closed at one end with a bit of glass rod, if they are not provided with glass stopcocks. If air is used for combustion, it may be driven through the train by aspirator bottles attached to the entrance end of the train, or it may be drawn through by attaching an aspirator bottle to the exit end. If oxygen is used, the flow is regulated by means of the valve on the oxygen tank. It is difficult to regulate the flow of oxygen through the combustion train from a tank at high pressure; it is therefore advisable to fill tanks at low pressure from a high-pressure tank for use in combustion. Rubber absorbs appreciable amounts of CCb; therefore the glass apparatus in the combustion train, connected by rubber tubing, should be made to touch inside the rubber tubing and thus protect the rubber from contact with the gas. When the boat is placed in the combustion tube, the train is CARBON IN STEEL 119 tested for leaks by closing the entrance end of the train and slowly exhausting the air from the exit end by suction. When the suction is removed, the atmospheric pressure will cause the caustic solution in the weighed bulb to rise in the side next the combustion tube. If there is a leak, the solution will gradually fall back to the original level. When the train is made perfectly tight, the air or oxygen is passed through at the rate of two bubbles per second and the furnace is gradually heated to a bright red heat. After burning out the furnace fifteen minutes, detach the potash bulb and its tube, cool them in the balance case fifteen minutes, and weigh. Connect them to the train again, pass the oxygen, and burn fifteen minutes, cool and weigh again. This is repeated until the weight is constant. In weighing the bulb and tube, they should always be coun- terpoised by a similar bulb and tube so that the error due to condensation of moisture on the apparatus may be avoided. Apparatus should not be weighed after it has been rubbed or wiped off with a cloth until it has stood at least thirty minutes for the dissipation of static charges of electricity. Richards and Shipley * found that a small quartz flask which was 2 mgms. too light from this cause was immediately restored to its nor- mal weight by bringing into the balance case a very small tube of impure radium chloride. If a gas furnace is used, the burners next the ends should be lighted first and after an interval of two minutes the burners next to these are turned on and so on until the last to be lighted are those directly under the platinum boat. C in Steel. Weigh 3 gms. (or ten times the factor weight, 2.727 gms.) of steel, transfer it to a 500-cc. beaker, and add 200 cc. of copper and potassium chloride solution. When ferro-alloys and chrome tungsten steels are dissolved in copper potassium solution, not all the carbon is left in the residue; * Jour. Am. Chem. Soc. 36 (1914) 4. 120 METALLURGICAL ANALYSIS therefore a direct combustion method (see p. 121) should be adopted for carbon in these materials. If a little fibrous asbestos is added, the finely divided carbon adheres to it, greatly facilitating filtering and washing. Keep the temperature of the solution below 40 C., and stir with the mechanical stirrer (see Fig. 60) until the steel is dissolved. Fe+CuCl 2 =FeCl 2 +Cu, Cu+CuCl 2 =2CuCl. The copper is first precipitated on the steel and is then slowly dis- solved by the solution of cupric chloride. When the steel is dissolved, filter the solution through as- bestos in a small Gooch crucible about 15 mm. in diameter or in a perforated platinum boat. The manner of attaching the Gooch crucible to the carbon filter is shown in Fig. 29, page 25. The perforated platinum boat is most conveniently attached to the filter flask by means of a specially made holder of soft rubber which is provided with a trough-like opening in the top into which the boat is pressed to make the connection air-tight. The asbestos should have been previously burnt to free it from carbonaceous matter. Wash the carbon with a little dilute hydrochloric acid (1:1) and then with water until it is free from acid. Filtering and washing should be done carefully by pouring the solu- tion down a glass rod into the boat. A jet of water from a wash bottle may throw particles of carbon from the boat. Dry the Gooch crucible or boat and its contents in an air-bath at a temperature not above 105 C. While the carbon is dry- ing, prepare the combustion furnace by passing oxygen through the hot tube until the combined weight of the bulb F and the tube G is constant. Attach the weighed bulb and tube to the train, place the crucible or boat containing the carbon in the combustion tube near the copper oxide and burn the carbon TOTAL CARBON IN IRON OR STEEL 121 in a current of oxygen or air at the rate of two bubbles per second until all the carbon has been converted to C02 and carried over into the absorption bulb. The operation should be complete within about thirty minutes. After the combustion is complete, remove the absorption bulb and drying-tube and close the ends with the stoppers described on page 118. The absorbents in the weighed bulb and tube should always be protected from moisture and C0 2 in the air by these stoppers when the bulb is not attached to the combustion train, and the stoppers should always be weighed with the bulb. The train itself should be closed with stoppers similar to those used on the bulb, when the bulb is removed for weighing. There should always be the same amount of air (or oxygen, if that is used for combustion) in the bulb when it is weighed. If air is used for combustion, the bulb may be closed by capillary stoppers to main- tain atmospheric pressure in the bulb; when oxygen is used, if the bulb is always closed when it is about the same temperature, the quantity of oxygen weighed will be the same. Let the bulb and tube stand in the balance case fifteen minutes before weighing. The increase in weight represents the CCb. The factor for C in CO 2 is 0.2727 or A. If the factor weight was used, multiply the weight of CO2 by 10. TOTAL CARBON IN IRON OR STEEL DIRECT COMBUSTION Outline. The steel is burnt directly in oxygen, the CO2 formed by the oxidation of the carbon in the steel is absorbed in a solution of potassium hydroxide and weighed. By this method the carbon from carbonaceous gases in the steel would also be included in the determination. Reagents. Alundum. Ignited alundum is placed in a platinum, nickel, alundum, porcelain, or clay boat about 7 cm. 122 METALLURGICAL ANALYSIS long. A depression is made in the alundum about 3 cm. in length, in which the sample is placed to be burnt (Fig. 65). FIG. 65. Boat with Steel Ready for Combustion and Semi-cylindrical Cover for the Protection of the Silica Tube from Iron Oxide. FIG. 66. Apparatus for the Direct Combustion of Steel for Carbon. Oxygen. The flow of oxygen is much more easily regulated if low-pressure cylinders are filled for use from the high-pressure tank. TOTAL CARBON IN IRON OR STEEL 123 Red lead oxide, PbaCU. Pig iron and ferro-alloys burn more completely at the usual temperature of the furnace if mixed with a little red lead oxide. Potassium hydroxide solution. Dissolve 300 gms. of KOH in 1 liter of water. Granulated zinc for the absorption of sulphuric acid. Calcium chloride, CaCl2 dehydrated. Apparatus. The combustion furnace (Fig. 66) is similar to that described on page 117, but in the direct combustion of steel the temperature of the furnace should be maintained at about 1000 C. It should not fall below 960 or rise above 1050 C. The furnace should, therefore, be provided with a pyrometer, or the resistance in the rheostat may be standardized once for all so that the temperature may be known approximately by the amount of resistance in the circuit. When the resistance is standardized, the hot junction of the pyrometer should be placed in the combustion tube at the point where the carbon is to be burnt. It should be kept in mind that this latter method of controlling the temperature is only approximate and may vary as much as 40 to 50 owing to changes in room temperature, air currents, and vari- ation in the electric current. Before the oxygen enters the combustion tube, it is passed through potassium hydroxide solution, sulphuric acid, soda- lime, and calcium chloride. After leaving the combustion tube, the gases pass through a column of granulated zinc, which removes sulphuric acid, derived from the sulphur in the steel, and through calcium chloride, which dries them before they enter the weighed bulb and tube. A roll of copper oxide enclosed in sheet asbestos is placed in the combustion tube to oxidize CO to C02, or, for this purpose, plantinized asbestos may be sub- stituted. (See p. 118.) The platinized asbestos occupies 12 to 15 cms. of the combustion tube immediately following the position of the boat and is held in place with thin plugs of platinum 124 METALLURGICAL ANALYSIS FIG. 67. Glass-stoppered Bulb and Tube. gauze. The stoppers in the combustion tube must be protected from heat in the way described on page 117. Before determina- tions begin, oxygen should be passed through the hot combus- tion tube at intervals and the ab- sorption bulb and tube brought to a constant weight. (See p. 119.) The absorption bulb should be provided with glass stop-cocks, and it should be filled with oxygen when weighed. (Fig. 67.) In weighing, the bulb and tube should be counter- balanced with a similar apparatus. C in Steel. Weigh 0.2727 gm. or twice the factor, 0.5454 gm., and transfer to the boat described above. The steel drillings should lie in a continuous mass so that when combustion begins it will be propagated throughout. Turn a semi-cylindrical cover of alundum or clay over the drillings to protect the silica tube from the iron oxide which is thrown from the boat during com- bustion. Push the boat thus covered into place in the combus- tion tube, which has been heated to 1000 C. Close the com- bustion tube and pass the oxygen through at a uniform rate of about four bubbles per second until the steel begins to burn, when the rate is increased until the rate of flow in the forward bulb is equal to that in the first absorption bulb. The com- bustion should be finished in about ten minutes. The gas is cut off and the absorption bulb with its calcium chloride tube is detached from the train, cooled and weighed. CARBON IN IRON AND STEEL WEIGHING AS BARIUM CARBONATE AFTER DIRECT COMBUSTION Outline. The steel is burnt in oxygen in a combustion furnace, the carbon of the steel is converted to CO2 which is purified and absorbed in a solution of barium hydroxide. The CARBON IN IRON AND STEEL 125 precipitated barium carbonate is filtered from the solution, burnt, and weighed. Reagents. Barium hydroxide solution. Dissolve 20 gms. of Ba(OH) 2 +8H 2 in 1 liter of freshly boiled hot water. Cover, and when cool filter as rapidly as possible into a receiver which is protected from the CO2 of the atmosphere. The solution should be withdrawn from the container, for use through a tap or siphon, and the air which replaces it should be admitted through a tube containing soda-lime or through a bulb containing caustic potash solution. Apparatus. Set up the combustion furnace in the manner described in the FlG 68 ._Bulb Tube for Barium method above, except that Hydroxide Solution. part of the train following the column of granulated zinc is replaced by the bulb tube (Fig. 68) which should contain 30 cc. of barium hydroxide solution. C in Iron and Steel. Weigh 1 gm. of the metal, or ten times the factor, 0.608 gm., and proceed in the manner described in the preceding method until combustion is complete. Ba(OH) 2 +C0 2 =BaC0 3 +H 2 0. Carefully wash the barium hydroxide solution with its pre- cipitate of barium carbonate from the bulb tube. Filter and wash the precipitate several times with freshly boiled water as quickly as possible to prevent absorption of C02 from the atmosphere. Burn the filter with its contents in a platinum crucible at a red heat with a Bunsen burner, cool in a desiccator, and weigh. The factor for carbon in BaCO 3 is 0.0608. If the factor weight, 0.608 gm., was used, multiply the weight of barium carbonate by 10. 126 METALLURGICAL ANALYSIS CARBON IN IRON AND STEEL TlTRATION OF THE EXCESS OF BARIUM HYDROXIDE Outline. The steel is burnt in a combustion furnace with oxygen. The C02 formed by the oxidization of the carbon in the steel is purified and passed into a definite volume of a standard solution of Ba(OH)2. The excess of Ba(OH)2 is measured by titrating with standard acid and the weight of carbon is calculated. Reagents. Standard hydrochloric acid. Dilute 8 cc. of HC1 (sp.gr. 1.2) to 1 liter with freshly boiled water. Standard barium hydroxide solution prepared in the manner described on page 125, and standardized according to the method given below. Phenolphthalein solution. One gram of phenolphthalein dis- solved in 1 liter of ethyl alcohol (p. 84). To determine the relative values of the acid and alkali solu- tions, titrate a definite volume of the barium hydroxide solu- tion with the dilute hydrochloric acid, after adding a few drops of phenolphthalein solution. To determine the value of the sodium hydroxide solution in carbon, weigh a steel in which the carbon has already been determined and treat it exactly as described in this method. Divide the weight of carbon in the steel by the number of cubic centimeters of barium hydroxide solution required to combine with it to form BaCOs. C in Iron or Steel. Weigh the iron or steel and proceed according to the last method (see p. 125), with the following modification. Measure into the bulb-tube with the pipette 30 cc. of standard barium hydroxide solution. Burn the sample, passing the oxygen in the usual way (p. 124). After the com- bustion is complete, empty the barium hydroxide solution with the precipitate of barium carbonate into a half-liter Erlenmeyer flask and wash out the tube well with freshly-boiled water. Add 3 drops of phenolphthalein solution and titrate the excess COMBINED CARBON IN STEEL 127 of barium hydroxide with standard hydrochloric acid. The value of 1 cc. of the barium hydroxide solution in carbon is then multiplied by the number of cubic centimeters of the solu- tion from which the barium had been precipitated by the COMBINED CARBON IN STEEL COLOR METHOD Outline. The steel is dissolved in a definite volume of dilute nitric acid. The intensity of the brown color of the solution depends upon the amount of carbon present. This solution is compared in a colorimeter with a solution of a standard steel prepared in the same way. Reagent. Dilute nitric acid (1 : 3). C in Steel. Weigh 0.5 gm. of steel (0.2 gin. if the steel is high in carbon) and transfer it to a large test-tube. Add 10 cc. of dilute nitric acid (1 : 3) measured with a pipette (Fig. 69). At the same time, weigh and treat in the same manner a standard steel in which the carbon has been determined by combustion. Place both test-tubes in a water bath (Figs. 70 and 71) and heat until the steel is dissolved. When in solution, remove the test-tubes and place them in cold water. Dilute the solutions to the same volume (50 cc.) and transfer to a colorimeter and read the percentage of carbon directly (see p. 44) ; or transfer the two solutions to Eggertz tubes and dilute until the two agree in color. Carbon in steel in the form known as hardening carbon does not give any color to the nitric acid solution. On the other hand, the solution is colored by copper, cobalt, and chromium. For these rea- sons the standard and the unknown steel should have as nearly the same composition as possible, and should have received the same treatment. FIG. 69. Auto- matic Filling Pipette. 128 METALLURGICAL ANALYSIS They should be annealed before sampling to convert the carbon in each to the same form. The standard should be near the unknown in its carbon content. The colors are matched best if the light comes directly from the sky or clouds, and it should be diffused by a ground glass. The color fades on exposure to light; therefore the solution should be kept in the dark until ready for comparison. If there is much difference between the standard and the unknown steel in carbon content, in using Eggertz tubes, there is a tendency to read the unknown too close to the standard. If the difference is as much as one-sixth of the standard, some chemists make a correction of 1 point for every time that one-sixth of the standard is contained in FIG. 70. Rack Made of Copper for Hold- ing Test Tubes in the Water Bath. FIG. 71. Water Bath. the difference between the two; for example, if the standard is 0.48 carbon and the unknown reads 0.56, the difference is 8 points, and one- sixth of the standard, that is, 8, is contained in this difference one time. Therefore add 1 to the reading of the unknown making it 0.57 as the correct percentage. If the standard were higher than the unknown, the correction would be subtracted from the reading of the unknown. A correction is also sometimes made if the standard and the unknown differ widely in manganese. Manganese causes the carbon color to be lighter, and if the unknown steel contains, for example, 10 points more of manganese than the standard, 1 point is added to the reading for carbon to give the correct percentage; if, on the other hand, the unknown were 10 points lower in manganese, 1 point would be subtracted from its carbon reading. GRAPHITIC CARBON IN IRON 129 GRAPHITIC CARBON IN IRON Outline. The iron is dissolved in dilute acid, the graphitic carbon filtered from the solution, dried, and weighed, or it may be burnt in a combustion furnace, the resulting C02 collected and weighed. Reagents. Dilute nitric add (1 : 3). ' Hydrofluoric acid, HF. Hydrochloric acid, dilute (1 : 3). C, graphitic, in Iron. Weigh 0.608 gm. of the sample and transfer it to a small beaker or Erlenmeyer flask. Add 40 cc. of dilute nitric acid. Heat gently to dissolve the iron. Add a few drops of hydrofluoric acid to dissolve silica, and boil a few minutes. Filter the carbon on asbestos in a small Gooch crucible or in a perforated platinum boat. Wash with hot dilute hydrochloric acid and water alternately, and finally wash with hot water to remove the acid. Dry the carbon in the boat at 110 C., burn in a combustion furnace, and proceed according to the method for carbon !n steel. (See p. 121.) The graphite may be filtered on asbestos in a Gooch crucible, washed, and dried at 110 C. to a constant weight. After weigh- ing, the graphite is burned, in the air or in oxygen, and the crucible and residue weighed. The loss in weight represents the graphite. PHOSPHORUS IN IRON AND STEEL Outline. The steel is dissolved in dilute nitric acid, the solution evaporated to dryness, the silica dehydrated, and the phosphorus oxidized to phosphate. The residue is taken up with hydrochloric acid, the free acid expelled by evaporation, nitric acid added, and the solution evaporated to displace all the hydrochloric acid. The solution is diluted, the silica filtered from it, and ammonia and nitric acid added to the filtrate. 130 METALLURGICAL ANALYSIS The phosphorus is then precipitated with ammonium molybdate, filtered, and weighed; or it may be measured by titration. Reagents and Notes. See phosphorus in iron ore, page 76. P in Steel. Weigh 1,63 gm. (if the material is low in phos- phorus 4.89 gm. 300 times the factor may be used). Trans- fer it to a porcelain casserole or dish and add from 25 to 60 cc. of dilute nitric acid (l':.l). Warm cautiously to dissolve the iron and evaporate the solution rapidly to dryness. Gradually increase the heat until the ferric nitrate is broken up and the acid is all expelled. Cool and add 30 cc. of strong hydrochloric acid, heat to dissolve the iron oxide, and evaporate the solution until chlorides begin to separate. Add 10 cc. of strong nitric acid and evaporate the solution to a syrupy consistency. Dilute with cold water to about 60 cc. Stir and filter into a half-liter Erlenmeyer flask. Wash alternately with 2 per cent solution of nitric acid and hot water until the residue is free from iron. If the iron contains an appreciable amount of titanium, ignite the filter and residue in a platinum crucible. Cool and treat the residue with hydrofluoric and sulphuric acids to remove the silica. Evaporate the solution to dryness, add a little sodium carbonate, and fuse. Treat the fusion with hot water and after disintegration filter the insoluble sodium titanate from the solution and add the filtrate containing the phosphate to the main solution. To the filtrate containing the phosphorus add 25 c. of strong ammonia. This filtrate should be clear and should have a volume of about 150 cc. Shake the solution vigorously, add nitric acid, and proceed according to the method for phosphorus in ores. (See p. 77.) Instead of weighing the yellow precipitate it may be dissolved, the phosphorus precipitated with magnesia mixture, and weighed as magnesium pyrophosphate as described on page 79; or the phosphorus in the yellow precipitate may be measured by Emmer- ton's volumetric method (p. 80), or by Pemberton's alkalimetric method (p. 83). PHOSPHORUS IN IRON OR STEEL 131 PHOSPHORUS IN IRON OR STEEL RAPID METHOD Outline. The iron is dissolved in dilute nitric acid, the carbon oxidized with ammonium persulphate, the solution filtered from the residue, the phosphorus in the filtrate oxidized to phosphate with potassium permanganate, the resulting man- ganese dioxide reduced and dissolved and the phosphorus pre- cipitated with ammonium molybdate, filtered, and measured by titration with standard sodium hydroxide solution. Reagents. Ammonium persulphate, (NH4) 28203. Dilute nitric acid (1 : 3). Wash solution of nitric acid (1 : 48). Potassium permanganate solution. Dissolve 25 gms. KMnO4 in water and dilute to 1 liter. Ammonium molybdate solution. (See p. 76.) Reducing Agents. Ammonium bisulphite solution. Dissolve 5 gms. NH 4 HSO 3 in 100 cc. of water. Ferrous sulphate solution. Dissolve 5 gms. FeS04+7H20 in 100 cc. of water. Sugar Solution. A saturated solution of Ci2H22Ou in water. P in Iron or Steel. Place 1.63 gms. (or other factor weight) of the iron in a half-liter Erlenmeyer flask. Add 40 cc. of dilute nitric acid (1 : 3) and heat until the iron is dissolved. When in solution wash down the sides of the flask, add 1 gm. of ammonium persulphate, and boil until the carbon is completely oxidized. Filter on an 11 -cm. filter paper and wash alternately with 2 per cent nitric acid and hot water until the iron is all removed. Heat the filtrate to boiling, add a slight excess of potassium permanganate solution and boil until the permanganate is decomposed and manganese dioxide is precipitated. Add a saturated solution of sugar or other reducing agent until the manganese dioxide is dissolved. Cool the solution to 80 C., 132 METALLURGICAL ANALYSIS and add 50 cc. of ammonium molybdate solution. Shake the flask five minutes, filter, and proceed according to Pemberton's method (p. 86). MANGANESE IN IRON AND STEEL WALTERS' COLOR METHOD Reagents. Nitric acid (sp.gr. 1.2). Ammonium persulphate (NELi) 28203. Solution of silver nitrate. (See p. 90.) Mn in Iron or Steel. Weigh 0.2 gm. of the sample and trans- fer it to an 8-in. test-tube or to a small Erlenmeyer flask. Add from a pipette 10 cc. of dilute nitric acid. Heat on a water bath until the steel is in solution. Add 0.5 gm. of moist ammonium persulphate and heat to oxidize the combined carbon. If the solution is not clear, filter and wash the residue with 15 cc. of silver nitrate solution. If filtering is not necessary, add the silver nitrate solution directly to the solution of steel. Add 1 gm. of moist ammonium persulphate and heat the solution until the pink permanganic acid color develops. Cool and dilute the solution. Transfer it to a colorimeter and match the color against the standard that has been treated in exactly the same manner. (See p. 44.) MANGANESE IN IRON AND STEEL TlTRATION WITH SODIUM ARSENITE Reagents. See page 90. Mn in Iron or Steel. Weigh 0.2 gm. of the material and treat it exactly as described in the method above to the development of the pink permanganic acid color. Add 10 cc. of sodium chloride solution and titrate with standard sodium arsenite solu- tion to the disappearance of the pink color. (See p. 91.) MANGANESE IN STEEL 133 MANGANESE IN STEEL SODIUM BISMUTHATE METHOD Reagents. See page 92. Weigh 1 gm. of steel and transfer it to a 200-cc. Erlenmeyer flask. Add 50 cc. of dilute nitric acid (1 : 3). Heat until the steel is dissolved. When in solution, cool and add 0.5 gm. of sodium bismuthate to oxidize carbonaceous matter. Heat until the pink color disappears with or without precipitation of manganese dioxide. Add sulphurous acid until the solu- tion clears. Boil out the excess of sulphurous acid. Cool to 15 C. and add an excess of sodium bismuthate (2 or 3 gms.). Agitate the flask for several minutes. Add 50 cc. of dilute nitric acid (3 : 100) and proceed according to the method on page 94. MANGANESE IN FERRO-MANGANESE AND SPIEGEL JULIAN'S METHOD Reagents. See page 95. Weigh 0.25 gm. of ferro-manganese and transfer it to a 200-cc. beaker. Add 40 cc. of nitric acid (sp.gr. 1.2). Cover and boil the solution almost to dryness. Add 50 cc. of nitric acid (sp.gr. 1.42). Heat to boiling. Take off the cover and add potassium chlorate, a little at a time, from a glass spatula, until the green fumes suddenly disappear and are replaced by white fumes; continue boiling for three or four minutes. Cool, dilute with cold water to about 200 cc., add 50 cc. of hydrogen peroxide solution and titrate with standard permanganate solu- tion. See the method on page 95. 134 METALLURGICAL ANALYSIS MANGANESE IN STEELS CONTAINING CHROMIUM AND TUNGSTEN WALTERS' METHOD * Reagents. Dilute sulphuric add (2:9). Solution of sodium carbonate. Dissolve 200 gms. N 10H 2 O in 1 liter of water. Emulsion of zinc oxide. Suspend ZnO in distilled water by shaking in a flask. Sodium bismuthate NaBiOa. For the preparation and standardization of ferrous sulphate and potassium permanganate solutions see page 93. Mn in Steel. Dissolve 2 gms. of the steel in 20 cc. of dilute sulphuric acid (2 : 9) adding enough water, from time to time, to keep the ferrous sulphate in solution. When the steel is dis- solved add 5 cc. of strong nitric acid. Evaporate until the sulphu- ric acid fumes, to destroy carbonaceous matter. Add 100 cc. of water and boil to dissolve ferric sulphate. Transfer the solution to a 500-cc. graduated flask. Add sodium carbonate solution until the solution of steel is dark in color and the pre- cipitate dissolves slowly. Add emulsion of zinc oxide, a little at a time, and shake until the iron and chromium are precipitated. Dilute to the mark with water. Let the precipitate settle. Decant 250 cc. through a dry filter into a quarter-liter graduated flask. Transfer it to a half-liter Erlenmeyer flask and acidify with 25 cc. of nitric acid (sp.gr. 1.42). Add 1 gm. of sodium bismuthate and shake the flask several minutes. Let the residue settle. Filter through asbestos with suction. Wash the flask and filter with water acidulated with nitric acid until the washings are free from the pink color of permanganic acid. Transfer the filtrate to a beaker, add a measured volume of standard ferrous sulphate solution in excess of the permanganic acid, and titrate the excess of ferrous sulphate with standard potassium per- * Met. and Chem. Eng., 9, 224. TITANIUM IN IRON 135 manganate solution. The ferrous sulphate solution should be of such strength that 1 cc. is equivalent to 1 cc. of the standard permanganate solution. TITANIUM IN IRON WELLER'S COLORIMETRTC METHOD * Reagents. See page 90. Ti in Iron. Weigh 5 gm. of the sample and transfer it to a No. 4 beaker. Add 50 cc. of strong hydrochloric acid, cover the beaker and heat until the iron is completely decomposed. Filter, wash with hot water, and ignite the filter in a platinum crucible. Cool, add a few drops of sulphuric acid and enough hydrofluoric acid to dissolve the silica. When the silica is dissolved, evaporate the solution to complete dryness. A very small proportion of the titanium remains in solution and passes through with the filtrate. It may be recovered in the following way. Dilute the filtrate to 250 cc., add strong ammonia until a precipitate appears which slowly dissolves upon stirring. Add 2 per cent ammonia water until a slight, permanent precip- itate is formed. Add 15 cc. of dilute hydrochloric acid (1 : 3). Stir vigorously to dissolve the precipitate. Add 100 cc. or more of a 20 per cent solution of sodium thiosulphate and stir until the iron is completely reduced and free sulphur begins to separate. Boil ten minutes. Let the precipitate settle, and filter. Wash with 2 per cent acetic acid solution and ignite in the crucible containing the silica-free titanium. Add to the crucible 4 gm. of sodium carbonate, and fuse. Cool the fusion and disintegrate it by boiling with water. Filter the sodium >titanate from the solution and wash with hot water in which has been dissolved a little sodium carbonate. Spread out the filter in a small beaker. Add to the crucible in which the fusion was made a little dilute sulphuric acid (1 : 3). * Camp, Met. and Chem. Eng., 10, 675. 136 METALLURGICAL ANALYSIS Boil to dissolve off any adhering titanium and pour the solution upon the filter in the beaker. Wash the crucible with hot water, adding the washings to the solution in the beaker. Heat the beaker to dissolve sodium titanate. Withdraw the filter paper from the solution, washing it carefully with hot water. If the solution contains fibers of filter paper, filter, and transfer the solution to a Nessler or other colorimeter tube. Add 5 cc. of hydrogen peroxide and compare with a standard solution in the manner described on page 92. TITANIUM IN STEEL COLOR METHOD Weigh 0.5 gm. of steel (1 gm. should be taken if it contains less than 0.05 per cent Ti) and transfer to a large test-tube (10" XI")- At the same time place in a similar test-tube an equal amount of a steel which contains no titanium and add to it a sufficient quantity of soluble ferro-titanium, in which the titanium has been determined, to bring its Ti content to within 0.05 per cent of that in the unknown steel. Add to each, 10 cc. of dilute sulphuric acid (1 : 3), to dissolve the steel. Add 5 cc. of concentrated nitric acid to oxidize the iron. Boil off the red fumes. Cool, add 5 cc. of hydrogen peroxide solu- tion, dilute to the same volume, transfer to a colorimeter and compare the colors; or rinse into Eggertz tubes and dilute until the two have the same color. Thymol is considered by Lehner and Crawford * to be more deli- cate for this purpose than hydrogen peroxide. The reagent is pre- pared by dissolving the thymol (CioHuO) in a little acetic acid and then adding sulphuric acid. The solution of thymol prepared in this manner is colorless and is fairly stable if kept out of a bright light. If exposed to a bright light it will darken in a few hours. * Eighth International Congress of Applied Chemistry, 1, p. 285. NICKEL IN STEEL 137 NICKEL IN STEEL ETHER METHOD Outline. The steel is dissolved in hydrochloric acid, the iron oxidized with nitric acid, the chloride solution is shaken with ether, the ether solution containing most of the iron and the aqueous solution containing the nickel are allowed to separate in a separating funnel and the aqueous solution is drawn off. The iron and manganese are precipitated and filtered from the aqueous solution. The nitrate is acidified and if copper is present it is precipitated with hydrogen sulphide and the solu- tion filtered, the filtrate is made ammoniacal, the nickel pre- cipitated with hydrogen sulphide, filtered from the solution, burnt, and weighed as NiO. Reagents. Dilute hydrochloric acid, (1:1). Ether, C 2 H5-O-C 2 H5. Bromine water; water saturated with Br. Hydrogen Sulphide. Generate H 2 S by adding dilute HC1 (sp.gr. 1 : 1) to FeS in a gas generator. (Fig. 53, p. 64.) Acetic acid. 90 per cent, CH 3 COOH. Ni in Steel. Dissolve 2 gm. of steel in 30 cc. of dilute hydro- chloric acid (1:1). Add 2 cc. of strong nitric acid to oxidize the iron. Evaporate to 10 cc. Cool and pour the solution into a 150-cc. separa- tory funnel with short stem (Fig. 72) . Wash out the beaker with dilute hydrochloric acid (1 : 1), using a small amount at a time, and adding the washings to the funnel. Do not let the volume exceed 40 cc. Cool and add 50 cc. of ether. Place the stopper in the funnel and shake ^ato ~Fun" gently at first. Keep the funnel cool by holding it under running water. If allowed to become hot the ether would reduce some ferric chloride to ferrous chloride. 138 METALLURGICAL ANALYSIS The greater part of the ferric chloride is taken up by the ether, leaving the nickel, cobalt, manganese, aluminum, and copper, and a little of the iron, in the original solution. Set the funnel in an upright position and let the ether and aqueous solutions separate. Complete separation is indicated by a sharp line between them. Take out the stopper, open the tap, and draw off the aqueous solution, leaving the ether in the funnel. Add 5 cc. of dilute hydrochloric acid (1 : 1) to the ether in the funnel. Only a small quantity of acid is used, because it takes some iron out of the ether solution. Shake again and separate as before. If the steel is high in nickel, wash a second time with hydro- chloric acid. Discard the ether solution, which contains most of the ferric chloride. Cover the beaker containing the aqueous solution and boil off the -ether, taking care that it does not take fire. Dilute to 200 cc., add 3 cc. of bromine water to precipitate manganese, add a decided excess of ammonia, and boil to pre- cipitate ferric hydrate. Filter, wash once with water, and wash the precipitate back into the beaker. Redissolve the precip- itate in hydrochloric acid, add bromine water, and precipitate again with ammonia. Filter, combine the filtrates, and boil off the ammonia. Make the solution distinctly acid with hydrochloric acid. If copper is present, pass hydrogen sulphide through the solu- tion and filter the precipitated copper sulphide. Evaporate the filtrate to 100 cc. and add ammonia until it is just alkaline. Saturate the hot solution with hydrogen sulphide to precipitate the sulphides of nickel and manganese. Neutralize the solu- tion with acetic acid and then add an excess of 4 cc. to dis- solve manganese sulphide. Filter off the nickel sulphide, wash well with hot water, and ignite it in an open, porcelain crucible. NICKEL IN STEEL 139 Burn the paper at as low heat as possible and then heat a few minutes at the highest temperature. Cool in a desiccator and weigh as NiO. The factor for nickel in NiO is 0.78576. If, in burning, any nickel is reduced to the metallic state, reoxidize it with a few drops of nitric acid, evaporate the excess of acid, heat to a high temperature, and weigh. NICKEL IN STEEL POTASSIUM CYANIDE METHOD* Reagents. Silver nitrate solution. Dissolve 1 gm. of AgNOs in 1 liter of water. Potassium iodide solution. Dissolve 20 gms. of KI in water and dilute to 1 liter. Standard solution of nickel. This solution may be made by dissolving pure metallic nickel, or a pure salt of nickel. A convenient strength is about 0.0005 gm. Ni per cubic centi- meter. Standard solution of potassium cyanide. Dissolve 4 gms. KCN in 1 liter of water. The cyanide solution is not permanent and must be stand- ardized frequently. It is standardized in the following way: Take 50 cc. of the standard nickel solution, dilute it to 100 cc., and add 20 cc. of hydrochloric acid. Neutralize with ammonia and add 1 cc. of ammonia in excess. Add 5 cc. each of the silver nitrate solution and the potassium iodide solution. AgN0 3 +KI=AgI+KN0 3 . The silver iodide renders the solution turbid. Titrate with the potassium cyanide solution until the solu- tion clears. NiCl 2 +4KCN =K 2 Ni(CN) 4 +2KCl. * Deniges, Chem. News, 69, p. 42. Moore, Chem. News, 72, p. 92. 140 METALLURGICAL ANALYSIS When the reaction with the nickel is complete, the silver iodide is dissolved by the excess of potassium cyanide. 2KCN+AgI =KAg(CN) 2 +KI. A blank should be run, leaving out the nickel and includ- ing all the reagents in the quantities given above to learn how much potassium cyanide is required to dissolve the silver iodide. The quantity of potassium cyanide thus determined should be deducted from all tit rations. Ni in Steel. Weigh 2 gms. of steel and treat it according to the ether method for nickel (p. 137) until the copper sulphide has been filtered from the solution. Evaporate the nitrate to 100 cc. Neutralize with ammonia and add 1 cc. in excess. Then add 5 cc. each of the silver and potassium iodide solutions and titrate with standard potassium cyanide solution. NICKEL IN STEEL DlMETHYLGLYOXIME METHOD* Reagents. Hydrofluoric acid, HF. Tartaric acid, C4H60e. Dimethylglyoxime solution. Dissolve 1 gm. of dimethyl- glyoxime(CH 3 -C-( : N-OH)C( : N-OH)CH 3 ) in 100 cc. of alco- hol, (C 2 H 6 0). Ni in Steel. Dissolve 1 gm. of steel in 25 cc. of hydrochloric acid. Add a few cubic centimeters of nitric acid to oxidize the iron. Boil out the chlorine and most of the hydrochloric acid. If silica should be precipitated in the solution, add a little hydrofluoric acid. When solution is complete, add about 3 gms. of tartaric acid and 300 cc. of water. Make the solution slightly ammoniacal. If iron is precipitated, acidify with hydrochloric acid, heat to dis- solve the precipitate, and add more tartaric acid. When the tartaric acid is dissolved add ammonia to render the solution alkaline. * O. Brunck. Stahl u. Eisen, 28, 331. CHROMIUM AND VANADIUM IN STEEL ' 141 If the iron remains in solution, heat nearly to boiling, and add 20 cc. of dimethylglyoxime solution. Let the solution stand for fifteen minutes at a temperature of between 80 and 90 C. 2C4H 8 N 2 2 +NiCl 2 =C 8 H 14 N 4 04Ni+2HCL If the flocculent precipitate of nickel stands long in the mother liquor at a high temperature, it becomes minutely crystalline and is filtered with great difficulty. Filter while hot in a Gooch crucible. Wash with hot water until it comes through colorless. Dry forty-five minutes at a temperature of 110 to 120 C. and weigh. The dried precipitate contains 20.325 per cent Ni. CHROMIUM AND VANADIUM IN STEEL Outline. The steel is dissolved in sulphuric and nitric acids, the chromium and vanadium are oxidized with potassium per- manganate, and the resulting manganese dioxide filtered from the solution. After adding sulphuric acid to the filtrate the chromium is titrated with a standard solution of ferrous ammonium sulphate. The excess of ferrous ammonium sulphate is titrated back with standard potassium permanganate solution, an indi- cator is added and the titration with standard ferrous ammonium sulphate solution is continued for the vanadium.* Reagents. Dilute sulphuric acid (1 : 3). Nitric acid (sp.gr. 1.2); add 40 cc. HN0 3 (sp.gr. 1.42) to 65 cc. of water. A strong solution of potassium permanganate for oxidizing chromium and vanadium; 20 gm. of KMn04 in a liter of water. Standard potassium permanganate solution; 2.83 gm. of KMn0 4 per liter. (See p. 51.) Standard solution of ammonium ferrous sulphate; 35.09 gm. of (NH 4 )2S04-FeS04+6H 2 O dissolved in 300 cc. of dilute sul- phuric acid (1:3) and diluted to 1 liter with water. * Johnson, " Chem. Anal, of Special Steels," p, 8, 142 METALLURGICAL ANALYSIS This solution should be standardized against the perman- ganate solution and corrected, if necessary, to be of exactly equal value. This solution will be equivalent to about 0.001555 gm. of chromium, but it should be standardized for chromium by tak- ing 2 gms. of steel in which the chromium has been determined (or a steel' free from Cr and adding a weighed quantity of pure K2O207) and treating it exactly according to the method given below. The solution should be standardized in a similar way for vanadium. Its value in vanadium should be about 0.00456. Solution of potassium ferricyanide. Dissolve 5 gms. of K 3 Fe(CN) 6 m 130 cc. of water. Cr and V in Steel. Weigh 2 gm. of steel, transfer it to a 600-cc. beaker, and add 30 cc. of dilute sulphuric acid (1 : 3) and 20 cc. of water. Heat; when the first vigorous reaction is over, add 60 cc. of dilute nitric acid (sp.gr. 1.2) to complete the solution and to oxidize the iron. After it is in solution, boil two minutes and add 200 cc. of water. From a small pipette add potassium permanganate solution, a little at a time, until there is a slight precipitate of Mn02, which does not dissolve after boiling twenty minutes. Chromium is converted to Cr0 3 and the vanadium to V 2 5 . Remove the beaker from the heat and place it in a dish of cold water. Filter by suction on asbestos which has been pre- viously washed with nitro-hydrochloric acid, and finally washed well with water. Wash the residue on the filter 15 times with very dilute sulphuric acid (1 : 600). Transfer the filtrate and washings, the volume of which should be about 300 cc., to the 600-cc. beaker. Add 30 cc. of dilute sulphuric acid and titrate with a standard solution of ferrous ammonium sulphate until the solution loses its brown tint and becomes practically colorless, if the steel has less than 1 per cent of chromium; and if higher CHROMIUM AND VANADIUM IN STEEL 143 in chromium (2 to 6 per cent), titrate until the chrome green no longer grows darker. 2Cr03+6FeS04+6H 2 S04=6H 2 0+3Fe 2 (S0 4 )3+Cr 2 2 is to be determined, weigh as WO 3 +Si02-f Fe2O 3 . Add a few drops of sulphuric acid and 10 cc. of hydrofluoric acid. Evaporate to sulphuric acid fumes and then drive off the sul- phuric acid by heating the crucible from the top. Heat at a high temperature. Cool and weigh as W0 3 +Fe20 3 . Add 5 gms. of sodium carbonate and fuse twenty minutes. Dissolve in a casserole with water. Filter the iron from the solution, wash with water to free the precipitate from sodium (about 40 washings should be sufficient). Ignite in a platinum crucible and weigh. Deduct the weight from the combined weight of W0 3 +Fe 2 O 3 . The difference is the weight of WO 3 . The factor for W in WO 3 is 0.7931. W in the Presence of Cr. If the steel contains chromium, the difference between the last two weights above will be W0 3 +Cr2O 3 . Therefore, to determine the percentage of tung- sten, the quantity of chromium which is in the filtrate with the tungsten is determined by the method described on page 141, for the determination of chromium in steel. That is, add sulphuric acid to the nitrate from the ferric oxide until the solu- tion is acid and boil it with a slight excess of potassium per- manganate. Filter, cool, and dilute to 300 cc., add 30 cc. of dilute sulphuric acid, and titrate with standard ferrous ammo- nium sulphate. The chromium found is calculated to and deducted from the combined weight of 148 METALLURGICAL ANALYSIS MOLYBDENUM IN STEEL LEAD MOLYBDATE METHOD* Reagents. Solution of sodium hydroxide. Dissolve 80 gms. NaOH in water and dilute to 1 liter. Methyl orange. Dissolve 1 gm. CuH^NsSOaNa in water and dilute to 1 liter. Lead acetate solution. A saturated solution of Pb (02^02) 2 +3H20 in water. Ammonium acetate, (NH4C2H3O2). Mo in Steel. Weigh 2 gms. of steel, dissolve it in 40 cc. of hydrochloric acid, oxidize by adding 5 cc. of nitric acid. Nearly neutralize the acids by adding sodium hydroxide solu- tion. If there is a precipitate (WOa or MoOs), filter through a little paper pulp, transfer the pulp to a flask, and add 100 cc. of sodium hydroxide solution. Heat nearly to boiling, shake vigorously, and add, through a funnel, while shaking, the hot filtrate. Dilute the solution to 500 cc. in a graduated flask. Filter off 250 cc. Add a drop of methyl orange and hydrochloric acid to decided acidity. Then add 20 cc. of lead acetate solution (if the steel has more than 5 per cent Mo, add more of the precipitant) and a sufficient amount of ammonium acetate to combine with all the hydrochloric acid and leave an excess. Heat to boiling. Let the precipitate settle, filter, wash with hot water, ignite at a low red heat, and weigh as PbMoCU. The factor for Mo in PbMoO4 is 0.2615. If the steel contains tungsten, the lead molybdate will not be pure, but will have mixed with it lead tungstate (PbWCU). To separate them, dissolve the ignited precipitate in hydrochloric acid. Add a few drops of nitric acid and evaporate nearly to dryness. Add 200 cc. dilute hydrochloric acid (1 : 4). Boil, * Chatard, Chem. News. 24, p. 175. MOLYBDENUM IN STEEL 149 and filter off WOs. Reprecipitatc the molybdenum from the filtrate with lead acetate, as in the method just described. Filter, burn and weigh it. MOLYBDENUM IN STEEL WEIGHING AS MoOs Reagents. Dilute nitric acid (2:3). Tartaric acid, C^eOe. Dilute sulphuric acid (1 : 3). Hydrogen sulphide, H^S from a generator. (See Fig. 53, p. 64.) Mo in Steel. Dissolve 2 gms. of steel in dilute nitric acid (2:3). Cool: and add 3 or 4 gms. of tartaric acid (a sufficient quantity to keep the iron in solution, after rendering alkaline with ammonia). Add ammonia until slightly alkaline. Dilute to 700 cc. Saturate with hydrogen sulphide by passing a current of the gas through the solution. Add dilute sulphuric acid (1:3), drop by drop, until the solution is slightly acid. When the solution becomes acid, the reddish brown MoSs forms and settles readily. Add a little paper pulp and pass H^S through the solution thirty minutes. Filter and wash quickly with hydrogen sul- phide water containing 2 drops of sulphuric acid per liter. Burn off the paper in a platinum crucible and roast the MoSs to MoOs at a very low red heat. MoOs is volatile at a strong red heat. Cool in a desiccator and weigh Mof 3. The factor for Mo in Mo0 3 is 0.6666. MOLYBDENUM IN MOLYBDENUM POWDERS Weigh 0.5 gm. of the powder. Treat with aqua regia. Dilute and filter. Burn the filter and fuse the residue with sodium carbonate and a small quantity of sodium nitrate. Dissolve the 150 METALLURGICAL ANALYSIS fusion in dilute hydrochloric acid and add it to the main solu- tion. Evaporate the solution to dry ness. Dissolve the residue in dilute hydrochloric acid. Filter and precipitate the molybde- num from the filtrate with a solution of lead acetate and pro- ceed according to the method given on page 148. COPPER IN STEEL GRAVIMETRIC METHOD Reagents. Dilute sulphuric acid (1 : 3). Sodium thiosulphate, Na2S2O3+5H2O. Weigh 5 gms. (or more if low in copper) . Transfer it to a 500-cc. beaker, add 50 cc. dilute of sulphuric acid (1:3), and heat to dissolve. If the steel does not readily dissolve in sulphuric acid, dissolve it in dilute nitric acid (2 : 3). Add 20 cc. of sulphuric acid (1:1) and evaporate until the sulphuric acid fumes. Dilute the solution to 400 cc. with hot water. Add 6 gms. of sodium thiosulphate and boil until the cloudiness due to the precipitated sulphur clears. Hydrogen sulphide may be used as the precipitant instead of sodium thiosulphate. Filter, wash with hot water, and ignite the filter and residue in a porcelain crucible over a Bunsen burner; cool in a desic- cator and weigh CuO. 2CuS+30 2 =2CuO+2S0 2 . The temperature should not be raised high enough to melt the copper oxide. The precipitate is usually contaminated with a little of the oxides of iron, silicon, and possibly chromium. The impurities may be removed as follows: Dissolve the weighed precipitate in a little strong hydrochloric acid. Dilute, COPPER IN STEEL 151 add an excess of ammonia, filter, burn, and weigh. Deduct the weight from the weight of the combined oxides. The dif- ference represents the weight of copper oxide. The factor for C in CuO is 0.7989. COPPER IN STEEL VOLUMETRIC METHOD Weigh the steel and proceed according to the method above until the copper sulphide is filtered from the solution and washed. Dissolve the copper sulphide in warm dilute nitric acid and proceed according to one of the volumetric methods for copper in ore. (See p. 168.) NITROGEN IN STEEL Outline. The steel is dissolved in hydrochloric acid, the solution distilled with sodium hydroxide solution, the dis- tillate containing the nitrogen is treated with Nessler reagent and compared with a standard solution similarly treated.* Reagents. Hydrochloric acid (sp.gr. 1-1) free from ammonia; or the ammonia in the acid may be determined and the correc- tion made for each estimation of nitrogen. To prepare ammonia-free hydrochloric acid, distil strong hydrochloric acid from a flask provided with a separatory funnel and delivery tube, to which has also been added some strong sul- phuric acid, free from nitrous acid. Pass the HC1 gas, which distils off, through a small wash bottle containing dilute hydro- chloric acid (1 : 1) and finally into distilled water free from ammonia. If the ordinary distilled water contains ammonia, redistil, and reject the first distillate, which will contain the ammonia. Solution of sodium hydroxide. Dissolve 300 gms. of fused NaOH in 500 cc. of distilled water. Heat for twenty-four hours * Allen, Chem. News, 41, 231. 152 METALLURGICAL ANALYSIS at 50 C. in contact with a copper-zinc couple, prepared by rolling together about 15 cm. 2 each of zinc and copper foil. The copper- zinc couple decomposes nitrates, so that ammonia will be expelled in the first distillation.* Nessler reagent. Dissolve 35 gms. potassium iodide in about 50 cc. of water. Add concentrated solution of mercuric chloride, little by little, shaking, until there is a permanent red precipitate. Filter and add to the filtrate 120 gms. of sodium hydroxide dissolved in about 200 cc. of water. Dilute to 1 liter. Add to this 5 cc. of a saturated solution of mercuric chloride in water. Mix thoroughly, let the precipitate settle, and decant the clear solution into a glass-stoppered bottle. Standard solution of ammonia. Dissolve in 1 liter of water 0.0382 gm. NH 4 C1 which has been dried at 100 C. One cubic centimeter will contain 0.01 mgm. of nitrogen. N in Steel. Place 40 cc. of the sodium hydroxide solution, which has been prepared with the copper-zinc couple, into a 1500-cc. Erlenmeyer distilling flask, provided with a separatory funnel and a condenser. Add 500 cc. of water and about 25 gms. of tin foil, to prevent bumping, and distil until the Nessler reagent gives no reaction with the distillate. While this is going on, weigh 3 gms. of steel free from oil and dissolve it in 30 cc. of ammonia-free hydrochloric acid. Transfer the solution to the bulb of the separatory funnel and when the soda solution is free from ammonia drop the ferrous chloride solution very slowly into the boiling solution in the flask and collect the distillate in a glass cylinder of about 160 cc. capacity. When about 50 cc. have been so collected, take away the cylinder and replace it with a fresh one. Measure the nitrogen collected as follows: Dilute the collected distillate with ammonia-free water to 100 cc. and pour it into one of the cylinders in which has been placed 1J cc. of the Nessler reagent. Prepare a standard solution, by adding to a similar cylinder * Sutton, " Volumetric Anal.," p. 446. HYDROGEN IN STEEL 153 \\ cc. of Nessler reagent, 100 cc. of ammonia-free water, and 1 cc. of the standard ammonia solution. If the colors do not agree, prepare other standards, varying the amount of the am- monia solution until the color of the standard matches that of the solution from the steel. When about 100 cc. of distillate has been collected in the second cylinder, replace it by another. Estimate its nitrogen content as before. Continue until the distillate comes over free from ammonia. Then add together the number of cubic cen- timeters of standard ammonium chloride solution used. Divide the sum by 3, and each cubic centimeter having the value of 0.01 mgm. of N will be equal to 0.001 per cent of N in the steel. De Osa * found that the method above gave low results and that the method of Boussingault was more satisfactory, although it did not always give concordant results. By this method the steel is dissolved in hydrochloric acid in the presence of C0 2 , the NH 3 is distilled into a measured quantity of very weak standard sulphuric acid solution (0.01 normal) and the uncombined acid measured by titrating it with a standard alkaline solution, or by treating it with a mixture of KIOi and KI and titrating the iodine liberated. HYDROGEN IN STEELf Outline. The steel is ignited in a silica tube in a current of oxygen. Hydrogen from the steel combines with the oxygen, and the water formed is absorbed in phosphoric anhydride and weighed. Apparatus. The operation is carried out in a combustion furnace provided with two silica tubes (Fig. 73), one above the other, each 75 cms. long. The lower one, in which the steel is placed, is 2 cms. in diameter; and the upper one, in which the oxygen is purified, 1 cm. in diameter. Each tube has placed within it a 15-cm. roll of platinum gauze to serve as a catalyzer. * Rev. Metal., 5, 493-504. t " Anal, of Iron and Steel," American Rolling Mill Co., Middletown, Ohio, p. 35. 154 METALLURGICAL ANALYSTS The oxygen is passed through the hot 1-cm. silica tube at the rate of 100 cc. per minute to oxidize whatever impurities it may contain. It then passes through the following purifying train: FIG. 73. Apparatus for the Determination of Hydrogen in Steel. first, a wash bottle containing a strong solution of potassium hydroxide; second, through a bottle con- taining sticks of potassium hydroxide; third, through concentrated sulphuric acid; and finally, through a tube containing phosphoric anhydride, held loosely in glass wool. The oxygen then enters the 2-cm. silica tube containing the steel, where it combines with the hydrogen liberated from the steel, forming water. It then passes into the 4-in. U-tube provided with glass stoppers, and containing phosphoric anhydride (held loosely in glass wool) in which the water is absorbed. From this tube the gas passes through a bottle containing concentrated sulphuric acid, which shows the rate at which .the gas flows. H in Steel. Heat the silica tubes to redness and pass oxygen through at the rate of 100 cc. per minute. Detach the U-tube, let it cool in the balance case fifteen minutes, and weigh. Then connect it with the silica tube, through a one-hole stopper, turn on the heat, and the apparatus is ready for combustion. Weigh from 10 to 40 gms. of the steel, in as large pieces as are available, and place the sample in a boat containing ignited alundum. Remove the stopper from the end of the silica tube at which the oxygen enters, insert the boat containing the steel into the red-hot tube. Close the tube and continue passing the oxygen, at the rate of 100 cc. per minute, for thirty minutes. OXYGEN IN STEEL 155 Then disconnect the U-tube, cool it in the balance case, and weigh. The weight of water, multiplied by the factor 0.1119, will give the weight of hydrogen in the steel. It is necessary to run a blank, using the same amount of oxygen that is required for the test, and it should be run for the same length of time. The increase in weight for the blank, which is due to the oxidation of the rubber connections, should not exceed 1 mgm. The temperature at which the combustion takes place should not be so high that the steel will absorb all the oxygen. It is not necessary to convert all the metal to oxide. OXYGEN IN STEEL LEDEBUR'S METHOD * Outline. The steel is ignited in a fused . silica combustion tube in a current of purified hydrogen. The oxygen liberated from the steel combines with the hydrogen, and the water formed is absorbed in phosphoric anhydride and weighed. Apparatus. The combustion furnace (Fig. 74) is the same as that described on page 154 in the Method for Hydrogen in Steel. The hydrogen is gen- erated from hydrochloric acid on pure iron or FIG. 74. Apparatus for the Determination of Oxygen in Steel. mossy zinc. It is purified and dried by passing it first over sticks of potassium hydroxide; second, through a 30 per * Cushman, Jour. Ind. and Eng. Chem., 3, 372. " Meth. for the Anal, of Iron and Steel," American Rolling Mill Co., Middletown, Ohio, 41. 156 METALLURGICAL ANALYSIS cent solution of potassium hydroxide; and finally, before entering the 1-cm. silica tube, through concentrated sulphuric acid. From the small silica tube the gas passes through a U-tube containing phosphoric anhydride (held loosely in glass wool) to remove the water formed from the small amount of oxygen that comes over with the hydrogen. From the U-tube the hydrogen passes to the large combustion tube and com- bines with the oxygen of the steel to form water. The water is absorbed in phosphoric anhydride in a U-tube, and weighed. A guard tube containing phosphoric anhydride (held loosely in glass wool) follows the U-tube to protect it from moisture in the air. Preparation of the Sample. The sample should be drilled with the machine drill, at low speed, to prevent partial oxidation. The drillings should be fine and should be free from all particles of oil or dust. O in Steel. Weigh accurately 25 gms. of the finely divided drillings and transfer the sample to a nickel or platinum boat. Place the boat in the combustion tube, close the tube, attach the weighed U-tube (which is provided with glass stoppers) and the guard tube. Pass hydrogen through the furnace until the air has all been swept out of the furnace and connections while it is cold. Turn on the heat and raise the temperature quickly to a bright red heat (about 850 C.) and hold at this temperature while the hydrogen is passed at- the rate of 100 cc. per minute, for thirty minutes. When the combustion is complete, turn off the heat and cool the furnace, as rapidly as possible, to the ordinary temperature. This may be done by turning on a blast of cold air. When the furnace is cold, detach the U-tube, with its guard tube. With an aspirator draw air into the U-tube through a drying tube to replace the hydrogen, and weigh the U-tube. The weight of water, multiplied by the factor 0.8889, will give the weight of oxygen in the steel. A blank should be run occasionally and the necessary correc- tion made on all determinations. ANALYSIS OF IKON SLAGS 157 ANALYSIS OF IRON SLAGS Sampling. If slags are chilled while hot, they are much more easily decomposed by acids than if left to cool slowly. Therefore the sample should be taken while the slag is molten and poured either into water or on a cold steel or iron plate. A steel rod may be stirred into the hot slag, withdrawn, and dipped into water, or left for the slag to cool on the rod in the air. Since the composition of slag differs from hour to hour, a sample should be taken each time the slag is tapped and the accumulated samples for the day mixed and crushed, and properly sampled for analysis. (See p. 8.) The samples should be ground in a mechanical grinder or on a bucking-board, and finally in an agate mortar. Pass a magnet through the ground slag, to take out particles of iron that may be included in it. It is then ready for analysis. Insoluble Residue. Weigh 0.5 gm. of slag and transfer it to a porcelain casserole. Add 20 cc. of water and stir until the slag is suspended in the water. Add 10 cc. of strong hydro- chloric acid, cover, and heat to dissolve. Add a few drops of nitric acid and evaporate to dryness. Add to the residue 3 cc. of strong hydrochloric acid and evaporate again to dryness. Cool, add 30 cc. of dilute hydrochloric acid (1 : 1), heat to dis- solve, and filter. Wash with hot dilute hydrochloric acid and hot water. Burn the filter with the precipitate in a platinum crucible, cool in a desiccator, and weigh as silicious residue. SiC>2 in Slag. After the silicious residue is weighed, add a few drops of sulphuric acid, and enough hydrofluoric acid to dissolve the silica. Evaporate and weigh in the usual manner. (See p. 71.) The loss in weight represents Si02. Al 2 O3+Fe2O 3 in Slag. Heat the filtrate from the silicious residue to boiling and add a slight excess of ammonia. Boil until the smell of ammonia is faint. Let the precipitate settle, filter, wash with hot water, burn, and weigh as 158 METALLURGICAL ANALYSIS CaO in Slag. Heat the filtrate from aluminic and ferric oxides to boiling. Add 25 cc. of a saturated solution of ammo- nium oxalate and 10 cc. of ammonia. CaCl 2 +(NH 4 ) 2 C 2 04 = CaC 2 4 +2NH 4 Cl. Boil a few minutes and let the precipitate settle. Filter, and wash with hot water. If the flux is dolomitic, for a complete separation of the magnesia, dissolve the precipitate of calcium oxalate in dilute hydrochloric acid, dilute, reprecipitate, and filter, as described above. This precipitate may be burned and weighed as CaO, or, where many determinations are to be made, it is better to measure the lime volumetrically, as follows: Remove the filter paper containing the precipitate of calcium oxalate from the funnel, carefully unfold it, and spread it out smoothly against the inside of a 500-cc. beaker, with the side of the paper containing the precipitate nearest the bottom of the beaker. (See Fig. 52 on p. 61.) With a jet of water carefully wash the precipitate from the paper. Withdraw the paper, add to the precipitate 100 cc. of dilute sulphuric acid (1 : 3). CaC 2 4 +H 2 S0 4 =CaS0 4 +H 2 C 2 4 . Heat to boiling, and while hot titrate with standard potas- sium permanganate solution. 5H 2 C 2 4 +2KMn0 4 +3H 2 S0 4 =K 2 S0 4 +2MnS0 4 +8H 2 0+10C0 2 . By combining the two equations above and comparing it with that on page 57 for the titration of Fe, it is evident that the value of 1 cc. of permanganate solution in Fe, multiplied by 0.50205, will give its value in CaO. 5CaC 2 04+2KMn04+8H 2 S04 = 5CaSO 4 -fK 2 S04+2MnS0 4 .+8H 2 0-hlOC0 2 . ANALYSIS OF IRON SLAGS 159 MgO in Slag. Add hydrochloric acid to the filtrate from the calcium oxalate until it is slightly acid, and then add 20 cc. of 10 per cent solution of microcosmic salt. Evaporate the solution to about 250 cc. and cool it. When cold add ammonia, drop by drop, stirring, until the solution is alkaline. Then add 25 cc. of strong ammonia. Let the solution stand several hours, stirring occasionally. Filter, wash with dilute ammonia (1:3), burn, and weigh. (See magnesia in limestone, p. 165.) FeO in Slag. Weigh 5 gms. of the sample and transfer it to a porcelain casserole. Add 30 cc. of water and stir until the slag is in suspension in the water. Add 30 cc. of dilute hydrochloric acid (1 : 1). Cover, and evaporate the solution to dryness. Cool, add 30 cc. of dilute hydrochloric acid (1 : 1), boil to dissolve the iron, filter, and wash. Then proceed with the reduction and titration of the iron by the potassium dichromate method given on page 62. The weight of iron, multiplied by 1.2865, will give the corresponding weight of FeO. A^Os in Slag (by difference). From the determination of Fe above, calculate the equivalent of the Fe in Fe2Oa by multiply- ing the weight of Fe by the factor 1.4298. Deduct the weight of Fe20s from the combined weight of Al2O 3 +Fe203 as de- termined by the method on page 157, and calculate the per- centage of A^Oa. A1 2 O 3 in Slag (Phosphate method). Weigh 0.5 gm. of the slag and treat it according to the method described above for the determination of insoluble residue. After the filtration and washing of the insoluble residue, proceed with the determina- tion of A^Oa in the filtrate according to the phosphate method given on page 87. S in Slag. Weigh 1 gm. of slag, and transfer it to a porcelain casserole. Add 5 cc. of bromine water and 50 cc. of aqua regia. Evaporate to dryness, dissolve in a little hydrochloric acid and water, filter, and proceed in the manner described for the determination of sulphur in ore. (See p. 75.) 160 METALLURGICAL ANALYSIS Mn in Slag. Weigh 1 gm. of slag and proceed according to the colorimetric method for manganese in ore (p. 92); or, if the slag is high in manganese, the bismuthate method or Julian's method may be used. ANALYSIS OF LIMESTONE Sampling. Limestone is sampled in a similar manner to that employed in the sampling of iron-ore (see p. 45), but usually so large a sample is not required, since it is a more uniform and less valuable material. The sample is crushed, mixed, divided, and ground to a fine powder for analysis in the usual manner. Reagents. Sodium carbonate. Dry Na 2 C03. Dilute hydrochloric acid (1 : 1). Oxalic acid. Dissolve 40 gms. (H 2 C 2 O 4 H-2H 2 O in 1 liter of water. Sodium phosphate. Dissolve 100 gms. HNa2PO4+12H 2 in 1 liter of water. INSOLUBLE SILICIOUS MATTER IN LIMESTONE Weigh 1 gm. of the powdered limestone and transfer it to a small beaker. Add 30 cc. of dilute hydrochloric acid and 1 cc. of nitric acid. Cover the beaker and heat it to dissolve as much as possible of the sample. Evaporate the solution to dryness and heat the residue in an air-bath one hour at 120 C. Cool, add 10 cc. of strong hydrochloric acid, warm gently and add 50 CO; of hot water. Filter, wash the residue with hot dilute hydrochloric acid, and then wash with hot water. Burn the filter and contents in a platinum crucible, cool in a desiccator and weigh. SILICA IN LIMESTONE 161 SILICA IN LIMESTONE After weighing the insoluble silicious matter (see above), add to, the crucible about 0.5 gm. sodium carbonate and fuse. Cool and dissolve the fusion in a casserole with dilute hydro- chloric acid. Carefully wash off the crucible and cover, letting the washings run into the casserole. Evaporate the solution to dryness and heat the residue in an air-bath one hour at 120 C. Cool, add 10 cc. of hydrochloric acid, warm and add 50 cc. of hot water. Filter, wash with dilute hydrochloric acid and then wash with hot water. Burn, cool in a desiccator, and weigh the Si0 2 . In carrying out this process about 1 per cent of the silica dissolves and passes through with the filtrate. For exact work, the filtrate should be taken to dryness again, dissolved, and filtered through a fresh paper, and the two papers burned together. If this treatment is adopted, the first heating of the residue need not be so prolonged. It is sufficient to evaporate the solution to dryness, take up the residue in dilute acid and filter. OXIDES OF IRON, ALUMINUM, ETC., IN LIMESTONE Combine the filtrates from the insoluble silicious matter and the silica, heat the solution to boiling and add a slight excess of ammonia. Boil until the odor of ammonia is faint. Aluminum hydroxide is slightly soluble in ammonia, but this effect is largely neutralized by the presence of ammonium chloride. Let the precipitate settle a few minutes, filter, and wash quickly with hot water. The solution absorbs C02 from the air, which precipitates calcium as CaCOs. If accurate results are required, wash the precipitate into a beaker, add hydrochloric acid, and heat to dissolve; dilute with hot water, add a slight excess of ammonia, boil until the odor is faint, let the precipitate settle, and filter and wash in the manner described above, 162 METALLURGICAL ANALYSIS Burn the filter and contents in a platinum crucible. Cool in a desiccator and weigh. The oxides weighed are chiefly those of iron and aluminum, but if the limestone contains titanium, phosphorus, vanadium, chromium, and zirconium, their oxides also will be present. For the separate determination of these elements in limestone, see the index for the methods for their determination in ores. LIME IN LIMESTONE GRAVIMETRIC METHOD Combine the filtrates from the hydroxides of iron, aluminum, etc. The total volume should measure about 250 cc. and there should be enough ammonium chloride present to prevent the pre- cipitation of magnesia when the solution is near the neutral point. Add 1 drop of methyl orange, heat to boiling, and add oxalic acid until the solution is acid. While boiling, stir, and add ammonia slowly until the solution is slightly alkaline. After the addition of the ammonia, boil and stir a few minutes. Let the precipitate settle. CaCl 2 +H 2 C 2 04+2NH 4 OH=CaC 2 04+2NH4Cl+2H 2 0. Decant the clear solution through a filter, wash once by decantation with hot water, leaving the precipitate in the beaker. To free this precipitate of magnesium oxalate which comes down with it, dissolve it in 10 cc. of dilute hydrochloric acid, add about 100 cc. of hot water, boil, and reprecipitate the cal- cium oxalate with oxalic acid and ammonia. Filter on the same filter paper used for the decantation, and wash thoroughly with hot water. Reserve both filtrates for magnesia. Place the filter and precipitate in a platinum crucible. Care- fully dry, and burn off the paper with a Bunsen burner. Finally heat with a blast lamp to drive off all the CO and CO2. 4 = CaO+C0 2 +CO. LIME IN LIMESTONE 163 Cool in a desiccator and weigh quickly. CaO readily absorbs moisture from the atmosphere. Repeat the burning and weighing until the weight is constant. The weight of CaO multiplied by 100 represents the percent- age of CaO, or lime, in the limestone. This percentage of CaO, multiplied by the factor 1.7847, will give the percentage of CaC0 3 . Burning large precipitates of calcium oxalate completely to CaO and weighing adds considerably to the time of making the analysis. If many determinations of lime are to be made, the following volumetric method is recommended. LIME IN LIMESTONE VOLUMETRIC METHOD After the calcium oxalate has been transferred to the filter (see the preceding method), wash it with hot water until the wash water comes through free from oxalates. Test by collecting a few cubic centimeters in a small beaker, acidi- fying with H 2 S0 4 , heating nearly to boiling, and adding a drop of KMn0 4 solution. If the color of the permanganate fades, oxalate is still present. When thoroughly washed, transfer the precipitate from the paper to a beaker, with hot water. (See p. 61 for the method of transfer.) Then wash off the paper with a little dilute H?SO4 (1:5) from a wash bottle, and finally, with hot water. Remove the paper. Add a few cubic centimeters of sulphuric acid to dissolve the precipitate. (1) CaC 2 4 +H 2 S0 4 = CaS0 4 +H 2 C 2 4 . Dilute with hot water and, while hot (70 C.), titrate with standard potassium permanganate solution. (2) 5H 2 C 2 4 +2KMn0 4 +3H 2 S0 4 =K 2 S0 4 +2MnS0 4 +8H 2 0+10C0 2 . The standard permanganate solution used for the titration of iron may be used for lime. Its value in iron, multiplied by 164 METALLURGICAL ANALYSIS 0.50206, will give the value per cubic centimeter , in CaO, or, multiplied by 0.89604, will give the value in CaC0 3 . These factors are calculated from the above reactions and the reaction of KMnCU with iron (p. 57). Two molecules of KMnCU react with 10 atoms of Fe in the one case (p. 57) and with 5 molecules of oxalic acid in the other (equation 2 above) which are equivalent to 5 atoms of Ca (equation 1 above). From the weight of Ca the corresponding weights of CaO and CaCOs are at once deduced. The more accurate and desirable method, however, is to standardize the solution against a weighed quantity of pure Iceland spar, which has been treated by this method. TITRATION OF BOTH CALCIUM AND MAGNESIUM A method for the titration of both calcium and magnesium in the same solution has been devised by P. J. Fox,* by which the calcium is precipitated as oxalate, and the magnesium as magnesium ammonium arsenate (MgNH^AsCU), by the addi- tion of ammonium arsenate. The precipitates are filtered to- gether from the solution, and transferred to a flask. Sulphuric acid is added, and the calcium is measured by titrating the lib- erated oxalic acid, after it is heated, with KMnCU solution. The solution is cooled, KI added, and the liberated iodine titrated with standard sodium tfyiosulphate solution, without the addition of starch. As 2 5 +4HI =As 2 3 +2H 2 0+2I 2 . The flask should be screened from the light with black paper during the titration to prevent the liberation of iodine by the action of light. * Jour. Ind. and Eng. Chem., 5, 910 (1913). MAGNESIA IN LIMESTONE 165 MAGNESIA IN LIMESTONE Combine in one solution . the filtrates from the calcium oxalate and acidify it with hydrochloric acid. Add 20 cc. of sodium phosphate solution (100 gms. HNa2PO4 + 12H2O per liter). Evaporate the solution until a precipitate begins to form. Add hot water until the precipitate dissolves. Add ammonia, drop by drop, stirring, until the solution is alkaline. Then add a volume of ammonia (sp.gr. 0.90) equal to about one-fourth the volume of the solution. Stir well and let the precipitate settle several hours. A mechanical stirrer is recommended. Where the stirring rod touches the sides of the beaker, the precipitate adheres and is removed with great difficulty. If the stirring is continuous, precipitation should be complete in half an hour. M g Cl 2 4-NH40H+HNa 2 P0 4 =MgNH 4 P04+2NaCl+H 2 0. Filter, and if the precipitate of magnesium ammonium phosphate is large, or if other salts have crystallized with it, dissolve the precipitate in a little hydrochloric acid, dilute the solution with water, add 5 cc. of sodium phosphate solution and ammonia, in the manner described above. Stir, let the precipitate settle, and filter. Wash with water containing 100 cc. NH 4 OH (sp.gr. 0.90) and 1 cc. HNO 3 per liter. Dry the precipitate; separate it from the paper. (See Fig. 31, p. 27.) Burn the paper in a porcelain crucible. When the carbon is all burnt, add the precipitate and heat at a red heat with a Bunsen burner until the precipitate is white. Then heat at a high temperature with the blast lamp a few minutes. Cool in a desiccator and weigh 2NH 4 MgP0 4 = Mg 2 P 2 7 +2NH 3 +H 2 0. The factor for MgO in Mg 2 P 2 7 is 0.36207; and for MgCO 3 is 0.75718. 166 METALLURGICAL ANALYSIS If the filter paper is burned in contact with the phosphate pre- cipitate, there is danger that phosphorus will be reduced and the deter- mination spoiled. If this takes place in a platinum crucible, the phos- phorus combines with the platinum, making it brittle and causing cracks to form. PHOSPHORUS AND SULPHUR IN LIMESTONE For methods for the determination of phosphorus, sulphur, and other elements in limestone see the methods for these ele- ments in iron ore. CARBON DIOXIDE IN LIMESTONE Apparatus and Reagents. The limestone is dissolved in a flask (Fig. 75 C), in dilute HC1. CaC0 3 +2HCl =CaCl 2 +H 2 0+C0 2 . FIG. 75. Apparatus for the Determination of Carbon Dioxide in Limestone. The liberated C02, after purification, is absorbed in a KOH bulb and weighed. A is a U-tube containing soda lime a mixture of calcium and sodium hydroxides which removes CO2 from the air drawn into the apparatus. B. A separatory funnel in which is placed 150 cc. of dilute HC1 (1 : 5). C. A Florence flask in which the sample is placed for solution. D. A bulb tube to serve as condenser- CARBON DIOXIDE IN LIMESTONE 167 E. A U-tube containing a solution of silver sulphate in sul- phuric acid to absorb hydrochloric acid. Sulphuric acid pre- vents evaporation of the silver sulphate solution. F. A U-tube containing dried but not fused CaCk which removes moisture from the gas. Calcium chloride sometimes contains impurities which absorb C02, therefore, before use, C02 should be passed through this tube to saturate the reagent, and then a current of air should be passed through half an hour to remove the excess of C02. G. A Geissler bulb with each of the small bulbs two-thirds filled with a KOH solution (1.27 sp. gr.) for the absorption of C02. The solution must be concentrated to insure the absorp- tion of CO2 and to prevent evaporation. H. A tube containing calcium chloride to absorb moisture that may be carried from the bulb G. (See Carbon in Steel, p. 117.) /. A second calcium chloride tube added to protect H from moisture from the air. /. An aspirator bottle by which air is drawn through the apparatus. When the apparatus is set up, test for leaks in the manner described on page 119. CO2 in Limestone. Connect the aspirator bottle J and draw air through the apparatus until it is filled with air free from carbon dioxide. Weigh G and H and attach them as shown in the figure, but do not connect the aspirator bottle J. Weigh 1 gm. of the finely ground limestone and transfer it to the flask C. Open the tap of B and let the acid drop into the flask C until the gas passes through the bulb G at the rate of two bubbles per second. When the passage of the gas falls below that rate, add more acid. Finally, when the addition of more acid does not increase the action, attach the aspirator to /, and begin the aspiration very gently, and open the screw clamp a. Then warm the flask C very gradually with a Bunsen 168 METALLURGICAL ANALYSIS burner and boil gently half an hour. Detach G and H, place them in the balance case, and after they have stood fifteen minutes, weigh them. The same precautions must be taken in weighing that are pointed out on page 119. The increase in weight represents the CO2 in the sample. METHODS OF ANALYSIS IN THE METALLURGY OF COPPER AND LEAD COPPER IN ORE POTASSIUM CYANIDE METHOD Outline. The copper is dissolved from the ore with nitric and hydrochloric acids, sulphuric acid is added and the solution is evaporated nearly to dryness. A little water is added and the copper is precipitated on metallic zinc or aluminum. The copper is separated from the solution, washed, and dissolved in nitric acid. An excess of ammonia is added and the cupram- monium nitrate is titrated with standard potassium cyanide solution. * Reagents. Dilute nitric acid (1 : 4). Bromine water; cold water saturated with Br. Sheet zinc or aluminum. Standard solution of potassium cyanide. Dissolve 21 gms. of KCN in water and dilute the solution to 1 liter. Standardize the solution as follows: Weigh accurately about 0.2 gm. of pure copper foil and transfer it to a 250-cc. Erlenmeyer flask. Add 5 cc. of strong nitric acid. When in solution, dilute with 25 cc. of water and add 5 cc. of bromine water. Boil out the bromine, and add 50 cc. of cold water and 10 cc. of ammonia. Cool to the temperature of the room, dilute to 150 cc., and titrate with the potassium cyanide solution. The cyanide solution does not hold its strength well. It * For the method of sampling see p. 8. COPPER IN ORE 169 should, therefore, be standardized frequently, the titration of the standard should be done at the same time that the ores are titrated, and all brought to the same tint for an end-point. When the blue color begins to fade, proceed more slowly with the titration, and after each addition of solution allow a little time for the reaction to take place before further additions are made. As the end-point is approached, the solution changes from pale blue to violet, and finally to faint pink. On standing, the color fades; therefore, all titrations should be made in about the same time. Cu in Ore. Weigh 1 gm. of ore (0.5 gm. if the ore contains more than 40 per cent copper) and transfer it to a 250-cc. Erlenmeyer flask. Add 10 cc. of nitric acid, and boil gently to decompose the ore. If decomposition is not complete, add 5 cc. of hydro- chloric acid and boil. Add 7 cc. of sulphuric acid and boil until dense sulphuric acid fumes are evolved. This operation is carried on best by holding the flask by the neck with a test- tube holder and shaking it over the open Bunsen flame under a hood. (Fig. 76.) It should be boiled almost to dryness to FIG. 76. Flask for Copper insure the expulsion of all nitric acid. Determinations. Cool, and add 20 cc. of cold water. If the ore contains silver, add 1 drop of hydrochloric acid to precipitate the silver. Shake the flask, let it stand hot until the ferric sulphate dis- solves, filter the solution into a small flask, and wash the residue with hot water, keeping the volume down to about 60 cc. Put into the flask three pieces of sheet aluminum, about 15 mm. X40 mm., with the ends bent to prevent the sheets from lying flat on the bottom of the flask. Boil the solution to precipitate the copper. The copper is not precipitated in a weakly acid solution, but is rapidly precipitated after boiling the solution 170 METALLURGICAL ANALYSIS down to the proper concentration. When the copper is com- pletely precipitated, . decant the solution through a filter and wash the copper and aluminum by decantation two or three times. A weak solution of hydrogen sulphide may be used as a wash to prevent the oxidation and solution of the finely divided copper. Place the flask under the funnel, pour through the filter 10 cc. of warm dilute nitric acid (1 : 4). Replace the flask with a beaker. Shake the flask and warm it slightly to dissolve the copper. Empty the flask into the beaker and pour the solution back into the flask, leaving the strips of aluminum in the beaker. Wash the aluminum well with water and add the washings to the solution in the flask. Place the flask under the funnel, pour 5 cc. of cold bromine water through the filter to oxidize arsenic and antimony, and then wash the filter with a little hot water. Boil the solution to expel the bromine, cool, and add 10 cc. of ammonia. Dilute the solution to 150 cc. and titrate with standard potassium cyanide solution. This method is not accurate unless the titrations of ore-solutions are carried out under exactly the same conditions as exist when the potas- sium cyanide solution is standardized; therefore, the volume of solu- tion, the excess of ammonia, the temperature, and the time required for titration should always be as nearly the same as possible. Sheet zinc may be used instead of aluminum for the precipitation of the copper. In this case, after the copper is precipitated, add 20 cc. of dilute sulphuric acid (1 : 1) to hasten the solution of the zinc. When the zinc is dissolved, fill the flask to the neck with cold water, let the copper settle, decant the clear solution, and fill and decant a second and a third time. Add 5 cc. of nitric acid to the copper in the flask and boil to expel red fumes. Add 50 cc. of water and 10 cc. of ammonia. Cool, dilute to 150 cc., and titrate with standard potassium cyanide solution. COPPER IN ORE 171 COPPER IN ORE POTASSIUM IODIDE METHOD Outline. The copper is dissolved from the ore with nitric and hydrochloric acids, sulphuric acid is added and the solution evaporated nearly to dryness. A little water is added and the cop- per is precipitated on metallic aluminum. The copper is separated from the solution, dissolved in nitric acid, the excess of acid neutralized with ammonia! Acetic acid and potassium iodide are added, and the iodine liberated is titrated with a standard solu- tion of sodium thiosulphate, which measures the quantity of copper indirectly. Reagents. Acetic acid (C 2 H4O2; sp.gr. 1.04). Starch solution. (See p. 111.) Potassium iodide, KI. Standard solution of sodium thiosulphate. Dissolve 19 gms. Na2S20s in water and dilute the solution to 1 liter. To stand- ardize this solution, dissolve about 0.2 gm. of pure copper foil in 5 cc. of strong nitric acid; dilute the solution with 25 cc. of water, and add 5 cc. of bromine water. Boil off the excess of bromine, remove from the heat, and add a slight excess of ammonia. Boil off the excess of ammonia, and acidify with acetic acid. Too great a concentration of ammonium salts interferes with the reaction between the copper and acetic acid. Boil until any precipitate present is dissolved, cool, add 3 gms. of potassium iodide, and titrate at once with sodium thiosul- phate solution to a faint brown color. Add a few drops of starch solution and continue the titration until the blue color disappears. 2Cu(C 2 H 3 2 ) 2 +4KI=Cu 2 I 2 +4KC 2 H 3 2 -fI 2 . I 2 +2Na 2 S 2 3 =2NaI+Na,S 4 0.. 172 . METALLURGICAL ANALYSIS Cu in Ore. Weigh 1 gm. of ore (0.5 gm. if the ore contains more than 40 per cent copper) and transfer it to a 250-cc. Erlenmeyer flask. Add 10 cc. of nitric acid, and boil gently to decompose the ore. If decomposition is not complete, add 5 cc. of hydrochloric acid and boil. Add 7 cc. of sulphuric acid and boil until dense sulphuric acid fumes are evolved. (See the preceding method for notes.) Cool, and add 20 cc. of cold water. If the ore contains silver, add 1 drop of hydrochloric acid to precipitate the silver. Shake the flask, let it stand hot until the ferric sulphate dis- solves, filter the solution into a small flask, and wash the residue with hot water, keeping the volume down to about 60 cc. Put into the flask three pieces of sheet aluminum, about 15 mm. X40 mm., with the ends bent to prevent the sheets from lying flat on the bottom of the flask. Boil the solution to precipitate the copper. The copper is not precipitated in a weakly acid solution, but is rapidly precipitated after boiling the solution down to the proper concentration. When the copper is com- pletely precipitated, decant the solution through a filter and wash the copper and aluminum by decantation two or three times. Place the flask under the funnel, pour through the filter 10 cc. of warm dilute nitric acid (1 : 4). Replace the flask with a beaker. Shake the flask and warm it slightly to dis- solve the copper. Empty the flask into the beaker and pour the solution back into the flask, leaving the strips of aluminum in the beaker. Wash the aluminum well with water and add the washings to the solution in the flask. Place the flask under the funnel, pour 5 cc. of cold bromine water through the filter to oxidize arsenic and antimony, and then wash the filter with a little hot water. Boil the solution to expel the bromine, cool, and add a slight excess of ammonia. Boil off the ammonia, acidify the solution with acetic acid, and boil until any pre- cipitate present is dissolved. Cool, add 3 gms. of potassium COPPER IN ORE 173 iodide, and titrate with standard sodium thiosulphate solution to a faint brown color. Add a few drops of starch solution, and continue the titration until the blue color changes suddenly to white or light cream color. COPPER IN ORE ELECTROLYTIC METHOD* Outline. The ore is dissolved in acids, and after adding sulphuric acid the solution is boiled nearly to dryness. A little nitric acid is added, the solution diluted and the copper precipitated by electrolysis. Cu in Ore. Weigh the ore and dissolve it according to the method described for the potassium cyanide assay of copper. After boiling until dense sulphuric acid fumes are evolved, cool, add 20 cc. of cold water, and warm the solu- tion to dissolve the soluble sulphates. Add 1 drop of hydrochloric acid to precipitate silver. Filter the solution into a No. 4 beaker, add 2 cc. of nitric acid and electrolyze. 2CuS0 4 +2H 2 0+electric current =2H 2 S0 4 +Cu 2 +0 2 . The electrodes are of platinum. The most satisfactory cathode is made of platinum gauze in cylindrical form, with platinum wire attached, by which it is connected to the negative pole of an electric circuit. The anode may be a coiled plati- num wire, about 16 gauge. (Fig. 77.) Before use the electrodes should be cleaned with nitric acid and washed with water, and the FIG. 77. Platinum cathode must be dried and weighed. Electrodes. The electrodes should be held firmly by a sup- port so that they do not touch, and the solution should be diluted to cover the cathode. * Stoddard, Jour. Amer. Chem. Soc., 31, 385. Price and Meade, " Tech. Anal, of Brass," 71. Smith, "Electro-analysis," 63, 174 METALLURGICAL ANALYSIS The solution may be eleotrolyzed in a platinum dish. The dish is connected by a wire to the negative pole and serves as the cathode. A platinum crucible cover partly submerged in the solution and connected by a wire with the positive pole serves as anode. The current should have a density per hundred square centimeters of cathode surface (D/100) of 0.5 ampere at 2.5 volts, and twelve hours should be a sufficient time for the com- plete precipitation of the copper. The ordinary 110- volt current may be conveniently and economi- cally reduced for this purpose by the use of a motor-generator set. The motor which drives the generator takes the current at 110 volts; the current from the generator is regulated by an easily variable resist- ance which controls the current in its field. For the proper regulation of the current a voltmeter and an ammeter are connected with the generator circuit. Ordinary electric batteries may be used for this purpose. Two or three gravity cells in good working order supply a satisfactory cur- rent for one set of electrodes of the usual size. When the current passes through the electrolyte, oxygen is set free at the anode and the copper should be deposited on the cathode in a smooth, bright copper-colored plate. If the copper is dull in color or granular in appearance, it is easily washed off and is also readily oxidized when dried in the air. When the solution has lost its blue color, test it to determine if all the copper has been precipitated, by taking out 1 cc. of the solution and adding to it a little strong solution of hydrogen sulphide. If copper is still present, continue the electrolysis until the solution gives no reaction for copper. If the resistance of the solution is high and the ^ deposition of the copper is too slow, add a little am- ^ monia to reduce the resistance. FIG. 78. Anode The time of deposition may be very much shortened Suitable for by increasing the current to 6-8 amperes and 3-4 volts; Rotating. but under these conditions the copper will be deposited in a granular condition, or some of it may be deposited as copper sulphide, unless the anode or the cathode or the solution be rotated at a high speed. With this provision the copper LEAD IN ORE 175 will be deposited as a smooth adherent plate even with a current strong enough to completely precipitate it in half an hour. Fig. 78 shows a suitable form of anode for rotating. It may be attached directly to the shaft of a small motor or to a belt-driven pulley. When deposition is complete, withdraw the electrodes from the beaker before breaking the current, at the same time wash- ing them off with distilled water to prevent re-solution of the copper. Disconnect the cathode from the circuit, wet it with a little alcohol, dry, and weigh it. From the combined weight of the cathode and copper must be deducted the weight of the cathode. If the copper plate is smooth with a fine metallic luster, it may be dried by burning off the alcohol, without danger of oxidizing the copper. After the copper has been weighed, it is dissolved from the cathode in a little warm nitric acid. LEAD IN ORE MOLYBDATE METHOD Outline. The ore is treated with hydrochloric, nitric, and sulphuric acids and the solution evaporated until the sulphuric acid fumes; water is added to take up soluble sulphates. The lead sulphate with other insoluble matter is filtered from the solution; the lead sulphate is dissolved in ammonium acetate and the lead measured by titrating it with a standard solution of ammonium molybdate. Reagents. Sulphuric acid, dilute (1 : 1). Sulphuric acid, dilute (1 : 10). Ammonium acetate; saturated solution of NILiCoHsC^ in water. Solution of tannin. Dissolve 1 gm. of CnHioOg in 200 cc. of water. Standard solution of ammonium molybdate. Dissolve 4.3 gms. (NH4)6Mo 7 024+4H 2 in 300 cc. of water, add a few 176 METALLURGICAL ANALYSIS drops of ammonia, and dilute to 1 liter. One cubic centimeter is equivalent to about 0.005 gm. of lead. To standardize this solution, weigh 0.2 gm. of pure lead foil. Dissolve it in dilute nitric acid, add ammonia until the solution is alkaline, boil, acidify the solution with acetic acid, and titrate with the am- monium molybdate solution, using tannin solution on a porcelain plate as indicator. Run a blank, by titrating the same volume of solution con- taining all the reagents used in the standardization, to determine how much molybdate solution is required to give the yellow color to the tannin when no lead is present. This amount is to be deducted from all titrations. Pb in Ore. Weigh 0.5 gm. of ore (1 gm. if it contains less than 30 per cent lead), and transfer it to a 200-cc. Erlenmeyer flask. Add 10 cc. of hydrochloric acid and boil. Hydrochloric acid attacks galena, ferric oxide, etc. Continue boiling and add, at short intervals, 20 cc. of water, 10 cc. of nitric acid, and 10 cc. of dilute sulphuric acid (1 : 1). Nitric acid is added to attack those sulphides not dissolved by hydro- chloric acid. Boil over the open flame (see p. 169) until dense sulphuric acid fumes are evolved. Cool, add 25 cc. of cold water, heat to the boiling-point, and let it stand to dissolve ferric sulphate. Cool, filter, and wash the residue with dilute sulphuric acid (1 : 10), and then with water. Spread the filter paper against the inside of a beaker, (Fig. 52, p. 61), and wash off the pre- cipitate with hot water, followed by hot ammonium acetate solution, and add a sufficient amount of ammonium acetate to dissolve all the lead sulphate. One part of lead sulphate is soluble in 47 parts of ammonium ace- tate solution of specific gravity 1.036. PbS0 4 +2NH4C 2 H 3 2 =Pb(C 2 H 3 O 2 ) 2 -i-(NH4) 2 SO4. LEAD IN ORE 177 Heat to boiling and titrate with standard solution of ammo- nium molybdate until a drop of the solution titrated tested with a drop of tannin solution on a porcelain plate gives a yellow color. LEAD IN ORE FIRE METHOD * This method for the assay of lead, although much used, is in- accurate. It gives too low results with pure ores, and too high results with ores containing arsenic, antimony, bismuth, etc. Flux. Sodium bicarbonate, NaHCOs, 64 parts. Potassium carbonate, K^COs, 50 parts. Borax glass, Na2B4C>7, 25 parts. Flour, 25 parts. The reducing power of the flour should be tested, and if found to be below 3, the quantity added to the flux should be increased. Mix the reagents thoroughly by rolling on a rubber cloth. Pb in Ore. Weigh 10 gms. of ore and mix it in a crucible (see Fig. 84, page 225) with 20 gms. of flux. Cover with 10 gms. of flux, and if the ore is low in sulphur, put into the charge one tenpenny nail ; if it is high in sulphur, put in two tenpenny nails. Put the crucible into a muffle heated to a moderately low temperature and raise the heat to a light yellow and fuse for thirty minutes. 7PbS+4K 2 C0 3 = 4Pb+ K 2 S+3(K 2 S -PbS)+4C0 2 . PbS+Fe=Pb+FeS. 2PbO+C=Pb+C0 2 . When the fusion is complete, withdraw the crucible from the muffle, take out the nails with a pair of short tongs, taking care to shake off into the crucible any adhering globules of lead. Shake the crucible and tap it gently several times to * See Fire Assaying, page 224. 178 METALLURGICAL ANALYSIS concentrate the lead in the bottom, and pour the fusion into the mold. When cold, break the slag from the lead button and weigh the lead. If the lead button is hard or brittle, it is alloyed with other metals and the assay is not accurate. ZINC IN ORE Outline. The ore is treated with hydrochloric and nitric acids, then with potassium chlorate and a fresh portion of nitric acid, after which the solution is evaporated to dryness. The residue is treated with ammonia , ammonium chloride, bromine, and water; zinc and copper are taken into solution and are filtered from the residue, which contains the other metals and the insoluble part of the ore. The solution is then acidified with hydrochloric acid, the cop~er precipitated, and the zinc titrated with a standard solution of potassium ferrocyanide.* Reagents. Potassium chlorate, KClOa. Ammonium chloride, NILiCl. Bromine water; water saturated with Br. Standard solution of potassium ferrocyanide. Dissolve 21.63 gms. K4Fe(CN)e and 7 gms. Na2SOs+7H2O in water, and dilute the solution to 1 liter. One cubic centimeter is equiv- alent to about 0.005 gm. Zn. To standardize, dissolve 0.2 gm. of chemically pure zinc or freshly ignited chemically pure zinc oxide in 15 cc. of hydrochloric acid, add 7 gms. of ammonium chloride, dilute to 200 cc. with boiling water, and titrate, using uranium nitrate solution on a porcelain plate as indicator. Indicators: uranium nitrate solution; 1 gm. U02(NO3)2+6H2O dissolved in 10 cc. of water. Other indicators are: Ammonium molybdate solution, 1 gm. dissolved in 100 cc. of water; or a saturated solution of uranium acetate. * Sutton, "Volumetric Analysis," 356. Low, "Tech. Meth. of Ore Anal.," 210. ZINC IN ORE 179 Run a blank in the usual manner and make the necessary correction. Zn in Ore. Weigh 1 gm. of ore, transfer it to a 200-cc. Erlenmeyer flask, add 15 cc. of hydrochloric acid, and boil. Add 25 cc. of nitric acid and boil down to a volume of 10 cc. Then add 10 cc. of nitric acid and 5 gms. of potassium chlorate, a little at a time. Evaporate just to dryness. A high heat after the mass is dry will volatilize zinc chloride. Cool, add 10 gms. of ammonium chloride, 15 cc. of ammonia, 25 cc. of water, and 10 cc. of bromine water. Instead of adding ammonium chloride, ammonia, and bromine water, Demorest * precipitates Fe, Mn, Pb, and Cd by adding 0.5 gm. KOH and 7 gms. (NH 4 ) 2 C0 3 with 50 cc. H 2 0, filtering, dissolving the precipitate in HC1, reprecipitating in the same manner and filter- ing. Boil two minutes, filter, and wash well with a hot solution of ammonium chloride (10 gms. NH 4 Cl+2 drops NH 4 OH + 1000 cc. of water). Acidify the filtrate with hydrochloric acid, dilute to 150 cc., add 20 gms. of granulated lead; and boil to precipitate copper. Remove from the heat, dilute again to 150 cc. with water, heat to 70 C. and titrate immediately with a standard solution of potassium ferrocyanide. (See zinc in matte, p. 186.) Hydrogen sulphide may be used as the precipitant of copper instead of granulated lead. If no copper is present, this step may be omitted. The solution, when titrated, should be at about 70 C., and there should be an excess of about 3 cc. of hydrochloric acid in the whole volume of 150 cc. * J. Ind. and Eng. Chem., 5, 302. 180 METALLURGICAL ANALYSIS ARSENIC SKINNER AND HAWLEY'S METHOD Reagents. Hydrogen sulphide-, H2S from a generator. Sodium sulphite, Na2SOs. Distilling solution: Mix 500 cc. of water with 1200 cc. of hydrochloric acid (sp.gr. 1.2), add the mixture gradually to 400 gms. of pure zinc, and heat to dissolve the zinc. Evaporate the solution to 1100 cc. and add to it a solution of 300 gms. of pure cupric chloride crystals in 1 liter of hydrochloric acid (sp.gr., 1.2). Sodium bicarbonate, NaHCOs. Starch solution. (See p. 111). Standard iodine solution. Weigh 16.932 gms. of pure iodine. Transfer it to a liter flask, add 30 gms. of potassium iodide, add water, and when the iodine is dissolved, dilute the solution to 1 liter. One cubic centimeter should be equivalent to about 0.005 gm. of arsenic. The solution may be standardized by weighing accurately about 0.2 gm. As 2 3 , dissolving it in dilute hydrochloric acid, neutralizing with ammonia, just acidifying the solution with hydrochloric acid, and adding sodium bicarbonate and starch solution, and titrating with the iodine solution. As in Ores and Furnace Products. Weigh 0.5 gm. of the sample (if the material is low in arsenic, as much as 5 gms. may be used) and transfer it to a small beaker. Add 5 cc. of nitric acid and a little potassium chlorate. When vigorous action has ceased, add 8 cc. of hydrochloric acid and evaporate the solution to dry- ness at about 100 C. Add 5 cc. of hydrochloric acid and 25 cc. of water, boil, and filter. Dilute the filtrate to 200 cc. with boiling water. Add sodium sulphite, a little at a time, until the solution becomes colorless. As 2 O s +3H 2 0+2Na 2 S0 3 =2As(OH) 3 +2Na 2 SC>4. Na 2 S0 3 +2HCl =2NaCl+H 2 0+S0 2 . ARSENIC 181 Boil off the excess of SOo, add 15 cc. of hydrochloric acid, and pass a current of hydrogen sulphide through the solution until the sulphides are completely precipitated. 2As(OH) 3 +3H 2 S =6H 2 O+As 2 S 3 . If there are present only small quantities of other hydrogen sul- phide metals, the precipitation of the arsenic is hastened by adding, to the sample 0.1 gm. of pure copper. Filter and wash the sulphide. Place the pre- cipitate in a flask fitted with a thermometer and connected with a condenser (8-in. Allihn, Fig. 79, is satisfactory), add 50 cc. of distilling solution, and distil carefully until the thermometer reads 115 C., letting the distillate run into a flask which con- tains dilute sulphuric acid (1 : 20).* Remove from the heat and add 25 cc. of hydrochloric acid, and distil again until the thermometer reads 115 C. As 2 S 3 +3CuCl 2 =2AsCl 3 +3CuS. 2AsCl 3 +6H 2 O = 2As(OH) 3 +6HCl FlG - 79. Al- lihn Con- Arsenious trichloride is volatile when boiled in a con- denser, cent rated solution of hydrochloric acid. Pour the distillate into a No. 3 beaker. Add ammonia until the solution is alkaline; then just acidify it with dilute sul- phuric acid. Cool, add about 10 gins, of sodium bicarbonate, 4 drops of a 10 per cent solution of KI, and a little starch solu- tion, and titrate with standard iodine solution. 2As(OH) 3 +4I+4NaHC0 3 =As 2 6 +4NaI+5H 2 0+4C0 2 . Sodium bicarbonate must be used, since the hydroxyl ion resulting from the use of caustic or neutral alkali reacts with iodine. * Price and Meade, " Tech. Anal, of Brass," p. 257. 182 METALLURGICAL ANALYSIS ARSENIC IN INSOLUBLE ORES AND FURNACE PRODUCTS.* Reagents. Sodium carbonate, Na^COs, and potassium nitrate, KNOs, mixed in equal parts. Acetic add, C 2 H 4 2 , (sp.gr. 1.04). Solution of phenolphthalein. (See p. 84.) Solution of sodium hydroxide. Dissolve 10 gms. NaOH in 100 cc. of water. Saturated solution of silver nitrate (AgNOs) in water. Granulated lead, Pb. As in Ore. Weigh 0.5 gm. of the sample, mix it with 3 gms. of the sodium carbonate and potassium nitrate flux. Transfer the mixture to a porcelain crucible, and add as a cover 2 gms. of the same fusion mixture. Gradually raise the temperature and fuse for a few minutes. As+3KN0 3 =K 3 As0 4 +2N0 2 +NO. Cool, treat the fusion with hot water, and filter. Strongly acidify the filtrate which contains the arsenic, with acetic acid. Boil to expel C02. Cool, add a few drops of phenolphthalein solution, and make alkaline with sodium hydroxide solution. Acidify with acetic acid, add a slight excess of silver nitrate solu- tion and stir vigorously. K 3 As0 4 +3AgNO 3 =3KN0 3 -fAg 3 As0 4 . Let the precipitate settle away from direct sunlight. Filter, and wash by decantation with cold water. Transfer the pre- cipitate to the filter and wash it well. Place the filter with pre- cipitate in a scorifier, dry, add granulated lead and borax, and make a scorification assay for silver. (See p. 234.) The weight * Bennett, Jour. Amer. Chem. Soc., 21, 431. ARSENIC IN ORE 183 of silver, multiplied by the factor 0.2316, will give the weight of arsenic. Wt. Ag. : Wt. As. = 3(107.88) : 74.96. If the ore contains soluble chlorides, they must be washed out before making the fusion. ARSENIC IN ORE BY TITRATING WITH AMMO- NIUM THIOCYANATE After obtaining the precipitate of Ag3AsO4, according to the method above, instead of determining the silver by a scorification assay, it may be determined as follows: Dissolve the precipitate of AgsAsOd in dilute nitric acid. This leaves silver chloride, if present, undissolved. Ag 3 As0 4 +3HN0 3 = 3AgN0 3 +H 3 As0 4 . Filter, add 5 cc. of a saturated solution of ammonium ferric sulphate, as indicator, and titrate with a standard solution of ammonium thiocyanate until brown ferric thiocyanate remains after shaking. AgN0 3 +NH 4 CNS =AgCNS+NH 4 NO 3 . When the silver thiocyanate has all been precipitated, the ammonium thiocyanate then combines with the ammonium ferric sulphate to form brown ferric thiocyanate. Fe 2 (S0 4 ) 3 +6NH 4 CNS=2Fe(CNS) 3 -f3(NH 4 ) 2 S0 4 . The ammonium thiocyanate solution is standardized against silver nitrate. 184 METALLURGICAL ANALYSIS ANALYSIS OF COPPER MATTE COPPER IN MATTE ELECTROLYTIC METHOD Weigh 1 gm. of matte and transfer it to a No. 4 beaker. Moisten it with a few drops of water, add 8 cc. of nitric acid and 1 cc. of sulphuric acid. Evaporate the solution to dryness. Dissolve the residue in 8 cc. of nitric acid. Dilute the solution, filter, and electrolyze. (See Copper in Ore, p. 173.) COPPER IN MATTE POTASSIUM IODIDE METHOD Weigh 0.5 gm. of matte, transfer it to a 150-cc. Erlenmeyer flask, add 5 cc. of nitric acid, and heat until the mass is pasty and red fumes have ceased to come off. Remove from the heat, add 15 cc. of water, and boil five minutes. Add ammonia to make the solution slightly alkaline, boil out the excess of ammonia, remove from the heat, make strongly acid with acetic acid, and cool. When cold, add 3 gms. of potassium iodide, shake, and titrate at once with standard sodium thiosulphate solution until the yellow color begins to fade. Add 20 cc. of starch solution and continue the titration until the bluish green color disappears and does not return for ten seconds. For reagents and notes see Copper in Ore, p. 171. Owing to impurities in the matte, the end-point is not permanent and a little experience is required to enable the operator to detect the correct end. COPPER IN MATTE 185 COPPER IN MATTE POTASSIUM CYANIDE METHOD Weigh 0.5 gm. of matte, transfer it to a small Erlenmeyer flask, add 5 cc. of nitric acid, and proceed according to the potas- sium cyanide method for copper in ore (see p. 168) ; or the some- what more rapid method given below may be used. Weigh 0.5 gm. of the matte and transfer it to a small beaker. Add 15 cc. of nitric acid and boil ten minutes. Remove from the heat, add 35 cc. of cold water, and make the solution strongly alkaline with ammonia to precipitate the iron. Filter rapidly, wash the precipitate back into the original beaker with as little hot water as possible, and redissolve in as small quantity as possible of dilute sulphuric acid (1 : 3). Reprecipitate the iron with ammonia and filter, letting this filtrate run into the first filtrate. Wash well with hot water, cool, and titrate with a standard solution of potassium cyanide. (See p. 168.) IRON IN MATTE POTASSIUM BICHROMATE METHOD Weigh 0.5 gm. of matte, transfer it to a small beaker, add 15 cc. of nitric acid, dissolve at a moderate heat, and evaporate the solution to dryness. When free from nitrous fumes, cool, add 25 cc. of hydrochloric acid, cover with a watch glass, and heat until the solution is clear and globules of sulphur float on the surface. Add 25 cc. of hot water and about 20 gms. of granulated lead, and boil until the copper is precipitated on the lead and the ferric chloride is reduced to ferrous chloride, leaving the solution clear. Remove from the heat and wash all particles of test lead to the bottom of the beaker. Decant the solution into a beaker, wash the lead with hot water by decantation, cool the solution to the temperature of the room, and titrate with a standard solution of potassium dichromate. (See Iron in Ores, p. 62.) 186 METALLURGICAL ANALYSIS ZINC IN MATTE Reagents. See Zinc in Ore (p. 178). Weigh 0.5 gm. of matte, transfer it to a small beaker, add 20 cc. of chlorate solution (saturated solution of KClOs in HNOs, sp.gr. 1.42). Heat to dissolve, and evaporate the solution at a moderate heat to dryness. Add about 10 gms. of ammonium chloride, 25 cc. of ammonia, and 25 cc. of boiling water. Cover, and boil two minutes. Filter and wash well with a hot solu- tion of ammonium chloride (10 gms. NH4C1+2 drops of NELiOH + 1000 cc. of water). Acidify the filtrate with hydrochloric acid, dilute the solution to 150 cc., add 20 gms. of granulated lead, and boil until the copper is all precipitated on the lead and the solution is clear. Remove from the heat and dilute again to 150 cc. with cold water and titrate immediately with a standard solution of potassium ferrocyanide, using a solution of uranium nitrate or acetate as indicator. (See p. 178.) White titrating, if a brownish or red precipitate forms, it indicates that the solution was not boiled long enough with the granulated lead to precipitate all the copper, and the determination must be discarded. LEAD IN MATTE Reagents. See Reagents for Lead in Ore (p. 175). Weigh 0.5 gm. of matte and transfer it to a 250-cc. Erlenmeyer flask, add 10 cc. of hydrochloric acid, and heat to boiling. Add 5 cc. of nitric acid and 7 cc. of sulphuric acid and boil over the open flame of the Bunsen burner (see p. 169) until dense white fumes of sulphuric acid are given off freely and the volume is reduced to only a few cubic centimeters. It is essential that all the nitric acid be expelled. Cool, add 50 cc. of cold water, heat, and let the solution stand at the boiling-point five minutes. Filter, and wash well with hot water. Spread out the filter paper with its contents SULPHUR IN MATTE 187 on the inside of a beaker and wash off the precipitate with a jet of hot water, using about 25 cc.; discard the filter paper. Pour 20 cc. of a saturated solution of ammonium acetate into the flask in which the precipitation was made, shake to dissolve any adhering lead sulphate, and pour the solution into the beaker containing the main precipitate of lead sulphate. Wash out the flask,, using about 25 cc. of hot water, and add it to the lead sulphate solution. Heat the solution to boiling and titrate it hot with the standard solution of ammonium molybdate, using tannin solution as an indicator, (See p. 176.) SULPHUR IN MATTE Weigh 0.5 gm. of the matte and transfer it to a porcelain casserole. Sprinkle 1 gm. of potassium chlorate over the sample, add 15 cc. of chlorate solution (saturated solution of KClOa in strong nitric acid), cover, and keep it cool until the sulphur is oxidized. Heat gradually and evaporate slowly to dryness. When thoroughly dry, cool, add 25 cc. of water and 15 cc. hydrochloric acid and boil until the solution is clear. Filter hot and wash with hot water. Add 5 cc. of a saturated solution of barium chloride and heat to the boiling-point. If the matte contains much lead, boil at least five minutes to dissolve lead chloride, and filter hot to prevent the contamination of barium sulphate with lead chloride. Remove from the heat and let the barium sulphate settle. Filter, wash with hot water, burn in an annealing cup in a muffle, or in a platinum crucible and weigh. The factor for S in BaSCU is 0.13738. MANGANESE IN MATTE Weigh 0.5 gm. of matte and transfer it to a small beaker. Add 35 cc. of water, boil, add 15 cc. of hydrochloric acid, and boil ten minutes. Add 5 cc. of nitric acid and continue boiling 188 METALLURGICAL ANALYSIS ten minutes. Remove the beaker from the heat, add an emulsion of zinc oxide until the solution when stirred is almost white. Dilute the solution to 150 cc. with hot water, heat to the boiling- point, and titrate hot, according to the Volhard method, with a standard solution of potassium permanganate. (See p. 88.) GOLD AND SILVER IN MATTE Weigh 0.1 assay-ton. Place it in a scorifier, add 70 gms. of granulated lead, a little borax glass, and a little silica. Place the scorifier in a hot muffle. After melting, reduce the tem- perature and complete the scorification at a moderate tem- perature. Cupel the lead button, weigh the bead of silver com- bined with gold, part in the usual way with nitric acid, and weigh the gold. The difference between the weight of gold and the combined weight of gold and silver will give the weight of silver. (See Fire Assaying, p. 224.) ANALYSIS OF CHILLED BLAST FURNACE SLAGS Sampling. Granulate the slag by dipping a sample from the molten slag with an iron ladle and pouring it into a pail of water. Then take out the granulated slag with the ladle and place it near the heat to dry. When the slag is dry, crush it and prepare the sample for analysis in the usual way. (See p. 8.) SILICA IN SLAG Weigh 0.5 gm. of slag and transfer it to a casserole. Moisten it with a few drops (6 or 7) of water. Stir with a glass rod, and while stirring add slowly about 4 cc. of hydrochloric acid. Con- tinue stirring until the slag gelatinizes. The slag is treated first with hydrochloric acid alone to insure the escape of sulphur as ELS. If nitric acid were added at the same time, LIME IN SLAG 189 the EUS would be oxidized and would combine with barium to form barium sulphate, which would come down with the SiO-2. Add about 1 cc. of nitric acid and stir, spreading the gelatinous precipitate smoothly on the inside of the casserole. This permits rapid dehydration without loss. Nitric acid is added to oxidize the lead and copper sulphides, which are not completely decomposed by hydrochloric- acid. The lead will be dissolved by the hot acids and pass through the filter. Take the cover off the casserole and heat until the acid has all evaporated. Do not prolong the heating at too high a temperature, since there is danger of recombining some of the silica with alumina, giving a gray-colored residue after ignition, and a high result. Cool the casserole, add about 15 cc. of hydrochloric acid, and boil. Dilute with a little hot water and filter hot. Wash the precipitate with hot water until it is free from chlorides. The residue may be black, owing to the presence of carbon. Place the filter and residue in a porcelain crucible, burn fifteen minutes in a hot muffle, cool, and weigh. By this method the result is insoluble silicious residue, but it is usually reported as silica, unless a fusion silica is especially asked for. In the latter case, follow the method for silica in ore, page 71, or purify the insoluble silicious residue with hydrofluoric and sulphuric acids. LIME IN SLAG Add to the filtrate from the silica, which should measure about 150 cc., ammonia in slight excess. Add just enough hot saturated solution of oxalic acid to dissolve the iron precipitate. Add ammonia again until a slight precipitate of iron is obtained, and then add oxalic acid to dissolve the iron. There should now be a white precipitate of calcium oxalate, and the solution should be slightly acid, and should have a clear greenish-yellow color. 190 METALLURGICAL ANALYSIS Boil, and let the precipitate settle ten minutes or more. Filter, wash the precipitate once by decantation with hot water, and then wash it on the filter until all the oxalic acid is removed. Test the wash water for oxalic acid by collecting a few cubic centi- meters as it runs from the funnel, heating it and adding a little sulphuric acid, and a drop of potassium permanganate solution. If the color of the permanganate fades, oxalic acid is present and the washing must be continued and the test repeated until no oxalic acid remains. Spread the filter paper, with the precipitate, on the inside of a beaker. Wash the precipitate from the paper with 200 cc. of hot water, using a strong jet from a wash bottle. Add 40 cc. of dilute sulphuric acid (1:1). Stir to dissolve the pre- cipitate and titrate the hot solution with standard potassium permanganate solution. For reactions and method of calculating the result, see Lime in Lime- stone, page 163. IRON IN SLAG Weigh 0.5 gm. of slag, transfer it to a small beaker, add 30 cc. of water, cover, and boil. While boiling, add 20 cc. of hydrochloric acid and continue to boil until the solution is clear. Add 2 or 3 drops of stannous chloride solution to the hot solu- tion and stir. Cool, and when cold add 20 cc. of mercuric chloride solution and titrate with standard potassium dichromate solution. (See Iron in Ore, p. 62.) MAGNESIA IN SLAG Weigh 0.5 gm. of slag and treat it according to the method for the determination of silica. To the filtrate from the silica add an excess of ammonia, and ammonium chloride. Add 10 cc. of bromine water and 0.03 gm. of ammonium persulphate for every 0.01 gm. of manganese in the solution. Boil to pre- cipitate iron, alumina, and manganese. Filter, redissolve the MANGANESE IN SLAG 191 precipitate in hydrochloric acid, and add ammonia, bromine water, and ammonium persulphate, as before. Boil and filter. Combine the nitrates and add ammonium oxalate to precipitate calcium. Filter, and wash the precipitate well. To the filtrate add a solution of sodium phosphate, or microcosmic salt, and proceed according to the method for the determination of magnesia in limestone. (See p. 165.) MANGANESE IN SLAG Weigh 0.5 gm. of the slag and transfer it to a small beaker. Add 30 cc. of water and 20 cc. of hydrochloric acid. Boil until the solution is clear. Add 5 cc. of nitric acid and boil five minutes. Remove from the heat and add very slowly, while stirring vig- orously, an emulsion of zinc oxide, and proceed according to Volhard's method for manganese in matte. (See p. 187.) ALUMINA IN SLAG Weigh 0.5 gm. of slag and treat it according to the method for the determination of silica. To the filtrate from the silica add ammonia to distinct alkaline reaction. Boil fifteen minutes and filter to remove the small amount of copper present. Spread the filter paper, with the precipitate, against the inside of a beaker, wash off the precipitate with a jet of hot water, dissolve in hydrochloric acid, dilute the solution to 400 cc., and proceed according to the phosphate method for alumina. (See p. 87.) ZINC IN SLAG Weigh 0.5 gm. of slag (if low in zinc, weigh 1 gm.), transfer it to a casserole, add 3 cc. of water, 5 cc. of hydrochloric acid, and 2 cc. of nitric acid. Stir, and when completely gelatinized, add 4 gms. of ammonium chloride and stir. Evaporate just to dryness. Heating at a high temperature when dry will volatilize zinc chloride. 192 METALLURGICAL ANALYSIS Remove from the heat and add 30 cc. of water. Boil, filter, and wash well with boiling water. Add to the filtrate 0.03 gm. of ammonium persulphate and 10 cc. of bromine water for every 0.01 gm. of manganese in the solution. Then add a slight excess of ammonia. Boil a few minutes, filter, and wash with a solution of ammonium chloride (100 gms. NH 4 C1+50 cc. NH 4 OH+1000 cc. H20). Redissolve the precipitate in dilute hydrochloric acid, add ammonium persulphate, bromine water, and ammonia, as before. Boil and filter. Combine the two filtrates, neutralize with hydrochloric acid, and add 5 cc. in excess. Add 2 gms. of granulated lead and boil fifteen minutes. Add 10 cc. of hydrochloric acid and titrate at a temperature of 60 C. with a standard solution of potassium ferrocyanide. (See the method for zinc in ore, p. 178.) LEAD IN SLAG Weigh 5 gms. of slag, transfer it to a casserole, add 10 cc. of water, stir and add 10 cc. of hydrochloric acid, and continue stirring until the slag is gelatinized. Add 5 cc. of nitric acid. Slowly increase the heat, stirring to break up lumps, and gradually evaporate the mass to dryness. When thoroughly dehydrated continue the heat a few minutes until the mass turns dark brown. Cool, add 20 cc. of water and 15 cc. of hydrochloric acid. Boil at least ten minutes. Filter while hot and let the filtrate run into a 500-cc. beaker. Dilute the filtrate to 400 cc., add 15 gms. of ammonium chloride, and add ammonia very slowly, stirring, until the solution becomes dark cherry red, without the precipitation of iron. Pass hydrogen sulphide through the solution for half an hour. Filter, spread the filter paper, with the precipitate, against the inside of a beaker, and wash off the precipitate with as little hot water as possible. Drop 10 cc. of nitric acid on the paper and wash off, with water, all traces of the precipitate. Remove the paper, add to the solution 5 cc, of hydrochloric acid and 10 cc, of sulphuric acid. COPPER IN SLAG 193 Boil the solution until dense white fumes of sulphuric acid are evolved. Cool, dilute with 40 cc. of cold water, boil five minutes, filter the lead sulphate, and wash it with hot water. Wash the lead sulphate back into the beaker with 40 cc. of hot water. Add 15 cc. of a saturated solution of ammonium acetate. Heat the solution to boiling, and titrate it while hot with standard solution of ammonium molybdate. (See the method for lead in ore, p. 175.) COPPER IN SLAG POTASSIUM IODIDE METHOD To the filtrate from the precipitate of lead sulphate (see the method above), add 15 cc. of a saturated solution of sodium thiosulphate and boil until the sulphides are precipitated and the solution is clear. Filter, place the filter paper, with the precipitate, in a porcelain annealing cup, and burn carefully at a very low heat until there is no longer a. flame of burning sulphur. Transfer the mass to a flask, and add a little potassium chlorate and 5 cc. of nitric acid. Boil until the solution is pasty. Add 20 cc. of water and boil out all traces of nitrous fumes. Make the solution slightly alkaline with ammonia, boil out the excess of ammonia, remove from the heat, and acidify with acetic acid. When cold, add 3 gms. of potassium iodide and titrate with a standard solution of sodium thiosulphate. (See the iodide method for copper in matte, p. 184.) After the copper sulphide has been filtered from the solution and dissolved, according to the method above, instead of follow- ing the iodide method, the copper may be measured either by electrolysis, or by the potassium cyanide method, as described for the determination of copper in matte. (See p. 185.) The copper may also be determined according to the following colori- metric method. 194 METALLURGICAL ANALYSIS COPPER IN SLAG COLORIMETRIC METHOD Weigh 3 gms. of the sample, moisten it with water, add 10 cc. of nitric acid and 1 cc. of hydrochloric acid, and heat a few minutes on a steam bath. Dilute with 100 cc. of water. Add a slight excess of dilute ammonia (1:1) and filter the solution into a colorimetric tube or bottle and wash the precipitate free from copper. For a standard, weigh 3 gms. of a sample in which the copper has been determined electrolytically and treat it exactly as described above for the unknown sample. Filter the solution into a similar tube or bottle, and match the colors in a colorim- eter, or dilute in Eggertz tubes. For colorimetric determinations of copper, it is convenient to pre- pare a set of standards, increasing in strength by 0.002 gm. of copper from the lowest to the highest required for low-grade materials. The unknown solution is placed in a bottle similar to those containing the standards, and diluted to the same volume, when its place in the series is easily found and its content in copper determined directly. (See P. 42.) BARYTA IN SLAG Weigh 1 gm. of slag, transfer it to a casserole, add potassium sulphate, moisten the contents of the casserole with water, and add nitric and hydrochloric acids. Heat to dissolve the slag, and evaporate the solution to dryness. Dissolve the residue in dilute hydrochloric acid, filter, wash, ignite, and weigh SiO2+BaSO4. Deduct the SiC>2, which has already been deter- mined in the slag, and multiply the remainder, which represents BaS0 4 , by the factor for BaO, 0.65699, ARSENIC IN SLAG 195 ARSENIC IN SLAG Treat 5 to 10 gms. of the slag with 10 cc. of nitric acid, 2 cc. of sulphuric acid, and, if the slag has not been chilled, add 10 cc. of hydrofluoric acid. Evaporate the solution until sulphuric acid fumes are evolved. Cool, add 10 cc. of hydrochloric acid and 25 cc. of water, and boil. Filter, wash, and dilute the fil- trate to 500 cc. Add ammonia until the solution is almost neutral. Reduce with sodium sulphite and proceed according to the method for arsenic in ores, etc., on page 180. ANALYSIS OF REVERBERATORY SLAG SiO2 in Slag. Weigh 0.5 grn. of the slag and transfer it to a platinum crucible or dish. Add about 6 gms. of sodium carbonate, mix, cover with 1 or 2 gms. of sodium carbonate and fuse. Raise the temperature gradually and keep the crucible at a bright red heat about fifteen minutes. Cool and dissolve the fusion in a casserole in hydrochloric acid and water. If the color of the fusion indicates the presence of much manganese, the fusion should be dissolved in water and the platinum removed from the solution before the addition of hydrochloric acid. The platinum would be attacked by chlorine liberated from the hydrochloric acid by the manganese. Evaporate the solution to dryness to dehydrate the silica. (See p. 70.) Cool, add 10 cc. of hydrochloric acid and 30 cc. of water to the residue, and boil. Filter, wash, ignite, and weigh Si02. FeO in Slag. To the filtrate from the silica, add a slight excess of ammonia. Boil, filter, and wash. Dissolve the pre- cipitate in dilute hydrochloric acid, reduce the iron and titrate it according to the method for iron described on page 62. The factor for converting Fe to FeO is 1.2865. CaO in Slag. To the filtrate from the hydrates of iron 196 METALLURGICAL ANALYSIS and aluminum obtained in the method for FeO, add ammonium oxalate and a little ammonia. Boil, let the precipitate settle, filter, and wash. Dissolve the precipitate of calcium oxalate in sulphuric acid and titrate the oxalic acid while the solution is hot with standard solution of potassium permanganate. (See p. 163.) Gold and Silver in Slag. Gold and silver are determined by crucible assay. Weigh 1 assay-ton, transfer it to a fire-clay crucible, and mix it with the following charge: gms. Litharge 80 Sodium bicarbonate 50 Flour 3J (or other reducing agent to yield an 18-gm. button). Mix thoroughly and cover with borax. Fuse in a muffle and complete the assay according to the method given on page 229. ANALYSIS OF BRIQUETTES AND OTHER INSOLUBLE COPPER-BEARING PRODUCTS SiO2, FeO, and CaO. Weigh 0.5 gm. of the sampie, and transfer it to a casserole. Add 6 cc. of hydrochloric acid and 3 cc. of nitric acid. Cover and slowly heat to boiling. Dilute the solution with boiling water, filter into a casserole, and wash. Ignite the filter in an annealing cup and place the filtrate on the heat to evaporate. Mix with the ignited residue in the annealing cup 8 gms. of sodium carbonate and transfer the mixture to a platinum crucible. Cover with 2 gms. of sodium carbonate and pro- ceed with the fusion according to the method above for the analysis of slag. When the filtrate in the casserole has been evaporated to dryness, dissolve the fusion from the crucible and add it to the ANALYSIS OF COPPER BULLION 197 casserole. Evaporate the contents of the casserole to dryness, and proceed with the determination of Si02, FeO, and CaO according to the method described above for the analysis of slag. GOLD AND SILVER IN COPPER-BEARING CONCEN- TRATES Mix 1 assay-ton of the concentrates in a fire-clay crucible with 150 gms. of litharge, 35 gms. of sodium bicarbonate, 10 gms. of silica, and 40 gms. of potassium nitrate. Cover with salt to a depth of half an inch, fuse, and complete the assay according to the method given on page 229. ANALYSIS OF COPPER BULLION Sampling. At the furnace, the metal is sampled in the molten condition while it is being poured. The sample is taken at regular intervals; the first is taken thirty minutes after the pour- ing begins, and the others at intervals of an hour, by batting the stream of molten metal with a wooden paddle, driving from 150 to 200 gms. of the molten metal into a pail of water, where it solidifies in the form of shot. The samples are collected, mixed, and screened through a 4-mesh screen, and then through a 10-mesh screen; that remaining on the latter is reserved for the sample. It is then halved with a riffle and one-half of the sample is sent to the laboratory for analysis.* When bullion cools, the impurities are not evenly distributed throughout the mass, but, according to Keller, f are segregated, either in those parts which cool first, if the impurities are high, or in those parts which cool last if the impurities are low. Converter copper, having more than 97 per cent of copper, usually has its impurities, including gold and silver, concentrated * Wraith, Trans. Amer. Inst. Min. Eng., 41, p. 318. t Trans. Amer. Inst. Min. Eng., 27, p. 106; 42, p. 905. 198 METALLURGICAL ANALYSIS in that part which cools last; while black copper, from the blast furnace, usually has its impurities concentrated in those parts that cool first. The sampling of plates and bars, therefore, requires great care. This is best done by taking the samples with a drilling-template. For sampling anodes, 36.75 ins. long, 28 ins. wide, and about 2 ins. thick, Kellar uses a 99-hole template (Fig. 80) . Every fourth anode in the lot is sampled, one sample being taken from each. The first anode is care- fully swept, the template laid upon it, and drilled through with a J-in. drill at the first hole in the tem- plate and all the drillings saved. The succeeding anodes are treated in the same way, the holes of the template being used in consecutive order, one hole to the anode. The drillings from the entire lot are then ground to pass through a 16- The sample is then mixed and quartered. The 1 Ib. is screened over a 40-mesh screen. -2ff.3}/ 4 in. Holes ^ o j ,1; FIG. 80. Template for Sampling Anodes. mesh screen. final sample of about The oversize and undersize are then weighed to determine the ratio of coarse to fine, the same ratio being maintained in the assay-ton made up for analysis. MOISTURE IN PIG COPPER When copper is cast into pigs in a casting machine, and left to cool under water, the water is taken into the pores of the metal. The pores are so small that the ordinary temperature at which moisture is determined (100 C. to 110 C.) is not suf- ficient to overcome the surface tension and expel it. Therefore, the sample of copper in which moisture is to be determined should COPPER IN COPPER BULLION 199 be weighed and heated to about 200 C., until the steam is observed to escape from the metal, and then cooled in a desiccator and weighed again. The loss in weight represents the moisture. COPPER IN COPPER BULLION * Weigh accurately about 10 gms* of the bullion and transfer it to a beaker. Add a drop or two of hydrochloric acid to pre- cipitate silver. Add 50 cc. of water and 50 cc. of nitric acid. When in solution, let the silver chloride settle, filter into a care- fully weighed flask, and dilute with water to about 300 cc. Weigh the flask. This requires a special balance. Take out about 25 cc. of the solution and reweigh the flask. Dilute the portion taken out and precipitate the copper from it by electrolysis. (See electrolytic method for copper, p. 173.) SILVER IN COPPER BULLION Weigh one assay-ton (the quantity depends upon the content of silver). Divide it into ten nearly equal parts and transfer each part to a beaker. Dissolve in nitric acid, dilute, and add a sufficient amount of a solution of sodium chloride to precip- itate the silver. Let the silver chloride settle over night, filter, place the filter papers with their contents in ten scorifiers, sprinkle with litharge, and burn the papers, Add granulated lead and scorify. (See assay of silver ores, p. 234.) Cupel, assemble the beads, and weigh. Part with nitric acid and weigh. The difference in the two weights represents the silver. * This method for copper and the following one for silver were com- municated to the author by D. W. Buckly, Butte, Mont. 200 METALLURGICAL ANALYSIS SILVER IN COPPER BULLION WASHOE METHOD Weigh a one assay-ton sample of the drillings and transfer it to a beaker. Add 160 cc. of cold water and 110 cc. of nitric acid (sp.gr. 1.42). Cover; when in solution, wash off the cover, add 100 cc. of cold water and 10 cc. of sodium chloride solution (2 gms. NaCl in 250 cc. of water). If the bullion carries more than 100 ounces of silver per ton, add more sodium chloride solution. Stir, and let the precipitate settle twelve hours. Filter and wash. Wipe out the beaker with pieces of filter paper and add these to the filter containing the silver chloride. Place the filter, with the precipitate of silver chloride, on a scorifier, add 3 gms. of litharge, and burn off the filter in a muffle, at a very low temperature. When the paper is burnt, add 35 gms. of granulated lead and a little borax glass, and scorify at a low heat. Cupel and weigh. Crush the top of the cupel containing lead oxide on a bucking- board, and mix it in a crucible with Gms. Sodium carbonate 35 Borax glass . 60 Litharge 30 Calcium fluoride 1 Flour 5 (or other reducing agent to yield a 15-gm. button). Cover with borax glass, fuse at a high temperature, and, after separating the lead button from the slag, cupel and weigh the silver bead, and add, as a correction, to the silver already found. (See Fire Assaying, p. 224.) GOLD IN COPPER BULLION 201 GOLD IN COPPER BULLION Weigh 10 portions of drillings, each 1/20 of an assay-ton, place each portion in a cupel, 38 mm. in diameter and 28 mm. in height. Fill the cupel with test lead, place it in a very hot muffle to melt the lead, reduce the heat as quickly as possible, and finish the cupellation at a moderate temperature. Assemble the beads, part, and weigh. The weight, multiplied by 2, will give the number of ounces of gold per ton of bullion. SILVER AND GOLD IN COPPER BULLION * Reagents. Solution of mercuric nitrate. Dissolve 40 gms. Hg(NOs)2 in 1 liter of water. Solution of sodium chloride. Dissolve 19 gms. NaCl in 1 liter of water (1 cc. will precipitate about 0.35 gm. of silver). Au and Ag in Copper-bullion. Weigh one assay-ton of the drillings which have been ground and divided into coarse and fine with a 40-mesh sieve, the assay-ton being made up of the coarse and fine in the ratio that exists in the sample as a whole. Transfer it to an 800-cc. Jena beaker. Add 30 cc. of water and 10 cc. of the mercuric nitrate solution ( = 0.25 gm. Hg). For comparatively pure copper the amount of mercuric nitrate may be reduced; but copper high in sulphur will require more than 10 cc. of the mercuric nitrate solution. Shake the beaker until the copper is amalgamated with mercury. Add 100 cc. of strong sulphuric acid, cover the beaker, and place it on a hot plate. The solution appears to boil, owing to the reduction of sulphuric acid and the evolution of sulphur dioxide gas. This continues about an hour. When this reaction is complete, the liquid is dark green in color, and finally changes to a light grayish blue. At this point, * Edward Keller, Trans. Amer. Inst. Min. Eng., Vol. 46, Bull. 80, 2101. 202 METALLURGICAL ANALYSIS remove the beaker and add 450 cc. of water and a sufficient amount of sodium chloride solution to precipitate the silver and the mercury (30 cc. will be sufficient for 100 mgms. of silver and 0.25 gm. of mercury. Heat the solution to the boiling-point to dissolve copper sulphate and to coagulate the silver chloride. Remove the beaker from the heat and add to its contents 150 cc. of water. Let the precipitate settle over night, if convenient, and filter. Place the filter with the precipitate in a scorifier, sprinkle with litharge, and burn the paper. Add granulated lead and scorify. Cupel and weigh the combined gold and silver. Part, and weigh the gold. (See Fire Assaying, p. 224.) COPPER, ARSENIC, AND ANTIMONY IN SILVER BULLION Outline. The bullion is treated with nitric acid and the insoluble residue (Au, Sn, part of the Sb, a little Pb, etc.) filtered from the solution. The antimony is extracted from the residue with tartaric acid and added to the first filtrate after silver and lead have been removed from it. The copper, arsenic, and antimony are then precipitated with hydrogen sulphide. The arsenic and antimony sulphides are dissolved in a solution of potassium hydroxide / the copper sulphide fil- tered from the solution, and the copper determined by elec- trolysis. From the solution of arsenic and antimony sulphides, the arsenic is precipitated and filtered as magnesium ammonium arsenate. It is burnt and weighed. The antimony is measured in the filtrate by adding potassium iodide and titrating with standard solution of sodium thiosulphate.* Cu in Bullion. Weigh 10 gms. of the bullion and dissolve it in 50 cc. of dilute nitric acid (1 : 4), free from chlorine. Evap- orate the solution to 25 cc. and add 25 cc. of hot water. Boil, * Method communicated to the author by Oliver C. Martin, Denver, Colo. COPPER, ARSENIC, ANTIMONY, IN SILVER BULLION 203 filter, and wash by decantation. Reserve this as Filtrate No. 1. Treat the residue in the original beaker with 10 cc. of water, 2 cc. of hydrochloric acid, and 1 cc. of nitric acid. When in solution, filter, and evaporate the filtrate to dryness. Do not heat to a high temperature when dry, since that treatment would form insoluble lead antimonate. Dissolve the residue in a solution of tartaric acid (1 gm. in 10 cc. of water) and reserve as Solution No. 2. To Filtrate No. 1 add a sufficient quantity of hydrochloric acid to precipitate the silver present. Then add the calculated quantity of sulphuric acid to precipitate the lead present. Add immediately 50 cc. of alcohol and stir vigorously. Lead sulphate is insoluble in alcohol. Let the precipitate settle, filter, by suction, wash the pre- cipitate with a mixture of alcohol and hydrochloric acid (4 : 1), first by decantation, and finally, on the filter. Evaporate the filtrate until most of the alcohol has been removed and the volume has been reduced to about 125 cc. Then filter into it the tartaric acid solution (No. 2), and wash well. Neutralize the solution with ammonia. Add 2 cc. of hydrochloric acid, boil, and pass H^S through the solution at the boiling temperature for forty-five minutes to precipitate the sulphides of copper, arsenic, and antimony. Filter at once and wash. Spread the filter paper on the inside of a beaker and wash off the precipitate with as little water as possible. Treat the precipitate with a solution of potassium hydroxide (2 gms. KOH dissolved in 10 cc. of water) to dissolve the sulphides of arsenic and antimony. Heat until the precipitate is black, and filter. Dissolve the copper sulphide with nitric acid and determine the copper by electrolysis. (See p. 173.) As in Bullion. To the filtrate from the copper sulphide, obtained according to the preceding method, which should not 204 METALLURGICAL ANALYSIS measure more than 40 cc., add 1 gm. KClOs and 50 cc. of hydro- chloric acid. Boil until the solution is clear and the chlorine is expelled. The sulphides are oxidized to sulphates. Cool, neutralize with ammonia, and let the solution stand -to permit the separation of the small quantity of lead sulphate which may be present. Filter, and add ammonia, ii quantity equal to one-third the volume of the solution. Add magnesia mixture. (See p. 79.) K 2 HAs0 4 +MgCl2+NH 3 +6H 2 0=2KCl+MgNH 4 As04-6H 2 0. Let the solution stand twenty-four hours or more. Filter in a porcelain Gooch crucible. Reserve the filtrate for anti- mony and burn the precipitate to convert the magnesium am- monium arsenate to magnesium pyroarsenate. 2M g NH4As0 4 -6H 2 0=Mg 2 As 2 7 +2NH 3 +7H 2 0. The factor for As in Mg 2 As 2 O 7 is 0.4828. Sb in Bullion. Boil off the excess of ammonia from the nitrate from the arsenic precipitate, cool, and add 50 cc. of hydrochloric acid and 3 gms. of potassium iodide. SbCl 6 +2KI = 2KCl+SbCl 3 +I 2 . Add a little starch solution and titrate with standard solution of sodium thiosulphate. I 2 +2Na 2 S 2 3 = 2NaI+Na 2 S 4 6 . For the method of making and standardizing the solution of sodium thiosulphate, see iodide method for copper, page 171. The solution may be standardized against copper and its value in antimony determined by multiplying its value in copper by the factor 0.9454. It will be observed in the reaction on page 171, that 2 atoms of copper, in the form of copper acetate, COPPER IX CONVERTER COPPER 205 liberate 2 atoms of iodine from potassium iodide; and the equa- tion above indicates that 2 atoms of iodine are liberated by one atom of antimony. The ratio of the value of this standard solu- tion in copper to its value in antimony will, therefore, be equal to the ratio of twice the atomic weight of copper (2X63.57) to the atomic weight of antimony (120.2), and this ratio is expressed by the factor 0.9454. COPPER IN CONVERTER COPPER Weigh 0.5 gm. of the sample and transfer it to a No. 4 beaker. Add 8 cc. of nitric acid, 8 cc. of water, and 1 cc. of sulphuric acid, and keep the beaker covered during the solution of the sample. When the metal is in solution, boil out the fumes, dilute the solution with water, and precipitate the copper by electrolysis. The silver present is precipitated with the cop- per on the cathode and the weight of silver, which has been pre- viously determined by the fire assay, should be deducted from the total weight (291.66 ounces = 1 per cent). The silver may be removed prior to the precipitation of copper by adding just enough hydrochloric acid to precipitate it, letting the chloride settle, and filtering it off. The solution is then electrolyzed and the copper weighed directly. ARSENIC AND ANTIMONY IN CONVERTER COPPER Outline. The sample is dissolved in sulphuric and nitric acids and most of the copper is precipitated from the solution by electrolysis; the remaining copper, with the antimony and arsenic, is precipitated with hydrogen sulphide, the sulphides of arsenic and antimony are extracted with potassium hydroxide solution, and the antimony determined by electrolysis. After the antimony has been withdrawn from the solution, the arsenic is precipitated with hydrogen sulphide, filtered from the solution, and dissolved in ammonia. Sulphuric acid is 206 METALLURGICAL ANALYSIS added, the solution evaporated, diluted, the acid neutralized with ammonia, hydrochloric acid added, and the solution fil- tered. An excess of sodium bicarbonate is added to the filtrate, and the arsenic is titrated with standard iodine solution.* Reagents. Standard iodine solution. Dissolve 5.2 gms. of iodine and 9 gms. of potassium iodide in 10 cc. of water and dilute the solution to 1 liter. Each cubic centimeter should be equivalent to about 0.0015 gm. of arsenic. To standardize the solution, dissolve 0.1 gm. of pure As20s and 1 gm. of potassium hydroxide in about 30 cc. of water. Acidify the solution with hydrochloric acid, add sodium bicar- bonate to render the solution alkaline, and then add about 4 gms. in excess. Add a little starch solution, and titrate with the iodine solution. The factor for As in As20s is 0.7574. Starch solution. (See p. 111.) Hydrogen sulphide, H^S from a generator. Potassium hydroxide, KOH. Sodium sulphide solution. Dissolve 25 gms. Na2S+9H2O in 100 cc. of water. Sb in Copper. Weigh 10 gms. of the sample (20 gms. if it contains less than 5 per cent of arsenic) and transfer it to a No. 5 beaker. Add 30 cc. of sulphuric acid, 20 cc. of nitric acid, and 50 cc. of water. When in solution, heat to drive off nitrous fumes, dilute with water, and electrolyze 2.5 hours at 4 amperes, using a cylindrical platinum gauze cathode about 75 mm. high and 50 mm. in diameter. The precipitation of the copper should be stopped when about 0.25 gm. of copper remains in solution, indicated by a faint blue color. Remove the cathode, rinsing back into the beaker the adhering solution with water from a jet. Neutralize the solution with ammonia and then acidify it with 3 cc. of hydrochloric acid. Pass hydrogen sulphide through the solution rapidly for thirty minutes and let the sulphides of *E. E. Brownson, Trans. Amer. Inst. Min. Eng., 46, Bull. 80, 1489. ARSENIC AND ANTIMONY IN CONVERTER COPPER 207 copper, arsenic, antimony, etc., settle thirty minutes. Filter and discard the filtrate. Wash the precipitate once on the paper, and then wash the sulphides into a No. 5 beaker with the smallest possible amount of water. Add to the precipitate in the beaker 10 cc. of aqua regia and place the beaker under the funnel. In another beaker, mix 5 cc. of water and 20 cc. of aqua regia, heat to boiling, and pour through the filter to dissolve the small amount of sulphides adhering to the paper. Wash the paper with a small amount of water, and keep the bulk of the solution low to save time in evaporating. Cover the beaker and boil the solution thirty minutes. Remove the cover, and, with a fine jet of water, wash off the cover and wash down the sides of the beaker. Evaporate the solution to dryness at a temperature low enough not to cause loss by spattering. The residue should be heated until there is no longer an odor of acid. Add about 5 gms. of potassium hydroxide and 30 cc. of water and boil vigorously about fifteen minutes. The arsenic and antimony will pass into solution. Add 25 cc. of sodium sul- phide solution (25 gms. Na2S+9H 2 O in 100 cc. of water) and boil vigorously about ten minutes. Cool, decant the clear solution through a filter paper into a No. 2 beaker. Again add 25 cc. of sodium sulphide solution to the black precipitate in the beaker, stir well, and transfer the precipitate to the filter paper. Wash well with a dilute solution of sodium sulphide (5 gms. Na2S+9H2O in 100 cc. of water) from a wash bottle. This precipitate may be washed with hot water if care is taken that it be kept wet. If allowed to dry, copper will be oxidized and dis- solved. Add to the filtrate, which should measure about 160 cc., 5 cc. of hydrogen peroxide and heat until the yellow color of the solution fades. The solution will become nearly colorless unless the aqua regia used on the filter paper was strong enough to attack it. 208 METALLURGICAL ANALYSIS Cool, and precipitate the antimony by electrolysis, at 0.1 to 0.15 ampere. The antimony should be precipitated in about twelve hours. Remove the cathode, carefully washing off the solution which contains arsenic. Then wash in alcohol, dry carefully over an alcohol flame, and weigh. The increase in weight is Sb. As in Copper. Add to the solution containing the arsenic (from which the antimony has been precipitated) dilute sulphuric acid (1:4) to distinct acidity. Pass through the solution a rapid stream of hydrogen sulphide about ten minutes. As 2 (S0 4 ) 3 +3H 2 S =3H 2 S0 4 +As 2 S 3 . Let the precipitate settle twenty-five minutes and decant the solution through a filter (some sulphur will run through the filter). Transfer the precipitate and remaining solution directly to a No. 2 beaker. Now decant again through the filter and place the beaker containing the arsenic sulphide under the funnel. Wash out the beaker in which the arsenic was precipitated with 15 cc. of dilute ammonia (1:4), pour this through the filter to dissolve the small amount of arsenic sulphide which it contains, let the solution run into the beaker with the main precipitate, and finally, wash with a little water. As 2 S 3 +6NH 4 OH = 2H 3 As0 3 +3(NH 4 ) 2 S. To the solution of arsenic add sulphuric acid to neutralize ammonia, and about 8 cc. in excess. Evaporate until the sul- phuric acid fumes and then heat the solution at a high tem- perature about 1.5 hours. Cool, wash down the sides of the beaker with water, and add water to half fill the beaker. Neu- tralize the acid with ammonia, add hydrochloric acid to dis- tinct acidity, and filter into a No. 4 beaker. Wash thoroughly with hot water. Add water to about half fill the beaker. Neu- tralize the acid with sodium bicarbonate, and then add 4 gms. in excess. SELENIUM AND TELLURIUM IN COPPER 209 AsCl 3 +3NaHC0 3 = H 3 As0 3 +3NaCl+3C0 2 . The solution must be neutral, but NaOH must not be used, since it reacts with I. Cool to the temperature of the room, add starch solution, and titrate with standard iodine solution. H,AsO,+I,+H,0 = H 3 As0 4 +2HI. HI+NaHCO 3 = NaI+H 2 0+C0 2 . COPPER IN MATERIALS CONTAINING ARSENIC, ANTIMONY, TELLURIUM, AND SELENIUM Weigh 0.5 gm. of the sample and transfer it to a beaker. Dissolve in nitric acid, dilute with water, and add just enough hydrochloric acid to precipitate the silver. Filter and wash. To the filtrate, add 0.1 gm. of iron. When the iron is dissolved add ammonia to precipitate the iron, boil, let the precipitate settle, and filter. Dissolve the precipitate in nitric acid, dilute, and precipitate, as before. To insure the separation of all the copper, dissolve the precipitate, reprecipitate, and filter a third time. The precipitate of ferric hydroxide carries down with it arsenic, antimony, selenium, and tellurium, leaving the copper in solution. Combine the filtrates and precipitate the copper by electrolysis SELENIUM AND TELLURIUM IN COPPER KELLER'S METHOD* Se in Copper. Weigh 5 to 100 gms. of copper, the quantity depending upon the amount of Se and Te present. Dissolve it in nitric acid and add an excess of ammonia to precipitate P, As, Sb, Sn, Bi, Se, Te, and Fe. Filter and wash the precipitate with dilute ammonia water to remove all the copper. * Jour. Amer. Chem. Soc., 19, 771; and 22, 242. 210 METALLURGICAL ANALYSIS Dissolve the precipitate in hydrochloric acid and saturate the solution with hydrogen sulphide in the cold to precipitate Se, Te, As, Sb, Sn, and Bi as sulphides. Filter the sulphides from the iron and phosphorus. Treat the precipitate with sodium sulphide and filter. The filtrate contains all the Se and Te with some As, Sb, and Sn. Acidify the filtrate with nitric acid and evaporate carefully to dryness. Dissolve the residue in 200 cc. of hydrochloric acid (1.175 sp.gr.) and boil to remove nitric acid. Saturate the solution with sulphur diox- ide and filter the elementary selenium in a Gooch crucible. Tellurium is not precipitated in a strongly acid solution. Wash the precipitate with a mixture of hydrochloric acid (1.175) and water (9:1), followed by dilute hydrochloric acid, then by water to remove the hydrochloric acid, and finally with absolute alcohol. Dry at 105 C. and weigh the selenium. Te in Copper. Dilute the filtrate from the selenium with an equal volume of water. Heat it to boiling and add sulphur dioxide to precipitate the tellurium. Filter in a Gooch crucible and treat the precipitate of tellurium in the manner described above for selenium. ANALYSIS OF ALLOYS BRASS AND BRONZE METHOD FOR THE DETERMINATION OF SN, PB, Cu, ZN, AL, AND FE This is a rapid method, which yields only approximately accurate results. Methods for the more accurate separation of these metals are given on pages 215 and 220. Sn in Bronze. Weigh 1 gm. of fine drillings for the sample, transfer it to a small beaker, and add 15 cc. of dilute nitric acid (2:3). Heat to dissolve the alloy and to convert the tin to metastannic acid. 5Sn+10HXO, = H w Sn*Ou+5NO a +5NO. BRASS AND BRONZE 211 Evaporate the solution nearly to dryness. Add 50 cc. of water and 5 cc. of nitric acid (sp.gr. 1.42). Boil, and let the precipitate settle. Filter, and wash by decantation four or five times. Transfer the precipitate to the filter and wash with boiling water. Dry, separate the precipitate from the filter (Fig. 31, p. 27), burn the filter in a porcelain crucible, add the precipitate, and ignite. H 10 Sn 5 Oi 5 =5Sn0 2 +5H 2 0. Cool in a desiccator and weigh. The factor for Sn in SnC>2 is 0.788. Pb in Alloy. To the filtrate from the metastannic acid, add 15 cc. of sulphuric acid. Pb(N0 3 ) 2 +H 2 S0 4 =PbS0 4 +2HN0 3 . Evaporate the solution nearly to dryness, cool, add 10 cc. of sulphuric acid, and dilute to 50 cc. with water. Filter, wash with dilute sulphuric acid (1 : 10), and finally, with water. Dry and ignite the filter and residue separately in a porcelain crucible. Cool in a desiccator and weigh PbSCU. The factor for Pb in PbS0 4 is 0.68311. Cu in Alloy. Boil the filtrate from the lead sulphate and pass a current of hydrogen sulphide through the solution for half an hour. Filter, and wash the precipitate with a solution of hydrogen sulphide water. Dissolve the copper sulphide on the filter with a little warm, dilute nitric acid, boil the solution, and if sulphur is still present, filter. To the solution add 5 cc. of sulphuric acid and 3 cc. of nitric acid. Dilute the solution and precipitate the copper by electrolysis. Fe2C>3 and A^Os in Alloy. Boil the filtrate from the copper sulphide to expel hydrogen sulphide. Add a few drops of nitric acid and boil. Add ammonia until the solution is alkaline. Heat to the boiling-point, filter, wash with hot water, burn, and weigh as 212 METALLURGICAL ANALYSIS Zn in Alloy. Heat the filtrate from the hydrates of iron and aluminum to the boiling-point and pass through it a current of hydrogen sulphide to precipitate the zinc. ZnS0 4 +H 2 S = ZnS+H 2 S0 4 . Filter, dissolve the precipitate in about 50 cc. of dilute hydro- chloric acid (1 : 4), dilute the solution, and boil to expel hydrogen sulphide. ZnS+2HCl = ZnCl 2 +H 2 S. Cool, and add to the cold solution a large excess (50 cc.) of a 10 per cent solution of sodium ammonium phosphate (NH4NaHP04+4H 2 O). Add ammonia carefully to neutralize the solution, using litmus as an indicator. Add two drops of ammonia in excess and then 1 cc. of acetic acid. Test with litmus to be sure the solution is acid. Heat for one hour, but do not boil. After the precipitate has become granular and has settled, filter, and wash it with hot water. Dry the precipitate and separate it from the paper (Fig. 31). Dissolve the precipitate which adheres to the filter paper in a little dilute nitric acid and collect the solution in a small, weighed porcelain dish. Evaporate the solution to dryness, add the dry precipitate which was sepa- rated from the paper and heat gently to a low red heat. Cool in a desiccator and weigh as zinc pyrophosphate (TxizPzfy). The factor for Zn is 0.4289. Instead of filtering on filter paper in the manner described above the zinc ammonium phosphate may be filtered in a porcelain Gooch crucible, dried at 100 C. and weighed directly. (See p. 25.) The zinc may also be determined by the volumetric method de- scribed on page 178. After the zinc sulphide has been filtered from the solution and dissolved in 50 cc. of hydrochloric acid (1 : .4), about 4 gms. of ammonium chloride are added, the solution diluted with 250 cc. of hot water, heated to 60 C. and titrated with a standard solution of potassium ferrocyanide. ALLOYS CONTAINING TIN, LEAD, COPPER, ETC. 213 Fe in Alloy. The precipitate formed by adding ammonia (see Al2Os+Fc2O3 in alloy, p. 211) may consist of aluminic hydrate or ferric hydrate or a mixture of the two. If it is brown in color, iron is present. To determine the iron in the alloy, weigh 1 gm. of the sample and treat it according to the process described above until the hydroxides of iron and aluminum have been filtered from the solution. Dissolve the precipitate in a little hydrochloric acid, reduce the iron with a little stannous chloride solution, add mercuric chloride solution, and titrate the iron with standard potassium dichromate solution; or the iron may be reduced with zinc in the presence of an excess of sulphuric acid, and titrated with standard permanganate solution. See Methods for iron in ores, page 50 et seq. Al in Alloy. From the weight of Fe, as determined above, calculate its value in Fe2Os by multiplying by the factor 1.4298. Deduct this weight from the weight of the combined oxides of iron and aluminum, and multiply the weight of A12O.3 remain- ing by the factor 0.5303 to obtain the weight of Al. WHITE ALLOYS CONTAINING TIN, LEAD, COPPER, PHOSPHORUS AND ANTIMONY Sn in Alloys. Weigh 1 gm. of the sample and transfer it to a small beaker. Add 20 cc. of dilute nitric acid (1 : 1), evaporate the solution nearly to dry ness, add 50 cc. of boiling water, boil, filter, and wash the precipitate with hot 2 per cent solution of nitric acid. Burn the filter and precipitate separately in a porcelain crucible, cool in a desiccator, and weigh Sn(>2. The factor for Sn in SnO 2 is 0.788. If the alloy contains phosphorus, the phosphorus will come down with the tin, providing the ratio of tin to phosphorus is as great as 8 to 1 . The phosphorus should be determined (see P in alloy, p. 214) and its equivalent in P 2 5 deducted from the weight of impure SnOa. Pb in Alloy. To the filtrate from the metastannic acid, add 5 cc. of sulphuric acid, evaporate the solution until dense 214 METALLURGICAL ANALYSIS fumes of sulphuric acid are evolved, cool, add 50 cc. of cold water, stir, and let the precipitate settle half an hour. Filter in a Gooch crucible, and wash with dilute sulphuric acid (1 : 9). Remove the filtrate and reserve it for the determination of copper and zinc. Then wash the lead sulphate once with alcohol. Dry the precipitate at about 250 C. and weigh the PbSO 4 . The factor for Pb in PbSO 4 is 0.6831. Cu in Alloy. To the nitrate from lead sulphate add 1 cc. of nitric acid, and determine the copper by electrolysis. (See p. 173.) Zn in Alloy. To the solution from which the copper has been precipitated add bromine water, ammonium persulphate, and ammonium chloride. Then add an excess of ammonia and heat to the boiling-point. If a precipitate forms Fe(OH)s, Mn02 filter, and add to the solution an excess of ammonium phosphate. Heat to the boiling-point and add dilute hydro- chloric acid until the solution is nearly neutral. Boil ten minutes, filter in a weighed Gooch crucible, and wash well with hot water. Dry at 100 C. to a constant weight. The factor for Zn in ZnNH 4 PO 4 is 0.3663. For other methods see page 178. P in Alloy. Weigh 1 gm. of the alloy and treat it accord- ing to the method described above for the determination of Sn, until the precipitate of tin and phosphorus has been ignited in a porcelain crucible. Add to the crucible 3 gms. of potassium cyanide, cover, fuse, and keep at a dull red heat for five minutes. Sn0 2 +2KCN = 2KCNO+Sn. Cool, treat the fusion with boiling water, and filter the tin from the solution. Add to the filtrate 20 cc. of strong hydrochloric acid and boil. This should be done under the hood. Then add 30 cc. of nitric acid and evaporate to dryness. Cool, treat the residue with nitric acid and water, filter, and determine the phosphorus in the filtrate by precipitating with ALLOY CONTAINING TIN, COPPER, ANTIMONY, ETC. 215 ammonium molybdate solution and weighing the yellow pre- cipitate. (See p. 75.) Sb in Alloy. (See p. 218.) ALLOY CONTAINING TIN, COPPER, ANTIMONY, LEAD AND ZINC * Reagents. Dilute nitric acid (3:7). Sodium carbonate, Sulphur, S. Sodium sulphite, Solution of hydrogen sulphide. Water saturated with Dilute sulphuric acid (1 : 1). Ammonium acetate, NH4C2HsO2. Acetic acid, C 2 H 4 2 (sp.gr. 1.04). Standard ammonium molybdate solution, page 175. Potassium iodide, KL Standard solution of sodium thiosulphate, page 171. Starch solution, page 111. Solution of sodium ammonium hydrogen phosphate. Dissolve Na(NH 4 )HPO 4 -4H 2 O in water. Sn in Alloy. Weigh 1 gm. of the sample and transfer it to a small beaker. Add 20 cc. of dilute nitric acid (3 : 7). Cover, and when the sample is in solution, remove the cover and evaporate the solution to dryness on a water-bath. Heat in an air-bath at 120 C. for an hour. Cool, moisten the residue with 4 cc. of nitric acid, and then add 30 cc. of water. Heat, filter, and wash the precipitate until the acid is all removed. Dry the precipitate and separate it from the paper. Ignite the paper in a weighed porcelain crucible, moisten the ash with a few drops of nitric acid, and ignite gently. Add the pre- cipitate to the ash in the crucible and ignite at a red heat. Weigh as impure Sb20 4 -fSn02. * Meade, Chem. Eng., 8, 45. 216 METALLURGICAL ANALYSIS Add to the crucible a mixture of dry sodium carbonate and sulphur, in equal parts, in quantity about six times the weight of the oxides in the crucible. Fuse at a low temperature until burning sulphur ceases to escape between the crucible and its cover. Cool, and dissolve the fusion in hot water; add sodium sulphite to the dark-brown-colored solution until the iron and copper sulphides are precipitated and the solution changes to a light yellow color. Filter off the iron and copper sulphides, wash well with water containing hydrogen sulphide, ignite and weigh the residue as CuO and Fe20s. Subtract this weight from the weight of impure Sb2O4 and Sn(>2 already determined. Dis- solve the copper and iron oxides in a little strong hydrochloric acid, dilute the solution to 25 cc., add an excess of ammonia to precipitate the ferric hydroxide, filter, and wash with water. Ignite and weigh the precipitate as Fe2Os. The factor for Fe in Fe 2 O 3 is 0.69939. Acidify the filtrate from the ferric hydrox- ide with dilute sulphuric acid and add it to the main solution for the copper. Determine the antimony according to the method described below, calculate its equivalent in Sb204, and subtract it from the combined weight of Sb2O4 and SnO2 to give the weight of SnO 2 . The factor for Sn in Sn0 2 is 0.7881. Pb in Alloy. To the filtrate from the antimony and tin, add 10 cc. of dilute sulphuric acid (1 : 1) and evaporate the solution until dense white fumes of sulphuric acid are evolved. Cool, and dilute the solution. Heat it, let the precipitate settle, decant the clear solution through a filter, wash the precipitate by decantation with 2 per cent sulphuric acid, and then wash it with cold water. Dissolve 10 gms. of ammonium acetate in 50 cc. of hot water, and pour it through the filter to dis- solve the small amount of lead sulphate deposited on the paper by decantation, letting the solution run into the beaker con- taining the main part of the precipitate. Wash the paper with hot water, and place the beaker over the heat until the ALLOY CONTAINING TIN, COPPER, ANTIMONY. ETC. 217 lead sulphate is dissolved. Dilute the solution to 200 cc., make it slightly acid with acetic acid, and titrate the lead with standard ammonium molybdate solution. (See p. 175.) Cu in Alloy. To the filtrate from the lead sulphate add ammonia until the solution is faintly alkaline, and then add 8 cc. of acetic acid and 3 gms. of potassium iodide. When the potassium iodide is in solution add a little starch solution and titrate with standard sodium thiosulphate solution. (See p. 171.) Cu in Alloy Containing Zinc. Heat the filtrate from the lead sulphate to boiling and pass through it a current of hydrogen sulphide until it becomes cold. Filter by suction and wash the precipitate with hydrogen sulphide water. Dissolve the precipitate in a little warm dilute nitric acid, evaporate the solution to 2 or 3 cc., dilute slightly, add ammonia until the solution is faintly alkaline, and then add 8 cc. of acetic acid, 3 gms. of potassium iodide, and a little starch solution, and titrate with standard sodium thiosulphate solution. The copper may also be determined in the filtrate from the lead sulphate by electrolysis. Zn in Alloy. To the cold filtrate from the copper, add 50 cc. of a 10 per cent solution of sodium ammonium hydrogen phosphate. Carefully neutralize the solution with ammonia, using litmus paper, and add 2 drops of ammonia in excess. Acidify the solution with acetic acid (1 cc. or more if neces- sary). Heat for one hour, but do not boil. Filter and wash the precipitate with hot water, dry, and transfer it to a watch glass. Dissolve the small amount of the precipitate on the filter in dilute nitric acid and let the solution run into a small, weighed, porcelain dish. Evaporate the solution to dryness, add the main precipitate from the watch glass, and heat gently at first, and then for a few minutes at a low red heat. Cool and weigh as Zn2?207. The factor for zinc is 0.4289. The zinc may also be determined volumetrically by the method described on page 178. 218 METALLURGICAL ANALYSIS Sb in Alloy.* Weigh 1 gm. of the sample, transfer it to a beaker, add 1 gm. of potassium iodide, 40 cc. of water, 40 cc. of concentrated hydrochloric acid, and boil gently one hour. The residue is metallic antimony precipitated from SbCla by the metals not yet dissolved. KI reduces SbCl 6 to SbCla. Filter on asbestos and wash five or six times with hot dilute hydrochloric acid (1 : 10). Wash the precipitate and asbestos into a small beaker with a little water and add 25 cc. of concen- trated hydrochloric acid and a few crystals of potassium chlorate. Cover and warm gently, stirring occasionally. When the antimony is dissolved, dilute the solution to 100 cc. and filter out the asbestos, washing it free of hydrochloric acid. Boil the solution vigorously five minutes to drive off the chlorine. The Sb is oxidized to SbCls. Cool to room temperature, add 1 gm. of potassium iodide, and titrate with standard sodium thiosulphate solution. (See p. 204.) BISMUTH IN ALLOYS Outline. The alloy is dissolved in acids and all the metals converted to sulphates. Insoluble sulphates are filtered from the solution. From the filtrate bismuth and the other metals of that group are precipitated with hydrogen sulphide. The sulphides of copper, arsenic, and antimony are dissolved from the precipitate with potassium cyanide solution; the remain- ing sulphides are dissolved and the bismuth precipitated and weighed as the oxychloride. Reagents. Dilute sulphuric acid (1 : 10). Hydrogen sulphide; H^S from a generator. Solution of potassium cyanide', concentrated solution of KCN in water. Dilute nitric acid (1:1) * H. Yockey, Jour. Amer. Chem. Soc., 28, 646 and 1435. Walters and Apfelder, Ibid., 25, 635. BISMUTH IN ALLOYS 219 Dilute ammonia (I : 2). Dilute hydrochloric acid (1 : 2). Bi in Alloy. Weigh 1 gm. of the alloy, transfer it to a 250-cc. Erlenmeyer flask, add 10 cc. of nitric acid, and evaporate the solution until the residue is pasty, but do not let it boil. Add 7 cc. of hydrochloric acid and heat to complete the decom- position of the alloy. Then add 8 cc. of sulphuric acid and boil until dense white fumes of sulphuric acid are evolved. Cool the solution, add 30 cc. of water, and boil until the bismuth sulphate dissolves. Cool, filter quickly before there is time for basic bismuth sulphate to precipitate, and wash with 10 per cent solution of sulphuric acid. Dilute the filtrate to 100 cc. and pass a current of hydrogen sulphide through the solution to precipitate bismuth, copper, arsenic, and antimony also lead if any remains. Filter and wash the precipitate with hydrogen sulphide water. Place the filter with its contents in a 250-cc. beaker, add a concentrated solution of potassium cyanide, using as little as possible to dissolve the sulphides of copper, arsenic, and antimony. Warm the solution for a few minutes, filter, and wash the sulphides with hot water. Dissolve the sulphides of bismuth, lead, and cadmium by placing the filter and precipitate in a 250-cc. beaker, and heating with 10 cc. of dilute nitric acid (1:1). Add 20 cc. of water and filter in a porcelain Gooch crucible. Wash the precipitate with dilute nitric acid. Transfer the filtrate to a 400-cc. beaker, dilute it to 300 cc., and heat the solution to boiling. Remove it from the heat and neutralize it by adding dilute ammonia (1 : 2), testing with litmus paper. Continue adding ammonia, cautiously, drop by drop, until the solution becomes slightly cloudy. Add 1 cc. of dilute hydrochloric acid and let the deter- mination stand on the hot-plate for an hour, but do not let it boil. Filter the bismuth oxychloride in a porcelain Gooch crucible, wash with hot water, dry at 100 C., and weigh as BiOCl. The factor for Bi is 0.80166. 220 METALLURGICAL ANALYSIS ANALYSIS OF COPPER CONTAINING LEAD, ANTIMONY, ARSENIC, TIN, IRON, COBALT, AND NICKEL, WHEN ONLY A SMALL SAMPLE OF THE MATERIAL IS AVAILABLE * Reagents. Sodium carbonate (Na2COs). Sulphur, S. Hydrogen sulphide ([28 from a generator). Solution of sodium sulphide; Na2$ dissolved in water. Sodium dioxide (Na202). Alcohol (C 2 H 6 sp.gr. 0.84). Tartaric acid (C^eOe). Ammonium nitrate (N^NOa). Solution of ammonium nitrate. Dissolve 10 gms. NH4NOs in 1 liter of water. Ammonium carbonate, (NH^COs. Ammonium acid sulphide, (NH4)HS. Solution of ammonium sulpho-cyanate. Dissolve 10 gms. NH 4 SCN in 1 liter of water. Bromine water; water saturated with Br. A. Weigh 0.5 gm. of the sample, transfer it to a small beaker, cover, and pour down the lip into the beaker 10 cc. of nitric acid (sp.gr. 1.42). Heat, or cool, to dissolve, at a moderate rate. Evaporate the solution to dryness and heat the residue at 110 C. Cool, moisten the deposit with nitric acid, add 50 cc. of water and then add ammonia to render the solution slightly alkaline and to precipitate the tin completely. Heat the solution to boiling, acidify it with nitric acid, filter, wash the precipitate, burn it in a porcelain crucible, and weigh it. Re- serve the nitrate for separate treatment (see E below). B. Cover the residue with a mixture of sodium carbonate and sulphur, in equal parts. Cover the crucible and fuse until sulphur has ceased to be volatilized. Cool, place the crucible in a beaker with water, and boil. Remove the crucible after * F. A. Gooch, Carnegie Publication, 1, 235. COPPER CONTAINING LEAD, ANTIMONY, ETC. 221 it has been washed off. Filter and wash the residue. If the precipitate is large, repeat this treatment. Combine the nitrates for treatment under D. C. Ignite the precipitate which may contain sulphides of lead, copper, and. iron in a porcelain crucible. Cool, treat the residue with aqua regia and a little sulphuric acid. Evaporate the solution until sulphuric acid fumes are evolved. Cool, add a little water, filter off the lead sulphate in a Gooch cru- cible, dry, and weigh the PbSCU. To the nitrate add ammonia to precipitate ferric hydroxide. Boil, filter, burn, and weigh the Fe20s. Through the filtrate from the iron pass a current of hydrogen sulphide, filter from the solution the copper sulphide, burn it in a crucible to CuO, and weigh it. D. Acidify the filtrate from B, containing arsenic, antimony, and tin, with hydrochloric acid. Filter, and reject the filtrate. Dissolve the precipitate on the filter with the smallest amount pos- sible of warm solution of sodium sulphide. Concentrate the solu- tion by evaporation. Cool and add sodium dioxide, a little at a time, until the liquid becomes colorless and oxygen is liberated freely. Add to the solution one-third of its volume of alcohol (sp.gr. .84). Filter, and wash with alcohol, gradually increasing the strength (1 : 2), (1 : 1), and then with (3 : 1). The precipitate should contain antimony as sodium antimonate; and the filtrate, sodium arsenate and sodium stannate in solution. Dissolve the precipitate of sodium antimonate in a mixture of dilute hydro- chloric acid (1:4) and 5 to 10 per cent of its weight of tartaric acid. Dilute and pass through the solution a current of hydro- gen sulphide. Filter on asbestos, and dry in an atmosphere of C02 at 240 C. (Paul's apparatus) and weigh as antimony trisulphide. Acidulate the filtrate containing arsenic and tin with hydro- chloric acid. Cool to C. Treat with twice its volume of hydrochloric acid (sp.gr. 1.2) also cooled to C. Filter out 222 METALLURGICAL ANALYSIS sodium chloride on asbestos and pass a current of hydrogen sul- phide through the solution 1.5 hours. Let the precipitate settle for two hours, filter on asbestos, wash with dilute hydrochloric acid (1:2), and then with hot alcohol. Dry at 110 C. and weigh as As2S5. To drive off most of the acid evaporate the filtrate from the arsenic pentasulphide. Dilute the solution largely and pass through it a current of hydrogen sulphide. Add ammonium nitrate to aid coagulation. Filter, and wash the precipitate with the solution of ammonium nitrate. Ignite with ammonium car- bonate and weigh as SnO2- E. To the filtrate from the residue, after the first solution of the metal, add 5 cc. of sulphuric acid, and evaporate until the sulphuric acid fumes. Dilute to 50 cc., filter on asbestos, wash with dilute sulphuric acid (1 : 3), ignite, and weigh as PbSCU. Proceed with the filtrate as follows. F. To the filtrate add 1 gm. of tartaric acid, nearly neutralize with ammonia, heat to boiling, and add 5 cc. of dilute sulphuric acid (1 : 4), 5 cc. of ammonium acid sulphide, and 100 cc. of solution of ammonium sulphocyanate. Let the determina- tion stand over night, decant the solution through asbestos in a Gooch crucible, and wash twice by decantation, leaving most of the precipitate of cuprous sulphocyanate in the beaker. Re- serve the filtrate for treatment under G. Place the Gooch crucible in the beaker with the greater part of the precipitate and dissolve the precipitate in a mixture of sulphuric and nitric acids. After the precipitate has dissolved, dilute the solution and filter the asbestos from it. Evaporate the solution to the evolution of sulphuric acid fumes. Dilute a little and neutralize with ammonia. Acidify with sulphuric acid, and precipitate the copper by electrolysis. G. Boil down the filtrate from the cuprous sulphocyanate to one-third its volume, in order to remove sulphur dioxide; and pass through the hot solution a current of hydrogen sul- COPPER CONTAINING LEAD, ANTIMONY, ETC. 223 phide to precipitate antimony, arsenic, lead, copper, and tin, if present. Filter, and reserve the filtrate for treatment under /. H. Treat the precipitate obtained above (under G) on the filter with sodium sulphide solution to dissolve arsenic, antimony, and tin, and wash the filter. Treat the filtrate according to the methods of section D. Burn the filter and treat the residue according to section C for lead sulphate and copper oxide. 7. Carefully neutralize the filtrate from G with ammonia and pass through it a current of hydrogen sulphide to pre- cipitate iron, nickel, cobalt, and possibly copper. Reject the filtrate. Treat the precipitate on the filter with dilute hydro- chloric acid and wash the residue. Reserve the filtrate for the estimation of iron. Ignite the filter and residue. Treat the residue with aqua regia, evaporate the solution to dryness, dis- solve the deposit in hydrochloric acid, and pass through the solu- tion a current of hydrogen sulphide. Filter from the solution the copper sulphide, ignite it, and weigh as copper oxide. Care- fully make the filtrate from the copper sulphide ammoniacal, pass through it a current of hydrogen sulphide, filter, ignite, and weigh as NiO+CoO. If the precipitate is large, the nickel and cobalt should be separated. To the filtrate reserved for the determination of iron, add bromine water, and then make the solution alkaline with ammonia, boil to precipitate the ferric hydroxide; filter, ignite, and weigh as 224 METALLURGICAL ANALYSIS METHODS OF ANALYSIS IN THE PRODUCTION OF THE PRECIOUS METALS. FIRE ASSAYING ASSAY OF GOLD AND SILVER ORES Sampling. It is extremely difficult to take a satisfactory sample of a high grade gold ore, since such ores usually lack uniformity in composition For the quantity of ore required for FIG. 81. Two-muffle Assay Furnace Designed for the Use of Coal. FIG. 82. Assay Furnace for Liquid or Gaseous Fuel. the sample, and for the fineness of crushing before dividing, see Richards' table, page 11. The sample is finally crushed on a bucking-board to pass an 80-mesh or a 100-mesh screen. If any particles of free gold or silver in the ore (metallics) cannot be crushed to pass the screen, they are collected, weighed and assayed separately by scorification assay (see below). The values thus found are properly apportioned to the whole of the sample, ASSAY OF GOLD AND SILVER ORES 225 Methods of Assaying. In the fire assay for gold and silver, the ore is fused in a muffle (Figs. 81 and 82) by the aid of fluxes in the presence of lead, and the gold and silver are collected by the lead. The lead " button " is separated from the slag and cupeled. By cupellation, the lead button containing the gold and silver is melted on a bone ash cup called a cupel (Fig. 83), the lead is oxidized to PbO, which is volatilized in part, and the re- mainder, and larger part, is absorbed by the bone ash, leaving the bead of gold and silver on the cupel. The bead is weighed and the silver dissolved from it with nitric acid, and the gold which remains is weighed. The gold and silver may be absorbed by lead and separated FIG. 83. Cupel. FIG. 84. Crucible. from the gangue by either the crucible method, or the scorifica- tion method of assay. By the crucible method, the ore is mixed with flux, lead oxide, and a reducing agent, and melted in a fire-clay crucible. (Fig. 84.) The flux combines with the gangue to make a fusible slag, at the same time liberating the gold and silver. These metals are then absorbed by the metallic lead, which has been reduced from the lead oxide by the reducing agent. When the fusion is complete, the charge is poured from the crucible into a cast- iron conical mold (Fig. 85) and allowed to cool. The lead but- ton, which settles to the bottom, is separated from the slag and is hammered into shape (usually a cube) for the cupel. By a scarification assay the ore is mixed in a scorifier (Fig. 226 METALLURGICAL ANALYSIS 86) with granulated lead, a little borax glass added, and the charge is placed in a hot muffle and scorified; that is, the lead melts, the ore floats on its surface, is roasted and oxidized, the basic elements combining with the borax glass, and the acid elements with the lead oxide, which form a slag on the surface of the molten lead. When the slag thus formed increases until it completely covers the surface of the lead, the charge is poured into a mold, and the assay finished as in the crucible method. In the scorification method of assay, only a very small quantity of ore can be used. It is, therefore, not a satisfactory method for low-grade ores. Neither is it satisfactory for basic ores, owing to the small amount of acid flux that can be used. FIG. 85. Cast Iron Mold for Receiving FIG. 86. Scorifier. the Fusions. It is, however, satisfactory for ordinary silver ores, and for rich gold ores and furnace products, though the losses are usually somewhat higher than in the crucible method. The Assay- ton. Gold and silver ores are usually weighed in tons of 2000 Ibs. avoirdupois, and the value of the ore is expressed in troy ounces per ton. In making the assay, gold and silver are weighed in milligrams. To avoid the necessity of changing milligrams into ounces per ton by calculation, Prof. Chandler devised the assay-ton. The assay-ton is that quantity of ore whose content of precious metal, weighed in milligrams, expresses the number of troy ounces of precious metal contained in a ton of ore of 2000 Ibs. avoirdupois. One ton avoirdupois contains 14,000,000 grains troy; and 1 oz. troy contains 480 grains. Therefore, there are 29,166 oz. ASSAY OF GOLD AND SILVER ORES 227 troy in 1 ton avoirdupois. If 1 ton contains 29,166 oz., 1 assay- ton must contain 29,166 mgm., or 29.166 gms., that is, 1 mgm. bears the same relation to 1 assay-ton that 1 oz. troy does to 1 ton of 2000 pounds^ avoirdupois. The troy ounce of gold is worth $20.67. The Metric Ton. In those countries where the metric system has been adopted, ore is weighed in metric tons of 1000 kgms. each, and the assay-ton is not necessary. The sample taken is usually 10 gms. for the crucible assay, and every 0.01 mgm. of the metal found in the assay equals the number of grams per metric ton. A gram of gold is worth $0.66. Reagents. Reducing agents. The reducing agent combines with the oxygen of the litharge (PbO) , setting free metallic lead throughout all parts of the charge, the lead falling through the molten mass to the bottom of the crucible collects the gold and silver. Various carbonaceous substances are used as reducing agents. The principal ones are charcoal, argols, and flour. 2PbO+C=Pb 2 +C0 2 . Reducing power. The power of a reducing agent must be known before it is used in a charge. To determine the redu- cing power, weigh 1 gm. of the reducing agent and mix it in a crucible with 60 gms. of sodium bicarbonate, 5 gms. of borax glass, and 30 gms. of litharge; cover with salt, fuse in a hot muffle, pour the fusion into a cast-iron mold, cool, separate the lead button from the slag, and weigh it. In making up a charge for assay, put in enough reducing agent to produce a lead button that weighs about 18 gms. Oxidizing agents. Oxidizing agents are added to the assay to take sulphur from the sulphides of the metals and to oxidize the base metals. In this form they are slagged by acid fluxes. The chief oxidizers are the nitrates of potassium and sodium. 4ZnS+6KNO, =4ZnO+3K,SO+SO,+3N,. 228 METALLURGICAL ANALYSIS Desulphurizing agents. In addition to the nitrates of the alkalies, iron, alkaline carbonates, and litharge are reagents that reduce metallic sulphides. PbS+Fe=FeS+Pb. 7PbS+4K 2 C0 3 =4Pb+3(K 2 S.PbS)+K 2 S0 4 +4C0 2 . K 2 S-PbS+Fe=Pb+K 2 S-FeS. PbS+2PbO=3Pb+SO.. Fluxes. Fluxes are added to the charge to combine with the gangue and form an easily fusible liquid slag, through which the metallic particles can readily settle. If the gangue is basic, the flux should be acid; and if the gangue is acid, the flux should be basic. The principal basic fluxes are: Melting-point. Litharge (PbO) ............................ 906 C. Sodium carbonate (Na 2 C0 3 ) ................. 814 C. Sodium bicarbonate (NaHCOs) loses CO2 and melts at ................................ 270 C. Potassium carbonate (K 2 CO 3 ) ................ 885 C. PbO+Si0 2 =PbSi0 3 , =Na 2 Si0 3 +C0 2 . The principal acid fluxes are: Melting-point. Silica (SiO 2 ) ................. , .......... 1775 C. Borax glass (Na 2 B 4 O 7 ) ......... " ........... 560 C. SiO,+CaCO, =CaSiG 3 +C0 2 . The cover. After the charge is mixed in the crucible, it is covered with a reagent of low melting-point to catch any particles that would otherwise be thrown out by the escape of gases and to protect the charge from the air. The agent often GOLD AND SILVER IN OKE 229 used for this purpose is salt (NaCl), which is neutral; but some- times, however, an acid cover, borax, is used; and sometimes, especially in the assay of telluride ores, litharge is used. Metals, as reagents. In addition to the reagents given above, pure granulated lead is used in scorification, pure silver for inquartation, and pure sheet lead in connection with silver for inquarting on a cupel. Purity of reagents. Litharge and lead usually contain small amounts of silver. Tests must be run to determine the amount of silver the reagents contain, and the proper correction made for each assay. It is also necessary to test all the reagents used for gold and silver. This is done by making up a crucible charge, with the same quantities of reagents that are used in the assay of an ore, but with the ore left out, and putting it through the regular process, as given below for ores. GOLD AND SILVER IN ORE The nature of the charge that is mixed with the ore will depend upon the character of the ore. If the gangue is silicious, and does not contain reducing agents, such as sulphides and arsenides, the charge taken may be as follows. Sodium bicarbonate 60 gm. Borax 5 gm. Litharge 30 gm. Ore 1 assay-ton Charcoal 1 gm. (if another reducing agent is used, the quantity taken should be sufficient to produce a lead button weighing about 18 gms.). Place the ore on the charge in a crucible, mix in the crucible with a spatula, and cover the mixture to the depth of half an inch with salt. Place the charged crucible in a hot muffle, using the crucible tongs (Fig. 87) and fuse for about thirty minutes. 230 METALLURGICAL ANALYSIS When fusion is complete, withdraw the crucible with the tongs (asbestos gloves should be worn to protect the hands), shake the crucible by giving it a rotary motion in a horizontal plane, and tap it gently to settle the lead in one mass. Pour the fusion into a mold and let it freeze. Separate the slag from the lead button and hammer the lead into a convenient form (usually a cube) for cupellation. Cupellation. Heat the cupel in a muffle, and with the cupel tongs (Fig. 88) place the lead button on the hot cupel. Close the muffle until the lead melts. Then reduce the heat and open the muffle so that the fumes of lead oxide are slowly carried from the cupel. Cupellation should be carried on at a moderately low FIG. 87. Crucible Tongs. FIG. 88. Types of Cupel Tongs. temperature to prevent loss of the precious metals by volatiliza- tion. The temperature should be low enough to permit the for- mation of lead oxide crystals, " feathers," on the cupel. When the lead is all oxidized, and only the gold and silver bead remains, it suddenly glows, or " blicks." After the blick the cupel is withdrawn from the furnace. If the bead is large, it should be cooled gradually to prevent " sprouting." This may be accomplished by covering the cupel before withdrawing it from the furnace with an empty hot cupel or scorifier. Weighing and Parting. When the metallic bead is cold, take it from the cupel with a pair of strong, pointed pliers, and carefully brush it with a stiff brush to remove adhering litharge or bone ash. Then flatten the bead with a small hammer to break off any adhering particles of bone ash, and weigh it as Ag+Au. Transfer the weighed bead to a porcelain crucible GOLD AND SILVER IN ORE 231 (Fig. 89) and add about 2 cc. of water from a wash bottle. Drop in nitric acid slowly, until the bead turns dark and begins to dissolve. Stop the addition of acid and warm gently. When the action ceases, add more nitric acid, and heat the solution to boiling. Fill the crucible with water from a wash bottle and carefully empty it by pouring the solution down a glass rod, leav- ing the gold behind. The crucible is then filled with water and emptied in the same way a second lain Annealing and a third time to free the gold from all traces c up . of silver nitrate. After the final decantation, carefully remove the last drop of water from the crucible with blotting paper or filter paper and carefully dry the crucible over a Bunsen burner, and then heat it until the black particle of gold is annealed and turns yellow. The gold is then transferred to the gold balance and weighed. The difference between the weight of gold and the combined weight of gold and silver represents the weight of silver. In parting by the above method the gold is sometimes left in a powdered condition, especially if the ratio of silver to gold is high. In this condition there is danger of loss in washing the gold to free it from silver nitrate. A more convenient method of parting, especially if many assays are to be made at the same time, and one which leaves the gold in a more coherent mass, consists in placing the metallic bead in hot dilute nitric acid (1 : 9) at once and boiling it at least fifteen minutes. Place 20 cc. of the dilute acid in each of the test-tubes (Fig. 90); heat in the bath until the acid boils; then add the metallic beads and continue boiling fifteen minutes. Fill each test-tube with distilled water; turn an annealing cup (Fig. 91) over the top of each test-tube. Invert the test-tube and let the particle of gold fall into the annealing cup. Fill up the annealing cup with distilled water from a wash bottle. Carefully raise the inverted test-tube to the top of the annealing cup, 232 METALLURGICAL ANALYSIS letting the cup fill with the solution, then quickly draw the test-tube to one side so that the remaining solution in the tube will flow into a receptacle below and leave the particle of gold undisturbed in the annealing cup. Give the gold three suc- cessive washings with warm distilled water. Take the last drop of water out of the cup with clean blotting paper, anneal the gold and weigh it. Inquartation. If the gold-silver bead has a higher ratio of gold to silver than 1 to 4, the silver is not readily dissolved from it with nitric acid. Therefore, when there is not four times FIG. 90. Test Tubes for Parting Ready for the Bath. FIG. 91. Clay An- nealing Cup. as much silver as gold present, or, in other words, if the total quantity of silver present is less than four times the amount of gold, a sufficient amount of silver should be added to the assay to produce this ratio. If silver is to be determined in the ore, as well as gold, the additional silver for inquartation must not be introduced until after the gold-silver bead has been weighed. The bead is then wrapped in a small piece of pure lead foil, together with the necessary weight of pure silver for inquar- tation, returned to the muffle, and cupeled.* The bead is then parted and the gold weighed. If the assay is for gold alone, and it is known that there is not a sufficient amount of silver in the ore to yield a button that will part readily, the necessary silver * The silver may be alloyed with the bead on charcoal before the blow-pipe. ASSAY OF SULPHIDE ORE 233 for inquartation may be added, either to the crucible, or to the cupel, since the gold in that case is not weighed until after parting. ASSAY OF SULPHIDE ORE Sulphide ores after they are weighed for the assay may be roasted in a roasting dish in a muffle, mixed with a charge similar to that given in the preceding method, and assayed in the same way. Roasting, however, may be avoided by making up a cru- cible charge, in which is included a desulphurizing agent. The following charge may be used. Gms. Sodium carbonate 60 Litharge 30 Borax 8 Silica 2 Place the flux in the crucible, add 1 assay-ton of ore, and mix thoroughly with a spatula. Add three twenty-penny iron nails. Put the nails in, points downward, and press them well into the charge. Add a half-inch cover of salt and fuse. For ores high in sulphur, reduce the sodium bicarbonate to 50 gms. and increase the borax to 20 gms. and the silica to 10 gms. For low sulphur ores, reduce the borax to 5 gms., leave out the silica and iron nails, and add 2 gms. of argols. After fusing about twenty minutes, it is advisable to inspect the nails to see if there is danger of their breaking, through corrosion, at the surface of the slag. If they are much corroded, they should be removed, and fresh nails added, since the fusion cannot be poured satisfactorily if it includes fragments of nails. When the fusion is complete, withdraw the crucible from the muffle, and with short tongs, take out the nail, shaking from them into the crucible any globules of adhering lead. Shake the crucible and settle the lead to the bottom. Pour the charge into a mold. When cold, separate the lead from the slag and hammer 234 METALLURGICAL ANALYSIS the lead into the usual form for cupellation. If the lead is soft complete the assay according to the method given above for silicious ores. If the lead is brittle, place it in a scorifier, add granulated lead, and a pinch of borax glass and scorify. When the scorifica- tion is complete, pour the contents of the scorifier into a mold and complete the assay in the usual way. Ores high in copper, arsenic or antimony should he done by the nitre method. The charge for one assay-ton would consist of 120 gms. litharge, 35 gms. sodium carbonate, 10 gms. silica, and from 10 to 20 gms. of nitre; the quantity of nitre depending upon the reducing power of the ore.* ASSAY OF TELLURIDE ORE Charge: Gms. Sodium carbonate 25 Potassium carbonate . 25 Litharge 50 Borax glass 14 Flour 2J or more. (See Reducing Power, p. 227.) Ore 0.5 assay-ton The ore is placed on top of the charge and then thoroughly mixed with the spatula. Cover with 40 gms. of litharge. Place the crucible in a moderately hot muffle and complete the fusion at about 1000 C. Pour the charge into a mold and complete the assay according to the method for silicious ores. SILVER IN ORE SCORIFICATION METHOD Weigh 0.1 assay-ton and mix it in a scorifier with 20 gms. of granulated lead. Cover with 20 gms. of granulated lead; * C. H. Fulton, "Fire Assaying," pp. 61 and 115. ASSAY OF BULLION 235 sprinkle about 1 gm. of borax glass over the surface, and with the scorifier tongs (Fig. 92) place in a hot muffle, and scorify. Keep the door of the muffle closed until the lead is thoroughly melted, then open the door of the muffle to admit air for the oxidation of the lead, as well as of sulphur, arsenic, antimony, etc. When ^. ^- "' --O the slag completely covers the lead, the scorification is com- plete. The assay is then poured into a mold, and when cold, the FIG. 92. Types of Scorifier Tongs. lead is separated from the slag. If the lead is soft, it is hammered into a cube, and cupeled. If it is hard and brittle, it is rescorified with a sufficient amount of granulated lead added to make a total of 60 gms. A second scorification should slag off the impurities sufficiently to give a soft lead button, which is cupeled, and the resulting silver bead cleaned and weighed in the usual manner. ASSAY OF BULLION Sampling. The bullion is melted and cast into bars. Chips are taken from diagonally opposite corners of the bars, the chips rolled into fillets, and each fillet assayed separately. Base bullion is best sampled while it is molten. The sample is dipped from the molten bullion with a graphite ladle and poured slowly into warm water. The granules are collected and as- sayed. SILVER IN BULLION FIRE METHOD Silver in bullion is determined by cupeling a weighed sample of the bullion with pure lead, weighing the gold-silver bead, parting, and weighing the gold. The difference between the two weights represents the weight of silver. When bullion is thus cupeled, considerable quantities of the 236 METALLURGICAL ANALYSIS precious metals are lost, the extent of the loss depending upon the amount and kind of base metals present and the temperature at which the bullion is cupeled. To make an accurate assay of bullion, it is, therefore, necessary to run at the same time a check assay in which the losses are determined, from which the bullion assay is corrected. It is necessary to make a preliminary assay of the bullion, to determine its approximate composition. The alloy for the check assay is then made to agree with the approximate com- position of the bullion. The quantities of the precious metals added must, of course, be accurately determined. The loss in cupellation is then determined by weighing the precious metals after cupellation. The Preliminary Assay. Weigh 0.5 gm. of bullion, wrap it in 5 gms. of pure lead foil and cupel carefully, at a temperature low enough for the formation of " feathers " on the cupel. Clean, hammer, and weigh the bead. Part and weigh the gold. The check assay is now made up to correspond in composi- tion with the bullion, except that about 5 mgms. more of silver are put in the check than were found in the bullion, because that amount of silver is usually lost under these conditions from such an assay in cupellation. Suppose the weight of the silver determined by preliminary assay on 500 mgms., of the bullion is 478 mgms., and the gold 2 mgms.; there is a toss then of 20 mgms. (500 480). Experience indicates that of this loss about 5 mgms. are silver and the remaining 15, probably copper (indicated by the color of the cupel). The check is then made by weighing very accurately 483 mgms. of silver, 15 mgms. of pure sheet cop- per, and 2 mgms. of gold, or the gold bead obtained in the pre- liminary assay. These metals are wrapped as closely as possible in pure lead foil and cupeled in the muffle with the bullion. The weight of lead foil required depends upon the amount of copper in the bullion. If there is less than 50 mgms. of copper SILVER IN BULLION 237 in 500 mgms. of the bullion, add 5 grns. of lead foil. If the bullion contains more than 50 mgms. of copper increase the amount of lead as the copper increases; about 5 gms. of lead for each 50 mgms. of copper. It is better, however, not to add more than 20 gms. of lead at once. If the copper is not all removed at one cupellation, add fresh lead and cupel again. Ag in Bullion. After making the preliminary assay, weigh two portions of the bullion, of 500 mgms. each, and make up a check assay in the manner described above; wrap each of the three assays closely in that weight of lead foil required for the copper in the bullion as determined in the preliminary assay. Place them in three hot cupels, arranged in a line across the muffle, the check assay being placed between the duplicates of the bullion. Close the muffle until the charges are melted; then open the muffle and cupel at a sufficiently low temperature to form feathers. When the beads " blick," cover them with hot cupels and cool slowly to prevent sprouting. If a bead sprouts, it must be discarded. Clean, hammer, and weigh the beads. The loss of silver in the check assay is supposed to be sustained in the same ratio by the bullion. This correction is added to each of the duplicate bullion assays and the results added. SILVER IN BULLION GAY-LUSSAC METHOD * Standard Solutions. (1) Solution of silver. Dissolve 1 gm. of pure silver in 10 cc. of nitric acid and dilute the solution to 1 liter. One cubic centimeter of this solution will contain 0.001 gm. of silver. The solution should be kept in a green glass bottle which is covered with black paper. (2) Standard solution of sodium chloride. Dry NaCl at 125 C. and weigh 5.4167 gms. Dissolve it in distilled water and * Frederick P. Dewey, Jour. Ind. and Eng. Chem., 5, 209. 238 METALLURGICAL ANALYSIS dilute the solution to 1 liter. One cubic centimeter of this solution, if properly prepared, will precipitate 0.01 gm. of silver. (3) Decime salt solution. Measure 10 cc. of solution No. 2 and dilute it to 100 cc. If correct, 1 cc. of this solution will precipitate 0.001 gm. of silver. Care should be taken that the temperature of these solu- tions is the same when they are prepared. The sodium chloride solution (No. 2), is standardized as follows. Weigh 1 gm. of pure silver, dissolve it in 10 cc. of nitric acid, dilute the solution to about 80 cc., add 100 cc. (measured with a pipette) of No. 2 solution, agitate violently, and let the silver chloride settle. Then add 1 cc. of the decime solution. If a precipitate appears, shake vigorously, let the precipitate settle and add another cubic centimeter. Shake and let the precipitate settle, and continue adding this solution, 1 cc. at a time, until no precipitate is produced. Then add 1 cc. of the silver solution (No. 1 above), and continue adding 1 cc. at a time until no precipitate forms. Suppose 100 cc. of the strong solution of sodium chloride are run in; then 7 cc. of the decime solution are added before a precipitate ceases to form. Now, if on adding the solution of silver, 1 cc. at a time, the first produces a precipitate and the second does not, 1 gm. of silver would be equivalent to 100.6 cc. of No. 2 solution. The solution is corrected as follows: 100 cc. of the sodium chloride solution should contain 0.54167 gm. of salt; but it requires 100.6 cc. of the solution to contain that amount. There- fore, 100 cc. contains ~ - =0.53844; that is, 0.00323 100 6 gm. (0.54167-0.53844) per 100 cc. should be added. If the solution is too strong, it may be corrected accord- ing to the method in the following example. Suppose after adding 100 cc. of No. 2 solution and 1 cc. of the decime solu- tion we titrate back with 8 cc. of the silver solution; then SILVER IN BULLION 239 99.4 cc. [100.1 -(0.8-0.1)] would contain 0.54167 gm. NaCl; and that is the amount of NaCl which should be contained in every 100 cc. Therefore, add 0.6 cc. (100-99.4) for every 99.4 cc. of solution left. After correcting the solution No. 2, make another decime solution from it, test again and correct, if necessary, until it is exactly right. Ag in Bullion. Make a preliminary test as follows: Weigh 0.5 gm. of bullion, dissolve it in dilute nitric acid, and titrate first with the standard sodium chloride solution, and finally with the decime solution. When the approximate fineness is determined, weigh that quantity of bullion which contains 1 gm. of silver, dissolve it in a 250-cc. flask in dilute nitric acid, and dilute with water to 80 cc. Add 100 cc. of the standard sodium chloride solution, shake vigorously, and let the precipitate settle Add decime sodium chloride solution, 1 cc. at a time, until no precipitate forms, shaking after each addition. Then add standard silver solution in the same way until a precipitate ceases to form. Example. Suppose we weigh and dissolve 1.02 gms. of bul- lion and add 100 cc. of standard sodium chloride solution and 9.5 cc. of decime solution, and then titrate back with 3 cc. of standard silver solution, the third producing no precipitate. The result is calculated as follows: Mgms. silver. 100 cc. standard salt solution are equivalent to. . 1000 9.5 cc. decime salt solution are equivalent to. . 9.5 Less 2 cc. standard silver solution. 1007.5 1.02 gms. of bullion then contain 1.0075 gms. of silver. One 240 METALLURGICAL ANALYSIS gram of the bullion contains ( - ) .9878 gm. of silver, and 1000 gms. of the bullion would contain 987.8 gms. of silver. The bullion is, therefore, 987.8 fine. GOLD IN BULLION Make a preliminary assay of the bullion to determine its approximate composition and make a check assay in a muffle similar to that described for preliminary assay of silver bullion (see p. 236). Weigh 0.5 gm. of the bullion and add enough pure silver to make the ratio of silver to gold 2 to 1; an experienced assayer can estimate this from the color of the bullion. Wrap the bullion and silver in about 8 gms. of pure lead foil and cupel, clean the button, and weigh. Part and weigh the gold. Suppose, for example, that from 0.5 gm. of bullion we obtain 380 mgms. of gold and 15 mgms. of silver. Since experience indicates that 0.3 mgm.* of gold is lost in the cupellation of 500 mgms., 395.3 mgms. of the bullion are made up of gold and silver, leaving 104.7 mgms. for base metal probably copper. To make the check assay, weigh 380.3 mgms. of pure gold, 760.6 mgms. of silver (380.3 X2), and 104.7 mgms. of pure copper. Wrap in 10 gms. of lead and cupel with the bullion. Au in Bullion. Weigh 500 mgms. of the bullion in duplicate. Add enough silver to make the ratio of silver to gold 2 to 1, as determined by the preliminary assay. [(380.3 X2) 15 = 745.6]. Wrap in lead foil, the weight of lead taken depending upon the amount of base metal in the bullion. For the quantity required, see assay of silver bullion (p. 236) Place the duplicate assay with the check in hot cupels in the muffle and cupel according to the method described for the fire assay of silver. T. K. Rose f has found that the losses of gold are slightly * Rose, " Metallurgical of Gold," p. 448. t Eng. and Min. Jour., 80, 492. GOLD AND SILVER IN LEAD BULLION 241 greater from the cupels next to the sides of the muffle than from those in the center, and recommends that the check assays be distributed throughout the muffle. After cupeling, each button is cleaned, hammered, annealed, rolled into a thin sheet, and then coiled into a " cornet." The cornets are parted, annealed, and weighed, and the weight of the gold found in the bullion corrected from the loss or gain in weight of the gold in the check assay. The results are reported as parts of gold in 1000 parts of the bullion. Bullion, for instance, which contains 984.6 parts gold in 1000 parts of the bullion is said to be 984.6 fine. GOLD AND SILVER IN LEAD BULLION Weigh four portions of the bullion, 0.5 assay- ton each, and mix each portion with 30 gms. of granulated lead in a scorifier. Add 1.5 gms. of borax glass and 0.5 gm. of silica and scorify. (See p. 234.) Separate the slag from the button and save it. Cupel the lead button and assay the scorifier slag and the cupel in a crucible, using the following charge: 15 gms. of sodium carbonate, 45 gms. of borax glass, 80 gms. of litharge, and 2 gms. of argols. Mix and cover with a little litharge. Complete the assay in the usual way and correct the original assay accordingly. If the bullion is free from copper, arsenic, antimony, zinc, sulphur, etc., it may be cupeled without scorification as follows: Weigh 0.5 assay-ton and wrap it in about 8 gms. of sheet lead and cupel. To correct the assay, the cupels are crushed and assayed by the crucible method, using the charge given above. The weights of the precious metals obtained in the correction assay are added to the weights obtained by the original assay. 242 METALLURGICAL ANALYSIS GOLD AND SILVER IN CYANIDE SOLUTIONS Measure 300 cc. of the solution and transfer it to a porcelain evaporating dish. Sprinkle 40 gms. of litharge over the surface of the solution. Evaporate the solution, without boiling, to dry- ness. When dry, scrape out the residue with a spatula and mix it in a fire-clay crucible with the following charge: Gms. Sodium carbonate 30 Borax glass 10 Silica 20 Charcoal 1 If any of the residue sticks to the dish, wipe it out with a moist- ened piece of filter paper and add it to the charge in the crucible. Cover the charge with litharge, fuse it in a muffle, and complete the assay in the usual way (See p. 229.) PREPARATION OF PURE SILVER Dissolve pure silver foil in nitric acid. Filter, dilute the nitrate, and precipitate the silver with hydrochloric acid. Filter and wash the silver chloride with dilute hydrochloric acid. Trans- fer the silver chloride to a beaker, and add pure sheet aluminum and hydrochloric acid. When the silver has been precipitated as metallic silver, and the aluminum is all dissolved, wash by decantation, dry, and fuse the silver in a cupel. The melting- point of silver is 960 C.* PREPARATION OF PURE GOLD Dissolve the purest gold obtainable (cornets) in aqua regia. Dilute and let the solution stand several days to allow the silver chloride to settle. Siphon off the clear solution and evaporate * Day and Sosman, 1910. FREE CYANIDE IN CYANIDE SOLUTIONS 243 it nearly to dryness. Dilute the solution largely with distilled water, add a little sodium bromide dissolved in water, and let the solution stand several days. Again siphon off the clear solution and precipitate the gold on aluminum by letting the solution drop slowly from a burette into a beaker containing pure aluminum foil. When the gold is precipitated, add hydro- chloric acid to dissolve the aluminum. Decant, and wash the gold by decantation. Dry, and melt it into a bead in a cupel. The melting-point of gold is 1062 C.* TESTING CYANIDE SOLUTIONS FREE CYANIDE IN CYANIDE SOLUTIONS Reagents. Standard solution of silver nitrate. Dissolve 13.04 gms. AgNOs in water and dilute^ the solution to 1 liter. One cubic centimeter of this solution is equivalent to 0.004 gm. CN or 0.01 gm. KCN. Solution of potassium iodide. Dissolve 10 gms. KI in a liter of water. FREE CYANIDE Measure 10 cc. of the cyanide solution with a pipette (if the solution is weak, take 50 cc.), and transfer it to a beaker. Add about 8 cc. of potassium iodide solution as an indicator and titrate with standard silver nitrate solution until a yellow tinge is given to the solution by silver iodide. AgN0 3 +KCN =AgCN+KN0 3 . AgCN+KCN =KAg(CN) 2 . AgN0 3 +KI =AgI+KNO 3 . If 10 cc. of the cyanide solution are tested, every cubic centimeter of the standard silver nitrate solution used will repre- * Day and Sosman, 1910. 244 METALLURGICAL ANALYSIS sent 0.04 per cent CN, or 0.1 per cent KCN, which is equivalent to 1 kilogram KCN per metric ton of 1000 kg. or 2 Ibs. per ton avoir. If 50 cc. are titrated every cubic centimeter of the standard solution will represent 0.008 per cent CN or 0.02 per cent KCN. When gold is dissolved in a solution of an alkaline cyanide, the double cyanide of the alkali and gold is formed. A given weight of cyanogen, then, whether combined with sodium or potassium, should always dissolve the same amount of gold, other conditions being the same, and, owing to the fact that sodium has a smaller atomic weight than potassium, a smaller quantity of sodium cyanide than of potassium cyanide will be required to dissolve a given weight of gold. In the method above, it is the quantity of cyanogen only that is measured by titration, but its equivalent in potassium cyanide is usually reported. This is due to the fact that potassium cyanide was the only cyanide available when the cyanide process was developed. Now that sodium cyanide is much used for this purpose, it is not accurate to report as potassium cyanide the equivalent of the cyanogen found. From the molecular weights KCN (65.11), NaCN (49.01), and CN (26.01), we find that the percentage of CN in pure KCN is 40, and in NaCN it is 53. If 40 per cent of cyanogen is found in cyanide, it is not correct to assume that the material is pure KCN (100 per cent); for, if the cyan- ide were NaCN, it would only have to be 75.5 per cent pure to yield that amount of CN. The remainder might consist of any adulterant wholly free from cyanogen. It is to be regretted that the cyanide proc- ess is not conducted on the basis of the active cyanogen present, instead of its equivalent in potassium cyanide. TOTAL CYANIDE Total cyanide has been denned as " the equivalent, in terms of potassium cyanide, of all the cyanogen existing as simple cyanides and easily decomposable double cyanides, such as K2Zn(CN)4." * It might be termed available cyanogen, since it is the cyanogen existing as a simple cyanide after the addition of an excess of sodium hydroxide. * Clennell, " The Cyanide Handbook," 440. PROTECTIVE ALKALI IN MILL SOLUTIONS 245 Reagents. Standard silver nitrate solution. (See p. 243.) Alkali?ie indicator: Take 100 cc. of the potassium iodide solution (p. 243) and add to it 4 gms. NaOH. Total Cyanide. Measure 50 cc. of the solution to be tested, add to it 10 cc. of the alkaline indicator solution, and titrate with the standard silver nitrate solution to a faint yellow turbidity. Na 2 Zn(CN) 4 +2NaOH =4NaCN+Zn(OH) 2 . Also see reactions on page 243. PROTECTIVE ALKALI IN MILL SOLUTIONS Reagents. Standard acid. Nitric, hydrochloric, sulphuric, or oxalic, acid may be used, and it is convenient to make the solution equivalent to 0.001 gm. of the alkali per cubic centimeter. If nitric acid is used, a solution containing 2.257 gms. HNOa (sp.gr. 1.42) per liter, will be equivalent per cubic centimeter to about 0.001 gm. of NaOH, or, a solution of the same strength is made if 1 cc. of nitric acid (sp.gr. 1.42) be added to 625 cc. of water. NaOH+HNOs =NaN0 3 +H 2 0. Nitric acid (sp.gr. 1.42) contains 69.77 per cent of HNOs by weight. If oxalic acid is used, 1.5753 gms. of crystallized H2C204+ 2H20 per liter will give a solution of the same strength; that is, 1 cc. will be equivalent to 0.001 gm. NaOH. 2NaOH+H 2 C 2 4 2H 2 O = Na 2 C 2 4 +4H 2 0. Phenolphthalein solution: 1 gm. C2oHi404 dissolved in 500 cc. alcohol (95 per cent C2HeO) . Silver nitrate solution. (See p. 243.) Alkali. Measure with a pipette a convenient volume of the solution to be tested (50 cc.) and, if it contains no zinc, 246 METALLURGICAL ANALYSIS add to it a solution of silver nitrate until a slight permanent turbidity is produced. 2KCN+AgN0 3 = KN0 3 +KAg(CN) 2 . If the simple cyanides were not broken up, they, as well as the free alkali, would react with the standard acid in titration. Add 3 drops of phenolphthalein solution and titrate with standard acid until the pink color disappears (See p. 84.) PROTECTIVE ALKALI IN THE PRESENCE OF ZINC Reagents. Potassium ferrocyanide solution. Dissolve 5 gms. K4Fe(CN)e in 100 cc. of water. For other reagents see the preceding method. Alkali. Measure with a pipette 50 cc. of the solution to be tested, add 10 cc. (an excess) of potassium ferrocyanide solution. If the solution contains zinc as well as an alkali, when silver nitrate is added the hydroxide is precipitated, according to Clennell,* in the following way. K 2 Zn(CN)4+2KOH+2AgN0 3 =Zn(OH) 2 +2KA g (CN) 2 -f2KN0 3 . The potassium ferrocyanide is added to liberate the alkali. 2Zn(OH) 2 +K 4 Fe(CN) 6 =Zn 2 Fe(CN) 6 +4KOH. Proceed according to the method above (p. 245) by adding silver nitrate to a slight turbidity and titrating with standard acid after the addition of phenolphthalein solution. ACIDITY OF ORE Reagents. Standard acid. (See p. 245.) Standard alkali: a solution of sodium or calcium hydroxide equivalent to the standard acid. Phenolphthalein solution. (See p. 245.) * " The Cyanide Hand Book," 439. CYANOGEN IN COMMERCIAL CYANIDE 247 Weigh 200 gms. of ore, transfer it to a suitable bottle for agitation, add 400 cc. of the standard alkali solution and agitate one hour. Filter 100 cc. of this solution from the bottle, add to it two drops of phenolphthalein solution, and titrate with standard acid. If the standard acid and alkali solutions are exactly equal in value, deduct the number of cubic centimeters of standard acid used in the titration from 100, and multiply the remainder by 4, since 400 cc. were used. The result, multiplied by 0.001, will give the acidity of 200 gms. of ore, or the weight in grams of the alkali required to neutralize the acid in 200 gms. of ore. This quantity multiplied by 5 will give the weight of the alkali in kilograms, required for a metric ton of the ore; or multiplied by 10, will give the number of pounds required for one ton avoirdupois. CYANOGEN IN COMMERCIAL CYANIDE Sampling. When a case of cyanide is opened, break off and select from many places small lumps of the cyanide to a weight of about 200 gms. Grind it quickly in a porcelain mortar, taking great care not to inhale the dust. It is well to grind it in a hood which is provided with a strong exhaust. Mix the powder and transfer a few grams for analysis to a well-stoppered bottle. Reagent. Standard silver nitrate solution. (See p. 243.) CN in Commercial Cyanide. Weigh from a weighing bottle about 0.5 gm. of the cyanide, transferring it directly from the weighing bottle to a quarter-liter Erlenmeyer flask. Add 100 cc. of water to dissolve the cyanide. Add 5 cc. of potassium iodide solution and titrate with standard silver nitrate solution. The result may be reported in CN or in its equivalent of KCN or NaCN. (See free cyanide in mill solutions, p. 243.) If the cyanide contains soluble sulphides, before titrating 248 METALLURGICAL ANALYSIS with silver nitrate solution, agitate the cyanide solution with a little alkaline solution of lead acetate and filter, to prevent the darkening of the solution while titration goes on. WEIGHT OF ORE IN SLIME The percentage of ore in mill pulp may be conveniently estimated at any time by weighing a flask or bottle filled with the pulp and calculating the percentage in the manner given below, by the use of the following data, previously determined, once for all: Weight of the bottle empty ......... =b Weight of the bottle filled with water =5 Determine the specific gravity of the dry slime as follows: Dry a quantity of the slime and weigh 200 gms. or any convenient quantity (S). Boil it in a small quantity of water to liberate entangled air, cool and wash it into the empty bottle. Add water to fill the bottle, and weigh. Let the weight equal C. The specific gravity (G) is calculated from the equa- Then to find the percentage of ore in pulp, fill the bottle with the pulp and weigh it. Let the weight = '. Then lOOQS' -ff)G - equals the percentage of ore in the pulp. (Or 1)(& o) THE PLATINUM METALS 249 THE PLATINUM METALS PLATINUM DEWEY'S METHOD* Weigh one assay-ton of the material (or 0.5 assay-ton if much platinum is present) and treat it according to the method for the assay of gold ore, page 229, until the metallic bead has been parted with nitric acid. If only a small quantity of platinum is present, it will be dissolved with the silver. If there is much platinum present, some will remain with the gold; in this case, the residue is annealed, inquarted and parted again, and perhaps a third time to insure the complete separation of the platinum. If the nitric acid solution containing the silver and platinum is strongly acid, dilute it. It may be evaporated to a small bulk before dilution if the volume is large. Now add slowly to the diluted nitric acid solution containing the silver and platinum, while stirring, 15 cc. hydrogen sulphide solution, made by diluting 1 cc. of concentrated hydrogen sul- phide water to 15 cc. The hydrogen sulphide precipitates all the platinum, if the amount is small, and enough silver to produce a bead of suitable size. If much platinum is present, it will be necessary to add 2 cc. of strong hydrogen sulphide water, diluted to 30 cc. Stir occasionally and let the precipitate collect three to four hours or over night, if convenient. Filter and reserve the filtrate for a second precipitation of platinum if the quantity of the metal should be large. Dry the filter in a porcelain crucible and burn at a low heat. Wrap the metallic sponge in a thin sheet of lead foil and cupel. Part the bead in strong sulphuric * Trans. Amer. Inst. Min. Eng., 43, 578. 250 METALLURGICAL ANALYSIS acid. If necessary, boil a second time in strong sulphuric acid, wash by decant ation, anneal and weigh. If there is doubt as to the identity of the metal, it may be dissolved in aqua regia and qualitative tests applied. See page 319. PLATINUM * Weigh 1 gm. of the sample and treat it in a 250 cc. Jena beaker with 10 cc. of nitric acid, 10 cc. of hydrochloric acid, and 5 cc. of water in a water-bath until action ceases; then boil on the hot plate with repeated additions of hydro- chloric acid until all the nitric acid is expelled. Evaporate the solution to 40 cc., dilute to 100 cc. with water and filter. Evaporate the nitrate to 40 cc., add 25 cc. of ethyl alcohol and 25 cc. of saturated solution of ammonium chloride. Stir well, heat to boiling, and let the precipitate settle over night in a cool place. Filter (NH^PtCle in a weighed Gooch crucible, wash with a 20 per cent solution of ammonium chloride, dry, ignite, and weigh as Pt. If the material is low in platinum, begin with 8 or 10 deter- minations of 1 gm. each and combine them at the end to obtain a convenient quantity to weigh. The precipitate of (NH 4 ) 2 PtCl 6 should be ignited very carefully to prevent loss of Pt mechanically by the sudden expulsion of gas.f PALLADIUM t Weigh 0.5 gm. of the material and transfer it to a 250-cc. Jena beaker. Add 10 cc. of nitric acid, 5 cc. of hydrochloric acid, and 5 cc. of water and heat on the water-bath until the action ceases. Boil on the hot plate, dilute to 100 cc. with water, and filter. * Greenwood, Eng. and Min. Jour., 96, 1175. fSmoot, Eng. and Mining Jour., 96, 1175. t Greenwood, Eng. and Min. Jour., 76, 1175. THE PLATINUM METALS 251 The residue may contain palladium oxides; it should, there- fore, be boiled with 3 cc. of formic acid (CH 2 O 2 ) and 5 cc. of water to reduce the oxides to metallic palladium, which is then dissolved by the treatment above. Evaporate the filtrate with repeated additions of nitric acid to expel all hydrochloric acid, dilute the solution to 100 cc. and add 25 cc. of a 10 per cent solution of mercuric cyanide, Hg(CN)2. Boil a few minutes and let it stand over night. Pd(N0 3 ) 2 +Hg(CN) 2 =Pd(CN) 2 +Hg(N0 3 ) 2 . Filter and wash with a 1 per cent solution of mercuric cyanide. Burn in a porcelain or silica crucible. Pd(CN) 2 +O 2 =PdO 2 +2CN. Boil the residue with 50 cc. of a 20 per cent solution of for- mic acid, filter in a weighed Gooch crucible and weigh as Pd. Pd0 2 +2CH 2 2 =Pd+2H 2 O+2C0 2 . If the material is low in Pd, begin the determination with several portions of 0.5 gin. each and combine them at the end to obtain a weigh- able quantity of Pd. THE .PLATINUM METALS METHOD OF DEVILLE AND STAS * Fuse 5 gms. of the alloy with 50 gms. of lead in a cruci- ble of purified retort carbon. Hold at a temperature of at least 1000 C. for four or five hours. Boil the resulting alloy with very dilute nitric acid, filter and wash. Retain the filtrate (see below). Boil the black residue with very dilute aqua regia; nitric acid (1) : hydrochloric acid (4) : water (45). Filter and add the filtrate to the nitric acid solution above. * Menschutkin, " Anal. Chem.," 164. 252 METALLURGICAL ANALYSIS Fuse the residue of lustrous flakes which contains all the indium and ruthenium with 3 gms. of potassium nitrate and 10 gms. potassium carbonate. Cool and extract the fusion with water. Transfer the solution and residue to a tall cylinder and let the residue settle. Decant the clear solution and wash the residue with a dilute solution of sodium carbonate and sodium hypochlorite until the wash is no longer yellow. Pour these solutions into a retort, pass chlorine gas into the solution to saturate it, and distill into a flask containing water, hydrohloric acid and alcohol (purified by distillation over potassium oxide). Perruthenic acid passes over into the flask and is converted to ruthenium chloride. Evaporate the distillate to dryness and reduce to metallic ruthenium in hydrogen. The residue in the retort and that on the filter contain all the iridium. Boil them in sodium hydroxide and alcohol; the iridium oxide obtained is purified, reduced in hydrogen, and weighed as iridium. Analysis of Nitric Acid and Aqua Regia Solutions. Add to these solutions combined (which contain all the Pb, Cu, Pd, Rh, Os) just enough H^SCU from a burette to precipitate the lead. Evaporate the solution to dryness. Treat the residue with hydrochloric acid. Filter off the lead sulphate. To the filtrate add ammonium chloride, filter, dry the precipitate at a low temperature and reduce to metals with hydrogen. Fuse the spongy metals with acid potassium sulphate. Platinum is not dissolved. Dissolve the fusion with cold water and filter off the platinum and weigh it. To the filtrate add mercuric cyanide to precipitate Pd(Cn)2. Filter, and complete the deter- mination for palladium according to the method on p. 250. Add formic acid to the filtrate to precipitate Rh, filter, and weigh as Rh.* * Mylius and Forster, Berichte der deutschen chem. Gesellschaft, 25, 665. COAL 253 ANALYSIS OF FLUXES Limestone. For the analysis of limestone see page 160. Silica. Materials high in silica and silicates generally may be analyzed by following the method for clay, page 286. For the determination of silica in such materials a sample of 0.5 gm. should be taken. Iron Oxide. Fluxes high in ferric oxide are analyzed by the methods used for iron-ore, page 50, et seq. The quantity of Fe multiplied by the factor 1.4298 will give the weight of Fe 2 O 3 . For methods for other materials see the Index. ANALYSIS OF FUELS COAL Sampling.* The sampling of coal, if the determinations of ash are to agree within 1 per cent, requires greater care than is usually exercised in the sampling of iron ore; that is, the total original sample should be larger and it should be made up of a greater number of individual samples. Iron ores are usually not sampled with so much care as is demanded of the lowest grade material referred to in the table on page 11, but by numerous tests it has been shown that analyses of coal are practically worthless if the coal has not been sampled at least as carefully as is required for " low-grade or uniform ore." Therefore, the figures in column 2, page 11, should be the guide in taking the original sample and in crushing for its reduction. The method for the crushing, dividing, and final grinding of iron ore, page 48, should be used for the preparation of the sample of coal. For the fine grinding of coal, it should first be air-dried and care should be taken that the grinder does not become heated * Bailey, Jour. Ind. and Eng. Chem., 1, 176 (1909). J. A. Holmes, U. S. Bureau of Mines, Technical Paper 1, 1911. 254 METALLURGICAL ANALYSIS since oxidation of some of the constituents of the coal begin at a comparatively low temperature. A ball mill of porcelain is recommended for the fine grinding (see Fig. 14 p. 14). After the coal passes a 12-mesh screen, it is put in the jar with inch quartz pebbles, or porcelain balls, and the jar is rotated until the coal will pass a 60-mesh sieve. PROXIMATE ANALYSIS OF COAL In the valuation of coal for technical purposes it is much more desirable to know how much of the coal is ash, fixed car- bon, and volatile matter than to know the percentage of the several component chemical .elements. By the proximate anal- ysis, the moisture, volatile matter, fixed carbon, and ash are de- termined. It also usually includes the determination of sulphur.* Moisture. Weigh 1 gm. of the finely powdered coal and transfer it to a porcelain crucible (18 mm.X40 mm.). Place it in an air-bath and heat one hour at 105 C. in a current of dry air. Remove the crucible from the air-bath, cover it, place it in a desiccator over sulphuric acid and, when it is cool, weigh it. The loss in weight multiplied by 100 gives the percentage of moisture. Volatile Matter. The quantity of volatile matter that a coal yields depends upon the degree of heat and the length of time it is applied, the size of the cru- cible in which it is heated, etc.; therefore, in order that results may have a comparative value, it is necessary, always, to carry out the operation, as nearly as possible, under the same conditions. A committee appointed by the American Chemical Society to stand- ardize coal analysis recommended the following method: Weigh 1 gm. of the fresh, powdered, undried sample and place it in a 20-gm. or 30-gm. platinum crucible which has a tightly fitting cover. Heat over the full flame of the Bunsen * U. S. Bureau of Mines, Technical Paper 8. PEOXIMATE ANALYSIS OF COAL 255 burner seven minutes. The crucible should be supported on a platinum triangle with the bottom 6 to 8 cm. above the top of the burner. The flame should be 20 cms. high, when burn- ing free, and should be protected from draughts. The carbon which collects on the outside of the cover should be burnt off, but not that which is deposited on the inside. Cool and weigh. From the loss in weight subtract the moisture previously deter- mined to obtain volatile combustible matter. In 1913 the Committee recommended the following methods: Volatile Matter. 1. Weigh 1 gm. of coal and place it in a 10-gm. crucible with a capsule cover, that is, one that fits inside the crucible, and not on top. Place the crucible on a platinum or nichrome wire tripod in a muffle maintained at a heat of approx- imately 950 C. and leave it there seven minutes. When the flame from the volatile combustible matter disappears, gently tap the cover to seal the crucible and exclude the air. At the expiration of seven mimltes withdraw the crucible, cool in a desiccator, and weigh. 2. Weigh 1 gm. of coal and place it in a 20-gm. crucible with capsule cover. Place the crucible in the flame of a No. 4 Meker burner, which gives a flame 15 cms. high. The bottom of the crucible should be 1 cm. above the top of the burner and the tem- perature inside the crucible should be from 900 to 950 C. When the flame from the volatile combustible matter disappears, tap the cover gently to exclude the air. At the expiration of seven minutes, place the crucible in a desiccator to cool. When cool, weigh. From the loss in weight deduct the moisture pre- viously determined. Coke. If the residue in the crucible is a firm coherent mass, the coal is a coking coal and the wieght of the mass may be used to calculate the percentage of coke the coal will produce. Ash. If coal is free from the carbonates of calcium, magnesium, etc., the ash may be determined by burning off, with the crucible uncovered, all the carbonaceous matter from 256 METALLURGICAL ANALYSIS the sample in which moisture was determined, or from a fresh sample, and weighing the residue. The burning should begin over a very low flame. The carbon is more easily burned from this sample than from the compact mass of coke. If the sample contains carbonates, some of the C(>2 will be driven off when the carbon is burned; the residue will, there- fore, not truly represent the ash. It is necessary in such a case to determine the C02 in a separate sample, by taking a 5-gm. sample of the coal and treating it according to the method on on page 166 for the determination of C02 in limestone. From the weight of CO2 calculate its equivalent in C. The factor is 0.2727. When the carbon has been burned from a 1-gm. sample, the ash is moistened with a few drops of dilute H2SO4 (1:1) and carefully heated to a temperature of 750 C. and held at that temperature five minutes. It is then cooled in a desiccator and weighed. Multiply the equivalent of the C02 in C by 3 and subtract this from the weight of the ash to convert the weight of sulphate to its equivalent weight of carbonate, since that is the form in which it exists in the coal. Fixed Carbon. The weight of ash subtracted from the weight of coke will give the fixed carbon; or the sum of the moisture, volatile matter, and ash deducted from the original weight of the sample (1 gm.) will give the fixed carbon. SULPHUR IN COAL The proximate analysis of coal usually includes the determi- nation of sulphur. The method of Eschka, as modified by the Committee of the American Chemical Society on Coal Analysis, is an excellent one.* Reagents. Eschka mixture. Two parts of light dry mag- * G. L. Heath, Jour. Amer. Chem. Soc., 20, 630; 21, 1127. A. H. White, " Gas and Fuel Analysis," 205. SULPHUR IN COAL 257 nesium oxide (MgO) and 1 part dry sodium carbonate (Na2CO3) thoroughly mixed by passing them at the same time through a 40-mesh screen. Bromine water. Water saturated with Br. Barium chloride solution. A 10 per cent solution of BaCl2 in water. S in Coal. Weigh 1.3737 gms. and mix it on glazed paper with 6 gms. of the Eschka mixture. As the sulphur in the coal burns, it is absorbed by the sodium car- bonate. Magnesium oxide renders the mixture porous, so that air is more freely admitted. It also prevents any tendency of the coal to cake. Transfer the mixture to a 25 cc. porcelain crucible and add, as a cover, about 2 gms. of the Eschka mixture. Heat the crucible gently with an alcohol lamp, stirring occasionally with a platinum wire, for about thirty minutes, or until the black particles of carbon have disappeared. The sulphur, being oxidized, replaces C0 2 in the Na 2 C0 3 and forms the sulphate, and probably some sulphite, of sodium. Instead of using an alcohol lamp, the burning out of the carbon may be accomplished in a gas muffle, if it is heated gradually, and if a blank is run in the muffle, at the same time, to determine the quantity of sul- phur absorbed from the gas. It is desirable, in any case, to run a blank to determine the amount of sulphur in the reagents. Cool the crucible and transfer the contents to a beaker, using hot water. Add about 200 cc. of hot water, and digest for thirty to forty minutes at the boiling-point or near it, stirring occasionally. Filter and wash the residue several times by decantation with hot water, and finally, transfer and wash the residue on the filter. Parr * has found that all the sulphur is not extracted by treatment with water alone. After extraction with water he treats the residue with acid to recover the remaining sulphur. * J. Ind. and Eng. Chem., 1, 690. 258 METALLURGICAL ANALYSIS To the filtrate add 20 cc. of bromine water and enough con- centrated hydrochloric acid to make the solution slightly acid. Bromine oxidizes sodium sulphite to sulphate. See sulphur in ore, page 73. Heat the solution to boiling and add, drop by drop, while stirring, 10 cc. of hot barium chloride solution. Boil the solu- tion gently fifteen minutes and let it stand, a little below the boiling-point, two hours or longer. Filter and wash, first with hot water acidulated with hydrochloric acid (1 : 1000), and then with hot water, until the washings are free from hydrochloric acid. Burn the filter in a platinum crucible, cool in a desiccator, and weigh. Make the correction indicated by the blank and multiply the result by 10. RAPID METHOD FOR SULPHUR IN COAL BY THE TURBIDIMETER * After the determination of the calorific power o. the coal with the bomb calorimeter (see p. 262), wash out the bomb carefully with hot water. Titrate for acidity. Add 5 cc. of hydro- chloric acid (1:2) and heat to boiling. Cool and precipitate the sulphur in the cold with a solution of barium chloride to which has been added a little oxalic acid. The precipitate is very finely divided and does not settle readily. Dilute to the mark in a graduated flask, mix, and take out an aliquot part of the turbid solution and compare it with a standard which has been prepared in the same way from a sample in which the sulphur is known. (See Colorimetry p. 42.) This method gives somewhat lower results than the Eschka method. The sulphur in the standard, therefore, should have been determined by the Eschka method and the standard burnt in the calorimeter in the usual way. *Parr, Jour. Amer. Chem. Sec., 26, 1139 (1904); Jour. Ind. and Chem. Eng., 1, 689 (1909). HYDROGEN AND OXYGEN IN COAL AND COKE 259 ULTIMATE ANALYSIS OF COAL HYDROGEN AND OXYGEN IN COAL AND COKE Weigh about 0.25 gm. of the coal, place it in a combustion boat, and burn in a combustion furnace in a current of pure dry oxygen. Pass the products of combustion through, first, an absorption bulb containing H2SO4, which removes the water, and then through a similar bulb containing KOH solution, which absorbs the CO2. The bulbs are weighed before and after combustion. ' From the weights of H^O and C02 found the H and C are calculated. NITROGEN IN COAL The percentage of nitrogen in coal indicates the quantity of ammonia that may be recovered as a by-product in coke- making. Nitrogen is determined by the Kjeldahl method.* N in Coal. Place 1 gm. of coal in a 500-cc. Kjeldahl flask with 30 cc. of dilute sulphuric acid (1 : 84) and 0.6 gm. of mer- cury and boil until the solution is nearly colorless (three hours). Add potassium permanganate crystals gradually until the solu- tion becomes permanently green. Cool, dilute the solution to about 200 cc. with cold water. Add 25 cc. of potassium sulphide solution (40 gms. KsiS per liter) to precipitate the mercury. Add 1 gm. of granulated zinc to prevent bumping and about 0.5 gm. of paraffine to pre- vent frothing. Add saturated solution of sodium hydroxide to distinct alkalinity (80 ec. to 100 cc.). Connect the flask at once with the condenser and distil the ammonia into a measured quantity of standard sulphuric acid solution (1 cc. equivalent to 0.05 gm. N) to which has been added cochineal indicator. Continue the distillation until * Technical Paper 8, U. S. Bureau of Mines. 260 METALLURGICAL ANALYSIS 200 cc. have passed over, then titrate the excess acid with stand- ard ammonia solution. The two solutions should be made so that 20 cc. NH 4 OH solution = 10 cc. H 2 SO 4 solution. OXYGEN IN COAL Oxygen is determined by difference. The sum of the per- centages of carbon, hydrogen, nitrogen, sulphur, and ash are deducted from 100; the remainder is assumed to be oxygen. PHOSPHORUS IN COAL Weigh 6.52 gms. of the coal and transfer it to a platinum crucible. Place the crucible in a muffle and burn the carbon. Add to the ash about six times its weight of sodium carbonate and 0.2 gm. of sodium nitrate. Fuse with a blast lamp. Cool and dissolve the fusion in water and hydrochloric acid. Evap- orate the solution to dryness. Dissolve the residue in dilute hydrochloric acid, filter, and determine the phosphorus in the filtrate according to one of the methods for phosphorus in ore (p. 75.) CALORIFIC POWER OF COAL The calorie is the quantity of heat required to raise 1 gm. of water 1 C. (between and 100). The calorific value, or power, of a coal is expressed by the number of calories that 1 gm. of the coal will yield when burnt in a calorimeter. A calorimeter of the usual type consists of a bomb of steel or alloy in which the coal is burnt, and its enclosing vessel of about 4 liters capacity which holds a definite weight of water, in which the bomb is submerged while a determination is being made. This vessel is usually made of copper, plated with nickel to diminish the loss of heat by radiation, and is pro- vided with a stirrer and an accurate thermometer graduated to CALORIFIC POWER OF COAL 261 hundrcdths of a degree centigrade. The bomb in some cal- orimeters is held in place centrally in the inner of two con- centric fiber pails to render the passage of heat between the water in the calorimeter and the atmosphere of the room slow and uniform. The bomb is usually made of steel and is lined with enamel or nickel, or, for very accurate work, with gold or platinum. Parr * has made a bomb of an alloy of nickel, copper, tungsten, etc., which resists well the action of nitric and sulphuric acids and, therefore, needs no lining. It is provided with rubber gaskets, well protected from the heat, and is there- FIG. 93. Bomb for Calorimeter. FIG. 94. Calorimeter Bomb with Fittings. fore more satisfactory to operate and to keep in working con- dition than are other types of bombs, which have metal valves and gaskets. (Figs. 93 and 94.) The bomb is provided with a tightly fitting cover, held firmly in place on the gasket by a collar screwed down on the outside. Through a valve in the cover, oxygen is admitted for combus- tion. The capsule in which the coal is placed for combustion is supported, near the center of the bomb, on one of the electrodes, which, in turn, is attached to the cover. The other electrode pierces the cover and is insulated from it. * Jour. Ind. and Eng. Chem., 4, 746 (1912). 262 METALLURGICAL ANALYSIS In the calorimeter vessel, a weighed quantity of water is placed (usually about 2000 cc.), in which the bomb is submerged for the combustion. Midway between the bomb and the side of the vessel, an accurate thermometer, which, with the aid of a cathetometer and telescope may be read to thousandths of a degree, is introduced through the cover of the calorimeter and fixed in place with the bulb of the thermometer opposite the center of the bomb. While a determination is being made, the water is thoroughly stirred at a uniform rate with a stirrer which projects through a hole in the cover. The air space between the inner and outer pails serves as an insulation from the heat of the room. For accurate work, this space is also filled with water, and, in that case, it also is provided with stirrer and thermometer. Calorific Power of Coal. Weigh in a shallow platinum capsule about 1 gm. of coal, and place it in position on the elec- trode. Weigh a length of about 5 cms. of 36 B. & S. gauge iron wire and with it connect the two electrodes above the capsule, bending a loop of wire down to touch the coal, but not the capsule. Powdered bituminous coal burns so violently that some of the dust may be thrown from the capsule before it is burnt. The powder should, therefore, be compressed into a pellet before weighing. Place in the bomb a few drops of water to absorb the nitric acid which is produced by the combustion. Put the cover in place on the bomb, taking care not to disturb the position of the capsule. With the spanner, screw the ring down to hold the cover firmly hi place, attach the oxygen tank with a flexible metal tube provided with a pressure gauge, open the valve of the bomb and then the valve of the oxygen cylin- der, and let the oxygen flow in gently until the gauge indicates 20 to 25 atmospheres. Close the valve of the oxygen tank and then the valve of the bomb and disconnect the cylinder. Weigh in the calorimeter 2000 gms. of water, which should be about 2 or 3 C. above the room temperature. The quan- CALORIFIC POWER OF COAL 263 tity of water used may be such that when combined with the water value of the calorimeter the total will be equivalent to 3000 gms. of water. If only an approximate determination is to be made, and no correc- tion for loss of heat, the water in the calorimeter should be about 3 C. below the room temperature, but not low enough to precipitate moisture from the atmosphere on the outside of the calorimeter. The gain and loss of heat due to the deposition and later evaporation of this moisture would interfere with the gradual and uniform change of temperature which is desirable within the calorimeter. Place the bomb in the center of the calorimeter, attach- ing the electric wires for ignition. Put on the cover, and adjust the thermometer and the stirrer. . The thermometer must be made especially for this purpose and must be carefully calibrated. After recording the readings of the thermometer, the corrected readings from the certificate must be added. Stir two minutes and then read the thermometer and record the reading. Continue the stirring at a uniform rate and read the thermometer each minute for five minutes. The thermometer should gradually fall, as the heat of the water passes out to the air of the room. On the minute that the fifth reading of the thermometer is taken, close the electric circuit to ignite the coal. The current from dry cells at about 12 volts ignites the coal promptly by heating the small iron wire. Continue stirring and read the thermometer every minute, for at least ten minutes after ignition. Note carefully the maximum temperature and the time of its occurrence. After all the readings have been taken and recorded, remove the bomb from the calorimeter, open the valve to relieve the pressure, and take off the cover. Rinse out the bomb carefully with hot water and titrate the acid in the solution with a standard alkali solution. If the sulphur in the coal has not been determined, after titrating the acid, which is a combination of nitric and sul- 264 METALLURGICAL ANALYSIS phuric acids, make the solution acid with hydrochloric acid and determine the sulphur by precipitating it with barium chloride. (See p. 73.) Weigh the lengths of unburnt wire to determine how much has been burnt. To prevent rusting of the valve, the bomb should not stand wet too long, but should be carefully dried in an air-bath. Corrections. The maximum reading of the thermometer cannot be taken as the correct figure by which to multiply the weight of water in the calorimeter and its water value, for there has been (1) a loss of heat from the calorimeter while the thermometer has been rising; on the other hand deductions must be made (2) for the sulphur, which in ordinary combustion is oxidized chiefly to 862, but in the bomb is oxidized almost entirely to SOs; (3) for oxidation of some nitrogen to nitric acid, which would not take place in the ordinary burning of the fuel on a grate; and (4) for the burning of the iron ignition wire. 1. The correction for the loss of heat by radiation may be done graphically by the method of Holman * described by Howe.f Plot on cross-section paper, on a large scale, the corrected read- ings of the thermometer as ordinates, and the times of the read- ings as abscissas, and draw a line through these points, as shown in Fig. 95. The line i-m-o-p-r shows the maximum reading at o. Through o draw a line parallel to pr and project it to cut the ordinate through m at n. The number of degrees represented by the line mn is the corrected rise in temperature due to the combustion. Multiply the weight of water in the calorimeter added to the water value of the calorimeter by the rise in tem- perature represented by the line mn', the result will be the total number of calories produced by the combustion. From * " Physical Laboratory Notes," 46 (1887). t " Metallurgical Laboratory Notes," 35 (1902). CALORIFIC POWER OF COAL 265 this total must be deducted the heat of formation of the acids and of the magnetic oxide produced by the burning of the iron wire. 2. The correction for the higher oxidation of sulphur in the bomb cannot be made with absolute accuracy, for the quantity of heat produced depends not only upon the quantity of sul- phur present, but upon the form in which it occurs and the com- pleteness of oxidation. It is customary, however, to assume FIG. 95. Graph for Correcting Total Rise in Temperature. that all the sulphur in the coal is in the form of pyrite, and to deduct for each milligram of sulphur 2 calories.* 3. When the sulphur present has been calculated to sul- phuric acid, deduct it from the total acidity; the remainder is nitric acid formed by the oxidation of nitrogen. The forma- tion of 1 gm. of HNOs produces 238 calories. The correction is usually not more than 8 calories, f * A. H. White, " Gas and Fuel Analysis," 231 (1913). t Ibid., 230. 266 METALLURGICAL ANALYSIS 4. When 1 gm. of iron is burnt to FeaO-i, it yields 1600 calories; therefore, 1.6 calories must be deducted for every milligram of fuse wire burnt. Water Value of the Calorimeter. Burn in the calorimeter exactly in the manner described for coal, either 2 gms. of pure cane-sugar, C^lfeOn (3945 calories per gm.), 1.5 gms. benzoic acid, C7H 6 02 (6321 calories per gm.), or 1 gm. camphor, CgHieCO (9290 calories per gm.) and make the corrections which are made in the method for coal, except that for sulphuric acid, which is omitted. Deduct the number of calories thus determined from the calculated value, using the values given above. The dif- ference represents the heat absorbed by the calorimeter. Divide this number by the total corrected rise in temperature (mn. Fig. 95, p. 22) and the quotient represents the equivalent in water of the calorimeter, or its water value. Formula for Calorific Power. The method for calculating the calorific power may be indicated by the formula ^_ C = the calorific power of the material. (Calories produced by burning 1 gm.); r = the corrected rise in temperature; W = the weight of water in the calorimeter in grams; w = the water value of the calorimeter; JV = mgm. of nitric acid; a = mgm. of sulphuric acid; F = mgm. of iron wire burnt; S = weight of the sample of coal burnt. If approximate determinations are to be made, and no corrections applied for loss or gain from the heat of the room, the error will be reduced by beginning the operation with the water in the calorimeter about 3 C. below the temperature of the room, for, since the rise of tem- perature due to combustion, under this condition, will bring the cal- CALORIFIC POWER OF COAL 267 orimeter to about room temperature, there will be only a slight tendency for gain or loss to the calorimeter. Dickinson's Formula. For calculating the calorific power by Dickinson's formula, the water in the calorimeter should be about 3 C. below room temperature when the operation begins. The thermometer is read every minute for five minutes, or until the rise in temperature is uniform; then, on the fifth minute, close the circuit to ignite the coal and note the time a and the temperature t. To the temperature t (corrected) add 60 per cent of the expected total rise in temperature and call iU 2 . The total rise of the thermometer for any calorimeter is nearly con- stant if the tests are always made on the same quantity of coal 60 per cent of the expected rise is therefore based upon previous determina- tions. When the thermometer has risen to fe, note the time b. Continue reading the thermometer every minute for about ten minutes until the change of temperature has become uniform. Observe which of these readings is the first one in the period of uniform change and mark it c. Now find the rate of rise in temperature r\ for the pre- liminary period, that is, from the first reading up to a, and the rate of cooling per minute, r2, during the final period, that is, from c to the end. Open the bomb, wash it out, and determine the amount of acid formed and the weight of wire burnt as directed on page 263. From the above data calculate the calorific power according to the formula given below. ri = rate of rise in temperature (preliminary); a = time of last reading preliminary period; t = temperature at time a; t2 = t-\-QO per cent of expected rise; 268 METALLURGICAL ANALYSIS 6 = time when thermometer reads fo; c = time when change in temperature has become uniform after combustion; tz = temperature at time c; r2 = rate of cooling in final period; [fi(b a)+Z] = total temperature rise T. The intervals of time c b and ba are to be expressed in minutes and tenths of minutes. T multiplied by the weight of water in the calorimeter plus its water value equals the total amount of heat liberated. This quantity corrected for the acid and FesCU formed, and divided by the weight of coal taken, will give the calorific power. CALORIFIC POWER OF COAL BY THE PARR CALORIMETER * In the Parr calorimeter the coal is burnt, not by oxygen under compression, but by oxygen furnished by sodium peroxide and potassium chlorate, which are mixed with the coal. The following reactions are believed to take place: 2Na 2 O 2 + C = Na 2 CO 3 +Na 2 0. Na 2 O 2 +H 2 = 2NaOH. Since there is no gas under compression, either before or after the combustion, a strong bomb is not required, but only a comparatively light " cartridge. " The cartridge is placed in a cylindrical brass calorimeter vessel, which is insulated from the heat of the room by two concentric fiber pails. The tem- perature of the water in the calorimeter is taken with an accurate thermometer, graduated to hundredths of a degree, and the water is stirred by rotating the cartridge, to which are clamped * Jour. Amer. Chem. Soc., 22, 646; Jour. Ind. and Eng. Chem., 1, 673. CALORIFIC POWER OF COAL BY PARR CALORIMETER 269 propeller-like wings. A belt from a motor drives the pulley attached to the stem of the cartridge, the cartridge turning on a pivot fixed in the bottom of the calorimeter vessel. (Fig. 96.) Operation of the Calorimeter. Weigh 0.5 gm. of the coal which has been ground to pass a 100-mesh screen, and transfer it to the cart- ridge, in which has already been placed 1 gm. of finely ground KC10 3 . Add about 10 gm. of Na2O2 (measured in a scoop fur- FIG. 96. Parr Calorimeter, nished with the calorimeter) . Close the cartridge with the false cover and shake to mix the coal and reagents thoroughly. The Na 2 2 must be fresh. It deteriorates rapidly on exposure to air and moisture. The cartridge must be thoroughly dry before putting in the charge. Attach a loop of 34 or 36 B. & S. gauge iron wire to the termi- nals so that it will be pressed down into the charge when the cap is put on. Screw the cap on, making sure there are no leaks, for a little water in the bomb would spoil the determination and might cause an explosion. Put in the calorimeter 2000 gms. of water at about 2 C. below room temperature. Place the cartridge on its pivot, adjust the cover, thermometer, electric wires for firing, and the belt on the pulley. Start the cartridge rotating at about 100 revolutions per minute and read the thermometer every minute (see p. 263). After four or five minutes, when the rise in temperature has become uniform, close the circuit to ignite the charge, and continue reading the thermometer for about eight minutes after igni- tion, noting the maximum temperature reached. The rise in temperature may be corrected according to the method given 270 METALLURGICAL ANALYSIS on page 265. According to Professor Parr * the increase in tem- perature should be further corrected by " a factor made up of the following components ": Each per cent of ash is multiplied by 0.00275 C. Each per cent of sulphur is multiplied by 0.005 C. Correction for heat reaction of 1 gm. KClOs-- , 0.130 C. Heat of combustion of fuse wire 0.008 C. The corrected rise in temperature T is multiplied by the water in the calorimeter (2000 gms.) added to its water value, which is for the Parr calorimeter 135. Professor Parr found, by care- ful tests, that the heat evolved in burning coal in oxygen is 73 per cent of that produced when the coal is burnt in Na2C>2; therefore, -the calorific power C may be calculated from the fol- lowing equation: _ 7(2135)0.73 W in which T represents the corrected rise in temperature and W the weight of the sample. When W equals 0.5 gm. the calorific power equals 73 117. CALORIFIC POWER FROM THE ULTIMATE ANALYSIS The calorific power of coal may be calculated from its ultimate analysis by multiplying the percentage of each of its constituent combustible elements by its calorific power and taking the sum of the products. The following correction, however, must be made for hydrogen. It is assumed (Dulong's formula) that all the oxygen in coal exists in combination with hydrogen as water; therefore, a sufficient quantity of hydrogen to combine with all * Jour Ind. and Eng. Chem., 1, 673. PETROLEUM 271 the oxygen present as H2O, is deducted from the total hydrogen before multiplying by its calorific power. Since the weight of the hydrogen in water is equal to one-eighth of the weight of the oxygen, deduct from the percentage of hydrogen one- eighth of the percentage of the oxygen in the coal; and then calculate the calorific power as follows: Percentage CX8100(C to CC^) calories produced by carbon. H-(J percentage of O)X 34,500 (H to H 2 O, liquid) = calories produced by hydrogen. SX2164(S to 802) = calories produced by sulphur. Take the sum of these products for the total calories produced by 1 gm. of the coal. This method usually gives lower results than those obtained with the calorimeter. The difference is not uniform, but the average for more than 50 determinations made by the U. S. Geological Survey is about 1 per cent. To convert calories to British thermal units multiply by 1.8. PETROLEUM Sampling. If the oil can be sampled while it is flowing from a pipe, the samples should be taken at regular intervals with a small dipper and collected in a pail. If the oil is in tanks or barrels, lower a long tube, which is open at both ends, vertically into the oil until it touches the bottom of the container, close the lower end of the tube by pressing into it a stopper held on the end of wire which passes through the tube; or, if the tube is small, close tightly the upper end and withdraw it with the sample. Instead of a tube, a bottle attached to a rod or stick may be depressed well into the oil, the stopper withdrawn by a string, and the bottle allowed to fill. 272 METALLURGICAL ANALYSIS FRACTIONAL DISTILLATION OF CRUDE PETROLEUM In the examination of crude petroleum the oil is divided into various products by fractional distillation and the quantity, specific gravity, color, etc., of the several products determined. The crude oil is placed in a still provided with a thermometer which has its bulb opposite the outlet of the still. The temper- ature is raised gradually and the distillate of light oil, naphtha, gasolene, etc., is collected, until the temperature reaches 150 C. This distillate is removed and another receiver is attached to collect the illuminating oil, which distils over while the heat is gradually increased from 150 to 300 C. After the illuminating oil, the lubricating oil is collected until there is only coke left in the still. For the test, Gray * recommends the following method: Measure from 2 to 4 liters of the crude petroleum and distil it at the rate of 5 to 10 cc. per minute and collect the distillate in 1 per cent fractions. Take the fractions of more than 58 B. for the naphtha fraction, all those between 58 and 36 B. for burning oils, and those below 36 B. for lubricating distillate; the residue is coke. Sulphur in Petroleum. Sulphur is best determined in petroleum by burning the oil in a calorimeter with oxygen under a pressure of 25 to 30 atmospheres, washing out the bomb, acidifying the washings with HC1, and precipitating the S as BaSO4 with BaCl2 solution. Calorific Power of Liquid Fuels. Place a weighed quantity of the liquid in a narrow platinum crucible, f If the liquid is burnt in a shallow capsule, combustion is not always complete. Above the liquid, on a glass platform in the crucible, place a weighed quantity of powdered sugar (3945 calories per gm.). * " Industrial Chemistry," p. 522. t Richards and Jesse: Jour. Amcr. Chem. Soc., 32, 268. WATER IN OIL 273 Place the crucible in the bomb of a calorimeter with the fuse wire adjusted in the sugar and carry out the operation in the manner described for determining the calorific power of coal on page 262. Of course the number of calories produced by the burning of the sugar must be deducted from the total. WATER IN OIL Distil 200 gins, of the oil in a small still and collect the dis- tillate until the temperature reaches 150 C. Collect the water from the distillate with a micropipette and weigh it. If any drops of water adhere to the inside of the condenser and do not run into the receiver, wet a small pellet of absorbent cotton,* squeeze it as dry as possible, weigh it, fasten it to a wire, and run it into the condenser to collect the drops, weigh it again and add the increase in weight to that of the water found in the receiver. GAS ANALYSIS Sampling. A tube of porcelain,- fused quartz, or glass is inserted through an opening in the side of the flue or chamber containing the gas and the sample is withdrawn through it, usually by aspirator bottles. The sample should be taken across the whole section of the moving gas, the greater portion from the central, or more rapidly moving part of the column. This may be accomplished by closing the inward end of the tube and admit- ting the gas through perforations along the side so spaced that the gas will enter in the proper proportion at different points in the cross-section of the flue. The same result may be accomplished by wiring together a number of small tubes of different lengths so that they terminate at different points in the flue. The end of the bundle of tubes which projects out of the flue is set with cement in an iron tube * U. S. Bureau of Mines, Technical Paper, 25, 10. 274 METALLURGICAL ANALYSIS just large enough to receive it. The iron tube is connected by a reducer to a rubber tube through which the gas is delivered to the receiver.* An iron sampling tube may be used for cool or moderately warm gases. The composition of gas is changed by contact with hot iron. The water used in the aspirator bottles should be thoroughly shaken with a quantity of the gas to be sampled before the sample is taken, to saturate it completely with the several com- ponent gases; otherwise the composition of the sample would be changed by the varying degrees of solublity of the components. The Gas Burette. Gas is measured for analysis in a burette, (Fig. 97) usually of 100 cc. capacity, provided with a stopcock and capillary, at the upper end. To dispense with the necessity of correcting the volume of gas for changes of temperature while the analysis is going on, due to changes in the temperature of the surrounding air, the burette is enclosed in a large glass tube which is filled with water and closed at each end with a rubber stopper, through which the burette projects. The water in the tube is allowed to 1Q ' attain the temperature of the room before the Burette. , . , . analyis begins. Gas Pipettes. A gas pipette is a bulb or tube, or a combina- tion of these, in which gaseous mixtures are brought into con- tact with absorbents. Each pipette contains an absorbent for a single gas or group of similar gases and is provided with a capil- lary tubular outlet, through which the gas is passed to the burette for measurement. (Figs. 98 and 99.) Explosion Pipette. For the determination of methane and hydrogen a measured quantity of the gas, which has had removed from it C02, heavy hydrocarbons, 62, and CO, is mixed with * A. H. White, " Gas and Fuel Analysis," p. 10. GAS ANALYSIS 275 an excess of air and exploded over mercury in a pipette of heavy glass (Fig. 100), provided with stopcocks and fused-in electric FIG. 98. Gas FIG. 99. Gas Pipette Pipette (Richards). (Hempel). FIG. 100. Explosion Pipette. terminals for the passage of an electric spark for the ignition of the mixture. The Gases in Gaseous Mixtures. In technical gas analysis the following gases are separated and measured : (1) Carbon dioxide, C0 2 ; f ethylene, C2H4 f C n H 2?1 | propylene, C 3 H 6 (2) Heavy hydrocarbons of 1 butylene, C4H 8 the series | C n H 2n _ 2 acetylene, C2H 2 I P H '*' I benzine, CeHe n 2n ~ 6 { toluene, C 7 H 8 * (3) Oxygen, O 2 ; (4) Carbon monoxide, CO; (5) Hydrogen, H 2 ; (6) Methane, CH 4 ; and (7) Nitrogen, N 2 . * Winkler and Lunge, " Technical Gas Analysis," 66. 276 METALLURGICAL ANALYSIS Absorbents. Absorbent for CC>2. Solution of potassium hydroxide. Dissolve 250 gms. of commercial potassium hydroxide (KOH) in 1 liter of water; 1 cc. contains 0.21 gm. KOH and absorbs 0.083 gm., or 42 cc. of CO2. Absorption should be complete within two or three minutes. This solution also absorbs acid fumes if they are present. Absorbent for Heavy Hydrocarbons. Fuming sulphuric acid, sp.gr. 1.938, which contains 24 per cent free SOs. Shake the acid in the pipette with the gas for five minutes. Absorbent for Oxygen. Alkaline solution of pyrogallol. Dissolve 250 gms. of KOH in a liter of water and add to it 50 gms. of CeH3(OH)3. Agitate the absorbent with the gas in the pipette five minutes. One cubic centimeter will absorb about 10 cc. of oxygen. If the solution is not fresh, it gives up CO after taking up oxygen, giving incorrect results for both oxygen and CO. Yellow phosphorus in sticks may be used for the absorp- tion of oxygen, but under certain conditions it is not satisfactory.* Phosphorus does not absorb oxygen readily if the temperature is low, 12 to 15 C. or lower; if the oxygen is not well diluted with nitrogen; and if certain gases are present, among the num- ber being acetylene, ethylene, etc. Absorbent for CO. Cuprous chloride solution. Dissolve 250 gms. HN4C1 in 750 cc. of water in a bottle provided with a rubber stopper. Add 200 gms. CuCl and a small strip of sheet copper to prevent oxidation to cupric chloride. For use in the pipette, add 50 cc. of ammonia to 150 cc. of the cuprous chloride solution. One cubic centimeter of this solution will absorb 16 cc. of CO. The gas should be passed into two pipettes of this solution in succession; the second one should contain very fresh solution, to effect complete absorption of all the CO. * Winkler and Lunge: " Technical Gas Analysis," 69. ANALYSIS OF A GAS 277 Methane and hydrogen arc best determined by explosion over mercury in an explosion pipette, in the manner described on page 278, and nitrogen is estimated by difference. ANALYSIS OF A GAS Measuring the Gas. Set up the burette with leveling tube attached to its lower end by means of a long rubber tube. Pour enough water into the leveling tube to bring the water sur- face near the lower end of the tube when the burette is full. The water should be rendered slightly acid and should be saturated with the gas to be analyzed before the analysis begins. Open the stopcock of the burette and raise the leveling tube until the water fills the burette and the capillary from the stopcock. Close the stopcock. With a small rubber tube, attach the burette to the capillary leading to the aspirator bottle, or other container of the gas to be analyzed. Open the stop- cock and lower the leveling tube to draw the gas into the burette. When the burette has been filled, close the stopcock and hold the leveling tube alongside the burette to bring the surface of the water in the burette and in the leveling tube to the same level. Read the burette. CO2 in Gas. Fill the bulb of the pipette and its capillary tube with the absorbent. Attach the pipette to the burette with a small rubber tube, open the stopcock, and raise the leveling tube to drive the gas into the pipette. When all the gas has been driven over and the water of the burette fills the capillary of the pipette, close the stopcock and shake the pipette carefully for four or five minutes. Open the stopcock, lower the leveling tube, and draw the gas into the burette until the absorbent in the pipette approaches the stopcock. Close the stopcock, bring the water in the burette and leveling tube to the same level, and read the burette. The loss in volume represents 278 METALLURGICAL ANALYSIS the C(>2 and this divided by the original volume gives the per- centage of C02 in the gas. Heavy Hydrocarbons in Gas. After the absorption of the C02, pass the remaining volume of gas from the burette into the pipette containing the absorbent of heavy hydrocarbons and agitate the pipette about five minutes. Return the gas to the burette and, since it may contain fumes of sulphuric acid, it should be passed into the KOH pipette, shaken, and returned to the burette before the volume is read. The decrease in volume represents the heavy hydrocarbons. Oxygen in Gas. After the determination of heavy hydro- carbons, pass the remaining gaseous mixture into the pipette for the absorption of oxygen in the manner described above for the determination of CCb, and, after agitation, return the remain- ing gas to the burette and note the diminution in volume, which represents the oxygen in the gas. The absorbent must be frequently renewed. See note under absorb- ent for oxygen. CO in Gas. Pass the gas next into the first absorption pipette for CO and, after agitation, pass it into the second pipette for CO containing fresh ammoniacal cuprous chloride solution, and, finally, return the remaining gas to the burette and read its volume for the estimation of CO. Nitrogen in Gas. If the gaseous mixture contains no hydrogen or methane, the volume in the burette, after the absorption of CO, is read and recorded as nitrogen. H and CH4 in Gas. If the gaseous mixture contains either or both of these gases, after the CO has been determined, a suitable volume 10 to 15 cc. of the remaining gas is measured in the burette, the stopcock closed, the leveling tube lowered, and the stopcock opened to admit 60 cc. to 70 cc. of air; the quantity must be sufficient to furnish more than enough oxygen to combine with the hydrogen and methane present. The vol- ANALYSIS OF A GAS 279 ume of the total mixture is read; it is passed into an explosion pipette containing mercury and is exploded by passing an electric spark through it. 2H 2 +O 2 = 2H 2 O. One volume of CH4 combines with two volumes of oxygen to form one volume of CO 2 and two volumes of water (in the gaseous form), but the water , condenses, leaving only the one volume of C0 2 . The free hydrogen combines with oxygen in the proportion of two volumes of the former to one of the latter, the three disappearing when the resulting water condenses. Pass the gas back into the burette and read its volume. Note the diminution in volume owing to the formation of water. Pass the gas now into the C0 2 pipette, agitate, return the gas to the burette, and read its volume. This diminution in volume is due to absorption of C0 2 formed from the methane and is equal to the volume of the methane. Twice the volume of the methane represents the volume of oxygen withdrawn from the mixture by the hydrogen of the methane. The remaining diminution of volume, owing to the formation of water, is due to the burning of the free hydrogen, and two-thirds of this reduction represents the volume of hydrogen. Example. Readings of Burette. Volume of Gas. cc. Sample of gas taken 98 8 98 8 After absorption of COz 97 2 Volume of CO 2 . 1 6 After absorption of heavy hydrocarbons 93 4 Volume of heavy hydrocarbons. 3 8 After absorption of oxygen ... . 93 Volume of oxygen . . 4 After absorption of CO. ... 84 2 Volume of CO 8 8 280 METALLURGICAL ANALYSIS Example. Readings of Burette. Volume of Gas. cc. Retained in the burette for determination of CH 4 and H 2 12 4 Air drawn in for explosion mixture 96 4 After explosion and cooling . . . 74 8 Contraction due to formation of H 2 O After absorption of CO 2 resulting from CH4. 68 21.6 Volume of CH 4 6 8 Contraction due to withdrawal of O 2 to combine with CH 4 to form H 2 O (2 X6.8) 13.6 Contraction due to H 2 O formed from free H 2 and O (216-13.6) 8.0 Contraction due to H 2 (f X8) 5.3 (> -y OA 9\ ^ ) . /5.3X84.2\ 46.2 QC A The composition of the gaseous mixture is therefore as follows: CO 2 1.6 Heavy hydrocarbons 3.8 2 .. CO. CH 4 H 2 .. N 2 ., 0.4 8.9 46.7 36.4 2.0 EXPLOSION METHOD FOR CARBON MONOXIDE, METHANE, AND HYDROGEN In the laboratories of the United States Steel Corporation * CO, CH4, and H 2 are determined as follows: Explode a sample of the gas with a known quantity of a definite mixture of nitrogen and oxygen ; note the contraction (I) . Pass the gas into a KOH pipette to absorb the CO 2 and measure * Met. and Chem. Eng., 9, 302 and 356. CARBON MONOXIDE, METHANE, AND HYDROGEN 281 the residue; note the contraction (II). Add a definite volume of hydrogen (sufficient to combine with all the remaining 2 as H 2 0) and explode with an electric spark. Measure the residue of nitrogen and hydrogen and note the contraction (III). From these data taken in conjunction with the reactions, 2CO+0 2 = 2C0 2 2H 2 +0 2 = 2H 2 O CH 4 +2O 2 = CO 2 +2H 2 O, the following equations are formed : Contraction I = | carbon monoxide+f hydrogen+2 methane. Carbon dioxide formed = carbon monoxide + methane. Oxygen consumed = f carbon monoxide +J hydrogen+2 methane. From these equations the following formulae for calculating the components of the original sample are derived: Oxygen consumed = oxygen added J Contraction III. Hydrogen = Contraction I oxygen consumed. Carbon monoxide _ Con. I+(4XCon. II)+Con. Ill-oxygen added 3 Methane = Contraction II carbon monoxide present. The Orsat Apparatus. This is a compact arrangement of a gas burette, absorption pipettes, etc., in a portable case (Fig. 101). The burette is attached permanently to the pipettes with capillary tubing provided with the necessary stopcocks. The manipulation in the process of analysis is practically the same as that described on page 277. Many modifications of the original Orsat apparatus have been described. Among them may be mentioned those of Allen and Moyer,* Williams, f and Burrel.t * Trans. Amer. Soc. Mech. Eng., 18, 901. f Jour, of Ind. and Eng. Chem., 4, 387 (1911). | Jour, of Ind. and Eng. Chem., 4, 297 (1911). 282 METALLURGICAL ANALYSIS Automatic Analysis of Gas. Apparatus of various types are in use for measuring and recording mechanically the percentage of a single gas in a gaseous mixture. They have been adapted to the estima- tion of C0 2 , SO 2 , HC1, and C1 2 . In the Simmance-Abady Automatic Gas Analyzer (Fig. 102)* the gas is drawn into a bulb in measured portions from the flue, from which it is forced through an absorbent into a second bulb which rises to a point on a scale indi- cating the volume of gas that has been absorbed. A pen records the percentage on a chart actuated by a clock, and the gas is automatically discharged as the bulb descends in position to receive the succeeding sample. The Uehling carbon dioxide meter FIG. 101. Orsat Apparatus. FIG. 102. Simmance-Abady Automatic Gas Analyzer. * Met. and Chem. Eng., 9, 327, and 10, 121. CALORIFC POWER OF GAS 283 (Fig. 103)* measures and records the drop in pressure between the orifices of admission and exit to the absorbent chamber. With this instrument the per cent of CO2 may be indicated at the boiler front and a continuous record made elsewhere at the same time, of both the CC>2 and the temperature. Calorific Power of Gas. The calo- rific power of gas is usually determined in a calorimeter of the Junkers type (Fig. 104). FIG. 103. Uehling Carbon Dioxide Meter. FIG. 104. Junkers Gas Calorimeter. A definite volume of the gas is burnt in a Bunsen burner, at a uniform rate, the flame being surrounded by a jacket', through which water flows at a rate regulated so as to absorb all the heat of the flame. A thermometer is fixed in the stream of water at its inlet and one at the outlet. To make a test, the gas is ignited and, while it is burning at a definite and uniform rate shown by the meter, and the * Met. and Chem. Eng., 9, 329, and 10, 497. 284 METALLURGICAL ANALYSIS water is flowing uniformly through the calorimeter, the two thermometers are observed until the readings have become con- stant. When the hand of the meter passes a certain point, the zero, for instance, the tube through which the water flows from the calorimeter is quickly turned to deliver the water to a receiver, where it is allowed to collect until the hand of the meter returns to the point selected for the beginning of the test. The thermometers are to be read frequently to see if they remain constant. If they do not, the readings are to be averaged. The water is then weighed and its weight multiplied by the difference in temperature between the inflowing and the out- flowing water. This gives the quantity of heat produced by the gas that was burnt while the water was being collected. In order that tests may be comparable, one with another, it is nec- essary in each test to correct the volume of the gas for tem- perature and pressure to a uniform standard; usually, when English units are used, to 60 F. and 30 ins. of mercury. In the laboratories of the United States Steel Corporation, 62 F. and 30 ins. of mercury have been adopted as the standard. A table for reducing volumes of gas to this standard is given on page 330.* At the time a test is made, a thermometer and barometer are read which give the conditions under which the gas is burned. The measured volume of gas is then reduced to standard conditions (usually expressed in cubic feet) and the total heat produced, divided by this corrected volume, gives the heating power in British thermal units if English units have been used throughout, and in calories if 15 C. and 760 mm. of mer- cury are taken as the standard, and the gram and centimeter as the units. Automatic Recording Gas Calorimeter. If the water is made to flow into a calorimeter at a constant temperature and uniform rate, and the gas is burnt at a constant rate, then any change in the heating value of the gas will be expressed by a change * Met. and Chem., Eng., 9, 358. CALORIFIC POWER OF A GAS FROM ITS ANALYSIS 285 in temperature of the water flowing from the calorimeter. A calorimeter, then, which has a self-registering thermometer to record continuously the temperature of the outflowing water becomes a self-registering calorimeter. CALCULATION OF THE CALORIFIC POWER OF A GAS FROM ITS ANALYSIS The heating value of a gas may be calculated with a fair degree of accuracy from its analysis, if, in addition to the H2, CHi, and CO, the components of the heavy hydrocarbons are identified and the quantity of each determined. This presents no difficulty with blast-furnace gas which is devoid of heavy hydrocarbons, and little difficulty is experienced with producer gas and natural gas, since the former usually contains only a very small quantity of such, and that is ethylene, C2H4, and the latter is composed chiefly of methane, CELi, and ethane, The quantity of each combustible component in a cubic foot of the mixture is multiplied by its heating value and the sum taken as the calorific power of the gas. The heating values of these gases are given below in B.t.u.'s per cubic foot at 62 F. and a pressure of 30 ins. of mercury, based on Earnshaw's calculations.* B. t. u.'s per cu. ft. at 62 and 30" mercury. Hydrogen, H 2 .................. . ....... 325.0 Methane, CH 4 ......................... 1005.3 Carbon monoxide, CO ................... 322.2 Ethylene, C 2 H 4 ........................ 1581.9 Ethane, C 2 H 6 .......................... 1757.6 * Jour. Franklin Inst., 146, 161. 286 METALLURGICAL ANALYSIS ANALYSIS OF CLAY The Sample. Clays should be sampled and the sample prepared for analysis according to the method described for sampling limestone, page 160. The clay must be dried before grinding. Moisture. Weigh 1 gm. of the sample, transfer it to a 30- gm. platinum crucible, heat at 110 C, for an hour, cool in a desiccator and weigh. The loss in weight represents the moisture. Combined water is best determined with the bulb tube (method of Brush and Penfield) described on page 49. Loss on Ignition. Weigh 1 gm., transfer it to a 30-gm. platinum crucible, cover, and heat with a blast lamp thirty minutes, cool in a desiccator and weigh. The loss in weight is reported as the loss on ignition. SiO2. To 1 gm. of the sample in a 30-gm. platinum crucible (or to the residue after the determination of moisture or loss on ignition) add 6 gms. of dry sodium carbonate, fuse, and com- plete the determination according to the method for 8162 on page 71. Fe2Os. To the filtrate from the Si02 (above) add ammonia to precipitate the hydroxides of iron, aluminum, etc. Filter, wash the precipitate into a beaker (see p. 61), dissolve it in sulphuric acid, reduce the iron with zinc to the ferrous condition, and titrate it with standard potassium permanganate solution (see p. 55) ; or the precipitate may be dissolved in hydrochloric acid and titrated with standard potassium dichromate solution after reduction with stannous chloride (see p. 62). If the latter method is used, see note in regard to effect of platinum (p. 63). CaO. To the filtrate from the precipitate of iron and aluminum hydroxides add ammonium oxalate and complete the determination according to the method described on page 162. MgO. Precipitate the magnesium as magnesium ammonium ALKALIES IN CLAY 287 phosphate and proceed according to the method for the determi- nation of magnesia in limestone, page 165. A^Oa. Weigh a separate portion and proceed according to the method (phosphate) described on page 87. ALKALIES IN CLAY J. LAWRENCE SMITH METHOD * Reagents. Pure dry ammonium chloride, NH4C1. Pure calcium carbonate, CaCOs. Ammonium carbonate, (NH^COs. Ammonium oxalate solution. Dissolve 40 gms. (N [4)20204 +2H 2 in 1 liter of water. Alcohol, 80 per cent strength. Solution of chlorplatinic acid. Weigh 1 gm. of the clay and transfer it to an agate mortar; add 1 gm. of ammonium chloride and grind well to mix. Add nearly all of 8 gms. of calcium carbonate and grind. Place a little calcium carbonate in a large platinum crucible, or better, in a long narrow crucible with close fitting cap, designed for the purpose (Fig. 106). r~, , . FIG. 105. Lawrence Smith The calcmm carbonate prevents the sm- Crudble for Alkali De _ tered cake from sticking, f termination. Transfer the charge from the agate mortar to the crucible. Grind the remaining part of the 8 gms. of calcium carbonate in the mortar to clean out the charge, and add it to the crucible. Put on the cover and heat *Amer. Jour. Sci., Second Series, 50, 269 (1871). Hillebrand, Bull. 422, U. S. Geological Survey, p. 171 (1910). t Schaller, Bull. U. S. G. S., 422, 173. 288 METALLURGICAL ANALYSIS gently the lower two-fifths of the crucible, keeping the top cool to prevent loss by volatilization of the alkaline chlorides formed. If an ordinary crucible is used, let it project through a hole in an asbestos board (see Fig. 58, p. 74) to protect the top from the heat of the flame. Keep the heat low for about ten minutes until the odor of ammonia no longer comes from the crucible, then heat the lower part of the crucible to redness and continue the heating at that temperature for about forty-five minutes. This converts the alkalies, and much of the calcium, to chlorides. Transfer the sintered cake to a platinum dish, and add 1 or 2 cc. of hot water.* When the cake is slaked, add hot water and stir to disintegrate thoroughly. Filter and wash by decanta- tion and finally wash thoroughly on the filter with hot water. Add to the filtrate ammonia and about 1.5 gm. ammonium carbonate, which will precipitate nearly all the calcium. CaCl-KNH 4 ) s CO 8 =CaCO,+2NH4Cl. Filter and wash. Evaporate the filtrate to dryness in a plat- inum dish and carefully heat to dull redness to drive off salts of ammonia. The dish should be fitted into a hole in an asbestos board to prevent the admission of sulphur to the solution from the gas flame. Dissolve the alkaline chlorides in a very little water. If the sample contains sulphur or if sulphur has been intro- duced from the flame, add a drop of BaCb solution. Then add a little ammonium carbonate solution to precipitate the remain- ing Ba, and finally, add a little ammonium oxalate solution to precipitate the remaining calcium. Filter into a platinum crucible and evaporate the filtrate to dryness, taking precau- tions in regard to the introduction of sulphur from the flame. * Steiger, loc. cit, 173. ALKALIES IN CLAY 289 Cool in a desiccator and weigh. Dissolve in a little water and, if there is an insoluble residue, filter into a small porcelain dish, wash, ignite the paper with the residue, cool, weigh, and deduct from the previous weight. The difference represents the com- bined weight of potassium and sodium chlorides. K 2 O. To the solution of the chlorides in the porcelain dish add an excess of a solution of chlorplatinic acid. Any precipitate which forms should dissolve when heated on the water-bath. Evaporate the solution until the residue solidifies on cooling Now treat the mass with 80 per cent alcohol, filter through a very small filter, and wash by decantation with more of the alcohol, retaining as much as possible of the precipitate in the dish. Dry the dish and filter a few minutes to drive off the alcohol. Transfer the precipitate to a weighed platinum crucible. Dis- solve with hot water any precipitate that adheres to the dish and wash it through the filter into the crucible. Evaporate the solution to dryness on a water-bath, cover the crucible to prevent loss by decrepitation and heat to 135 C. Cool in a desiccator and weigh K 2 PtCl 6 . The factor for KC1 in K 2 PtCl 2 is 0.30674 and the factor for K 2 O in K 2 PtCl 6 is 0.19376. Na 2 O. Deduct the weight of KC1 from the combined weight of KC1 and NaCl and multiply the difference by the factor for Na 2 in NaCl, which is 0.53028. The sodium may be determined directly from the filtrate from the potassium platinic chloride by evaporating the solution and precipitating the platinum with H 2 S, filtering and evaporat- ing the filtrate to dryness and weighing as NaCl. 290 METALLURGICAL ANALYSIS METHODS FOR THE DETERMINATION OF SOME OF THE MINOR METALS CHROMIUM * Weigh 1 gm. of the sample, which must be ground extremely fine, and fuse it one hour in a platinum crucible with about 10 gms. of a basic mixture composed of 4 parts of lime or magnesia and 1 part each of potassium and sodium carbonates. Transfer the sintered mass to a beaker and dissolve it in water and sul- phuric acid. If any black particles remain undissolved, filter them off and fuse them again with the basic mixture; dissolve and add to the first solution. Add an excess of standard ferrous ammo- nium sulphate solution, accurately measured, and titrate the excess with standard potassium permanganate solution. (See p. 141.) NICKEL AND COBALT Add to 1 gm. of the sample in a 200-cc. Erlenmeyer flask 15 cc. of NHOs and boil until the solution becomes syrupy. Add 10 cc. NHOs and 5 gms. KClOs and boil ten minutes. Add 5 cc. more of HNOs and 5 gms. KClOs and boil until yellow fumes are no longer produced. Cool, add 40 cc. of hot water, filter, and wash. Reserve the filtrate (a). Wash into the flask the residue on the filter. Place the flask under the funnel and pour through the filter 15 cc. of warm dilute hydrochloric acid (1:2) and wash with a little hot water. Heat the flask to dissolve the residue. Add 20 cc. bromine water and an excess of ammonia. Boil, let the precipitate settle, filter, and wash with hot water. Combine this filtrate with the filtrate (a), and boil off the excess of ammonia. Neutralize the solution with hydrochloric acid and add 10 cc. in excess. Boil, dilute * Sutton, "Volumetric Analysis," p. 182. NICKEL AND COBALT 291 to 300 cc. and saturate the solution with hydrogen sulphide by passing through it a current of the gas. Filter and wash the precipitate with dilute hydrogen sulphide water. Boil the solution down to about 25 cc. and add NaOH to neu- tralize the acid. Pour this solution, which contains the nickel, cobalt, and zinc, slowly into 50 cc. of a 10 per cent solution of sodium hydroxide, stirring constantly. Dilute the solution with an equal volume of water and filter. Dissolve the pre- cipitate in a little hydrochloric acid, nearly neutralize with sodium hydroxide, and pour again into a 10 per^cent solu- tion of sodium hydroxide, stirring. Dilute and filter. Dis- solve the hydroxides of nickel and cobalt, in a little dilute [2804; wash the filter free from acid. Dilute the filtrate to 125 cc., add 5 gms. ammonium sulphate and 40 cc. of ammonia. Electrolyze several hours with a current of Dioo = 0.5 to 0.7 am- peres and 2.8 to 3.3 volts. When precipitation is complete, a few drops on a porcelain plate with ammonium sulphide should show no trace of black color. With rotating anode or cathode the current may be increased to Dioo = 4 amperes and 5.5 volts and the time of deposition thereby shortened to about half an hour. Ni. After weighing, dissolve the nickel and cobalt in nitric acid. Add hydrochloric acid and boil the solution down to convert nitrates to chlorides. Dilute so that there will be not more than 0.1 gm. cobalt per 100 cc. to prevent solution of the precipitate.* Heat to boiling, precipitate the nickel with dimethylglyoxime, and complete the determination according to the method on page 140. Co. When the nickel has been determined by the dimethyl- gloxime method, deduct its weight from the combined weight of nickel and cobalt and calculate the percentage of Co. * Trice and Meade ; " Brass Analysis/' p. 115. 292 METALLURGICAL ANALYSIS CADMIUM METHOD OF BEILSTEIN AND JAWEIN * Add 10 cc. of nitric acid to 0.5 gm. of the ore in a 250-cc. Erlenmeyer flask. Boil down to about 5 cc., add 7 cc. of sul- phuric acid and boil over a free flame to dense fumes of sul- phuric acid. Cool, add 25 cc. of water, heat to boiling, and let it stand hot to dissolve iron sulphate. Cool, filter, and wash with dilute sulphuric acid (1:1). Dilute the filtrate to 200 cc. and pass through it a current of hydrogen sulphide. Filter and wash with dilute hydrogen sulphide water acidulated with hydrochloric acid. Wash the precipitate into a beaker, using as little water as possible. Place the beaker under the funnel and pour through the filter a strong cold solution of potassium cyanide. Use as little potassium cyanide solution as possible to dissolve the sulphides of copper, etc., that may be present and leave the yellow or orange sulphide of cadmium. Filter through the same paper and wash with dilute hydrogen sulphide water. Dissolve the cadmium sulphide on the filter with as little hot dilute hydrochloric acid (1 : 1) as possible. Add 5 cc. of sul- phuric acid and boil to white fumes. Cool and dilute to 20 cc. Add a drop of phenolphthalein solution and then add pure sodium hydroxide solution until a permanent red color is produced. Stir and add a solution of potassium cyanide slowly, until the cadmium hydroxide dissolves, being very careful not to add an excess. Dilute to a volume of 100 to 150 cc. and electrolyze in the cold five to six hours with a current of Dioo = 0.5 to 0.7 amperes and 4.8 to 5 volts. After the expiration of this time, increase the current to about 1 or 1.2 amperes and continue the electrolysis one hour more. Wash the cathode successively with water, alcohol, and ether. Dry and weigh. * Berichte, 12, 466, through Treadwell-Hall, " Analytical Chemistry," Vol. 2, 150. MERCURY 293 If the stronger current is run from the beginning, the metal will be spongy; if the weaker current is continued, more than twelve hours will be required for total precipitation. MERCURY * Treat 1 gm. of the ore with 15 cc. of nitric acid and 10 cc. of hydrochloric acid at a gentle heat until the ore is decomposed. Add more nitric acid if necessary, but do not evaporate to too small a volume, since there is danger of volatilizing some mercuric chloride. Filter into an Erlenmeyer flask and wash. Nearly neutralize the filtrate with sodium carbonate and add a slight excess of freshly prepared ammonium sulphide. Shake the flask to rotate the solution and add a solution of pure sodium hydroxide until the dark liquid begins to clear. Heat to boil- ing and add more NaOH until the solution is perfectly clear. The mercury is now in solution as Hg(SNa)2. If any precipitate forms, filter; precipitate the mercury from the filtrate by adding ammonium nitrate. Boil until the odor of ammonia is very faint. Let the precipitate settle. Hg(SNa) 2 +2NH 4 N0 3 =2NaN0 3 + (NH 4 ) 2 S+HgS. If any free sulphur has precipitated with the sulphide of mercury, before filtering, boil with a little sodium sulphite to remove the sulphur. Na 2 S03+S=Na 2 S 2 3 ; The sulphur may be dissolved from the precipitate with carbon disulphide after filtering. Filter in a Gooch crucible and wash by decantation with hot water until the washings do not react with silver nitrate solution. Transfer the pre- cipitate to the crucible, dry at 110 C. and weigh as HgS. * Treadwell-Hall, " Analytical Chemistry," 2, 134. 294 METALLURGICAL ANALYSIS TIN If the ore is practically pure cassiterite the metallic tin may be reduced and recovered in a suitable bead for weighing by fusing the finely ground ore with potassium cyanide in a por- celain crucible. The fused mass, after cooling, is dissolved in water, and the metallic tin is dried and weighed. If the ore is impure, other metals may be reduced with the tin, and if silica is present, some of the tin will combine with it and go into the slag. The following method by Milon and Fouret * is recommended. Sn in Ore. Mix 2 gms. of the finely ground sample with 20 gms. of sodium dioxide in a 6-cm. sheet-iron crucible. Fuse carefully twenty minutes, cool and place in a 500-cc. beaker with 150 cc. of water. Cover with a watch glass and when the action becomes quiet, add, a little at a time, 70 cc. of hydro- chloric acid. When the mass is decomposed take out the crucible and wash it off. Heat the solution to 60 C. and add 4 gms. of iron filings to precipitate arsenic, antimony, and copper, and to reduce the stannic to stannous chloride. This operation requires about half an hour. Filter into a 500-cc. Erlenmeyer flask and wash the residue well with hot water. Heat the filtrate to 95 C. and add 10 gms. of pure zinc to precipitate the tin. Drops of the solution should be tested from time to time on a porcelain plate with hydrogen sulphide water. A brown precipitate indicates that tin is still in solution. When the tin is all precipitated, decant the solution through a funnel containing a plug of glass wool, leaving most of the tin and the zinc in the flask. Put the glass wool with the tin, which was carried over, into the flask. Fit the flask with a two-hole rubber stopper carrying glass tubes for the passage of CO2. Pass CO2 through the flask several minutes. Remove * Eighth International Congress of Applied Chemistry, 1, 373. TIN 295 the stopper and pour into the flask 30 cc. of hydrochloric acid. Replace the stopper and warm the flask gently until the tin and zinc are completely dissolved. Close the exit tube and cool the flask. When cold, disconnect the CO2 generator, remove the stopper and wash off the tubes with water from which the air has been expelled by CO2 (1 liter of water +3 gms. NaHCOs+HCl), dilute the solution to 250 cc. with the same water, add a few drops of starch solution, and titrate with standard iodine solution. Low * fuses 0.5 gm. of the ore mixed with a little charcoal in an iron crucible with sodium hydroxide, dissolves in hydro- chloric acid, reduces the stannic to stannous chloride with metallic iron, and titrates with standard iodine solution (9.7 gms. iodine per liter = about 1 per cent Sn per cubic centimeter when 0.5 gm. of ore is used). TIN GRAVIMETRIC METHOD Mix 1 gm. of the finely ground ore in a porcelain crucible with 3 gms. of dry Na2COs and 3 gms. of S. Cover the crucible and heat gently over a low flame until the sulphur has ceased to escape and burn (about twenty minutes). Cool the cru- cible and treat the fusion with hot water in a casserole. The tin should dissolve as sodium sulpho-stannate. Filter and wash the precipitate with hot water. If the residue feels gritty under the glass rod, burn the filter, add sodium carbonate and sulphur and repeat the process described above. Add the filtrate containing the residue of tin to the first filtrate. * " Technical Methods of Ore Analysis," 164a. fTreadwell-Hall, "Analyt. Chem.," 1, 222. 296 METALLURGICAL ANALYSIS Acidify the filtrate with sulphuric acid to precipitate the tin as 81182. Keep the solution warm while the precipitate settles. Decant the clear solution through a filter and wash by decantation with ammonium acetate solution made by adding an excess of acetic acid to dilute ammonia to prevent the precipitate from running through the filter. Transfer the precipitate to the filter and finally wash it with hot water. Place the filter and its contents in a weighed porcelain cru- cible. Heat very gently with free access of air until there is no longer an odor of burning sulphur. Gradually increase the heat to a high temperature. A high temperature at first may volatilize SnS 2 . Add about half a gram of ammonium carbonate and heat to drive out sulphuric acid completely. Cool, weigh, and repeat the treatment with ammonium carbonate several times until the weight of Sn02 is constant. The factor for Sn in SnC>2 is 0.78808. TIN IN CONCENTRATES Tin in cassiterite concentrates may be determined by the fire assay. Mix 5 gms. of the ore in a fire-clay crucible with 2 gms. of charcoal, 12 gms. of NaHCOs, and 1 gm. of borax glass. Cover with salt and place on top of the charge several lumps of char- coal. Fuse in a muffle at a little below white heat for about one hour. Withdraw the crucible from the furnace. When cool break the crucible and remove the slag from the tin button and weigh the tin. TUNGSTEN Fuse 1 gm. of the ore in a platinum crucible with 4 gms. of sodium carbonate for about forty minutes. Cool and extract the fusion by boiling in water. Filter. The tungstate and silicate of sodium are soluble. VANADIUM 297 Add to the filtrate an excess of nitric acid and evaporate the solution to dryness. Add a little hydrochloric acid, warm, and dilute with hot water. Boil and filter. Burn the residue in a platinum crucible to SiO 2 +WC>3. Add hydrofluoric acid and sulphuric acid to the crucible and evaporate to dryness to volatilize the silica. If necessary, repeat the treatment to volatilize the silica completely. Burn with the blast lamp and weigh as WOs. VANADIUM HILLEBRAND'S METHOD * Fuse 1 to 5 gms. of the ore with 4 to 20 gms. of sodium car- bonate and 0.5 to 3 gms. of potassium nitrate. Treat the fusion with hot water, add a few drops of alcohol to precipitate man- ganese, and filter. If the ore contains much vanadium, some will be retained by the residue on the filter. In this case, burn the filter with the residue and fuse it again in the manner directed above. Nearly neutralize the filtrate containing all the vanadium with nitric acid to precipitate aluminum hydroxide and silicic acid. Be careful not to make the solution acid on account of the reducing action of nitrous acid formed from nitrates in the fusion. The quantity of acid required to neutralize the sodium carbonate in the fusion can be determined on a separate portion. Evaporate the solution nearly to dryness. Treat with hot water and filter. When the filtrate is cold, add a nearly neutral solution of mercurous nitrate to precipitate vanadium. It also precipitates mercurous carbonate and, if the elements are present, the chromate, molybdate, arsenate, and phosphate. * Amer. Jour. Science, 6, 209; Treadwell-Hall, "Analytical Chemistry," 2, 277. 298 METALLURGICAL ANALYSIS Heat to boiling, filter, wash with a dilute solution of ammonium nitrate. Dry and burn in a platinum crucible at as low a tem- perature as possible. Add a little sodium carbonate and fuse. Cool and .treat with hot water. If a determination of chromium is desired, filter and determine it colorimetrically, using potassium chromate for a standard. Then acidify the solution slightly with sulphuric acid and precipitate the molybdenum, arsenic, and platinum with hydro- gen sulphide. Filter, boil the filtrate, and pass a current of CO2 through it to remove H 2 S. Titrate the hot solution with standard potassium permanganate solution. For the most accurate work, reduce the solution with sulphur dioxide, titrate again, and average the two titrations. For reactions see page 143. URANIUM Treat 1 gm. of ore with strong nitric acid until there is no further action; add 5 cc. of hydrochloric acid and evaporate the solution to dryness. Cool, add 3 cc. of hydrochloric and 25 cc. of hot water. Boil, filter, and wash with hot water. Dilute the filtrate to 150 cc. and pass a current of hydrogen sulphide through the solution. Filter, and wash with hydrogen sulphide water. Boil the filtrate to expel the hydrogen sulphide and oxi- dize by adding strong nitric acid. Add ammonia until nearly neutral. Pour the solution into 50 cc. of a 20 per cent solution of ammonium carbonate. Boil, let the precipitate settle, filter, and wash. Acidify the filtrate with hydrochloric acid and boil off all the carbon dioxide. Add an excess of ammonia, boil a few minutes, filter, wash with ammonium chloride solution and once with water. Burn and weigh UsOg. The U may be measured by titration as follows: Dissolve the precipitate of ammonium uranate in dilute LITHIUM 299 sulphuric acid, reduce with zinc for thirty minutes, completely dissolve the zinc, and titrate with standard permanganate solu- tion. U0 2 S04+H 2 +H 2 S0 4 = U(S0 4 ) 2 +2H 2 0. 5U(S0 4 ) 2 +2KMn04+2H 2 0=5U0 2 S04+K 2 S04+2MnS04+2H 2 S0 4 . The permanganate solution may be standardized against iron and its value in uranium calculated. 238 5 The value of the solution in iron multiplied by : - gives the value in uranium. METHODS FOR THE DETERMINATION OF SOME OF THE RARER METALS LITHIUM GOOCH'S METHOD * Reagent. Amyl alcohol. C 5 Hi 2 (boiling-point 131 C.). Weigh and treat the sample according to the Lawrence Smith method for alkalies in clay, p. 287, until the alkaline chlorides have been weighed. Evaporate the solution of the alkaline chlorides, which should not contain more than 0.2 gm. lithium chloride, to a very small bulk. Transfer the solution to a 50-cc. Erlenmeyer flask, add 6 cc. amyl alcohol, and care- fully heat the mixture to boil off the water. It is advisable to fit the flask with a two-hole stopper provided with intake and delivery tubes and draw a current of dry air through the flask to assist in the removal of water vapor and thereby prevent bumping. When the water has all been boiled out, the chlorides of potassium and sodium being insoluble in amyl alcohol, are * Proceedings Amer. Acad. of Arts and Sci., N. S., 14, 177. 300 METALLURGICAL ANALYSIS precipitated. Add 2 to 3 drops of strong HC1 to convert to chloride the small amount of LiOH that has been produced by hydrolysis. Boil a few minutes and filter while hot on asbestos. Wash with hot amyl alcohol that has been boiled. The filtrate, which contains the lithium and a very small amount of potassium and sodium, if they were present in the original material, is evap- orated to dryness. Add a little dilute sulphuric acid, and filter the solution from the carbonaceous residue into a weighed plati- num crucible. Evaporate the solution to dryness, ignite and weigh the Li2S04. Deduct from this weight, if K and Na were present, 0.00041 gm. for Na and 0.00051 for K and 0.00092 gm. if both were present for each 10 cc. of amyl alcohol in the filtrate. The factor for Li 2 in Li 2 S0 4 is 0.27176. STRONTIUM * Reagent. A mixture of absolute alcohol and ether in equal parts. Strontium is precipitated with calcium as oxalate. There- fore, after obtaining the oxalate precipitate according to the method for limestone (p. 162), or for clay (p. 286), burn the oxalates to the oxides in a platinum crucible and weigh. Then dissolve the oxides in nitric acid and transfer the solution to a 20-cc. flask. Evaporate the solution to dryness and raise the temperature to between 150 and 160 C. Cool and add about 2 cc. of a mixture of equal parts of absolute alcohol and ether (as small a quantity is used as will dissolve the calcium nitrate). Agitate to hasten solution of the calcium nitrate. Cork the flask and let it stand over night. Filter on a very small paper and wash with the mixture of absolute alcohol and ether. Let the filter dry and dissolve the strontium nitrate on the filter in a few cubic centimeters of hot water, letting the solution run into a small beaker. After washing the filter, precipitate * Hillebrand, Bull. 422, U. S. Geological Survey, p. 119. BARIUM 301 the strontium by adding to the filtrate a few drops of sulphuric acid. Add to the solution an equal volume of alcohol. Let the precipitate settle twelve hours, filter, burn, and weigh as SrS0 4 . The factor for SrO in SrSO 4 is 0.5641. If the material under examination contains only a small quantity of barium, it will all pass into solution if the precipitation of the oxa- lates of calcium and strontium is repeated in a fresh solution. If a considerable quantity of barium is present, a little will come down with the strontium. After weighing the strontium precipitate, it should be tested for barium. BARIUM Treat 1 gin. of the material according to the method for the analysis of clay (p. 286) until the oxalates are filtered from the solution. If the oxalates are dissolved and reprecipitated in fresh solution once or twice, all the barium will pass into solution with the magnesium. Evaporate the solution to dryness and drive off the ammonium salts by heat. Dissolve the residue in a little water, add a little hydrochloric acid and a few drops of sulphuric acid. Let it stand in a warm place over night, filter, burn, and weigh BaS04. The factor for BaO in BaSO 4 is 0.65699. COLUMBIUM AND TANTALUM Fuse the sample with acid potassium sulphate until the ore is in solution. Cool, add water, and boil for some time. Colum- bic acid remains as a precipitate (impure). Filter by decanta- tion and digest with ammonium sulphite to dissolve stannic and tungstic acids. Wash with water and treat the precipitate on the filter with very dilute hydrochloric acid to dissolve iron sulphide. Ignite the filter after adding ammonium carbonate and weigh as Cb2Os and 302 METALLURGICAL ANALYSIS CAESIUM * The alkalies are obtained as chlorides. (See the Lawrence Smith Method, p. 287.) Add to the cold, strongly acid solu- tion of the chlorides a cold solution of antimonous chloride acidified with hydrochloric acid. Filter off the white precipitate of CsC SbCls and wash with cold concentrated hydrochloric acid. Wash the precipitate into a beaker with warm water and warm to decompose it. Pass a current of hydrogen sulphide through the solution to precipitate antimony sulphide. Filter off the sulphide, evaporate the nitrate to dryness and weigh the residue as CsCl. Caesium chloride melts at a dull red heat and is volatile; there- fore, after evaporating to dryness, the temperature should not be raised. GERMANIUM Fuse the ore in a porcelain crucible with 2 parts of sulphur and 5 parts of sodium carbonate. Cool the fusion, treat it with boiling water, and filter. Add to the filtrate an excess of hydrochloric acid to precipitate germanium disulphide. Filter and wash with dilute hydrochloric acid (5 : 100). Dry the precipitate and heat it in a current of hydrogen or coal gas to reduce it to germanous sulphide. Dissolve the sulphide in hot hydrochloric acid and pass through the solution a current of hydrogen sulphide. Filter and treat the precipitate with nitric acid to convert the sulphide to insoluble GeC>2, which is recovered in a Gooch crucible and weighed. * Cahen and Wootton, " The Mineralogy of the Rare Metals," 180. GLUCINUM (BERYLLIUM) 303 GLUCINUM (BERYLLIUM) * Weigh 1 gm. of the sample and treat it according to the method for the analysis of clay, page 286, to the precipitation of iron and aluminum as hydroxides. Dissolve this precipitate, which also contains the glucinum hydroxide, in as little hydrochloric acid as possible and oxidize by adding a little nitric acid. Nearly neutralize the solution with ammonia and evaporate it to 25 cc. While hot, pour this solution into 75 cc. of a 20 per cent solution pure sodium bicarbonate, heated to 75 C. Boil for one-half minute after all the carbon dioxide has escaped. Let the solution cool and the precipitate settle. Filter off the hydroxides of iron and aluminum, which will contain a little glucinum. Wash with a 10 per cent solution of sodium bicar- bonate heated to 75 C. Dissolve the precipitate in hydrochloric acid, reprecipitate as before, and filter into the first filtrate. Acidify the filtrate with hydrochloric acid, boil off the carbon dioxide, add only a slight excess of ammonia to precipitate the G1(OH)2, filter, and wash by decantation. Redissolve the precipitate in a little hydrochloric acid and precipitate again with ammonia to free it from sodium. Filter and wash the precipitate free from chlorides with a 2 per cent solution of ammonium nitrate or acetate. Ignite and weigh as G10. THALLIUM Treat 1 gm. of the sample with 10 cc. of nitric acid and 5 cc. of hydrochloric acid; then add 7 cc. of sulphuric acid and boil until the fumes of sulphuric acid are evolved. Dilute, filter, wash, pass a current of hydrogen sulphide through the filtrate, filter, boil off the excess of hydrogen sulphide, nearly neutralize with sodium carbonate and add an excess of potassium iodide. The thallium is precipitated as bright yellow TIL Let the * Parsons, " The Chemistry and Literature of Beryllium." 304 METALLURGICAL ANALYSIS precipitate settle, filter in a Gooch crucible, wash with cold water and then with a little alcohol. Dry at 100 C. and weigh. CERIUM Decompose the sample by several partial evaporations with hydrofluoric acid. Filter off the fluorides and silicofluorides, supporting the paper on a platinum cone; wash the residue with water acidulated with hydrofluoric acid, and then wash it into a platinum crucible, add sulphuric acid, and evaporate to complete dryness to expel all the fluorine. Burn the filter paper and add the ash to the crucible. Dissolve the contents of the crucible in dilute hydrochloric acid, filter, add ammonia to the filtrate to precipitate the rare earths with possibly some alumina, filter, wash the precipitate, dissolve it in hydrochloric acid, and evaporate the resulting solution to dryness. Add a little oxalic acid solution and heat. Filter off the oxalates of the rare earths and burn them to oxides. Dissolve the oxides in dilute sulphuric acid. When cold, add an excess of standard hydrogen peroxide solution and titrate the excess of EbCb with standard permanganate solution. 2Ce(S04).+H a O,=Ce(S0 4 )i+H,SO4+0,. If the permanganate solution has been standardized against iron, the ratio of the value in cerium to its value in iron will be as 140 is to 56. THORIUM IN MONAZITE * Heat gradually to a gentle fusion 0.5 gm. of the sample with 10 gms. of potassium bisulphate and 0.5 gm. of sodium fluoride in a platinum crucible. Cool and dissolve in water and a little hydrochloric acid. Filter by decantation, add hydro- * Benz, Zeit. f. Angew. Chein., 15, 297 (1902). YTTRIUM 305 chloric acid to the residue, and boil. Dilute and filter. Nearly neutralize the combined nitrate with ammonia, being careful not to produce a precipitate. Heat to boiling, add about 4 gms. of ammonium oxalate (the salt) and stir vigorously. Let the precipitated oxalates of the rare earths stand twelve hours, filter, wash once with water acidulated with nitric acid. With the wash bottle wash the precipitate into a porcelain dish, using strong hot nitric acid to dissolve off the last traces. Evaporate the solution to dryness. Add to the residue 10" cc. of nitric acid (1.42) and 20 cc. of fuming nitric acid, cover and heat on the water-bath. When the oxalates are decomposed, wash off the cover and wash down the sides of the dish. Evaporate the solution to dryness. Cool, add a little water, boil, and filter. Dilute the filtrate to 100 cc. with a 10 per cent solu- tion of ammonium nitrate. Heat to about 70 C., and add 20 cc. of a 3 per cent solution of hydrogen peroxide. Filter at once and wash with hot water containing ammonium nitrate. The precipitate may be yellow owing to traces of cerium per- oxide. Ignite in a platinum crucible and weigh as ThO2. YTTRIUM Treat 5 gms. of the sample in a porcelain dish with aqua regia and evaporate the solution to dryness. Cool, add water and a little hydrochloric acid and boil. Dilute the solution and filter. Add ammonium oxalate to the filtrate until a pre- cipitate ceases to form. Filter off the oxalates of yttrium and cerium with a little of the oxalates of calcium and manganese. Dry and ignite the precipitate and redissolve it in a little hydro- chloric acid. Add a saturated solution of potassium sulphate to precipitate cerium. Filter and wash the precipitate with a saturated solution of potassium sulphate. Add to the filtrate a solution of potassium hydroxide or ammonium oxalate to 306 METALLURGICAL ANALYSIS precipitate the yttrium. Filter and to remove calcium and manganese, " which contaminate the precipitate dissolve in a little nitric acid, evaporate to dryness, and bake to decompose the manganese salt. Cool, add hot water, boil, and filter. Add ammonia to the filtrate to precipitate yttrium. Stir well until the calcium is dissolved, filter, wash, dry, burn, and weigh as Y 2 3 . ZIRCONIUM * Fuse 2 gms. of the sample in a platinum crucible with Na2COs. Cool and digest the fusion with hot water, filter, and wash the residue with a dilute solution of Na2COs. The zirconium is filtered off with the residue. Wash the precipitate into a small beaker and treat it with a little more than enough warm dilute sulphuric acid to take up all that is soluble. Do not digest it so long that dissolved silica gelatinizes. Filter through the same paper used for the first filtration and bt the filtrate run into a 100 or 150-cc. Erlenmeyer flask, wash the residue, ignite it in a platinum crucible, add to the res- idue hydrofluoric and sulphuric acids, and evaporate. Dilute the solution and filter off barium, strontium, and calcium sulphates and add the filtrate to the last filtrate, which will now contain all the zirconium and rare earths. Add to the combined filtrates hydrogen peroxide to oxidize titanium, and a few drops of a solu- tion of disodium phosphate. Let the precipitate settle twenty- four to forty-eight hours; all the zirconium is precipitated as phosphate with a little titanium. If the yellow color of the solution should fade and disappear, add more H202. Filter and treat the residue as follows to free it from titanium: Ignite the precipitate, fuse it with Na2COs, cool the fusion and treat it with hot water, filter, ignite the precipitate, and fuse with potassium pyrosulphate. Dissolve the fusion in hot water * Hillebrand, Bull. 422, U. S., Geological Survey, p. 140. LUBRICATING OIL 307 to which has been added a few drops of dilute BkSCU. Pour the solution into a 20-cc. Erlenmeyer flask, add a few drops of 4 per cent H202 solution and a few drops of solution of disodium phosphate. Let the precipitate settle one to two days, filter, ignite the precipitate and weigh as zirconium phosphate, 50 per cent of which is taken as ZrC^, although the theoretical factor is 0.518. LUBRICATING OIL Viscosity. The viscosity of oil is determined by a test with the viscosimeter, and is expressed by the time required for a given quantity of oil at a definite temperature to run through an orifice of definite dimensions. The lighter oils are tested at 100 F. or lower and the heavier at 210 to 212 F. Viscosim- eters of many designs can be had of dealers in chemical supplies. Flashing-point and Fire Test. The oil is very gradually heated in a cup in which is placed a thermometer so that the bulb is submerged. At regular intervals a flame or electric spark is passed near the surface of the oil and the temperature noted when the first flash is observed. The heating is con- tinued until the oil burns, and the temperature is recorded as the burning test, which is usually 60 to 80 F. above the flash- point. Cold Test. A four-ounce bottle of thin glass is filled one- third full of the oil. The bottle is closed with a stopper which carries a thermometer so adjusted that the bulb is just sub- merged in oil. The oil is now cooled down gradually, being finally placed in a freezing mixture of ice and salt. The bottle is frequently withdrawn and examined to see when the oil ceases to flow. The temperature at which it just ceases to flow is taken as the setting point, or cold test. Cold Test for Lighter Oils. To determine the setting point of lighter oils (solidifying above 45 F.), it is customary to cool 308 METALLURGICAL ANALYSIS the oil to about 20 F. below its freezing-point and then gradually warm it until it just begins to flow, at which point the temperature is taken as the cold test. EXAMINATION OF BOILER WATER Total Solids. Evaporate 1 liter of the water to dryness in a weighed platinum dish on a water-bath. If the water is low in total solids, 2 liters or more should be taken; if high in total solids, half a liter may be used. The water is added to the dish, a little at a time. When dry, weigh the dish and contents; the weight of the empty dish deducted leaves the weight of the total solids. Mineral Matter. Ignite the residue (Total Solids above) in the platinum dish. This burns organic matter, expels combined water and C0 2 from calcium and magnesium carbonates. Moisten the residue with a very little water and place it in an atmosphere of CO 2 for an hour.* Dry at 100 C., cool in a desiccator and weigh. This gives the total mineral matter as it existed in the water. Organic Matter. Deduct the total mineral matter from the total solids and the difference represents the organic matter. Scale-forming Constituents. Treat the total mineral matter with hot water free from CO2, a little at a time, filter and wash with boiling water, using not more than 50 cc. in all. Burn the filter in the platinum dish and weigh. The weight of the residue represents the scale-forming constituents. Non-scale-forming Constituents. The difference between the total mineral matter and the scale-forming constituents repre- sents the non-scale-forming constituents. *Stillman, "Engineering Chemistry," p. 57. EXAMINATION OF BOILER WATER 309 SiC>2, Fe 2 O?i AkOs, CaO, and MgO in the Scale-forming Constituents. Dissolve the scale-forming constituents in hydro- chloric acid and proceed according to the method for limestone (p. 160), for the determination of insoluble silicious matter, iron and aluminum oxides, lime, and magnesia. SO 3 in the Scale-forming Constituents. Acidify the filtrate from the magnesium ammonium phosphate with hydrochloric acid, add barium chloride solution, boil, let the precipitate settle, filter, burn, and weigh the BaS04, from which calculate the percentage of SO 3 . The factor for S0 3 in BaSO 4 is 0.343. Composition of the Scale-forming Constituents. The SO 3 is combined with CaO to form CaSO4. The remaining CaO and the MgO are calculated to carbonates. The sum of the CaSO4, CaCOs, MgC0 3 , insoluble siliceous matter, Fe2O 3 , and A^Os should be equal to the weight of scale-forming con- stituents. For a complete report on the total solids, the filtrate from the scale-forming constituents should also be analyzed for iron, lime, and magnesia. Cl in Water. Add to 100 cc. of the water two or three drops of 20 per cent solution of K^CrOi and titrate with standard AgN0 3 solution to the faint reddish color due to silver chromate. NaCl+AgNO, = AgCl+NaNO,, 2AgNO,+K,CrO 4 = Ag 2 Cr0 4 +2KNO 3 . Run a blank with 100 cc. of distilled water and a few drops of 20 per cent solution of potassium dichromate to determine how much AgNO 3 solution is required to produce the red color in the absence of Cl. Total SO 3 in Water. Add to 100 cc. of the water 5 cc. of hydrochloric acid and 20 cc. BaCb solution. (See p. 73.) Boil and let the solution stand in a warm place several hours. Filter, burn, and weigh BaS04, from which calculate the per- centage of SO 3 . The factor for SO 3 in BaSO 4 is 0.343. 310 METALLURGICAL ANALYSIS NO2 in Water. Sprengel's Color Method, modified by Gill.* Reagents. Phenoldisulphonic acid. Mix 3 gms. of pure phenol (CeHsOH) with 37 gms. (20.1 cc.) of pure sulphuric acid (1.84) in a flask and heat six hours on a water bath at 100 C. C 6 H 6 OH+2H 2 S0 4 = C 6 H 3 OH(SO 3 H) 2 +2H 2 0. If the acid crystallizes out on cooling, it will be redissolved when heated. Standard potassium nitrate solution. Dissolve 2.197 gms. of KNOs in 1 liter of water. One cubic centimeter of the solu- tion will contain 1 mgm. of N(>2. To avoid errors of measuring 1 cc. dilute 100 cc. to a liter and take out 10 cc. for the analysis. Place the 10 cc. in a small evaporating dish and treat it exactly in the manner described below for the sample of water. NC>2. Take 5 cc. of the water, add to it enough pure silver sulphate to precipitate all the Cl from the water. Filter into a small porcelain dish and wash. Evaporate the filtrate on a steam bath until only a drop of water remains. Add 1 cc. of pure phenoldisulphonic acid and stir; add 7 cc. of distilled water and stir. Add an excess of ammonia (about 20 cc. of sp.gr. 0.96), dilute to 100 cc. with distilled water, and compare the solution in a colorimeter with a standard, similarly treated, or place the solution in a Nessler tube and match it with a standard. +2(NH 4 ) 2 S0 4 +6H 2 0. Treating phenoldisulphonic acid with nitric acid and ammonia pro- d,uces ammonium picrate, which gives the solution a distinctly yellow color. Free CO2 in Water. (Seyler's method.) * Tech. Quarterly, 7, 55. TEMPORARY HARDNESS OF WATER 311 Reagents. N/50 solution of sodium carbonate. Dissolve 1.06 gm. of freshly ignited Na2COs in freshly boiled water and dilute to 1 liter with cold water, free from air. This solution must be protected from the air. Phenolphthalein solution. (See page 84.) Measure 50 cc. of the water into a Nessler tube. Add 25 to 30 drops of phenolphthalein solution and titrate with the standard sodium carbonate solution, stirring with a glass rod bent at the lower end into a circle at right angles to the rod. The end-point is more easily detected if another Nessler tube containing water is placed alongside the tube containing the test. TEMPORARY HARDNESS OF WATER Reagents. N/10 solution of hydrochloric acid. Dilute 8 cc. of hydrochloric acid to 1 liter, test it against N/10 sodium carbonate solution, and correct it if necessary. (See the method below.) Hydrochloric acid of 1.20 sp.gr. at 15 C. contains 469 gms. HC1 per liter. Measure 100 cc. of the water, add 5 drops of methyl orange solution and titrate with N/10 hydrochloric acid. At the same time, run a blank on 100 cc. of distilled water and 5 drops of methyl orange, titrating both to the same color. PERMANENT HARDNESS OF WATER Reagents. N/10 alkaline solution made of equal parts of sodium, carbonate and sodium hydroxide solution, as follows: Make a N/10 solution of sodium hydroxide (4.0008 gms. NaOH per liter), and a N/10 solution of sodium carbonate (5.3 gms. per liter). Take 25 cc. of each solution for the test. Measure 200 cc. of the water into a platinum or porcelain 312 METALLURGICAL ANALYSIS dish, or a Jena flask (not ordinary glass). Add to it 50 cc. of N/10 alkaline solution (mixed Na2COs and NaOH solutions). Boil until the volume is reduced to a little less than 200 cc. CaH 2 (C0 3 ) 2 +2NaOH=CaC0 3 +Na 2 C0 3 +2H 2 CaS0 4 +Na 2 C0 3 = CaC0 3 +Na 2 S0 4 . MgH 2 (C0 3 ) 2 +4NaOH=Mg(OH) 2 +2Na 2 C0 3 +2H 2 0. MgS0 4 +2NaOH =Mg(OH) 2 +Na 2 S0 4 . Dilute with water to make the volume just 200 cc. when cold. Let the precipitate of calcium carbonate and magnesium hydroxide settle. Filter or siphon off 100 cc. of the clear solution. If filtered, discard the first 50 cc. of the filtrate, since filter papers are usually not neutral. Add 5 drops of methyl orange solution and titrate with N/10 hydrochloric acid, running a blank at the same time. The difference between the titration and 25 represents the amount of alkali used in the reactions above. Multiply this difference by 5 to give milligrams per 100,000 in terms of CaCOs.* SOFTENING WATER Water is usually softened by adding lime and sodium car- bonate. The lime precipitates calcium from solution as car- bonate and the magnesium as hydroxide. CaH 2 (C0 3 ) 2 +CaO =2CaCO 3 +H 2 O. MgH 2 (C0 3 ) 2 +2CaO = 2CaC0 3 +Mg(OH) MgS0 4 +CaO+H 2 =CaS0 4 +Mg(OH) 2 . The sodium carbonate precipitates calcium as carbonate. CaS0 4 +Na,CO, = CaC0 3 +Na 2 S0 4 . * Procter, Jour. Soc. Chem. Jnd., 23, 8. SOFTENING WATER 313 To determine how much of these reagents to use, boil an accurately measured sample of the water with a measured volume of standard solution of Ca(OH) 2 . Let it cool and settle; then filter and titrate the excess of Ca(OH) 2 with standard acid, as described above for permanent hardness. Ca(OH) 2 +2HCl = CaCl 2 +2H 2 0. Then add to the titrated solution a measured volume of a standard solution of sodium carbonate, boil, cool, settle, filter, and titrate the excess of NaoCOs in the filtrate. It must be kept in mind that the sodium carbonate reacts, not only with the sulphates originally in the water, but also with the CaCb formed in the previous titration for the excess of lime, and the necessary correction must, therefore, be made.* CaCl 2 +Na 2 C0 3 = CaC0 3 +2NaCl. * Drawe, Zeit. Angew. Chem., 23, 52. 314 METALLURGICAL ANALYSIS DETECTION OF THE METALS Aluminum is precipitated as white gelatinous hydroxide by ammonia. When the oxide is strongly heated on charcoal with cobalt nitrate a bright blue mass is obtained. Antimony. When a small quantity of an antimony compound is heated in the upper reduction zone of a Bunsen burner on a thread of asbestos, the flame is given a bluish tinge and when a small porcelain basin rilled with cold water is held above it, a brownish black deposit of metallic antimony is deposited upon the basin, and this is but slightly attacked by cold nitric acid and is insoluble in sodium hypochlorite. Arsenic gives a similar reaction, but arsenic gives a garlic-like odor during the reduc- tion, and the metallic film is readily soluble in the hypochlorite. Antimony compounds may be obtained in solution by treating with HC1 or by fusing first with potassium carbonate and potassium nitrate. Hydrogen sulphide produces in acid solution a very characteristic orange-red colored precipitate of antimony trisulphide. Arsenic. Mix with sodium carbonate and heat on charcoal with the blowpipe. All arsenic compounds give a garlic odor. Add to 1 concentrated hydrochloric acid a few drops of an arsenite solution and half a cubic centimeter of saturated solution of stannous chloride in hydrochloric acid, warm, and the solution turns brown, then black. Barium. The Bunsen flame is colored a yellowish-green tint when any volatile barium compound is brought into it. Soluble barium salts are distinguished from those of strontium and calcium inasmuch as they are immediately precipitated by a solution of calcium sulphate. Bismuth. On charcoal with soda, bismuth gives a very char- acteristic orange-yellow sublimate. Brittle globules of the metal are also reduced on the charcoal when treated with soda. Hydrogen sulphide precipitates from solutions of bismuth DETECTION OF THE METALS 315 salts a blackish brown sulphide (61283) insoluble in ammonium sulphide and easily soluble in nitric acid. Ammonia throws down a white basic salt insoluble in excess. Cadmium. Cadmium is precipitated as a yellow sulphide by hydrogen sulphide. The sulphide is insoluble in ammonium sulphide and in the caustic alkalies. On charcoal with soda, compounds of cadmium give a characteristic sublimate of the reddish-brown oxide. To test for cadmium in a sulphide, roast it to oxide, and reduce some of the oxide in the upper reducing flame of the Bunsen burner, at the same time holding a glazed porcelain dish which contains water just above the flame to receive a brown coating. To the brown coating add a drop of AgNOs solution; if Cd is present, black metallic silver will be deposited. Caesium. H^PtCle produces a bright yellow crystalline pre- cipitate, a brighter color than the potassium salt thus produced, and is much more soluble than the potassium salt. The flame test is reddish violet, similar to potassium. Calcium. Calcium compounds moistened with hydrochloric acid and placed on a platinum wire in the hottest part of a Bun- sen flame, impart a red color to the flame. Calcium may be precipitated from solution as oxalate by first making the solution ammoniacal and then adding ammonium oxalate or oxalic acid. Cerium. Fuse with sodium carbonate. Treat with dilute hydrochloric acid, evaporate to dryness and bake. Take up with dilute hydrochloric acid, filter. Add ammonia to the filtrate, filter. Dissolve the precipitate in hydrochloric acid, add ammonia and oxalic acid, filter. Dissolve the precipitate in concentrated hydrochloric acid, nearly neutralize with ammonia; add 1 cc. of hydrogen peroxide and then ammonia, drop by drop, until just alkaline. When .just neutral, white thorium peroxide is precipitated; when ammoniacal, the orange cerium peroxide is precipitated. 316 METALLURGICAL ANALYSIS Chromium. Chromium oxide is detected in its insoluble compounds by its characteristic green color. It forms an emerald- green head with borax or microcosmic salt. Caustic potash or soda gives a green precipitate in solutions of chromic salts. This dissolves in an excess of alkali in the cold, but is precipitated on boiling the solution. The detection of chromic acid is rendered easy by the bright yellow color of its salts. The yellow color of the normal chromates becomes red on the addition of an acid, and again yellow when made alkaline. Cobalt. Ammonium sulphide produces a black precipitate (CoS) insoluble in acetic acid and in dilute hydrochloric acid. Ammonium sulphocyanate produces a beautiful blue color, Co(CNS) 2 . With a borax bead cobalt gives the characteristic cobalt- blue color. Columbium. Fuse with potassium bisulphate. Pulverize the fusion and treat it with hot water; then treat it with dilute hydrochloric acid. Digest the residue with ammonium sul- phide to remove W, Sn, etc. Wash and treat again with dilute hydrochloric acid. The residue should be colorless and contain only silica and the oxides of columbium and tantalum. This residue in a bead of microcosmic salt is colorless if no columbium is present or if heated in the oxidizing flame; but if heated in the reducing flame, columbium imparts a violet color to the bead, or blue if saturated with oxide. Adding ferrous sulphate turns the bead blood red. If, when the mixed oxides are boiled in dilute sulphuric acid with metallic zinc, the white precipitate turns intensely blue, and remains so on dilution, columbium is present; if it turns bluish gray and colorless on dilution, tantalum is predominant. Copper. Copper can easily be detected by the reduction to the red metallic bead on charcoal before the blowpipe. Copper compounds moistened with HC1 color the non- luminous flame green. DETECTION OF THE METALS 317 An excess of ammonia added to a nitric acid solution of copper produces an azure-blue color. Erbium. Erbium oxide heated on a platinum wire colors the flame distinctly green. Gallium. If a neutral solution of gallium chloride be warmed with zinc, gallium oxide or basic salt separates but not the metal. Germanium. Fuse with sulphur and sodium carbonate. Treat with hot water, filter, add a few drops of hydrochloric acid to the nitrate to precipitate white germanium sulphide. Filter and heat the residue in a current of hydrogen to reduce it to gray-black crystalline germanous sulphide. Dissolve the crystals in hydrochloric acid and pass hydrogen sulphide into the solution to precipitate reddish-brown germanous sul- phide. Glucinum. Ammonium carbonate produces a white precipi- tate, GlCOs, soluble in an excess of the reagent; by boiling the solution it is precipitated as a basic carbonate. Gold. Gold may be reduced from its ores on charcoal to a yellow malleable bead which is soluble in aqua regia; if the solution be dropped on filter paper and one drop of stannous chloride added, a purple-red color is produced. Indium. Heated on charcoal before the blowpipe it colors the flame blue, and gives an incrustation of the oxide. It slowly dissolves in hydrochloric and dilute sulphuric acids, but readily in nitric acid. Indium. Ammonium chloride produces in a tolerably con- centrated solution of iridium a dark-red crystalline precipitate. Indium is distinguished from platinum by the formation of a colorless solution of potassium chloriridiate when caustic potash is added to the chloride of the metal, and on exposure to the air this colorless solution first becomes red colored and afterward blue. Hydrogen sulphide precipitates brown iridium sulphide, which is soluble in ammonium sulphide, 318 METALLURGICAL ANALYSIS Iron. Ferrous salts with potassium ferricyanide produce a dark-blue precipitate. Ferric salts with ammonia or the fixed alkalies produce a brown precipitate. Ferric salts with potassium or ammonium sulphocyanate pro- duce a blood-red colored precipitate. Ferrous salts with a bead of microcosmic salt or borax is colored dark green. This color readily changes to yellow or reddish brown by oxidation. Lead. With soda on charcoal a malleable globule of metallic lead is obtained from lead compounds; the coating has a yellow color near the assay. In nitric acid solution dilute sulphuric acid gives a white precipitate of lead sulphate. Lithium. In the Bunsen flame .a fine carmine-red color is produced, visible if sodium is present by viewing the flame through cobalt glass. Magnesium. To a solution of magnesium add ammonium chloride, ammonia, and sodium phosphate; a white precipitate (MgNJrUPCU) 'forms. The action is hastened by rubbing the sides of the beaker with a glass rod. Manganese. Ammonium sulphide produces a flesh-colored precipitate. A solution containing traces of manganese boiled in con- centrated nitric acid with lead peroxide or sodium bismuthate and allowed to settle gives a violet-red colored solution (HMnO4). The borax bead with manganese in the oxidizing flame gives an amethyst-colored bead, and this in the reducing flame becomes colorless. Mercury. Stannous chloride heated with a solution of mer- cury precipitates gray metallic Hg. Mercury compounds mixed with sodium carbonate and heated in a closed tube produce a gray mirror of metallic Hg. Molybdenum. To a strong nitric acid solution of molybde- num add nearly enough ammonia to neutralize the acid and DETECTION OF THE METALS 319 then add a few drops of sodium phosphate solution. A bright yellow crystalline precipitate forms when the solution is warmed. A hydrochloric or sulphuric acid solution of molybdenum, to which zinc or stannous chloride is added, turns first blue, then green, and finally brown. Neodymium. The didymium salts are violet and are identified by a characteristic absorption spectrum. Nickel. Potassium cyanide produces a bright green precip- itate, Ni(CN) 2 . When nickel compounds are heated with reducing agents before the blowpipe, an infusible magnetic powder is produced. If this powder is dissolved in a drop or two of dilute nitric acid and evaporated to complete dryness, a characteristic green stain is obtained which becomes yellow on further heating. Nickel compounds color the borax bead brownish yellow in the oxidizing flame, the bead becoming gray and opaque in the reduc- ing flame, owing to the separation of the metallic nickel. Nickel is precipitated in alkaline solution by ammonium sulphide, which dissolves in an excess of ammonium sulphide, forming a dark-colored solution. Osmium. It is dissolved in fuming nitric acid, or by fusing with sodium hydroxide and potassium nitrate and then treating with nitric acid and distilling. Osmic oxide (OsCU), which sublimes at a moderately low temperature, passes over and con- denses as a colorless crystalline mass. The osmic pxide has an odor similar to chlorine and is poisonous. Palladium. Dissolve in nitric acid or aqua regia. Potassium iodide added produces a black precipitate, palladous iodide (Pdl2), soluble in an excess of the reagent, but not soluble in water, alcohol, or ether. Mercuric cyanide, Hg(CN)2, produces a yellowish-white gelatinous precipitate, Pd(ON)2, which, on ignition, leaves the spongy metal. Platinum. When heated with sodium carbonate on char coal, gray spongy metal is reduced. This, rubbed on a mortar with 320 METALLURGICAL ANALYSIS a pestle, gives a metallic luster and is insoluble in any single acid. Potassium. A solution of H 2 PtCl 6 added to concentrated solutions of potassium gives a yellow precipitate K 2 PtCl6. In the Bunsen flame potassium gives a violet color, visible if sodium also is present if viewed through cobalt glass. Praseodymium. See Neodymium. Radium. To the Bunsen flame a radium salt imparts an intense carmine-red color. Radium rays discharge a charged eletroscope and may be used for making photographs on ordinary X-ray plates. Rhodium. Before the blowpipe on charcoal with sodium carbonate the salts of rhodium are reduced to the metal, which is insoluble in aqua regai, bat may be dissolved by fusing it with potassium pyrosulphate and then treating the fusion with water. By adding to this solution potassium hydroxide and a little alcohol the brown rhodium hydroxide is formed. Rubidium. A solution of H 2 PtCle produces a white crys- talline precipitate, Rb 2 PtCl 6 , which is less soluble than the cor- responding potassium salt and more soluble than the caesium salt. The flame test gives a color similar to the caesium test. Ruthenium. Ruthenium is practically insoluble in all acids and in aqua regia. Fuse it with potassium hydroxide and potas- sium nitrate. The resulting K 2 RuO4 heated with NaCl in a current of chlorine yields soluble K 2 RuCl6. The greenish- black fusion treated with water yields an orange-yellow solution, which stains the skin black. Scandium. A hydrochloric acid solution of scandkim treated with solid sodium silicofluoride and boiled thirty minutes gives a precipitate containing scandium free from the rare earth metals. Silver. When fused with sodium carbonate on charcoal before the blowpipe, a bright metallic silver bead is produced, which may be dissolved in nitric acid and precipitated from the solu- DETECTION OF THE METALS 321 tion by hydrochloric acid as a curdy precipitate of silver chloride, or, if only a trace of silver is present, as a mere opalescence. Sodium. To a neutral or weakly alkaline solution add potas- sium pyroantimonate, E^EbSl^Os, and a heavy white crystalline precipitate, Na2H2Sb2Os, is quickly formed by rubbing the sides of the beaker with a glass rod. Solutions of sodium on a platinum wire in a Bunsen flame give a yellow color. Strontium. Solutions on a platinum wire color the Bunsen flame carmine red. Strontium sulphate is less soluble than calcuim sulphate, but more soluble than barium sulphate. Tantalum. See Columbium. Thallium. Dissolve in dilute acid, add H^S, filter. Add to the filtrate ammonium sulphide, and filter. If thallium is present in the precipitate it will color the Bunsen flame emerald green. Thorium. Fuse in a platinum crucible with sodium carbo- nate. Cool, dissolve in water and hydrochloric acid. Evaporate to dryness and bake. Take up with dilute hydrochloric acid, filter. Add ammonia to the filtrate, filter. Dissolve the pre- cipitate in hydrochloric acid; reprecipitate with oxalic acid, filter, ignite the residue. Dissolve in hydrochloric acid. Evap- orate to dryness. Take up with water. Add an excess of sodium thiosulphate and boil to precipitate. Tin. Mercuric chloride added to a solution of a stannous salt precipitates white mercurous chloride. A trace of stannous chloride in solution added to a solution of gold chloride precipitates finely divided gold, brown by transmitted light and bluish green by reflected light. Metallic zinc precipitates tin from solution as a spongy mass, which adheres to the zinc. Heat the ore on charcoal with sodium carbonate or potassium 322 METALLUKGICAL ANALYSIS cyanide; a metallic bead is produced which is coated with white oxide when the flame is removed. Casserite in lumps in a test-tube with metallic zinc and dilute sulphuric acid is soon coated with metallic tin. Titanium. Titanium sulphate with hydrogen peroxide in a slightly acid solution produces an orange-red color, or a clear yellow with small amounts of titanium. Vanadic acid with hydrogen peroxide produces a similar effect. Tin or zinc in hydrochloric acid solutions of titanium pro- duces a violet color, Ti2Cl2. Tungsten. Treat with hydrochloric and nitric acids (4:1) and take to dryness, wash by decantation, add dilute hydro- chloric acid and metallic zinc, aluminum, or tin and shake; a fine blue coloration or precipitate is produced, W2O5; the color disappears when diluted with water. Fuse in platinum with potassium bisulphate, digest with a solution of ammonium carbonate, filter, add to the nitrate a few drops of SnCl2 solution, acidify with hydrochloric acid, warm gently; a fine blue color is produced. The microcosmic salt bead made in the reducing flame is clear blue; if iron is also present, the bead will be red-brown. In the oxidizing flame the bead is colorless. Uranium. Potassium ferrocyanide produces a brown pre- cipitate, in dilute solution a brownish-red coloration. The borax (or microcosmic salt) bead is yellow in the oxidiz- ing flame and green in the reducing flame. Vanadium. Vanadium compounds can be dissolved by a treatment with acids or alkalies. The hydrochloric acid solu- tion assumes a bright blue color on addition of zinc. A solu- tion of hydrovanadic sulphate cannot be distinguished in color from one of copper sulphate when sufficiently diluted with water, but, of course, does not become colorless in the presence of metallic iron. Solutions of certain vanadates also closely resemble solu- DETECTION OF THE METALS 323 tions of the chromates. For instance, a solution of the tetra- vanadate of potassium, K^V-iOn, does not differ in appearance from one of potassium dichromate. They may, however, be distinguished from one another, since the vanadate solution be- comes blue and the chromate assumes a green color on deoxida- tion. When a solution of vanadic acid or an acid solution of an alkali vanadate is shaken up with ether containing hydrogen peroxide, the aqueous solution assumes a red color like that of ferric acetate. This reaction serves to detect one part of vanadic acid in 4000 parts of the liquid. Chromic acid does not interfere with the reaction. Yttrium. Extract the yttrium in the manner described under Cerium and separate it from the other rare earths in a solution of their sulphates by adding a saturated solution of potassium sulphate. Yttrium sulphate is soluble; the others are not. Zinc. Ammonium sulphide precipitates ZnS. Potassium ferrocyanide produces a white precipitate, Zn2Fe(CN)e. Before the blowpipe on charcoal with sodium carbonate a coating of oxide is produced which is yellow while hot and white when cold. With cobalt nitrate on charcoal an infusible green mass is produced. Zirconium. Treat with dilute sulphuric acid (2:1), filter, add ammonia to the cold filtrate, filter; wash, dissolve the precipitate in hydrochloric acid, evaporate to dryness. Take up with a little water and add to the cold saturated solution hydrochloric acid, drop by drop; if zirconium is present, the oxychloride will be precipitated. Heat to dissolve the precipitate. Cool and after some time fine silky needles of ZrOCl 2 +8H 2 O will precipitate. 324 METALLURGICAL ANALYSIS PROPERTIES OF THE ELEMENTS Symbol. Atomic Weight. Melting- point. Boiling-point. 760 mm. Density at Ordinary Temp, unless otherwise Stated. Aluminum Al 27 1 658 7 1800 2 65 Antimony Argon. Sb A 120.2 39 88 630 -188 1440 -186 6.62 f liq- \ 185 Arsenic Barium Bismuth Boron. . .... As Ba Bi B 74.96 137.37 208.0 11.0 850? 850 271 2200-2500 / Sublimes V 450 1420 | Sublimes I 1.4 } 5.73 3.75 9.80 ) 2 5? Bromine. Br 79 92 -7 3 \ 3500? 63 / ' / 25 Cadmium Caesium. . . . Cd Cs 112.40 132 81 320.9 26 778 670 \ 3.102 8.64 1 87 Calcium. Ca 40 07 810 f 29 ( \ 1.55 Diamond 3.52 Carbon. . ... C 12 00 > 3600 < Cerium. . Ce 140 25 640 { Graphite 2.3 6 68 Chlorine. Cl 35 46 101 5 33 6 / liq. Chromium Cobalt Cr Co 52.0 58.97 1510 1490 2200 \ 2.49 6.50 8.6 Columbium (Niobium) Copper. . Cb Cu 93.5 63 57 2200? 1083 2310 12.75 8 93 Dysprosium Dy 162 5 Erbium Er 167 7 4 77? Europium Eu 152 Fluorine. F 19 223 187 f Hq. J igy Gadolinium. Gd 157 3 1 1.11? PROPERTIES OF THE ELEMENTS 325 PROPERTIES OF THE ELEMENTS Continued Symbol. Atomic Weight. Melting- point. Boiling-point. 760 mm. Density at Ordinary Temp, unless otherwise Stated. Gallium .... Ga 69.9 30 5.95 Germanium Glucinum (Beryllium). Ge Gl 72.5 9.1 958 > 1800? 5.47 1 93 Gold Helium Au He 197.2 3.99 1063 <-271 2530? -268.6 19.32 Holmium. Ho 163.5 Hydrogen Indium H In 1.008 114 8 -259 155 -252.7 1000? 7 12 Iodine . . I 126 92 113 5 184.4 4 95 Iridium Ir 193.1 2300? 2550? 22.41 Iron Krypton Fe Kr 55.84 82 92 1520 -169 2450 151 7 7.86 liq. 2.16 Lanthanum. La 139.0 810? 6 12 Lead Pb 207 . 10 327.4 1525 11.37 Lithium Li 6.94 186 >1400 .534 Lutecium Magnesium IVIan^anese Lu Mg Mn 174.0 24.32 54 93 651 1225 1120 1900 1.74 7 39 Mercury Molybdenum Neodym ium Hg Mo Nd 200.6 96.0 144 3 -38.7 2500? 840? 356.7 3200? 13.56 8.6 6 96 Neon Ne 20 2 -253? -239 Nickel Ni 58.68 X452 2330? 8 9 Niton (radium emanation) Nt 222 4 Nitrogen N 14.01 -210 195 7 Osmium Os 190.9 2700? 22.5 Oxygen O 16.00 -218 -182.9 Palladium Phosphorus Pd p 106.7 31 04 1549 44 2540 287 ] 11.4 Yellow 1 83 Platinum Pt 195 2 1755 I 2450? Red 2.20 21 50 Potassium K 39 10 62 3 758 862 Praseodymium Pr 140.6 940? 6 48 326 METALLURGICAL ANALYSIS PROPERTIES OF THE ELEMENTS Continued - .' Symbol. Atomic Weight. Melting- point. Boiling-point. 760 mm. Density at Ordinary Temp, unless otherwise Stated. Radium Rhodium Ra Rh 226.4 102 9 1940 2500? 12 44 Rubidium Rb 85.45 38 696 1 532 Ruthenium Samarium . . Ru Sa 101.7 150.4 >1950 1300-1400 2520? 12.3 7 8 Scandium Sc 44.1 Selenium . . . .' Silicon Se Si 79.2 28.3 217-220 1420 690 3500? 4.8 2 3 Silver Ae 107 88 960 5 1955 10 5 Sodium Na 23.00 97.5 877 971 Strontium Sr 87 63 2 54 Sulphur S 32.07 f Si 112.8 1 Su 119.2 | 444 . 7 f 2.07 { 1 96 Tantalum . . . Ta 181 5 [ S m 106.8 2850 I 1.92 16 6 Tellurium Te 127.5 452 1390 6 25 Terbium Tb 159 2 Thallium Tl 204.0 302 1280? 11 9 Thorium Thulium Th Tm 232.4 168.5 >1700 11.3 Tin Sn 119 231 9 2270 7 29 Titanium Tungsten Ti W 48.1 184.0 1900? 3000 3700? 3.54 17-18 8 Uranium Vanadium U V 238.5 51 1730? 18.7 5 5 Xenon Xe 130 2 -140 -109 Ytterbium (Neoytterbium) . . Yttrium. Yb Yt 172.0 89 3 8? Zinc Zirconium Zn Zr 65.37 90.6 419.4 1700? 918 7.1 4.15 FACTORS 327 TABLE OF FACTORS Sought. Found. Factor. Log. Ae AgCl 7526 87656 Al A1 2 O 3 . 5303 72455 A1 2 O 3 Ba A1P0 4 A1PO 4 BaSO 4 0.22187 0.41873 . 58846 34,610 62,193 76,972 BaO BaSO 4 0.65699 81,756 Bi BiOCl 8017 90401 C CO 2 . 27273 43.573 (BaCO 3 ) BaSO 4 BaCO 3 0.05154 06080 71,214 78 390 CaO . . . . CaSO 4 0.4118 61,469 CaCO 3 CaO 1.7847 25,156 Cl. Fe AgCl Fe 2 O 3 0.2474 . 6994 39,340 84472 FeU Fe 1.2865 10,942 FeaOs Fe. 1 4298 15 527 K 2 O KC1 0.6317 - 80051 KC1 ...... K 2 PtCl6 K 2 PtCl 6 0.19376 0.30674 28,727 48,676 MgO Li 2 O Mg 2 P 2 7 Li 2 SO 4 0.3621 0.27176 55,879 43,418 Na*O Ni NaCl NiO ' 0.53028 78576 72,450 89529 p Mg 2 P 2 O 7 . . 27873 44,518 P 2 O 5 Mg 2 P 2 O 7 0.6379 80,475 Pb PbSO 4 0.6831 83,449 s BaSO 4 13738 13793 SO 3 . BaSO 4 0.34300 53,529 Si SiO 2 46932 67 147 Sn SnO 2 0.78808 89,657 Sr SrSO 4 0.47703 67,855 SrO SrSO 4 5641 75,136 Ti TiO 2 0.60051 77,852 W WO 3 0.7931 89,933 328 LOGARITHMS 1 2 3 4 5 6 7 8 9 123 456 789 10 0000 0043 0086 0128 0170 0212 0253 0294 0334 0374 4813 17 21 25 2933 38 11 12 13 0414 0792 1139 0453 0828 "73 0492 0864 1206 0531 0899 1239 0569 0934 1271 0607 0969 1303 0645 IOO/ 1335 0682 1038 1367 0719 1072 1399 0755 1106 1430 4 8n 15 19 23 26 30 34 3 6 10 13 6 19 23 26 29 14 15 16 1461 1761 2041 1492 1790 2068 1523 1818 2095 1553 1847 2122 1584 1875 2148 1614 1903 2175 1644 I93T 2201 1673 1959 2227 1703 1987 2253 1732 2014 2279 369 36 8 35 8 12 5 18 ii 4 17 ii 3 16 21 24 27 2O 22 25 iS 21 24 17 18 19 230^ 2553 2788 2330 2577 2810 2355 2601 2833 2380 2625 2856 2405 2648 2878 2430 2672 2900 2455 2695 2923 2480 2718 2945 2504 2742 2967 2529 2765 2989 257 257 247 IO 2 15 9 2 14 9 i 13 I/ 2O 22 16 19 21 16 18 20 20 3010 3032 3054 3075 3096 3118 3139 31603181 3201 246 8 i 13 15 i? 19 21 22 23 3222 3424 3617 3243 3444 3636 3263 3464 3655 3284 3483 3674 3304 3502 3692 3324 3522 3711 3345 3541 3729 3365 356o 3747 3385 3579 3766 3404 3598 3784 24 6 246 246 8 10 12 8 10 12 7 9 ji 14 16 8 14 iS 7 13 15 7 24 25 26 ^7 28 29 30 3802 3979 4150 3820 3997 4166 3838 4014 4183 3856 4031 42OO 3874 4048 4216 3892 4065 4232 399 4082 4249 3927 4099 4265 3945 4116 4281 3962 4133 4298 245 235 235 7 9 ii 7 9 10 7 8 10 12 14 6 12 14 5 " 13 5 43M 4472 4624 4330 4487 039 4346 4502 4654 4362 4518 4669 4378 4533 4683 4393 4548 4698 4409 4564 4713 4425 4579 4728 4440 4594 4742 4456 4609 4757 2 3 5 235 134 689 689 679 " 13 4 II 2 4 10 2 3 477i 4786 4800 4814 4829 4843 4857 4871 4886 4900 134 $79 10 i 3 31 32 33 4914 5051 5185 4928 5065 5198 4942 5079 5211 4955 5092 5224 4969 5105 5237 4983 5H9 5250 4997 5132 5263 5011 5145 5276 5024 5159 5289 5038 5172 5302 * 3 4 134 134 678 5 7 8 5 6 8 IO I 2 9 i 2 9 10 12 34 35 36 5315 544i 5563 5328 5453 5575 5340 5465 5587 5353 5478 5599 5366 5490 5611 5378 5502 5623 5391 5514 5635 5403 5527 5647 54i6 5539 5658 5428 5551 5670 '34 i 4 i 4 5 6 8 5 6 7 5 6 7 9 10 ii 9 10 ii 8 10 ii 37 38 39 5682 5798 59" 5694 5809 5922 5705 5821 5933 5717 5832 5944 5729 5843 5955 5740 5855 5966 5752 5866 5977 5763 5877 5988 5775 5888 5999 5786 5899 6010 * 3 * 3 i 3 5 6 7 5 6 7 457 8 9 10 8 9 10 8 9 10 40 6021 6031 6042 6053 6064 6075 6085 6096 6107 6117 1 3 456 8 9 10 41 42 43 6128 6232 6335 6138 6243 6345 6149 6253 6355 6160 6263 6365 6170 6274 6375 6180 6284 6385 6191 6294 6395 6201 6304 6405 6212 6314 6415 6222 6325 6425 i 3 i 3 i 3 4 5 6 4 5 6 4 5 6 7 8 9 7 8 9 7 8 Q 44 45 46 47 48 49 6435 6532 6628 6444 6542 56 3 7 6454 6551 6646 6464 6561 6656 6474 6571 6665 6484 6580 6675 6493 6590 6684 6503 6599 6693 6513 6609 6702 6522 6618 6712 1 3 * 3 1 3 4 5 6 4 5 6 4 5 6 7 8 9 7 8 9 7 7 8 6721 6812 6902 6730 J82I 6911 6739 6830 6920 6749 6839 6928 6758 6848 6937 6767 6857 6946 6776 6866 6955 6785 6875 6964 6794 6884 6972 6803 6893 6981 i 3 i 3 i 3 455 445 445 678 6 7 8 6 7 8 50 6990 6998 7007 7016 7024 7033 7042 7050 7059 7067 i 3 345 6 7 8 51 52 53 7076 7160 7243 7084 7168 7251 7093 7177 7259 7101 7185 7267 7110 7193 7275 7118 7202 7284 7126 7210 7292 7135 7218 7300 7143 7226 7308 7152 7235 7316 * 3 Z 2 Z 2 345 3 4 5 345 6 7 8 6 7 7 667 54 7324 7332 7340 7348 7356 7364 7372 7380 7388 7396 i a a 345 667 LOGARITHMS 329 1 2 3 4 5 6 7 8 9 123 456 789 55 7404 7412 7419 7427 7435 7443 745i 7459 7466 7474 122 345 5 6 7 56 57 58 7482 7559 7634 7490 7566 642 7497 7574 7649 7505 7582 7657 7513 7589 7664 7520 7597 7672 7528 7604 7679 7536 7612 7686 7543 7619 7694 755i 7627 7701 122 122 112 3 4 5 345 344 567 5 6 7 5 6 7 59 60 61 "62 63 64 7709 7782 7853 7716 7789 7860 7723 7796 7868 773i 7803 7875 7738 7810 7882 7745 7818 7889 7752 7825 7896 7760 7832 7903 7767 7839 7910 7774 7846 7917 112 112 112 344 344 344 5 6 5 6 5 6 7924 7993 8062 7931 Sooo 069 7938 8007 8075 7945 8014 8082 7952 8021 8089 7959 8028 8096 7966 8035 8102 7973 8041 8109 7980 8048 8116 7987 8055 8122 112 112 112 334 334 334 5 6 5 5 5 5 65 8129 8136 8142 8149 8156 8162 8169 8176 8182 8189 112 334 5 5 66 67 68 ^9 70 71 8i95 8261 8325 202 267 S33i 8209 8274 8338 8215 8280 8344 8222 8287 8351 8228 8293 8357 8235 8299 8363 8241 8306 8370 8248 8312 8376 8254 8319 8382 112 112 112 334 334 334 556 556 456 8388 8451 8513 3395 8457 8519 8401 8463 8525 8407 8470 853i 8414 8476 8537 8420 8482 8543 8426 8488 8549 8432 8494 8555 8439 8500 8561 8445 8506 8567 112 I I 2 I I 2 234 234 234 456 456 455 72 73 74 8573 8633 8692 8579 8639 8698 8585 8645 8704 859 1 8651 8710 8597 8657 8716 8603 8663 8722 8609 8669 8727 8615 8675 8733 8621 8681 8739 8627 8686 8745 112 112 234 234 4 5 5 455 75 76 77 78 79 80 81 0751 8808 8865 8921 Vb^ 8814 8871 8927 8762 8820 8876 8932 8700 8825 8882 8938 [774 8831 8887 8943 ?779 8837 8893 8949 070^ 8842 8899 8954 8791 8848 8904 8960 8797 8854 8910 8965 0002 8859 8915 8971 112 112 I X 2 233 233 233 455 445 4 4 5 8976 9031 9085 8982 9036 9090 8987 9042 9096 8993 9047 9101 8998 9053 9106 9004 9058 9112 9009 9063 9117 9015 9069 9122 9020 9074 9128 9025 9079 9133 1X2 112 112 233 233 233 445 445 445 82 83 84 ~85 86 87 88 "89 90 91 92 93 94 9138 9191 9243 9*43 9196 9248 9149 9201 9253 9 J 54 9206 9258 9*599165 9212 9217 9263 9269 9170 9222 9274 9175 9227 9279 9180 9232 9284 9186 9238 9289 112 I Z 2 I Z 2 233 233 233 4 4 5 445 4 4 5 9 2 91 9299 9304 9309 9315 9320 9325 9330 9335 9340 112 233 445 9345 9395 9445 9350 9400 9450 9355 9405 9455 9360 9410 9460 9365 9415 9465 9370 9420 9469 9375 9425 9474 9380 9430 9479 935 9435 9484 939 9440 9489 112 Oil Oil 233 223 223 445 344 344 9494 9542 9590 9499 9547 9595 9504 9552 9600 9509 9557 9605 9513 9562 9609 9518 9566 9614 9523 9571 9619 9528 9576 9624 9533 958i 9628 9538 9586 9633 Oil Oil Oil 223 223 223 344 344 344 9638 9685 9731 9643 9689 9736 9647 9694 9741 9652 9699 9745 9657 9703 9750 9661 9708 9754 9666 9713 9759 9671 9717 9763 9675 9722 9768 9680 9727 9773 Oil Oil Oil 2 23 223 223 344 344 344 95 9777 9782 9786 9791 9795 9800 9805 9809 9814 9818 Oil 223 344 96 97 98 9823 9868 9912 9827 9872 9917 9832 9877 9921 9836 9881 9926 9841 9886 9930 9845 9890 9934 9850 9894 9939^ 9854 9899 9943 9859 9903 9948 9863 9908 9952 T I Z I Z I 223 223 233 344 344 344 99 9956 9961 99 6 5 9969 9974 9978 9983 9987 9991 9996 Z I 223 3 3 4 330 GAS FACTORS 000 ir- m CM 888 ! lO*rH Tf-lt-l tHiHi-H OOO OOC DO OOO OOO OOO OOO OOO OOO OO< i T*< COCO ooo ICCO-H 888 8? c-inco ooo 888 503 CO >OO 0-88 (NOCO S83 588 888 333 338 888 8! >oo ooo OOO CO COCMCN OOO CNOC OOC coc c 5OO OOO ;8g 3^ Is 1I si! )O OOO OC >Tt< (MOCO O^CO HC ScoSt- t-c-t- t-< 03010 OJCiOi OC >coco 5OO si! 5-H Oit-lO CO"-! t t OCOCO ^CNH m^i^< T^T*<^ TEMPERATURE IN DEGREES FAHRENHEIT. GAS FACTORS 331 OOO OOO OOO C~m CO>-I COCO COCDC 0000 COt~D- C~C-t 00 OSO5O1 OJO5C >T*CM OOC- J^H oc-m T*- ThCO i-HOO "Tf^ rim m m m ooo >t- in^cj ococ^ m< >m miOLO m^T* ^< 50 OOO) OOO O< >coco inco 1 * ococo HOOCO COCOCO CJfNCN 5OO OOO IOCO<-I O OJCMO5 CN 0)0)05 05 eoi-ioi cocoio OOO coco 1 * mmm O5O5O5 CMOC inm-< t-mco CNOOO c-mco CNOOO comoo COCOCO COCO )(NO OOt-m COCMO )COCO NOJIM (N(NCN ) O O5 OOO OOO COt-iO CO CACAO 05 glOC io 05C35 >* Ti4^1 500 OOC O505O) 05O5O5 O5O5O5 5lO U3U51 50) 050JC CO^HC t-OO OOO OOO OCOCO TjMr-l 2 COCO COCOCO 00 000 O5O5O5 O5O5O5 C-iOCO T*<^Tl4 O)O)O) JCMCM CM 1OO O Oi O) O) O) O5 O) C ;s s (Nr-IO SCN--! 00 OOO) OOC COCO U5 5COCO CO C-lOC co< 0)< comco ^HOOO CN 0)0)0) sinco *-i >OO O )OO O 000 000 000 )00t- lOCO^H )00 OOO) TEMPERATURE IN DEGREES^FAHRENHEIT. 332 METALLURGICAL ANALYSIS HYDROCHLORIC ACID DENSITY Table showing the approximate quantities of hydrochloric acid (sp.gr. 1.20), and water required to make 1 liter of any desired density at 15 C., and also the weight of HC1 per liter for each density. Density. Cubic Centimeters Required for 1 Liter. Grams HCl in 1 Liter.* HC1 1.20. Water, Approx. 1.01 50 950 22 1.02 100 900 42 1.03 150 850 64 1.04 200 800 85 1.05 250 750 107 1.06 300 700 129 1.07 350 650 152 1.08 400 600 174 1.09 450 550 197 1.10 500 500 220 1.11 550 450 243 1.12 600 400 267 1.13 650 350 291 1.14 700 300 315 1.15 750 250 340 1.16 800 200 366 1.17 850 150 392 1.18 900 100 418 1.19 950 50 443 1.20 1000 469 * Lunge and Marchlewski, 1891. DENSITY OF ACIDS 333 SULPHURIC ACID DENSITY Table showing the approximate quantities of sulphuric acid (sp.gr. 1.84), and water required to make 1 liter of any desired density at 15 C., and also the weight of EkSCU per liter for each density. Density. Cubic Centimeters Required for 1 Liter. Grams * H 2 S04 in 1 Liter. Density. Cubic Centimeters Required for 1 Liter. Grams HsSO* in 1 Liter. H 2 S04 1.84. Water. H 2 S0 4 1.84. Water. .02 18 987 31 1.44 443 624 779 .04 35 976 62 1.46 465 604 817 .06 53 960 93 1.48 487 584 856 .08 71 949 125 .50 509 564 896 .10 90 934 158 .52 532 540 936 .12 108 921 191 .54 555 521 977 .14 126 908 223 .56 575 502 1015 .16 146 891 257 .58 598 479 1054 .18 166 874 292 .60 621 457 1096 .20 186 858 328 .62 646 432 1139 .22 207 839 364 .64 671 406 1181 .24 227 822 400 .66 695 382 1222 .26 247 805 435 .68 720 356 1267 .28 268 786 472 .70 745 329 1312 .30 290 767 510 .72 772 298 1357 .32 312 746 548 1.74 798 271 1404 .34 333 726 586 .76 823 245 1451 1.36 354 709 624 .78 854 208 1504 1.38 376 688 662 .80 893 157 1564 1.40 399 665 702 1.82 932 105 1639 1.42 421 645 740 1.84 1000 1759 * Lunge and Isler, 1895. 334 METALLURGICAL ANALYSIS NITRIC ACID DENSITY Table showing the quantities of nitric acid (sp.gr. 1.42), and water required to make 1 liter of any desired density at 15 C., and also the weight of HNOs per liter for each density. Density, sp.gr. Cubic Centimeters Required for 1 Liter. Grams * HNOs in 1 Liter. Density, sp.gr. Cubic Centimeters Required for 1 Liter. Grams HNOs in 1 Liter. HNOs 1.42. Water. HNOs 1.42. Water. 1.01 19 983 19 1.22 434 605 430 1.02 38 966 38 1.23 456 584 452 1.03 57 949 57 1.24 479 562 475 1.04 76 932 75 1.25 503 538 499 1.05 95 915 94 1.26 527 514 521 1.06 114 898 113 1.27 550 491 545 1.07 133 881 132 1.28 573 468 568 1.08 152 864 151 1.29 598 442 592 1.09 171 847 170 1.30 623 417 617 1.10 190 830 188 1.31 649 389 643 1.11 209 813 207 1.32 675 362 669 1.12 229 795 227 1.33 701 334 695 1.13 248 777 246 1.34 732 302 725 1.14 268 759 266 1.35 761 271 754 1.15 288 741 286 1.36 790 239 783 1.16 309 722 306 1.37 822 203 814 1.17 329 704 326 1.38 854 168 846 1.18 350 684 347 1.39 888 129 880 1.19 370 665 367 1.40 922 90 914 1.20 391 646 388 1.41 961 45 953 1.21 412 626 409 1.42 1000 991 Lunge and Rey, 1891. GENERAL REFERENCES AARON, C. H.: Assaying. 6th Ed. San Francisco. Mining and Scientific Press. 1906. ALLEN, J. A.: Tables for Iron Analysis. New York. J. Wiley & Sons. 1896. Analysis of Iron and Steel. Middletown, Ohio. American Rolling Mill Co. 1912. ARGALL, P. H.: Smelter and Mill Methods of Analysis. Boulder, Colo. University of Colo. 1904. BARR, J. A.: Testing for Metallurgical Processes. San Francisco. Mining and Scientific Press. 1910. BERINGER, C. AND J. J.: Assaying. 3d Ed. London. Griffin & Co. 1895. BLAIR, A. A.: The Chemical Analysis of Iron. 7th Ed. Philadelphia. Lippincott & Co. 1908. BLASDALE, W. C.: Principles of Quantitative Analysis. New York. D. Van Nostrand Co. 1914. BREARLEY, H., AND IBBOTSON, F.: The Analysis of Steel Works Materials. London. Longmans, Green & Co. 1902. BROWNING, P. E.: Introduction to the Rarer Elements. 3d Ed. New York. J. Wiley & Sons. 1914. CAIRNS, F. A.: Quantitative Chemical Analysis. 3d Ed. New York. H. Holt & Co. 1896. CARNOT, A.: Traite d'analyse des substances minerales. Dunod. Paris. 1910. CHEEVER, B. W.: Select Methods in Inorganic Quantitative Analysis. Revised by F. C. SMITH. 3d Ed. Ann Arbor, Mich. G. Wahr. 1896. CHESNAU, M. G.: Analytical Chemistry, New York. Macmillan & Co. CLASSEN, A.: Handbuch der analytischen Chemie. Stuttgart. 1891. CLASSEN, A.: Quantitative Chemical Analysis by Electrolysis. 5th Ed. Trans, by W. T. HALL. New York. J. Wiley & Sons. 1914. CLENNELL, J. E.: Chemistry of Cyanide Solutions. New York. Engineering and Mining Journal. 1904. CROBAUGH, F. L.: Methods of Chemical Analysis and Foundry Chemistry. Cleveland, O. 1901. CROOKES, W.: Select Methods in Chemical Analysis. 3d Ed. London. 1894. 335 336 METALLURGICAL ANALYSIS CUMMINGS, A. C., AND KAY, S. A.: Quantitative Chemical Analysis. New York. J. Wiley & Sons. 1914. DENNIS, L. M.: Gas Analysis. New York. Macmillan & Co. FRESENIUS, K. M.: Quantitative Chemical Analysis. 6th ed. Trans, by A.I. CORN. New York J. Wiley & Sons. 1911. FULTON, C. H.: Fire Assaying. 2d Ed. New York. McGraw-Hill Book Co. 1911. FURMAN, H. VAN F.: Practical Assaying. 5th Ed. New York. J. Wiley & Sons. 1901. GILL, A. H.: Gas and Fuel Analysis for Engineers. 3d Ed. New York. J. Wiley & Sons. 1903. GOOCH, F. A.: Methods in Chemical Analysis. New York. J. Wiley & Sons. 1912. HEESS, J. K.: Practical Methods for the Iron and Steel Works Chemist. Easton, Pa. The Chemical Publishing Co. 1908. HEMPEL, W.: Gas Analysis. New York. Macmillan & Co. HILLEBRAND, W. F.: The Analysis of Silicate and Carbonate Rocks. Bull. 422, U. S. Geological Survey, Washington, Government Printing Office. 1910. HOWE, H. M.: Metallurgical Laboratory Notes. Boston. Boston Testing Laboratories. 1902. JOHNSON, C. M.: Rapid Methods for the Chemical Analysis of Special Steels. 2d Ed. New York. J. Wiley & Sons. 1914. JULIAN, F. : A Textbook of Quantitative Analysis. St. Paul, Minn. Ram- sey Publishing Co. 1902. KRAYER, P. J. : The Use and Care of a Balance. Easton, Pa. The Chemical Publishing Co. 1914. LODGE, R. W.: Notes on Assaying. New York. J. Wiley & Sons. 1906. LORD, N. W., AND DEMOREST, D. J.: Metallurgical Analysis. New York. McGraw-Hill Book Co. 1913. Low, A. H.: Technical Methods of Ore Analysis. 6th Ed. New York. J. Wiley & Sons. 1914. LUNGE, G.: Techno-Chemical Analysis. Trans by A. I. COHN. New York. J. Wiley & Sons. 1905. MAHIN, E. G.: Quantitative Analysis. New York. McGraw-Hill Book Co. 1914. MERCK, E.: Chemical Reagents, Their Purity and Tests. 2d Ed. New York. D. Van Nostrand Co. 1914. MENSCHUTKIN, N.: Analytical Chemistry. Trans, by J. LOCKE. London. Macmillan & Co. 1895. GENERAL REFERENCES 337 MILLER, E. H. : Quantitative Analysis for Mining Engineers. 2d ed. New York. D. Van Nostrand Co. 1907. MITCHELL, J.: Practical Assaying. 5th Ed. Edited by W. CROOKES. London. Longmans, Green & Co. 1881. MORGAN, J. J.: Tables for Quantitative Metallurgical Analysis. London. Griffin & Co. 1899. NEUMANN, B.: Theorie und Praxis der analytischen Elektrolyse der Metalle. Halle. W. Knapp. 1897. Trans, by J. B. C. KERSHAW. London. Whittaker & Co. OLSEN J. C.: Quantitative Chemical Analysis. 4th Ed. New York. D. Van Nostrand Co. 1911. OSTWALD, W. : The Scientific Foundations of Analytical Chemistry. Trans. by G. McGowAN. 2d Ed. London. Macmillan & Co. 1900. PHILLIPS, F. C.: Methods for the Analysis of Ores, Pig-iron, and Steel. 2d Ed. Easton, Pa. The Chemical Publishing Co. 1901. PHILLIPS, H. J.: Engineering Chemistry. 2d Ed. London. C. Lockwood &Son. 1894. POST, J.: Chemisch-technische Analyse. Braunschweig. F. Vieweg & Sohn. 1909. PRICE, W. B., AND MEADE, R. K.: The Technical Analysis of Brass. New York. J. Wiley & Sons. 1908. PROST, E.: Chemical Analysis. Trans, by J. C. SMITH. New York. D. Van Nostrand Co. 1904. RHEAD, E. L., AND SEXTON, A. H.: Assaying and Metallurgical Analysis. London. Longmans, Green & Co. 1902. RICKETTS, P. DE P., AND MILLER, E. H. : Notes and Assaying. 3d Ed. New York. J. Wiley & Sons. 1903. SEAMON, W. H.: Manual for Assayers and Chemists. New York. 1910. SEXTON, A. H. : The Chemistry of the Materials of Engineering. Manchester. Technical Publishing Co. 1900. SIDENER, C. F.: Quantitative Metallurgical Analysis. Minneapolis. H. W. Wilson Co. 1904. SMITH, E. A.: Sampling and Assay of the Precious Metals. London. Griffin & Co. 1913. SMITH, E. F.: Electro-Analysis. 4th Ed. Philadelphia. P. Blakiston & Sons 1907. STILLMAN, T. B.: Engineering Chemistry. 4th Ed. Easton, Pa. The Chemical Publishing Co. 1910. SUTTON, F.: A Systematic Handbook of Volumetric Analysis. 10th ed. Philadelphia. P. Blakiston & Sons. 1911. 338 METALLURGICAL ANALYSIS TALBOT, H. P.: An Introductory Course in Quantitative Analysis. New York. Macmiilan & Co. 1899. THORPE, T. E.: Quantitative Analysis. 9th Ed. New York. J. Wiley & Sons. 1891. TREADWELL, F. P.: Analytical Chemistry. Trans, by W. T. HALL. 3d Ed. New York. J. Wiley & Sons. 1914. TROILIUS, M.: Notes on the Chemistry of Iron. 3d Ed. New York. J. Wiley & Sons. 1889. WASHINGTON, H. S.: The Chemical Analysis of Rocks. 2d Ed. New York. J. Wiley & Sons. WHITE, A. H.: Technical Gas and Fuel Analysis. New York. McGraw-Hill Book Co. 1913. WiNKLER, C.: Technical Gas Analysis. 3d Ed. Trans, by G. Lunge. London. Gurney & Jackson. 1902. WOEHLER, F.: Mineral Analysis. Edited by H. B. Mason. Philadelphia. H. C. Baird. 1871. WYSOR, H.: Analysis of Metallurgical and Engineering Materials. Easton, Pa. The Chemical Publishing Co. INDEX Absorbents of hydrochloric acid, 11G of moisture, 30, 115 Absorption bulb and tube, glass- stoppered, 124 Acidity of ore, 246 Adsorption, 27 Air bath, 70 Alkalies in clay, 287 Allen, nitrogen in steel, 151 Allen and Moyer, Gas Analysis, 281 Allihn condenser, 181 Alloys, analysis of, 210 Alumina, determination of, in ore, phosphate method, 87 in blast furnace slag, 191 in iron slag, 159 Aluminum, detection of, 314 in alloy, 213 Alundum, reagent, 121 American Foundrymen's Associa- tion method for sulphur in iron, 110 Ammonia, standard solution of, 152 Ammonium acetate, solution of, 175 bisulphate, reducing agent, 131 carbonate, reagent, 220 ferrous sulphate, determination of iron in, 52 ferrous sulphate, standard solu- tion of, 141 molybdate, standard solution of, for lead, 175 Ammonium oxalate solution, 96 Ammonium nitrate, solution of, 220 wash solution, 76 phosphate solution, 97 phosphate solution for alumina 87 phosphomolybdate, reaction with sodium hydroxide, 85 phosphomolybdate, solution of in ammonia, 79 sulphate, wash solution of, 81 sulphocyanate, solution of, 220 Amyl alcohol, 299 Analyses, purposes for which they are made, 1 Analysis of a gas, 277 of iron ores, 45 of iron slags, 157 volumetric, 33 Annealing, 231 Annealing cup, 231, 232 Annealing steel for color carbon determinations, 127 Anodes, sampling of, 198 Anode suitable for rotating, 174 Antimony, detection of, 314 Antimony in copper, 220 in silver bullion, 202 Apparatus for carbon in steel, com- bustion, 117, 122 for sulphur in iron, 112, 114 Apparatus, volumetric, 33 Argols, reducing agent, 227 339 340 INDEX Arsenic and antimony in converter copper, 205 Arsenic, detection of, 314 Arsenic in copper, 220 Arsenic in ores, 180 in ores and furnace products, 182 in ore, titrating with ammonium thiocyanate, 183 in silver bullion, 202 in slag, 195 Arsenious acid method for manganese in ore, 90 Asbestos felt for filtering, 25 Ash in coal, 255 Aspirator bottles, 117, 118 Assay furnaces, 224 Assay of bullion, 235 of gold and silver ores, 224 of silicious gold and silver ore, 229 of sulphide ores, 233 of telluride ores, 234 Assay-ton, 226 Atomic weights of the elements, 324 Automatic analysis of gas, 282 Available cyanogen, 244 Bailey, coal sampling, 253 Balance, care and use of, 15 Ball mill, 14 Barium chloride solution, 108 Barium, detection of, 314 determination of, 301 Barium hydroxide solution for car- bon dioxide, 125 sulphate, contamination of, 74, 75 sulphate, precipitation of, 109 Baryta, 194 Bead of gold and silver, 225 Beilstein and Jawein, cadmium, 292 Bennett, arsenic, 182 Benz, thorium, 304 Benzoic acid, calorific value of, 266 Beryllium, determination of, 303 Berzelius method for silica, 69 Bismuth, detection of, 314 Bismuth in alloys, 218 Blair, A. A., fusion of ferro-silicon, 107 standard solution of iron, 54 the reductor, 57 Blank test, 58 Blast furnace slags, chilled, analysis of, 188 sampling, 188 " Blick," assaying, 230 Boat for combustion of iron or steel, 122 Boiler water, examination of, 308 scale-forming constituents in, 309 Bomb for calorimeter, 261 Borax glass, melting-point of, 228 Boiling-points of the elements, 324 Brass and bronze, 210 Briquettes and other copper-bear- ing products, analysis of, 196 British thermal units, 271 Bronze, analysis of, 210 Brownson, E. E., copper analysis, 206 Brunck, O., nickel in steel, 140 Brunton, D. W., sampling, 10 Bucking plate, 14 Buckly, D. W., bullion analysis, 199 Bulb tube for barium hydroxide solution, 125 Bullion, assay of, 235 gold in, 240 sampling of, 235 silver in, fire method, 235 Burettes, 33, 34 Burning precipitates, 27 Burrel, gas analysis, 281 INDEX 341 Cadmium chloride solution for hydro- gen sulphide, 1 1 2 Cadmium, detection of, 315 determination of, 292 Cadmium sulphide, action of hydro- chloric acid on, 114 Caesium, detection of, 315 determination of, 302 Cahen and Wootton, caesium, 302 Calcium and magnesium, titration of, 164 Calcium chloride, action of ammo- nium oxalate on, 158 action of oxalic acid on, 162 Calcium, detection of, 315 Calcium oxalate, action of sul- phuric acid on, 158, 163 Calculating results of analysis, 31 Calorie, definition of, 260 Calorific power by the Parr calorim- eter, 268 Dickinson's formula, 267 formula for, 266 of coal, 260 of coal from the ultimate analysis, 270 of gas, 283 of liquid fuels, 272 Calorimeter, 260 water value of, 266 Calorimetry, corrections in, 264 Camera for Eggertz tubes, 43 Camp, J. M., gas factors, 330 sampling iron, 103 sampling iron-ore, 46, 47 sulphur in iron, 111 silicon in iron and steel, 105 Weller's method for titanium, 135 Camp's shaking machine, 78 Camphor, calorific value of, 266 Carbon, combined, in steel, 127 Carbon, combustion apparatus, 117, 122 Carbon filter, 25 Carbon, filtering of, 120 fixed in coal, 256 hardening, in steel, 127 in iron or steel, titration of excess of barium hydroxide, 126 in steel, 115 total, in iron or steel, direct combustion, 121 weighing as barium carbonate, 124 Carbon dioxide, absorbent for, 274 absorption of, by barium hydrox- ide, 125 apparatus for, 166 generator, 64 in limestone, 166 Carbon monoxide, explosion method for, 280 absorbent for, 276 calorific power of, 285 Care and use of the balance, 15 Care of platinum, 29 Cargo sampling, 47 Cast iron, sample, 104 Cerium, detection of, 315 determination of, 304 Chandler, assay-ton, 226 Charcoal, reducing agent, 227 Chatard, tungsten, 148 Check assay, 236 Chlorate solution, 187 Chlorine, absorbents of, 116 in water, 309 Chromium and vanadium in steel, 141 Chromium, detection of, 316 determination of, 290 Classification of materials for sam- pling, 8 342 INDEX Clay, analysis of, 286 alkalies in, 287 Cleaning solution, 35 Clennell, J. E., precipitation of zinc hydroxide, 246 total cyanide, 244 Coal, 253 calorific power of, 260 nitrogen in, 259 oxygen in, 260 phosphorus in, 260 proximate analysis of, 254 sampling, 253 sulphur in, 256 ultimate analysis of, 259 Cobalt, detection of, 316 determination of, 290 Cochineal, 42 Coke, 255 Cold test of lubricating oil, 307 Colorimeter, 42, 44 Colorimetry, standard solutions for, 43 Color method for carbon in steel, 127 for manganese in iron and steel, 132 for manganese in ore, 92 Columbium, detection of, 316 Columbium and tantalium, deter- mination of, 301 Combined carbon in steel, 127 Combined water in ore, 49 Commercial cyanide, cyanogen in, 247 sampling of, 247 Coning and quartering samples, 12 Constant temperature bath, 70 Converter copper, arsenic and anti- mony in, 205 copper in, 205 Cooke's apparatus for ferrous iron, 66 Cooke's method for ferrous iron, 65 Copper acetate, action of potassium iodide on, 171 Copper, analysis of, 220 Copper and potassium chloride solu- tion, 115 Copper bullion, analysis of, 197 gold in, 201 sampling of, 197 silver in, 199, 200 Copper, detection of, 316 Copper determinations, flask for, 169 Copper matte, analysis of, 184 Copper in alloy, 211, 214, 217 Copper in blast furnace slag, colori- metric method, 194 iodide method, 193 Copper in converter copper, 205 in copper bullion, 199 in matte, 184, 185 in ore, electrolytic method, 173 potassium cyanide method, 1 68 potassium iodide method, 168 in silver bullion, 202 in steel, 150 volumetric method, 151 Copper in the presence of arsenic, antimony, tellurium, and selen- ium, 209 Copper oxide in the combustion fur- nace, 123 Copper sulphate, anhydrous, absorb- ent of hydrochloric acid, 116 Correcting a standard solution, 39 Corrections in calorimetry, 264 Correct sampling, necessity of, 8 Cover of charge in assaying, 228 Counterpoise in weighing, 119 Crucible assay, 225 Crucible, fire clay, 225 Crucible tongs, 230 INDEX 343 Crude petroleum, fractional distil- lation of, 272 Crusher, 13 Cullen, J. F., free metallic iron, 67 Cupel, 225 Cupcllation, 225, 230 losses in, 236 Cupel tongs, 230 Cupric chloride, action of, on iron, 120 Cushman, oxygen in steel, 155 Cyanide, action of silver nitrate on, 243, 246 free, in solutions, 243 Cyanide method for copper in matte, . 185 Cyanide solutions, gold and silver in, 242 testing of, 243 Cyanogen in commercial cyanide, 247 quantity in potassium and sodium cyanides, 244 reporting as potassium cyanide, 244 Day and Sosman, melting-point of gold, 243 melting-point of silver, 242 Decime salt solution, 238 Definition of metallurgical analysis, 1 Densities of the elements, 324 Dehydration of silicic acid, 70 Deposition of moisture while weigh- ing, 31 Demorest, D. J., separation of zinc from other metals, 179 Deniges, nickel in steel, 139 De Osa, nitrogen in steel, 153 Desiccator, 30 Desulphurizing agents for assaying, 228 Deville and Stas, platinum metals, 251 Dewey, F. P., Gay-Lussac method for silver, 237 platinum, 249 Dickinson's formula for calorific power, 267 Dimethylglyoxime method for nickel in steel, 140 Direct combustion of iron or steel for total carbon, 121 apparatus for, 122 Dissolving, 18 Dissolving a fusion from a platinum crucible, 72 Distilling solution for arsenic, 180 Drawe, water analysis, 313 Drown, T., titanium, 98 Drown's method for silicon in iron and steel, 106 Dulong's formula, 270 Duplicate sampling, 10 Earnshaw, calorific power of gas, 285 Economy in the laboratory, 5 Eggertz color method, 44 tubes, 43 Electric current, density of, for cop- per precipitation, 174 Electrodes, platinum, for copper, 173 Electrolytes, ionization of, 20 Electrolytic method for copper in matte, 184 in ore, 173 Elements, table of, 324 Emmerton's method for phosphorus in ore, 80 Empirical standard solutions, 37 End-point, 41 Equipment of the laboratory, 5 Erbium, detection of, 317 344 INDEX Eschka mixture for sulphur in coal, 256 Ethane, calorific power of, 285 Ether method for nickel in steel, 137 Ethylene, calorific power of, 285 Evolution method for sulphur in iron or steel, 111 Explosion pipette, 274 Factors, table of, 327 Factor weights, 32 for standard solutions, 40 " Feathers " assaying, 230 Ferric oxide, determination of, 65 Ferric salts, reduction of, with zinc, 56 Ferric sulphate, standard solution of, 101 Ferro-manganese and spiegel, man- ganese in, 133 Ferro-silicon, silicon in, 107 Ferrous iron, Cooke's method, 65 determination of, 64, 67 Ferrous oxide, determination of, 65 in iron-slag, 159 in reverberatory slag, 195 Ferrous salts, oxidation of, by potas- sium permanganate, 57 Ferrous sulphate, reducing agent, 131 Ferrous sulphate, standard solution for manganese, 93 Filtering by suction, 23, 24, 25 Filtration, 35 Fire assaying, 224 Fire test of lubricating oil, 307 Fixed carbon in coal, 256 Flashing-point of lubricating oil, 307 Flask for copper determinations, 169 Flour as reducing agent, 177, 227 Fluids, sampling of, 9 Fluxes, analysis of, 253 Fluxes for assaying, 228 Ford's method for silicon in iron, 107 accuracy of, 105 Formula for calorific power, 266 Fox, P. J., titration of calcium and magnesium, 164 Fragmental materials, sampling of, 9 Free cyanide in solutions, 243 Free metallic iron, determination of, 66 Fuels, analysis of, 253 Furnace, electric, for combustion of carbon, 117 Fusion, dissolving from a platinum crucible, 72 Fusions, contamination of, by sul- phur in gas, 73 Gallium, detection of, 317 Gas analysis, 273 automatic, 282 record of, 280 Gas burette, 274 Gas, calorific power of, 283 from its analysis, 285 Gas calorimeter, automatic recording, 284 Gas combustion furnace, method of heating, 119 Gaseous mixtures, gases in, 275 Gas measuring, 277 Gas pipettes, 274 Gay-Lussac method for silver in bullion, 237 Geissler bulb, 167 General principles of sampling, 8 Germanium, detection of, 317 determination of, 302 Glucinum, detection of, 317 determination of, 303 Gold and silver bead, 225 INDEX 345 Gold and silver in copper-bearing concentrates, 197 in cyanide solutions, 242 in lead bullion, 241 in matte, 188 in slag, 196 Gold and silver ores, assay of, 229 Gold, detection of, 317 Gold in bullion, 240 in copper bullion, 201 Gold-ore, sampling, 224 Gold, pure, preparation of, 242 value of, 227 Gooch, F. A., analysis of copper, 220 lithium, 299 titanium, 98 Graduated cylinder, 19 Graph for correcting total rise in temperature in calorimetry, 265 Graphitic carbon in iron, 129 Gravimetric analysis, the operations of, 15 Gray, distillation of petroleum, 272 Greenwood, palladium, 250 platinum, 250 Heath, G. L., sulphur in coal, 256 Hempel, gas pipette, 275 Hillebrand, W. F., strontium, 300 titanium, color method, 101 vanadium, 297 zirconium, 306 Hofman, Heine, and Hochtlen, for- mation of Turnbull's blue, 64 Holman, temperature corrections in calorimetry, 264 Holmes, J. A., sampling coal, 253 Hood for the laboratory, 4 Howe, H. M., segregation, 104 temperature correction in calorim- etry, 264 Hydrocarbons, heavy, absorbent for, 276 Hydrochloric acid, absorbents of, 116 action of, on permanganate solu- tion, 56 ammonia free, 151 density table, 332 normal solution of, 36 standard solution of, 126 Hydrofluoric acid method for silica, 69 Hydrogen, calorific power of, 285 explosion method for, 278, 280 Hydrogen in steel, 153 apparatus for, 154 Hydrogen peroxide reaction with potassium permanganate, 96 standard solution for manganese, 95 Hydrogen sulphide, action of iodine on, 114 generator, 137 Hydrogen, weight of, 69 Hygroscopic water, determination of, 49 Ignition, loss on, 50 Indicator, 35, 41 Indium, detection of, 317 determination of, 252 Inquartation, 232 Insoluble silicious matter in lime- stone, 160 Iodide method for copper in matte, 184 Iodine, action of on hydrogen sul- phide, 114 action of sodium thiosulphate on, 171 normal solution of, 36 standard solution of, 111, 206 346 INDEX Iodine, for arsenic, 180 lonization of electrolytes, 20 Iridium, detection of, 317 determination of, 252 Iron and aluminum in alloy, 211 in iron-slag, 157 Iron and steel, analysis of, 103 manganese in, by Walters' color method, 132 phosphorus in, 129 sampling, 103 silicon in, 105 Iron, burning precipitate of, 54 calorific value of, 266 detection of, 318 determination of, in ammonium ferrous sulphate, 52 free metallic, in the presence of titanium, 68 graphitic carbon in, 129 Iron in alloy, 213 in matte, 185 metallic, determination of, 66 Iron in blast furnace slags, 190 in ore, potassium permanganate method, 50 dichromate method, 62 in copper, 220 Iron-ore, rare elements in, 193 analysis of, 45 sampling, 45 Iron, oxidation of, by potassium dichromate, 64 oxidation of, with nitric acid, 53 precipitation of, with ammonia, 53 reducing agents for, 59 reduction of with sodium sulphite, 99 reduction of with thiosulphate, 88 Iron-slags, analysis of, 157 sampling, 157 Iron, solution of, by mercuric chloride solution, 67 sulphur in, American Foundry- men's Association method, 110 by evolution method, 111 Johnson, C. M., chromium in steel, 141 fusion of ferro-silicon, 107 tungsten, 146 Jones reductor, 57 Julian's method for manganese in ferro-manganese and spiegel, 133 in ore, 95 Junkers' gas calorimeter, 283 Keller, E., bullion assay, 201 method for selenium and tellurium in copper, 209 segregation in bullion, 197 works laboratory, 7 Kober and Marshall, indicators, 84 Laboratory, economy in, 5 equipment of, 5 hood for, 4 working table, 3 Lead acetate, solution of, 148 Lead bullion, gold and silver in, 241 Lead button, 225 Lead, detection of, 318 Lead in alloy, 211, 213, 216 fire method for, 177 in blast furnace slag, 192 in copper, 220 in matte, 186 in ore, 175 Lead molybdate method for tungsten in steel, 148 INDEX 347 Lead, quantity added, in the bullion assay, 237 reduction of, by carbon, 227 Lead sulphate, action of ammonium acetate on, 176 Leaks in combustion train, 119 Ledebur's method for oxygen in steel, 155 Lehner and Crawford, titanium, color method, 136 Lime in blast furnace slags, 189 in iron-slag, 158 in limestone, gravimetric method, 162 in ore, 96 in reverberatory slag, 195 in slag, volumetric method, 158 volumetric method, 163 Limestone, analysis of, 160 carbon dioxide in, 166 lime in, 162, 163 magnesia in, 165 phosphorus and sulphur in, 166 sampling, 160 silica in, 161 Liquid fuels, calorific power of, 272 Litharge, melting-point of, 228 Lithium, detection of, 318 determination of, 299 Logarithmic table, 328 Loss on ignition, 50 Low, A. H., tin, 295, zinc by potas- sium ferro-cyanide, 178 Low-carbon steel, solubility of, in nitric acid, 105 Lowe, fusion apparatus, 74 Lubricating oil, 307 Lunge's method of standardizing potassium permanganate solu- tion, 55 Lyon, D. A., free metallic iron, 67 Magnesia in blast furnace slag, 190 in iron-slag, 159 in limestone, 165 in ore, 97 Magnesia mixture, 79 Magnesium ammonium phosphate, burning of, 80 Magnesium chloride, action of sodium phosphate on, 165 Magnesium, detection of, 318 Magnetic oxide, to prevent the formation of, in burning iron precipitates, 54 Magnetized wire for transferring steel drillings, 18 Manganese, detection of, 318 Manganese dioxide, action of hydro- gen peroxide on, 96 precipitation of with alcohol, 74 precipitation of with potassium chlorate, 96 Manganese, effect of, on color carbon determinations, 128 Manganese in blast furnace slag, 191 in ferro-manganese and spiegel, 133 in iron and steel, with sodium arsenite, 132 in iron-slag, 160 in matte, 187 in ore, color method, 92 Julian's method, 95 sodium bismuthate method, 92 titration with sodium arsenite, 90 Volhard's method, 88 Walters' method for, 132 Manganese in steel, sodium bis- muthate method, 133 in steels containing chromium and tungsten, 134 Manganese sulphate, reaction of with potassium permanganate, 89 INDEX Manganese sulphate, use of, in the permanganate method, 61 Manganese sulphide, action of hydro- chloric acid on, 113 action of nitric acid on, 108 Margueritte method for iron in ore, 50 Marshall, catalytic action of silver nitrate, 91 Martin, O. C., analysis of silver bullion, 202 Meade, R. K., analysis of alloy, 215 Measuring flasks, 33, 34 Measuring solvents, 19 Melting-points of the elements, 324 Meniscus, to render, visible, 35 Menschutkin, platinum metals, 251 Mercaptans, 113 Mercuric chloride, reduction of, to mercury by stannous chloride, 61 solution of, 59 Mercury, detection of, 318 determination of, 293 Metallic iron, determination of, 66 " Metallics " in ore, 224 Metals as reagents in assaying, 229 Metals, detection of, 314 reduction of, in contact with plati- num, 27 sampling of, 9 Metallurgical analysis, definition of, 1 Methane, 277 calorific power of, 285 explosion method for, 278, 280 Methods of analysis, selection of, 1 Methyl orange, 42 Metric ton, 227 Mill solutions, protective alkali in, 245 Minor metals, determination of, 290 Mixer and Dubois, reduction of iron with stannous chloride, 60 Moisture, absorbents of, 30, 115 deposition of while weighing, 31 in coal, 254 in ore, 48 Moisture sample of iron-ore, 47 Mold, cast-iron, for fusions, 226 for sample of cast iron, 104 Molybdate method for lead in ore, 175 Molybdate solution, 76 Molybdenum, detection of, 319 in steel, 148, 149 Molybdenum powders, molybdenum in, 149 Molybdic acid, reduction of, in the reductor, 82 with powdered iron, 83 Moore, nickel in steel, 139 Muffle furnaces, 224 Muller, 14 Mylius and Forster, rhodium, 252 Nails, iron, in assaying, 233 Necessity of correct sampling, 8 Neodymium, detection of, 319 Nessler reagent, 152 Nickel and cobalt, determination of, 290 Nickel chloride, action of dimethyl- glyoxime on, 141 action of potassium cyanide on, 139 Nickel, detection of, 319 Nickel in copper, 220 in steel, dimethylglyoxime method, 140 ether method, 137 potassium cyanide method, 139 Nickel, standard solution of, 139 INDEX 349 Nitric acid density table, 334 Nitric acid, standard solution of, 245 standard solution for phosphorus, 84 Nitrogen in coal, 259 in steel, 151 Normal solution of hydrochloric acid, 36 of iodine, 36 of potassium dichromate, 36 of potassium permanganate, 36 of sulphuric acid, 36 Normal solutions, 36 Occlusion of solutes in precipitates, 27 Oil, water in, 273 Olsen, J. C., standardization of per- manganate solutions, 55 Operations of analysis, 15 Ore, acidity of, 246 Orsat apparatus, 281 Osmium, detection of, 319 Ostwald, W., adsorption, 27 indicators, 84 precipitation, 20 Oven, Freas electric, 70 Oxalic acid, action of potassium per- manganate on, 158 solution of, 160 standard solution of, 245 Oxides of iron, aluminum, etc., 161 Oxidizing agents for assaying, 227 for carbon monoxide, 116 Oxygen, absorbents for, 276 Oxygen for combustion, 122 apparatus for, 155 in coal, 260 Oxygen, use of in burning precipi- tates, 28 Palladium, detection of, 319 determination of, 250 Palladium nitrate, action of mercuric cyanide on, 251 Palladium oxide, formation of, 251 Palladium, reduction of with formic acid, 251 Parr, bomb for calorimeter, 261 calorimeter, 269 sulphur in coal, 257, 258 Parsons, beryllium, 303 Parting in assaying, 230 Pemberton's alkalimetric method for phosphorus in ore, 83 Penfield, S. L., method for combined water, 49 Penny's method for iron, 62 Permanganic acid, formation of with ammonium persulphate, 91 Peters, E. D., sampling, 10 Petroleum, 271 sulphur in, 272 Phillips, mercaptans, 113 Phenoldisulphonic acid, reagent, 310 Phenolphthalein, 41 solution of, 84, 126, 245 Phosphate method for alumina in ore, 87 Phosphate precipitate, care in burn- ing, 98 Phosphorus and sulphur in lime- stone, 166 Phosphorus, determination of, in ore in the presence of titanium, 86 Phosphorus from the filtrate from silica, 78 in alloy, 214 in coal, 260 in iron and steel, 129 in ore, Emmerton's method, 80 rapid method, 131 350 INDEX Pemberton's alkalimetric method, 83 weighing as magnesium pyro- phosphate, 79, 82 weighing the yellow precipitate, 75 Phosphorus, precipitation of, with ammonium molybdate, 77 temperature for precipitating, 78 Pick for sampling, 45 Pig-copper, moisture in, 198 Pincette, use of, 18 Pipette, automatic filling, 127 how to fill, 34 Pipettes, 33, 34 Plan of a school laboratory for metal- lurgical chemistry, 2 of a works laboratory, 6 Platinized asbestos in the combustion furnace, 123 Platinum, 249, 250 action of phosphorus on, 166 care of, 29 detection of, 320 how to clean, 29 Platinum metals, 249, 251 Platinum in iron solution, effect with stannous chloride, 60, 63 Platinum, reagents which attack, 29 Point of rest of the balance, 16 Potash-bulb, 117, 124 stoppers for, 118, 121 weighing, 119, 121 Potassium carbonate, melting-point of, 228 Potassium cyanide method for nickel in steel, 139 standard solution for nickel, 139 standard solution of, for copper, 168 Potassium, detection of, 320 Potassium dichromate method for iron, 62 Potassium dichromate, normal solu- tion of, 36 standard solution of, 62 Potassium ferricyanide solution as indicator, 62 Potassium ferrocyanide, solution of, 246 standard solution of, for zinc, 178 Potassium hydroxide solution for carbon dioxide, 115, 123 Potassium iodide, action of silver on, 243 Potassium iodide method for copper in ore, 171 solution of, 243 Potassium nitrate, standard solution of, 310 Potassium permanganate method for iron in ore, 50 reduction with stannous chloride, 59 Potassium permanganate, normal solution of, 36 reaction of with ferrous iron, 57 reaction with manganese sulphate, 89 Potassium permanganate solution, how to make and standardize, 51 Lunge's method of standardiza- tion, 55 standardization of, for phosphorus, 81 standardization with iron wire, 54 standardization with oxalic acid, 55 Praseodymium, detection of, 320 Precautions in weighing, 18 Precious metals, assaying, 224 Precipitates, burning of, 27 occlusion of solutes in, 27 solubility of, 20 washing of, 26 INDEX 351 Precipitates, weighing of, 30 Precipitate, transferring to a crucible, 27 transfer of, from filter paper to beaker, 61 Precipitation, 20 Preliminary assay, 236 Preparation of pure gold, 242 of pure silver, 242 of sample of iron-ore, 48 Preuss, fusion of ferro-silicon, 107 Price and Meade, copper by electrol- ysis, 173 distillation of arsenic, 181 nickel, 290 Proctor, hardness of water, 312 Protective alkali in mill solutions, 245 in the presence of zinc, 246 Proximate analysis of coal, 254 Prussian blue, 64 Pulverizer, 14 Pure silver, preparation of, 242 Pure gold, preparation of, 242 Purity of reagents, 19 in assaying, 229 Purposes for which analyses are made, 1 Radium, detection of, 320 Rapid burning of precipitates with oxygen, 28 Rapid method for phosphorus in iron and steel, 131 Rare elements in iron ore, 103 Rarer metals, determination of, 299 Reading the burette, 35 Reagents, 19 purity of, in assaying, 229 Recording and checking a weight, 18 Red lead oxide, reagent, 123 Reducing agents for assaying, 227 Reducing agents for iron, 59 Reducing power, 227 Reduction of ferric salts with zinc, 56 Reduction of metals in contact with platinum, 27 Reductor, Jones, 57 use of, 58 Reed, S. A., sampling, 10 References, general, 335 Reinhardt, G. A., free metallic iron, 67 Reverberatory slag, analysis of, 195 Rhodium, detection of, 320 determination of, 252 Richards, R. H., sampling table, 11 Richards, T. W. and Jesse, R. H. calorific power, 272 Richards, T. W. and Shipley, static electric charges in weighing, 119 Richards, T. W., gas pipette, 275 occlusion, 27 Rickard, T. A., sampling ore in place, 8 Riffle for dividing sample, 13 Rope-net system of sampling ore, 47 Rose, T. K., losses of gold in cupel- lation, 240 Rubidium, detection of, 320 Ruthenium, detection of, 320 determination of, 252 Sample for moisture, 47 Sample grinder, mechanical, 14 Sample of iron-ore, preparation of, 48 Sample, quantity to be taken, 10 Sampler, Vezin, 12 Sampling, 8 Sampling a cargo of iron-ore, 47 Sampling, A. Van Zwaluwenburg, 10 Sampling blast furnace slags, 188 352 INDEX Sampling, classification of materials | for, 8 coning and quartering, 12 done by chemist, 8 D. W. Brunton, 10 E. D. Peters, 10 Sampling fluids, 9 fragmental materials, 9 gas, 273 general principles of, 8 Sampling in duplicate, 10 iron and steel, 103 iron-ore, 45 limestone, 160 metals, 9 Sampling, object of, 8 of bullion, 235 of copper bullion, 197 ore in cars, 45 ore in place, 8 petroleum, 271 pick, 45 riffle, 13 rope-net system, 47 S. A. Reed, 10 split shovel, 12 Sampling table, R. H. Richards, 11 trowel, 45 Sand-soap for cleaning platinum, 29 Sauveur, A., forms of carbon in steel, 115 segregation, 104 Scandium, detection of, 320 Scorification assay, 225 of silver ores, 234 Scorifier, 225, 226 Scorifier tongs, 235 Sea-sand for cleaning platinum, 29 Segregation of impurities in iron and steel, 104 of sulphur in iron, 104 Selection of methods of analysis, 1 Selenium and tellurium in copper, 209 Separatory funnel, 137 Seyler, carbon dioxide in water, 310 Shaking machine, Camp's, 78 Silica, action of as a flux, 228 fusion with sodium carbonate, 71 hydrofluoric acid method, 69 in blast furnace slags, 188 in iron-slag, 157 in limestone, 161 in ore, Berzelius method, 69 in reverberatory slag, 195 melting-point of, 228 purification of with hydrofluoric acid, 71, 105 Silicates, solution of in hydrochloric acid, 70, 72 Silicious fluxes. 253 Silicic acid, dehydration of, 70 Silicide of iron, action of nitric acid on, 105 Silicon in ferro-silicon, 107 Drown's method, 106 Ford's method, 107 in iron and steel, 105 in steel, Drown's method, 106 Silicon mixture, Drown's, 106 Silicon tetrafluoride, formation of, 71 Silver and gold in copper bullion, 201 Silver bullion, copper, arsenic, and antimony in, 202 Silver, detection of, 320 Guy-Lussac method, 237 in bullion, fire method, 235 in copper bullion, 199 in ores, scorification method of assay, 234 Silver foil, absorbent of chlorine, 116 Silver nitrate as catalyzer, 91 INDEX 353 Silver nitrate, standard solution of, 243 Silver, standard solution of, 237 Silver sulphate, absorbent of hydro- chloric acid, 116 Simmance-Abady automatic gas ana- lyzer, 282 Size of sample, 10 Skinner and Hawley's method for arsenic, 180 Slawik, vanadium, color method, 145 Slime, weight of ore in, 248 Smith, E. F., copper by electrolysis, 173 Smith, J. Lawrence, alkalies in clay, 287 Smoot, loss of platinum, 250 Soda-lime, 116 Sodium arsenite, standard solution, 90 Sodium bismuthate method for mag- ganese in ore, 92 Sodium carbonate, melting-point of, 228 normal solution of, 311 Sodium chloride, standard solution of, 237 Sodium, detection of, 321 Sodium hydroxide, action of oxalic acid on, 245 standard solution for phosphorus, 84 Sodium phosphate, solution of, 160 Sodium silicate, formation of, 72 Sodium thiosulphate, standard solu- tion of, 171 Sodium zinc cyanide, action of so- dium hydroxide on, 245 Solubility of precipitates, 20 Solution for cleaning glass, 35 Solvents, measuring of, 19 Split shovel, 12 " Sprouting " of the button in assay- ing, 230 Standardizing solutions, 38 Standardization of potassium di- chromate solution, 62 Standard potassium permanganate solution, 51 Standard solution, 35 definition of, 36 Standard solution of iodine, 111 of potassium dichromate, 62 Standard solutions, correction of, 39 empirical, 37 for colorimetry, 43 normal, 36 Stannous chloride, oxidation of, by mercuric chloride, 60 reduction of iron by, 60 solution of, 59 Starch solution, 111 Static electric charges, effects in weighing, 119 Steel, carbon in, solution and com- bustion, 115 copper in, 150, 151 Steel drillings, magnetized wire for transferring, 18 Steel, hydrogen in, 153 nitrogen in, 151 oxygen in, 155 solution of, for total carbon, 119 solvents for carbon, 115 sulphur in, oxidation method, 108 tungsten in, 146 Steiglitz, J., indicators, 84 Stillman, water analysis, 308 Stirrer operated by compressed air, 98 Stoddard, copper by electrolysis, 173 Strontium, detection of, 321 354 INDEX Strontium, determination of, 300 Sugar, calorific value of, 266 as reducing agent, 131 Sulphide ores, assay of, 232 Sulphides, action of iron on, 228 and oxides, reaction between, 228 oxidation of, by nitrates, 227 Sulphur, forms of, in iron, 104 Sulphuric acid density table, 333 normal solution of, 36 Sulphur in coal, after burning in a calorimeter, 263 Eschka method, 256 rapid method, 258 Sulphur in iron, American Foundry- men's Association method, 110 apparatus for, 112, 114 Sulphur in iron or steel, evolution method, 111 in iron-slag, 159 in matte, 187 in ore, 73 in steel, oxidation method, 108 oxidation of, with sodium nitrate, 73 precipitation of with cadmium chloride, 113 Sutton, F., chromium, 290 sodium hydroxide solution, 152 zinc by potassium ferrocyanide, 178 Table for sampling, R. H. Richards, 11 Tannin, solution of, 175 Tantalum, detection of, 321 determination of, 301 Titanium fluoride, volatility of, 71 Tartaric acid, reagent, 220 Telluride ores, assay of, 234 Tellurium in copper, 209 Temperature for precipitating phos- phorus, 78 Template for sampling anodes, 198 Testing of cyanide solutions, 243 Testing weights, 16 Test tubes for parting gold and silver, 232 Test-tube holder for the water bath, 128 Thallium, detection of, 321 determination of, 303 Thorium, detection of, 321 in monazite, 304 Thymol for titanium, color method, 136 Time in metallurgical analysis, im- portance of, 1 Tin, detection of, 321 determination of, 294, 295, 296 Tin in alloy, 213, 215 in bronze, 210 in copper, 220 Titanium, detection of, 322 color method, 100 determination of in ore, 98 in iron, 135 in steel, color method, 136 phosphorus in the presence of, 86 Titanium sulphate, reaction of, with sodium acetate, 100 standard solution of, 101 " Titrating mixture " for iron deter- minations, 59 Ton, assay, 226 avoirdupois, 226 metric, 227 Tongs, crucible, 230 cupel, 230 1 scorifier, 235 Total cyanide, 244 INDEX 355 Transferring a precipitate to a cruci- ble, 27 Treadwell-Hall, formation of Prus- sian blue, 64 mercury, 293 tin, 295 use of manganous sulphate in the permanganate method, 61 vanadium, 297 Trowel for sampling, 45 Tube for determining combined water, 49 Tungsten, detection of, 322 determination of, 296 in steel, 146 in the presence of chromium. 147 Turbidimeter method for sulphur in coal, 258 Turnbull's blue, 64 Uehling, carbon dioxide meter, 283 Ultimate analysis of coal, 259 calorific power from, 270 United States Steel Corporation method of sampling iron-ore, 46, 47, 48 Uranium acetate, solution of, 178 Uranium, detection of, 322 determination of, 298 Uranium nitrate, solution of, 178 Use of the reductor, 58 Vanadium, chromium and, in steel, 141 Vanadium, detection of, 322 determination of, 297 in steel, 144, 145 Vaseline and paraffine for the desic- cator, 30 Vezin sampler, 12 Viscosity of lubricating oil, 307 Volatile combustible matter in coal, 255 Volatile matter in coal, 254 Volhard's method for manganese in ore, 88 Vblumetric analysis, 33 Volumetric apparatus, 33 Walters and Apfelder, antimony in alloy, 218 Walters' method for manganese in steel, 134 Washing precipitates, 26 by gravity, 26 Washoe method for silver in copper bullion, 200 Watch glasses for the balance, 15 Water bath for dissolving steel, 128 Water, combined, 49 hygroscopic, 49 in oil, 273 permanent hardness of, 311 softening of, 312 temporary hardness of, 311 Water value of calorimeter, 266 Weighing, 15 Weighing bottle, 16 Weighing for analysis, 18 Weighing, operation of, 16 Weighing potash bulb, 119, 121 Weighing, precautions in, 18 precipitates, 30 temperature for, 30 Weight book, 18 Weight box, 18 Weight of ore in slime, 248 Weights, 16 testing, 16 Weller's color method for titanium in iron, 135 356 INDEX White, A. H., correction in calorim- etry, 265 sampling gas, 274 sulphur in coal, 256 White alloys, analysis of, 213 Williams, gas analysis, 281 Winkler and Lunge, gases, 275 oxygen absorbents, 276 Working table for the laboratory, 3 Works laboratory, plan of, 6 section through, 7 Wraith, sampling bullion, 197 Yockey, H., antimony in alloy, 218 Yttrium, detection of, 322 Yttrium, determination of, 305 Zero-point of the balance, 16 Zimmerman-Reinhardt method for iron, 59 Zinc chloride in starch solution, 112 Zinc, detection of, 323 Zinc in alloy, 212, 214, 217 in blast furnace slag, 191 in matte, 186 in ore, 178 Zinc oxide, emulsion of, 88, 135 Zirconium, detection of, 323 determination of, 306 Zwaluwenburg, A. Van, sampling, 10 819524 UNIVERSITY OF CALIFORNIA LIBRARY