REESE. LIBRARY UNIVERSITY OF CALIFORNIA. TH E QHEMICAL ANALYSIS OF IRON A COMPLETE ACCOUNT OF ALL THE BEST KNOWN METHODS FOR THE Analysis of Iron, Steel, Pig-iron, Iron Ore, Limestone, Slag, CJay, Sand, Coal, Coke, and Furnace and Producer Gases. BY ANDREW ALEXANDER BLAIR, Graduate United States Naval Academy, 1866; Chief Chemist United States Board appointed to Test Iron, Steel, and other Metals, 1875 '> Chief Chemist United States Geological Survey and Tenth Census;. 1880; Member American Philosophical Society, etc. THIRD EDITION. "VX 0NIVERSITYJ ^ PHILADELPHIA: B. LIPPINCOTT COMPANY. 1896. Copyright, 1888, by ANDREW ALEXANDER BLAIR. Copyright, 1891, by ANDREW ALEXANDER BLAIR. Copyright, 1896, by ANDREW ALEXANDER BLAIR. TO MY WIFE, WITHOUT WHOSE ASSISTANCE IT WOULD NEVER HAVE BEEN WRITTEN, THIS VOLUME IS DEDICATED. OF THE 0NIVERSITT TIVERSITT PREFACE TO THE THIRD EDITION SUCH changes as were necessary to bring the methods for the determination of the various elements in accord with the present state of the science have been made in this edition. The method for the " Volumetric Determination of Phos- phorus in Steel" is that worked out by the Sub-Committee on Standards of the International Steel Standards Committee, and as such is merely tentative. Its publication here is not official, but through the courtesy of the committee it is placed before the profession in the hope that criticism may confirm its value or point out its errors. The modifications in the method for the determination of sulphur in pig-iron are improvements, but no method is perfectly satisfactory. Two new methods for the determination of carbon are given, and some modifications of Volhard's method for the determination of manganese in high grade manganese ores are introduced. Many minor changes have been made, and it is hoped that this edition may meet the same cordial reception as the two former. LABORATORY OF BOOTH, GARRETT & BLAIR, PHILADELPHIA, September, 1896. PREFACE TO THE SECOND EDITION. IN preparing the second edition of this book I have tried to correct the mistakes that were apparent in the first edition, and to add such matter as the advance in analytical chemistry seemed to justify. In effecting the first of the objects I have been aided by such kindly criticism as the profession and reviews offered me, and in the second by the advice and assistance of many of my fellow-workers. Among others my thanks are due to Messrs. Maunsel White and A. L. Colby, of the Bethlehem Iron Company, Mr. Clemens Jones, of the Thomas Iron Company, Mr. E. F. Wood, of the Homestead Steel-Works, Mr. T. T. Morrell, of the Cambria Iron Company, Mr. H. C. Babbitt, of the Wellman Steel Company, Prof. F. W. Clarke, Chief Chemist U.S. Geological Survey, Mr. J. E. Stead, of Middlesbo rough, England, and Mr. J. Edward Whitfield, of Philadelphia. It will be seen that the "Table of Atomic Weights" has been revised ; the latest and most reliable values for the elements are given, and the "Table of Factors" has been changed to corre- spond to these values. LABORATORY OF BOOTH, GARRETT & BLAIR, PHILADELPHIA, June, 1891. PREFACE TO THE FIRST EDITION THE various methods for the analysis of iron and steel, as well as the descriptions of special apparatus to facilitate the perform- ance of the analytical work, are so widely distributed through transactions of societies, journals, reviews, periodicals, and works on general analytical chemistry, that only the possessor of a chemical library can command the literature of the subject. It is my object in the following pages to bring within the compass of a single volume, as nearly as possible, all the methods of real value to the iron analyst, and in doing this to give the credit of originality for the different methods and improvements to the proper persons. In many cases this has been very difficult, and I shall be glad to have any mistake that I have made brought to my attention. This work presupposes some knowledge of general and analytical chemistry, and some practical experience in laboratory work and manipulation, as it is intended to be a guide for the student of iron chemistry only. For such persons the details of the descriptions of the methods will, I hope, often prove of great assistance. With very few exceptions, these descriptions are the results of my own experience in the use of the methods, and the details are those that seemed to me to be of importance in their practical performance. Many of the special forms of apparatus are of my own contrivance ; they have proved extremely useful to me, and I hope may facilitate in some cases the work of iron chemists, to whom often very little is given and of whom very much is required. CONTENTS. PAGE APPARATUS II APPARATUS FOR THE PREPARATION OF THE SAMPLES n GENERAL LABORATORY APPARATUS 19 REAGENTS 37 ACIDS AND HALOGENS, 38. GASES, 42. ALKALIES AND ALKALINE SALTS, 44. SALTS OF THE ALKALINE EARTHS, 50. METALS AND METALLIC SALTS, 52. REAGENTS FOR DETERMINING PHOSPHORUS, 58. METHODS FOR THE ANALYSIS OF PIG-IRON, BAR-IRON, AND STEEL . . 59 DETERMINATION OF SULPHUR. By evolution as H 2 S. Absorption by alkaline solution of nitrate of 'lead ', 59. By ammoniacal solution of sulphate of cadmium, 62. By am- moniacal solution of nitrate of silver, 62. Absorption and oxidation by bromine and HCl, 63. Absorption and oxidation by permanganate of potassium, 64. Absorption and oxidation by peroxide of hydrogen, 65. By oxidation and solution, 65. Special precautions in the determination of S in pig-irons, 66. RAPID METHOD. Volumetric determination by iodine, 68. DETERMINATION OF SILICON, 72. By solution in HNO 3 and HCl, 72. By solution in HNO 3 and H 2 SO 4 , 73. By volatilization in a current of chlorine gas, 73. RAPID METHOD, 77. DETERMINATION OF- SLAG AND OXIDES, 78. By solution in iodine, 79. By volatilization in a current of chlorine gas, 80. DETERMINATION OF PHOSPHORUS, 81. The acetate method, 81. When titanium is present, 86. The molybdate method, 89. The combination method, 93. When titanium is present, 94. RAPID METHODS, 95. Volumetric method, 95. Direct weighing, 108. DETERMINATION OF MANGANESE, 109. The acetate method, 109. General remarks on the acetate method, 114. The HNO 3 and KC1O 3 method (Ford's), 115. Steel con- taining much silicon, 117. Pig iron, 117. Spiegel and ferro-manganese, 1 18. RAPID METHODS, 1 1 8. Volumetric methods. Volhard's method, 118. Williams' s method, 1 20. Deshays's method, 124. Pattinson's method (for Spiegel and ferro-manganese], 125. The color method (for steel), 126. DETERMINATION OF CARBON, 129. TOTAL CARBON, 129. Direct combustion in a cur- rent of oxygen, 131. Combustion with PbCrO 4 and KC1O 3 , 132. Combustion with CuO in a current of oxygen, 135. Combustion with Potassium Bisulphate, 135. Solution and Oxidation in Sulphuric, Chromic, and Phosphoric Acids, the volume of CO 2 being measured, 136. Solution and Oxidation in Sulphuric, Chromic, and Phosphoric Acids, the CO 2 being weighed, 140. Volatilization of the iron in a cur- rent of Cl, and subsequent combustion of the residue, 142. Volatilization of the iron in a current of HCl gas, and subsequent combustion of the residue, 148. Solu- tion in NH 4 C1, CuCl 2 , nitration, and weighing or combustion of the residue, 148. 9 10 CONTENTS. PAGE Solution in CuCl 2 and KC1, filtration, and combustion of the residue, 161. Solution in CuCh, and combustion of the residue, 162. Solution in I or Br, and combustion with PbCrO4, or weighing, of the residue, 162. Solution by fused AgCl, and com- bustion of the residue, 163. Solution of the iron in CuSO 4 , filtration, and combus- tion of the residue in a current of oxygen, 163. Solution of the iron in CuSO 4 , and oxidation of the residue by CrO 3 -f- H 2 SO 4 , 164. Solution in dilute HC1 by the aid of an electric current, and combustion of the residue, 165. DETERMINATION OF GRAPHITIC CARBON 166 DETERMINATION OF COMBINED CARBON, 167. Indirect method, 167. Direct method (color method), 167. DETERMINATION OF TITANIUM, 178. By precipitation, 178. By volatilization, 180. DETERMINATION OF COPPER 181 DETERMINATION OF NICKEL AND COBALT 184 DETERMINATION OF CHROMIUM AND ALUMINIUM, 187. Stead's method, 191. Carnot's method, 192. Volumetric method for chromium, 193. DETERMINATION OF ARSENIC 195 DETERMINATION OF ANTIMONY 196 DETERMINATION OF TIN 197 DETERMINATION OF TUNGSTEN 198 DETERMINATION OF VANADIUM 200 DETERMINATION OF NITROGEN 201 DETERMINATION OF IRON 204 METHODS FOR THE ANALYSIS OF IRON ORES 205 Remarks on sampling, 205. Determination of hygroscopic water, 206. Determination of total iron, 207. Methods for standardizing the solutions, 218. Determination of FeO, 223. Of S, 226. OfP 2 O 5 , 229. OfTiO 2 , 231. Of Mn, 233. Of SiO 2 , A1 2 O 3 , CaO, MgO, MnO, and BaO, 238. Of SiO 2 , 247. Separation of A1 2 O 3 and Fe 2 O 3 , 248. Determination of NiO, CoO, ZnO, and MnO, 251. Of CuS, PbS, As 2 O 6 , and Sb 2 O 4 , 253. Of the alkalies, 255. Of CO 2 . 257. Of combined water and carbon in car- bonaceous matter, 259. Of Cr 2 O 3 . 262. Of WO 3 , 264. Of V 2 O 5 , 264. Of sp. gr., 265. METHODS FOR THE ANALYSIS OF LIMESTONE 267 METHODS FOR THE ANALYSIS OF CLAY 271 METHODS FOR THE ANALYSIS OF SLAGS 276 METHODS FOR THE ANALYSIS OF FIRE-SANDS 281 METHODS FOR THE ANALYSIS OF COAL AND COKE 282 Proximate analysis, 282. Analysis of the ash, 283. Determination of sulphur, 284. De- termination of phosphoric acid, 286. METHODS FOR THE ANALYSIS OF GASES 288 Collecting samples, 288. Preparation of the reagents, 291. Analysis of the samples, 293. Determination of CO 2 , 295. Of O, 296. Of CO, 296. Of H, 296. Of CH 4 , 298. Example of calculation, 302. TABLES 303 Table I. Atomic weights of the elements, 303. Table II. Table of factors, 304. Table III. Percentages of P and P 2 O 5 for each m.g. of Mg 2 P 2 O 7 , 306. Table IV. Tension of aqueous vapor, 307. Table V. Table for reducing volumes of gases to the normal state. 308. INDEX 315 UNIVERSITY ^yfO^NlA^x THE CHEMICAL ANALYSIS OF IRON APPARATUS. THE speed and facility with which results may be obtained, and often the accuracy of these results, are dependent upon various mechanical appliances as well as upon the skill of the analyst. These appliances will be considered under separate heads. APPARATUS FOR THE PREPARATION OF THE SAMPLES. For crushing iron ores, a mortar and pestle, such as are ordinarily used, have caused much trouble. In breaking up hard ores the wear, especially on the pestle, is considerable, and the particles of cast iron may cause the sample to yield too high a result in the determination of metallic iron. Of course in non-magnetic ores these particles may be removed with a magnet, but in the case of magnetic or partly magnetic ores this cannot be done, and a hardened steel mortar and pestle should be used. The sample should be broken to about pea size, well mixed, and quar- tered, this quarter broken still finer, and mixed and quartered in the same way until the resulting portion is small enough to be bottled. The final grinding can be best made on a chilled-iron plate with a hardened steel muller. Except with unusually refractory ores, further grinding is unnecessary, but with such ores the final grinding must be in an agate mortar. In large laboratories and where many ores are analyzed, arrange- ii 12 APPARATUS FOR THE PREPARATION OF THE SAMPLES. ments such as are shown in the accompanying sketches will prove very useful. Fig. I shows a steel mortar, the pestle worked by power, and a chilled plate and muller. A is the mortar ; B, a wooden stem in which the pestle fits. The cams H fit on the shaft and raise the pestle by means of the tappets a, which are faced with raw hide. An iron hoop shrunk on the mortar has a ring, in which is fastened the low^r block of the pulley D ; the upper block is attached to a traveller, E. When in use the mortar is covered with a leather cap, which prevents the pieces of ore from flying out of the mortar. To transfer the powdered ore to FIG. i. the chilled plate F, remove the leather cap, raise the pestle clear of the mortar, and fasten it up by a hook from the framework to the tappet a. Raise the mortar by pulling the fall from the upper block and fastening the hook in its end into a ring at the lower block. By means of the traveller, run the mortar over the plate and turn the ore out. After quartering the sample down, finish the grinding on the chilled plate with the muller C. The sheet-iron troughs G serve to catch any ore that falls from the plate. In some laboratories a small Blake crusher is used AGATE MORTARS. for crushing the ore, but it is more liable to get out of order, and is not so easily cleaned as the mortar and pestle. Fig. 2 shows an arrange- ment for facilitating the final grinding in the agate mortar, in which the pestle is rotated by a Stow flexible shaft. FIG. 2. The apparatus shown in Fig. 3, designed by Mr. Maunsel White, has been in use several years at the chemical laboratory of the Beth- lehem Iron Company, and has worked very satisfactorily. The power is applied from an overhead countershaft not shown in the cut. The lower portion of the vertical shaft carries two horizontal pulleys, A and B; these pulleys are connected, as shown, with the spindle carrying the pestle and with the circular box D, in which the mortar is securely fastened by four claw-bolts, which may be seen in the drawing. The piece D is made with a spindle which extends down into a bearing in the supporting piece H. The piece H, which may be called a lever, is secured to the frame F by a bolt which passes through it, and around which it can be turned through an angle sufficient to per- mit of the easy emptying of the mortar without displacing the belt. !4 APPARATUS FOR THE PREPARATION OF THE SAMPLES. A groove at the farther end of H, as shown, carries a weighted rod which supplies the pressure of the mortar against the pestle. The weights are made movable so that the pressure can be varied for special cases. FIG. 3. The agate pestle is secured in a brass spindle with a grooved collar for carrying the belt; this spindle revolves in a bored socket in the piece E, and is secured from dropping out by means of a small nut, shown at the top of the piece. The piece E is connected to the frame F by a circular bolt, the end of which is supplied with an arm for rocking the piece E; this obtains by fastening the bolt with dowel-pins where it passes through the piece E while free to move in the frame F. The pulley C is run from the countershaft, and revolves a small shaft whose end carries a crank connected by a short rod to the bolt- arm of the piece E, and supplies the power and means for the rocking motion. It will now be seen that while the mortar revolves, the pestle, revolving more rapidly, sweeps across the face of the mortar by the DRILLING-MA CHINES. rocking motion of the piece E, thus constantly changing the material between the grinding surfaces. In taking samples of iron or steel, a perfectly clean dry drill should be used, and the utmost care taken to prevent grease, oil, or dirt of any kind from getting in the sample. With bar-iron or steel the scale on the FIG. 4. outside of the piece should be removed as carefully as possible, the first drillings from each hole thrown away, and the remainder thoroughly mixed and placed in a perfectly clean dry bottle. Fig. 4 shows a convenient form of drill-press ^br the purpose. A half-inch Morse twist-drill is the best for general use. In taking samples of pig-iron, the loose sand should be carefully removed from the outside of the pig and a piece of stout paper wrapped around it to prevent the sand and FlG- slag from the outside getting mixed with the clean drillings, which are received on a piece of glazed paper turned up at the edges (Fig. 4). Drillings from pig-iron can be best mixed by rubbing them up in a small porcelain mortar. At. blast-furnaces, to save the trouble of breaking pieces from the pigs the arrangement shown in i6 APPARATUS FOR THE PREPARATION OF THE SAMPLES. Fig. 5 is very convenient, as half a pig can be placed in the press. The framework is securely bolted to the table on which the press stands, and the pig is secured by means of the iron clamps. By removing the pieces of wood under the pig it is lowered so that two or three holes can be bored in different parts of the face of the pig to get an average. By taking one pig from the first bed, one from the last, and one from an intermediate bed, a good average of each cast may be obtained. When the ore varies, or when mixtures of different ores are used, these pre- cautions are very necessary to get a sample that will really represent an average of the cast. Drillings from large ingots must be taken by means of an ordinary brace. FIG. 6. Fig. 6 shows an apparatus for the drilling and weighing of samples of steel for colorimetric carbon or other rapid determinations, designed by Mr. Maunsel White, and in use at the laboratory of the Bethlehem Iron SPIEGEL MORTAR. 7>X I7 Company. The drill is mounted above the balance, the point of the drill directly overhanging the balance-pan. The piece to be drilled is placed against the semicircular plate carried by the two rods that pass through the drill-frame ; on the rear end of each rod is a coiled spring which supplies the pressure necessary for drilling. The rear ends of the rods are held together by a tie-piece, which is connected to a lever operated by the foot, so that the rods and plate can be forced forward for the reception of the piece to be drilled. The balance is supplied with an overhead pan which receives the drillings guided to it through the funnel fixed in the top of the balance- case for this purpose. When the pan falls, showing that sufficient sample has been drilled, pressure is applied to the lever by the foot and the piece taken out. The balance-case rests upon an iron plate grooved on the bottom ; these grooves engage with guides screwed to the table and permit the balance-case to be pulled forward, which facilitates the cleaning of the funnel from all clinging particles. This operation is done with a camel-hair brush or a feather. A magnet is run around in the lower pans to guard against the chance of falling particles interfering with the accuracy of the weights. The upper door of the balance-case is then lowered into the position shown in Fig. 6, which gives free access to the upper pan containing the sam- ple. The sample is now accurately weighed, the pan lifted out, and the drillings transferred to the test-tube. The use of a J^-inch twist-drill has been adopted and found to give good results. The pans and funnel are aluminium and the bearings agate; the beam is short, 5^ inches in length, in consequence of which the weighing is done rapidly. In taking samples of spiegel or of white-iron, small clean pieces from FIG. 7. jg APPARATUS FOR THE PREPARATION OF THE SAMPLES. a number of pigs should be taken and powdered in a hardened steel mortar. The mortar shown in the sketch (Fig. 7) is forged from high carbon steel, hardened, and the temper drawn from the outside. This makes the mortar both hard and tofrgh. The sheet-iron cover prevents the pieces from flying. The face of the pestle is very hard, and the handle comparatively soft, so that it will not break when struck by the hammer. In taking samples for analysis, when the method used requires the sample to be in a fine state of subdivision, the very fine part of the sample should never be separated from the coarser particles by a sieve or screen, but the sample should be mixed thoroughly, and a portion, fine and coarse together, taken and powdered, so that all may pass through the sieve. FIG. 8. AIR-BA TH. GENERAL LABORATORY APPARATUS. Sand-Bath gmd Air-Bath. Fig. 8 shows a very convenient form of sand-bath, and Fig. 9 an air-bath. This air-bath is made from an ordinary cast-iron sink, which is supported on fire-bricks. The top is of asbestos board, with a piece FIG. 9. of sheet-iron underneath to strengthen it. The holes are large enough to take tho largest-sized beakers, while the smaller beakers are supported by asbestos rings. An ordinary gas-regulator or governor, which supplies 20 GENERAL LABORATORY APPARATUS. FIG. 10. the gas at a constant pressure, keeps the temperature sufficiently uni- form. Evaporations may thus be effected with great saving of time and with little danger of loss by spirting. The products of combustion of the gas are carried off by a separate flue, and the H 2 SO 4 formed does not come in contact with the solutions in the baths. Instead of sand-bath the term hot plate is generally used for this piece of apparatus, the surface of the iron being kept clean and free from rust by an occasional coat of stove-polish. Evaporations on the hot plate may be hastened by standing the beaker containing the solution inside another beaker with the bottom cut off. Beakers may be readily cut in this way by starting a crack and leading it around with a red-hot iron or glass rod. For evaporating solutions in capsules or dishes a beaker cut off in this way and placed on a tripod covered with wire gauze, as shown in Fig. 10, may be used with great advantage. The cap- sule is supported on an asbestos ring, A, the bottom being about J^ inch (12 mm.) from the wire gauze. A piece of thin asbestos board, B, about y^ inch (18 mm.) in diameter, rests on the gauze and covers the point of the flame of the Bunsen burner, and, by throwing the heat more on the sides of the capsule, tends to pre- vent spirting when the solution in the capsule gets thick and pasty. Apparatus for Hastening Evaporations. The little piece of apparatus shown in Fig. II was designed by Mr. ]. E. Whitfield, and is most useful in hastening evaporations. It consists of a platinum tube ^- of an inch in diameter, coiled above the burner to present more heating surface, through which passes a blast of air. As the platinum tube and Bunsen burner are both supported on the arm of the stand, the level of the tube may be made to accommodate itself to a crucible on a stand, to a capsule on a tripod (Fig. 10), or to APPARATUS FOR HASTENING EVAPORATIONS. 21 a beaker on the air-bath. In the treatment of the insoluble residues from ores by hydrofluoric and sulphuric acids it is quite invaluable, as it not only hastens the evaporation but prevents loss by spirting. FIG. ii. The blast of hot air breaks the bubbles on the surface of the liquid, and when properly directed it gives the liquid a rotary motion that tends to throw onto the sides of the crucible any particles of the liquid thrown up by the bubbles. The amount of heat that can be applied to a crucible under these circumstances, without causing loss, is really surprising. It is equally useful when evaporating solutions in beakers on the air-bath or hot plate. In laboratories where a blast of air is always at command, the principle may be applied in many ways (or hastening evaporations Even a cold blast of air from a drawn-out glass tube directed on the surface of a liquid hastens the evaporation very materially. 22 GENERAL LABORATORY APPARATUS. Igniting- Precipitates. For ignitions, a Bunsen burner with a ring to regulate the supply of air, provided with an ordinary glass chimney, as shown in Fig. 12, is most convenient. By shutting off the air entirely a very low heat may be obtained, which is not rendered variable by air-currents, and the heat of the full flame of the burner is increased by the greater draft caused by the chimney and the perfect steadiness of the flame. By using a small platinum rod or wire to support the cover of the crucible, as shown in Fig. 12, a gentle current is induced in the crucible, which, while it greatly facilitates burning off carbon, is not sufficiently strong to cause loss by carrying off even the lightest ash. The crucible may also be FIG. 12. FIG. 13. FIG. 14. inclined on its side, as in Fig. 13, the heat in this case being applied near the top of the crucible. Fig. 14 shows an easy method of fitting a chimney t;o a Bunsen burner by means of a cork and an ordinary Argand chimney-holder. When a higher temperature than that obtain- able by a Bunsen burner is required, a blast-lamp, worked by a foot- bellows, by a water-blast, or by a small blower, is used. FIL TER-PUMPS. FIG. 15. Tripods. The most convenient arrangement for heating liquids in beakers, flasks, etc., is the iron tripod (Fig. 15). It consists of a cast-iron ring with three legs of heavy iron wire ^ inch (6 mm.) in diameter. The ring is covered with brass wire gauze, 40 meshes to the inch, which can be replaced when it is burned out, but which lasts a long time. The vertical height of the tripod is about 7^ inches (191 mm.). A very convenient form of burner is the Finkner ratchet- burner, as the flame can be raised or lowered by means of the ratchet on the burner, thus avoiding the necessity of reaching back over the table to the gas-cock. As the air and gas are both turned off at once, there is less danger of the flame blowing out when it is turned very low. Filter-Pumps. The use of filter-pumps for Bunsen's method of rapid filtration is now very general, and greatly facilitates many operations. The kind of pump is usually determined by the water-supply. With a good pressure of water, the most convenient form of pump is the injector. Fig. 16 shows the Richards' injector united with a blast-cylinder, by the use of which a good air-pressure for use with the blast-lamp may be obtained. When the pump is used for filtering strong solutions of HNO 3 a glass injector may be used, and the water allowed to flow at once into the sink or waste-pipe. When the pressure of water is not great enough for an injector the Bunsen pump may be used, the vacuum obtained of course depending on the amount of fall. A tank with a ball-cock attachment makes this form of pump most convenient. An ordinary air-pump may also be used for many purposes, but of course is unsuitable for filtering corrosive liquids, such as HNO 3 , unless a wash-bottle containing a caustic alkali is interposed between the flask and 24 GENERAL LABORATORY APPARATUS. the air-pump. The apparatus shown in Fig. 17 will give a very good idea of an arrangement which is very convenient when a water-supply is not FIG. 16. available. The jug, which may be of three or five gallons capacity, serves as a reservoir. It connects directly with the air-pump. Bunsen's Method of Rapid Filtration. This method is too widely known to make a detailed description neces- sary, but some hints in regard to the details may be useful. In the first place, it is very difficult to get good 60 funnels, so that the little perforated cones of platinum to support the point of the filter, which are sold by chem- ical dealers, rarely fit the funnel, and when they do not fit, the filters are FILTERING APPARATUS. apt to tear. The small funnel of platinum foil, as recommended by Bunsen, can be made to fit the funnel better, but the edges sometimes cut the filter. FIG. 17. FIG. 18. A small funnel of parchment pricked full of pin-holes, and of the size and shape of the platinum-foil funnel, works very well. It is a mistake to use too great a pressure, especially at first, and the filter should be kept full. The filtering flask should always be connected, not with the vacuum- pipe directly, but with another flask fitted with a little Bunsen valve, which allows the air to pass into the vacuum-pipe, but, in case of a sudden stoppage in the pump, prevents the back pressure from entering the filter- ing-flask and blowing out the contents of the funnel. Fig. 1 8 shows an arrangement for filtering into a beaker instead of into a flask. It is necessary to have a glass cover over the beaker, as shown in the sketch, on account of the ten- dency the solution has to spatter, particles of the solution being carried out of the beaker in the current of air flowing into the vacuum-pipe. 26 GENERAL LABORATORY APPARATUS. Gooch's Method of Rapid Filtration. The pierced crucible and cone, with asbestos felt, devised by Gooch,* are almost indispensable to the iron analyst for the proper and rapid execution of many operations, as will be seen by the frequent references to them in the descriptions of the methods given farther on. Fig. 19 shows the crucible and cap, and Fig. 20 the cone. The asbestos, which should be of a soft, silky, flexible fibre, is scraped longitudinally (not cut) to a fine, soft down, and purified by boiling in strong HC1, and washed thoroughly on the FIG. 19. FIG. 20. FIG. 21. cone. It may be dried and kept in a bottle. The perforated crucible is placed in one end of a piece of soft rubber tubing, the other end of which is stretched over the top of a funnel, as shown in Figs. 19 and 21. The neck of the funnel passes through the stopper of a vacuum-flask. To pre- pare the felt, pour a little of the prepared asbestos suspended in water into the crucible and attach the pump. The asbestos at once assumes the con- dition of a firm, compact layer, which is washed with ease under the pressure of the pump. After washing the felt, suck it dry on the pump, remove the crucible, detach any little pieces of fibre that may be on the outside of the bottom of the crucible, slip on the little cap, dry, ignite, and weigh. Remove the cap, place the crucible in the rubber holder, start the pump and pour the liquid and precipitate to be filtered into the crucible, wash, dry, ignite, if required, cool, and weigh as before. The cone is fitted to a funnel by means of a rubber band stretched over the top of the funnel. Proceedings Am. Acad. Arts and Sciences, 1878, p. 342; Chem. News, xxxvii. 181. COUNTERPOISED FILTERS. 2 j The pressure of the pump pulls the cone down so that the overlapping part of the band forms a tight joint between the cone and the upper part of the funnel (Fig. 22). The felt is prepared in the same manner as in the crucible. Fill the cone with the asbestos suspended in water, FIG. 22. start the pump, press down the cone into the funnel, and, if necessary, pour in more of the asbestos, letting it run all around from the upper edge of the cone so as to fill all the holes and make a firm, cohesive layer all over the inside of the perforated portion of the cone. Wash it well with water and suck it dry. It will then be ready for use. The cone is not intended for use when the precipitate is to be weighed, but, as it presents a very large filtering surface, it is most useful for such precipitates as MnO 2 precipitated by Ford's method, etc. In this case, when the precipi- tate has been washed and sucked dry, by removing the cone from the funnel and carefully separating the felt from the sides of the cone with a little piece of flattened platinum wire, it may be removed from the cone with the pre- cipitate enclosed in it, and the whole mass transferred to a beaker or flask for resolution. The cones may be of various sizes ; for ordinary use, a cone 1 2^ inches (45 mm.) in diameter is very convenient. They may also be used with a paper filter. In both the crucibles and cones the holes should be very small, and drilled (not punched) as closely together as possible. Counterpoised Filters. The Gooch crucible and felt are most useful for weighing precipitates which are to be dried and not ignited, as in the direct weighing of the phospho-molybdate of ammonium. When they are not available, however, recourse must be had to counterpoised filters. The best method for preparing and using them is as follows : Take two washed filters of the same size and about the same thickness, fold them as if about to fit them in funnels, and, by cutting from the upper edge of the heavier of the two with a pair of scissors, make them nearly balance. Place them between a pair of watch-glasses, as shown in Fig. 23, dry them at 100 C, and allow them to cool in a desiccator. Place one in each pan of LIBRA?. OF THE 2 8 GENERAL LABORATORY APPARATUS. the balance, and, handling them with a pair of forceps, clip them until they balance exactly. Place each filter in a funnel, filter the precipitate Fl on one of them, pass the clear filtrate (not the washings) through the other, and wash them both in the same manner. Remove them from the funnels, turning over the top edges of the filter containing the precipitate to prevent any of the latter from falling out, place them in a watch- glass, dry them at 1 00 C. (or at the required temperature, whatever it may be), cover them with the other watch-glass, cool in a desiccator, place them on opposite pans of the balance, and the weight added to the pan containing the empty filter, to make them balance, is the weight of the precipitate. Filter-Paper. All filter-paper contains more or less inorganic matter, which remains, after burning the paper, as a white or brownish ash. The Swedish paper with the water-mark J. H. Munktell leaves the smallest amount of ash, and this ash contains from 35 to 65 per cent, silica, besides ferric oxide, alumina, lime, and magnesia in varying proportions. Schleicher & Schull prepare some very pure filters by washing them with HC1 and HF1, and these should always be used for very accurate work unless the analyst prepares ashless papers for himself. The com- moner kinds of German paper contain much larger amounts of inorganic matter than the Swedish paper, and it usually consists principally of carbonate of calcium, but sometimes contains appreciable amounts of phosphates. Filters of this kind should always be washed with HC1 before they are used. They may be washed by fitting them in a funnel, pouring on hot HC1 and water (i part acid to 3 parts water), and washing thoroughly with hot water. They may also be washed in the apparatus shown in Fig. 24. It consists of a bottle of the proper size with the bottom cut off with a hot iron. It contains a disk of wood cut to fit the shape of the bottle and perforated with a number of gimlet-holes. Fill the bottle half full of cut filters, pour on a mixture of HC1 and water (1-3), allow APPARATUS FOR WASHING FILTERS. 2 9 them to stand about half an hour, and wash thoroughly with distilled water. The bottle may be attached to the vacuum-pump and washed under pressure. Dry the filters at a temperature below 100 C. For prepar- ing ashless filters the apparatus shown in Fig. 25 is used. It is of spun copper, lined with platinum throughout. Over the vertical tube is a perforated platinum disk countersunk to the level of the bottom of the FIG. 24. FIG. 25. dish. It is attached to the pump, and the filters are washed first with HC1 and water (1-3), then with water to remove the lime, then with HF1 and water (1-3) to dissolve the silica, and finally with distilled water. Swedish filters washed in this way are practically ashless, the ash from five filters, each 3 inches (75 mm.) in diameter, weighing less than -j 1 ^ mg. Filters may be cut out, using tin disks of the proper diameter as patterns ; they may be bought ready cut, or they can be cut out at shops where circular labels are cut at very small cost. The best way is to buy Swedish paper and a good tough German paper, by the ream, have the paper cut into filters of the proper sizes, say 5^ inches (140 mm.), 4}^ inches (108 mm.), and 3 inches (76 mm.) in diameter, and wash the Swedish with HC1 and HF1 and the German with HC1. The ashless filters can GENERAL LABORATORY APPARATUS. be used for final filtrations when the precipitate is to be ignited and weighed, and the German for all other work. Washing-Bottles. Figs. 26, 27, and 28 represent different forms of washing-bottles. For ordinary use that represented in Fig. 26 is the best. The neck is wrapped with thin asbestos board, covered with a piece of wash- leather or chamois, which is sewed to keep it from slipping. This is very necessary when hot water is used. A piece of soft rubber tubing at A is more pleasant for the mouth than the glass, and after com- pressing the air in the flask the tube can be grasped with the teeth, thus keeping up the stream of water for some time without effort. It FIG. 26. FIG. 27. FIG. 28. also prevents the lips from being scalded when using very hot water. Fig. 27 shows a movable tip, which allows the stream of water to be directed by means of the finger. The form of flask shown in Fig. 27 is very convenient to use with ammonia-water, etc. The tube a is closed with the index finger, while the Bunsen valve b closing as soon as the air is compressed in the flask prevents the vapors from coming back into the mouth, and the stream of liquid is stopped instantly by removing the finger from a. Fig. 28 shows the Berzelius form, which is sometimes very useful. The air is compressed by blowing into the bottle through the jet, and by quickly inverting the bottle the stream MEASURING- GLASSES. of liquid is forced out until the equilibrium is restored. It requires a little practice to use this form of bottle easily, but when the art is once acquired it can be used with ammonia-water as well as pure water, and the facility with which it can be moved and pointed in any direction with the hand makes it most convenient for some purposes. Removing Precipitates from Beakers. A feather trimmed in the way shown in Fig. 29 may be used to remove particles of adhering precipitates from beakers, evaporating-dishes, etc. A piece of soft rubber tubing on the end of a piece of glass rod or sealed glass tube is much more effective and convenient in most cases. FIG. 31. FIG. 29. FIG. 30. It is made by taking a short length of rubber tubing, placing a little pure caoutchouc dissolved in chloroform or naphtha in one end, squeezing the sides together between two pieces of board (Fig. 31), and allowing it to remain for at least twenty-four hours. It may then be trimmed down and placed on the end of a piece of glass rod or on the end of a piece of glass tubing having the ends fused together (Fig. 30). This little instru- ment has acquired the name of " policeman." Measuring-Glasses. In adding reagents to a sample or to a solution, measured amounts should nearly always be used, and, as it is generally well under all circumstances to avoid adding them from the bottle direct, little beakers of the form shown in Fig. 32 are very useful. They can be graduated and marked by covering the side with a thin coating of paraffine, measuring in water from a burette, marking the levels and amounts in the paraffine with a sharp- pointed instrument, and etching them in the glass by filling the marks FIG. 32. 3 2 GENERA L LAB OR A TORY A PPA RA TUS. with HF1. After standing a few minutes the HF1 may be washed off under the hydrant and the paraffine removed with hot water. As the amounts are intended to be only approximate, no great degree of care need be exercised in the graduation. Caps for Reagent-Bottles. The stoppers and lips of reagent-bottles are very apt to become covered with chloride of ammonium, dust, etc., when exposed in the laboratory, and especially such as are not in constant use, volumetric solutions, stock-bottles, etc. It is well to keep them always covered with caps, which may be bought from the dealers, or with cracked beakers, which answer the purpose nearly as well in most cases. Rubber Stoppers. Rubber stoppers are now generally used instead of cork. Solid stoppers should always be purchased, and the holes cut with the ordinary cork-borers. This is readily done by moistening the cork-borer with water or alcohol. A little practice will enable any one to do this with great ease. Desiccators. Crucibles should always be cooled before weighing in desiccators. The form shown in Fig. 33 is most convenient. The FIG. 33. desiccator should contain fused chloride of calcium. The crucible rests on a small triangle, which may be made of copper wire, each side being covered by winding a thin strip of platinum foil around it to prevent the crucible from coming in contact with the copper, which may become more or less cor- roded. PLATINUM APPARATUS. Crucibles. The shape of the crucible is of considerable importance as regards its wearing properties. Fig. 34 shows the best form for general use. PLATINUM CRUCIBLES. 33 A crucible \y 2 inches (38 mm.) high, i^- inches (33^ mm.) wide at the top, with a capacity of 20 c.c., and weighing with the lid about 25 grammes, is well adapted for weighing the usual precipi- F|G tates found in the course of iron analysis. For fusions a much larger crucible is necessary: one i-ff inches (46 mm.) high, i-J-| inches (46 mm.) wide on top, with a capa- city of 55 cc., and weighing about 60 grammes, will be found convenient and serviceable. Pure platinum is the best metal for crucibles. The iridium alloy, at one time so popular, has not been found to wear well. It is stiffer than the pure metal, but much more liable to crack. The endurance of a crucible depends very much upon the treatment it receives. The salts of easily reduced metals fusing at a low temperature, such as lead, tin, bismuth, antimony, etc., should never be ignited in platinum ; besides these, the phosphoric acid in some phosphates is occasionally partly reduced, rendering the platinum very brittle. A platinum crucible should never be bent out of shape when it can be avoided, and a wooden plug exactly the shape of the crucible (Fig. 35) is very useful to straighten it on when it has been bent. It should always be carefully cleaned before use : the precipitate FlQ last ignited should be dissolved in acid if possible, and the crucible washed out with water, dried, ignited, and cooled in a desiccator before weighing. A precipitate of Fe 2 O 3 will sometimes stain a crucible very badly ; this stain may be removed by allowing the crucible to stand with cold HC1 for twelve hours, and then warming it for a short time. Stains that are not removed by HC1 may be removed by fusing KHSO 4 in the crucible, or by fusing Na 2 CO 3 in it, dissolving in water, and then treating the crucible with HC1. Whenever a crucible begins to look dull and tarnished it should be cleaned inside and out with very fine sea-sand (not sharp sand) by moistening the finger, dip- ping it in the sand, and rubbing the crucible with it. This method of cleaning decreases the weight of the crucible very slightly, the sea-sand burnishing without cutting the crucible. It is very convenient to have each crucible and its cover marked with a number, as shown in Fig. 34. 3 34 GENERAL LABORATORY APPARATUS. Dishes. Fig. 36 shows a very convenient form of dish for the determination of Si in pig-iron, SiO 2 in iron ores, etc. It is 3^ inches (83 mm.) in diameter and 2 1 / inches (57 mm.) high. FIG. 37. Fig. 37, for such work as precipi- tation of Fe 2 O 3 , etc. It is 5 inches (127 mm.) in diameter and 3 T 5 g- inches (84 mm.) high. The wire which is fused into the top of the dish makes it much stiffer than it would otherwise be, and consequently it may be made lighter and cheaper than would be possible without the wire. The wire is hammered out and helps to form the lip. A platinum stirring-rod, formed from a piece of seamless tubing, rounded and fused together at the ends, is useful for many purposes. It may be from 5/^ to 7 inches (140 to 179 mm.) long, y^ inch (6 mm.) in diameter, weighing from 7.5 to n grammes. Spatula. Fig. 38 shows a very convenient and useful form of spatula. The blade, which is made of the platinum-iridium alloy, is fused into a tube of the same alloy which forms ^~ the handle. The weight of the spatula shown in the sketch is 14 grammes, length 6^4 inches (165 mm.). Triangles and Tripods. The triangles for supporting the crucibles during the ignition are shown in Figs. 12 and 13, as are also tripods for holding the lids, etc. These are made from wire about -^ inch (1.6 mm.) diameter, the ends are fused, and the wire, where it is twisted, has the parts in contact fused together almost to the inside of the triangle, which makes it much stiffer. The triangles should be attached to the iron rings of the sup- ports with a few turns of fine platinum wire. BALANCES. 35 Crucible-Tongs. Fig. 39 shows the best form of crucible-tongs. The part from a to b is of platinum, the straight part from a to c fitting over the end of the iron. The surfaces at d are in contact when the tongs are closed, and with this portion the lid can be handled, and the crucible is clasped by the curved ends, which hold it firmly without any danger of bending the crucible. FIG. 40. They are especially useful in handling a crucible containing a liquid fusion. Another form, shown in Fig. 40, is generally of brass, the points and bend being lined with platinum. A small pair of forceps (Fig. 41) is useful for taking the crucible from the desiccator and placing it on the balance, the lid of the crucible being slipped a little to one side to allow one of the points of the forceps to go inside the crucible. Balances. The balance is one of the most important things in the equipment of a laboratory, and a cheap balance is nearly always a very poor investment. The quality of balances has improved greatly in the last few years, and it is now possible to get a most admirable instrument of this kind at a comparatively low price. Fig. 42 shows a balance which for sensitiveness and quickness is unsurpassed. It is made to carry up to 200 grammes in each pan. The beam is of aluminium, as are also the pans. The stirrups are of nickel, the knife-edges and bearings of agate, while the arrangement for carrying the riders (Fig. 43) is most ingenious and effective. It is of course very convenient to have one balance for weighing crucibles, etc., and another for weighing samples for analysis. The balance for the latter pur- pose may be much smaller than the balance for the former, and should be GENERAL LABORATORY APPARATUS. FIG. 42. (D jTol ^aa^ provided with a small aluminium pan with a spout (Fig. 44), to facilitate T- the transfer of samples to r IG. 43* flasks, test-tubes, etc. This pan should have a coun- terpoise. A pair of small forceps, slightly magnetized, may be used to advantage Fie;. 44- in getting exact weights of steel drillings, and a camel's-hair brush is necessary to detach small particles of ores, etc., from the aluminium pan or balanced watch-glasses. DISTILLED WATER. 37 Factor- Weights. The use of factor weights is in many cases extremely convenient, as it does away with all calculation, and is to that extent time-saving and valuable in avoiding one source of error. Thus, in determining carbon by combustion in steel, using 2.7273 grammes of the steel, o.i milligramme of carbonic acid is equal to o.ooi per cent, of carbon in the steel. For determining silicon in pig-iron the ^ factor weight, or 1.1755 grammes, is very convenient. When the weight of SiO 2 is multiplied by 4, one milli- gramme is equal to o.oi per cent, of silicon. Or, for rapid silicon deter- minations, the Y 1 ^ factor weight, 0.4702 gramme, is used. REAQBNTS. Distilled Water. When only a small amount of distilled water is needed, a tin-lined copper still and condenser, such as are furnished by all dealers, may be FIG. 45. 2 8 REAGENTS. used, but where there is a supply of steam, an arrangement like that shown in Fig. 45 will be found most useful. A is a tin-lined copper cylinder, with a dome-shaped top, E, fitted to A by the joint shown in the sketch, which may be made tight by paper or a linen rag. Two perforated shelves, a, a, support layers of clean quartz-gravel or pieces of block-tin, which wash the steam and prevent dirt from being carried over mechanically. The steam enters at B, and the water condensed in the cylinder A passes off through the pipe C. The washed steam passes up through the block-tin pipe G, and is condensed in the worm-tub F. A glass worm should never be used, as the water condensed in it dis- solves notable amounts of elass. o ACIDS AND HALOGENS. Hydrochloric Acid. HC1. Sp. gr. 1.2. Chemically pure hydrochloric acid is readily obtained. It should be free from chlorine, sulphuric and sulphurous acid, arsenic, and fixed salts. To test for sulphuric and sulphurous acid, evaporate 100 c.c. to dryness with a little pure nitrate of potassium, redissolve in water with a few drops of HC1, filter, if necessary, and add chloride of barium. To test for arsenic, put into a clean dry test-tube a few centigrammes of pure stannous chloride, pour in carefully 6 or 8 c.c. HC1, and gradually 2 or 3 c.c. pure H 2 SO 4 , shaking the test-tube gently. If the HC1 is free from arsenic the solution remains clear and colorless, but if arsenic is present the solution becomes yellowish, then brownish, and finally metallic arsenic is deposited. The test-tube should be gently warmed if no reaction occurs at first. To test for chlorine, pour some of the acid into a solution of iodide of potassium containing a little starch solution. A blue coloration indicates chlorine or ferric chloride. To test for metallic salts, neutralize about 100 c.c. of the acid with ammonia and add sulphide of ammonium. To test for salts of the alkalies, evaporate about TOO c.c. of the acid to dryness, and test any residue which may remain. HYDROFLUORIC ACID. 39 Nitric Acid. HNO 3 . Sp. gr. 1.41. Nitric acid should be free from nitrous acid, the presence of which may be known by the yellowish color it produces. It may be freed from this gas by passing a current of air through the acid until it becomes colorless. To test for HC1 or Cl, dilute largely and add a solution of nitrate of silver. To test for fixed salts, evaporate about 100 c.c. to dryness. The ordinary acid diluted with an equal volume of water gives the acid of 1.2 sp. gr. used to dissolve steel for the color carbon test. It should be carefully tested for Cl or HC1. Sulphuric Acid. H 2 SO 4 . Sp. gr. 1.84. Sulphuric acid should be colorless. To test for oxides of nitrogen, Warington* suggests placing about two pounds of the acid in a bottle, which it half fills, and shaking violently. The air washes the gases out of the acid, and the presence of the oxides of nitrogen may be detected by placing in the mouth of the bottle a piece of filter-paper saturated with iodide of potassium and starch solution, which is colored blue when any of these oxides are present. To test for lead, supersaturate some of the acid with ammonia and add sulphide of ammonium. Hydrofluoric Acid. The use of Ceresine bottles, suggested by Prof. Edward Hart, of Lafayette College, has made it quite possible to ob- tain pure hydrofluoric acid, but the crude acid may be redistilled in the laboratory into platinum bottles. The crude acid, which may be pur- chased from glass engravers and etchers, is distilled from a platinum, silver, or lead still, as shown in Fig. 46. The head of the still Crookes's Select Methods, 2d ed., p. 494. 40 REAGEN'IS. and condensing-tube is of platinum. The condensing-tube runs through a copper box filled with ice, and a platinum bottle receives the condensed acid. Where the tube comes through the lower part of the box it is secured by a rubber stopper, and a small bit of paper around the tube prevents any condensed moisture on the outside of the tube from running into the bottle. Before distilling the acid, put into it a few crystals of permanganate of potassium and a few c.c. of H 2 SO 4 . The redistilled acid should leave no residue upon evaporation. Acetic Acid. H,C 2 H 3 O 2 . Sp. gr. 1.04. Acetic acid of the strength given above is the best for use in iron analy- sis. It should give no residue on evaporation, and no precipitate upon neu- tralization with ammonia and the addition of sulphide of ammonium. It should be free from phosphoric acid. To test it for phosphoric acid, evapo- rate 100 c.c. nearly to dryness, add a little magnesium mixture and a large excess of ammonia, cool in ice-water, and stir vigorously. When phos- phoric acid is present, a precipitate of ammonium magnesium phosphate will be obtained. Citric Acid. H 3 ,C 6 H 5 O 7 ,H 2 O. Citric acid is easily obtained in a state of purity in the form of crys- tals having the above composition. It should be kept in the solid condi- tion, and dissolved as needed. It is soluble in ^ part of water at 15 C. Tartaric Acid. H 2 ,C 4 H 4 O 6 . Tartaric acid is also easily obtained sufficiently pure for use in iron analysis. The crystals should be dissolved only as needed. The only impurity is a small amount of lime. It is soluble in y 2 part of water at 15 C. Oxalic Acid. H 2 ,C 2 O 4 . Oxalic acid crystallizes from its aqueous solution as H 2 ,C 2 O 4 ,2H 2 O, soluble in 8.7 parts of water at 15 C. It loses its water of hydration very easily even at the ordinary temperature in dry air, and very quickly at 100 C. ACIDS. ,[ Bromine. Br. Bromine is easily obtained in a condition sufficiently pure for use as a reagent. It is a dark brown, extremely corrosive liquid, of sp. gr. 2.97. It is soluble in about 30 parts of water at 15 C. It is best kept in a glass-stoppered bottle with a ground cap. As the aqueous solution is generally used, it is convenient to put only a small amount, say 20 or 30 c.c., in the bottle, fill the bottle nearly full of cold distilled water, shake it up well, and pour off the saturated solution as required. There usually remains in the bottom of the bottle a small amount of impurity, which is insoluble in water. Iodine. I. Iodine is a metallic-looking crystalline solid, of sp. gr. 4.95. Resub- limed iodine is not sufficiently pure for use, and must be redistilled with great care, unless it is used as iodine dissolved in iodide of iron, and filtered. To distil it, place about y 2 kilo, in a large glass retort of about 2 litres capacity connected with an adapter about 1 8 inches (456 mm.) long and 3 inches (75 mm.) in diameter at the largest part. The heat from a Bunsen burner turned quite low will cause the violet vapors of iodine to pass rapidly into the adapter, where they will condense without any means being taken to cool it. By gently warming the outside of the adapter after the distillation has been finished, the iodine may readily be detached in large masses and removed. It should be kept in a wide- mouth, glass-stoppered bottle. Chlorine. Cl. Chlorine is a yellowish gas about two and one-half times heavier than air. It is sparingly soluble in water. When required it must be made. The details are given under " Determination of Silicon in Iron and Steel." Sulphurous Acid. To make sulphurous acid gas, mix powdered charcoal and strong sulphuric acid until a thin paste is formed, heat the paste in a flask, 42 REAGENTS. very gently at first, and pass the gas through a washing-bottle containing a little water. The reaction is C+ 2H 2 SO 4 = CO 2 + 2SO 2 + 2H 2 O. The tube leading from the flask into the washing-bottle should have a bulb in it to prevent the reflux of water into the flask in case of sudden cooling. Clippings of sheet copper, or copper turnings, may be used instead of charcoal, and are generally to be preferred. The best propor- tion is 250 grammes of copper to 500 c.c. of strong sulphuric acid. The aqueous solution of the gas is made by passing the washed gas into dis- tilled water. The gas, SO 2 , has a specific gravity of 2.21 (air = i.). i c.c. of water at 15 C. dissolves 0.1353 gramme of SO 2 . Chromic Acid. CrO 3 . Chromic anhydride as a red powder or in the form of scarlet crystals is easily obtained in a state of purity. It is deliquescent, and dissolves in a small quantity of water, forming a dark brownish-colored liquid. It may be made by pouring i volume of a saturated solution of bichromate of potassium into \y 2 volumes of strong sulphuric acid, stirring con- stantly. The liquid on cooling deposits needles of chromic anhydride, which must be separated from the mother-liquid and purified by re- crystallization. GASES. Carbonic Acid Gas. CO 2 . The best form of generator is shown in Fig. 47. It was first sug- gested by Casamajor.* It consists of a large tubulated bottle, the bottom of which is covered to the depth of about I inch (25 mm.) with buck- shot, on top of which rest lumps of marble. Dilute hydrochloric acid (i acid to 5 water) is admitted through the tube which enters at the tubulure at the bottom of the bottle, bending down so as to reach the bottom of the bottle. The wash-bottle A contains water. By blowing in the rubber tube attached to the acid-bottle the acid passes over into the tubulated bottle. When the stopcock K is closed, the pressure in * American Chemist, vi. 209 GASES. 43 the tubulated bottle forces the acid back into the acid-bottle. When the acid becomes exhausted and remains in the tubulated bottle, pour a little strong HC1 into the acid-bottle and blow it over into the tubulated bottle. The generated gas will force the liquid back into the acid-bottle, when it can be replaced by fresh acid. A slightly different form is shown in Fig. 50. Sulphuretted Hydrogen Gas. H 2 S. The same form of apparatus is used for generating H 2 S. Ferrous sulphide is substituted for marble, but HC1 is used instead of H 2 SO 4 , as is generally advised, for the ferrous sulphate formed crystallizes out and clogs the apparatus. Hydrogen. H. The same form of apparatus as that used for CO 2 and H 2 S can be used to advantage for generating hydrogen gas. Pieces of zinc, which may be obtained by melting the zinc and pouring it in a sheet about y^ inch (6 mm.) thick, so that it can be easily broken, are to be used, and not granulated zinc. Hydrochloric acid is better than sulphuric. Oxygen Gas. O. Oxygen compressed in cylinders can be obtained from most dealers in chemicals, but it should always be carefully tested before being used for the determination of carbon in steel or iron, as the cylinders are sometimes filled with coal-gas, and a cylinder which has once held coal- gas is rarely free from hydrocarbons. The gas may be made on a small scale in the laboratory by care- fully mixing in a porcelain mortar 100 grammes chlorate of potassium and 5 grammes powdered binoxide of manganese, transferring to a retort, which the mixture should not more than half fill, and heating carefully over a Bunsen burner. The evolved gas may be collected in a gas- holder or in an india-rubber bag. The latter is not to be recommended for use for carbon determinations, as rubber is very liable to give off hydrocarbons. 44 RE A GENTS. ALKALIES AND ALKALINE SALTS. Ammonia. NH 4 HO. The solution of ammonia gas (NH 3 ) commonly used is of sp. gr. 0.88, and contains about 30 to 35 per cent, of ammonia. It should be kept in glass-stoppered bottles and in a cool place, as the gas passes off very rapidly even at the ordinary temperature when open to the air. It should be colorless, leave no residue upon evaporation, be free from chlorides and sulphates, and give no precipitate with H 2 S. Bisulphite of Ammonium. NH 4 HSO 3 . Bisulphite of ammonium is made by passing sulphurous acid gas into strong ammonia until the solution becomes yellowish in color and smells strongly of sulphurous acid. By the first method of manufacture of SO 2 given on page 42, a large amount of CO 2 is formed at the same time, which is absorbed by the ammonia. This is gradually displaced by the SO 2 , and if the solution is kept cool, white crystals of the neutral sulphite, (NH 4 ) 2 SO 3 H 2 O, are deposited. These are gradually dis- solved by the excess of SO 2 until the solution becomes quite clear, assuming a yellowish tint. When copper is used instead of charcoal, no CO 2 is evolved and no carbonate of ammonium is formed. By exposure to air bisulphite of ammonium is gradually oxidized to sulphate. Old bisulphite of ammonium always contains a small amount of hyposulphite, which occasions a precipitate of sulphur when deoxidizing solutions of ferric salts. It is not now difficult to purchase pure bisulphite of ammo- nium, but bisulphite of sodium is very apt to contain phosphoric acid. When made from strong ammonia-water, 18 c.c. of bisulphite will deoxidize a solution of 10 grammes of iron or steel. Sulphide of Ammonium. (NH 4 ) 2 S. Sulphide of ammonium is made by saturating strong ammonia with H 2 S and adding an equal volume of ammonia. The reactions are NH 4 HO + H 2 S = NH 4 HS + H 2 O and NH 4 HS + NH 4 HO=-(NH 4 ) 2 S+H 2 0. The solution becomes yellow by age or by exposure to the air. ALKALIES AND ALKALINE SALTS. 45 Chloride of Ammonium. NH 4 C1. Chloride of ammonium is a white, crystalline, anhydrous salt, soluble in about its own weight of water at 100 C., and in 2.7 parts of water at 1 8 C. It is volatilized when heated without previous fusion. The salt is usually purified by sublimation. It generally contains a little iron, but is free from other impurities. To prepare chloride of ammonium for use in J. Lawrence Smith's method for decomposition of silicates, dis- solve it in boiling water and evaporate down on a water-bath or air-bath. When the salt begins to crystallize out, stir vigorously. The crystals formed will be very small. Drain off the liquid and dry. The salt can then be readily powdered. Nitrate of Ammonium. NH 4 NO 3 . Nitrate of ammonium is a white, crystalline salt, soluble in one-half its weight of water at 1 8 C., and in much less at 100 C. When dissolved in water it produces great cold. By evaporation it loses ammonia and becomes acid. When heated it fuses at 108 C., and is decomposed between 230 C. and 250 C. into water and nitrous oxide, NH 4 NO 3 =2H 2 O + N 2 O. It should leave no residue when volatilized. Fluoride of Ammonium. NH 4 P1. Fluoride of ammonium may be made by saturating hydrofluoric acid by ammonia. The salt crystallizes when left to evaporate over quicklime. It is slightly deliquescent, and therefore difficult to keep, as the solution attacks glass. Acetate of Ammonium. NH 4 C 2 H 3 O 2 . Acetate of ammonium is best made by slightly acidulating ammonia by acetic acid. One volume of strong ammonia-water requires about 2 volumes of acetic acid, 1.04 sp. gr., to neutralize it. It is best to make it as needed, as it decomposes when kept. Oxalate of Ammonium. (NH 4 ) 2 C 2 O 4 + H 2 O. Oxalate of ammonium is a white salt, crystallizing in long prisms united in tufts. It is soluble in 20 parts of water at 18 C. 4 6 REAGENTS. Caustic Soda. NaHO. Fused sodic hydrate purified by alcohol is sufficiently pure for ordinary purposes. It forms white opaque masses, having a strong affinity for water. It dissolves in water with evolution of heat. Pure sodic hydrate is prepared by allowing metallic sodium to decompose water in a platinum dish. It must be kept in a silver or platinum bottle, as the solution acts very rapidly on glass. Phosphate of Sodium and Ammonium. NaNH 4 HPO 4 ,4H 2 O. Phosphate of sodium and ammonium (microcosmic salt) is a white, crys- talline salt, soluble in 6 parts of cold and I part of hot water. It should not be kept in solution for any great length of time, as it attacks glass very readily. It loses its water of crystallization very easily, and when heated gives off its ammonia, leaving pure metaphosphate of sodium, which in the fused condition dissolves metallic oxides in many cases with the production of characteristic colors, which makes it a valuable reagent for blow-pipe analysis. It is easily obtained in a state of purity. Carbonate of Sodium. Na 2 CO 3 . Carbonate of sodium is never quite pure. It always contains small amounts of silica, alumina, lime, and magnesia, besides sulphuric acid. It may generally be obtained quite free from phosphoric acid. Every lot should be carefully examined for all the above impurities, and the amount per gramme noted, so that the proper subtraction may be made in each analysis. It is used in solution only for the neutralization of solutions, as in the determination of manganese by the acetate method, and, as the solu- tion attacks glass very rapidly, it is best to dissolve the salt only as it is needed. Nitrate of Sodium. NaNO 3 . Nitrate of sodium is used occasionally instead of nitrate of potassium in making fusions of ores containing titanic acid. It may be prepared by acidulating a strong solution of carbonate of sodium with nitric acid, heating until the water and excess of nitric acid are driven off, and powder- ing the dry salt. ALKALINE SALTS. ^ Hyposulphite of Sodium. Thiosulphate of Sodium. Na 2 S 2 O 3 -f SH^O. Hyposulphite of sodium is very soluble in water, but decomposes even in tightly-stoppered bottles, sulphate of sodium being formed and sulphur precipitated. It should, therefore, be dissolved only as used. The ordinary salt of commerce is sufficiently pure for use. Acetate of Sodium. NaC 2 H 3 O 2 -f 3H 2 O. Crystallized acetate of sodium dissolves in 3.9 parts of water at 6 C. It is rarely quite pure, containing, usually, calcium and iron salts, but it may be used after solution and filtration for partial analyses, as in the determination of manganese by the acetate method, etc. In complete analyses it is better to use acetate of ammonium. When the use of acetate of sodium is unavoidable, it can be made by dissolving C. P. car- bonate of sodium in acetic acid, boiling off the liberated carbonic acid, and adding acetic acid to slight acid reaction. Caustic Potassa. KHO. Caustic potassa purified by solution in alcohol, filtration, and subse- quent evaporation to dryness and fusion, is quite pure enough for all the ordinary purposes of iron analysis. An aqueous solution of 1.27 sp. gr. is used to absorb carbonic acid in the determination of carbon in iron and steel, in the determination of carbonic acid in ores, etc. 300 grammes of fused KHO dissolved in I litre of water will give a solution of about this strength. Nitrite of Potassium. KNO 2 . Nitrite of potassium is used to separate nickel and cobalt. It is very difficult to buy the pure salt, but it is easily made as follows : Heat I part of nitrate of potassium in an iron dish until it is just fused, then add, with constant stirring, 2 parts of metallic lead. Raise the heat slightly to complete the oxidation of the lead, and allow the mass to cool. Treat the mass with water, filter from the oxide of lead, pass CO 2 through the solution to precipitate the greater part of the dissolved lead, and filter. To the filtrate add a little sulphide of ammonium to precipitate the last traces 48 REAGENTS. of lead, filter, evaporate to dryness, and fuse in a platinum dish to decom- pose any hyposulphite that may have been formed, and preserve the fused salt for use. Nitrite of potassium is deliquescent. Nitrate of Potassium. KNO 3 . Nitrate of potassium is a white, crystalline salt, anhydrous, and soluble in 7^ parts of water at o C, and in 0.4 part of water at 1 00 C. It melts below a red heat to a colorless liquid, and at a red heat gives off oxygen gas more or less contaminated by nitrogen, being converted into nitrite and oxide of potassium. The salt may be purchased in a sufficient state of purity for all purposes of iron analysis, but, as it may contain small amounts of sulphuric acid, the amount should always be determined and the proper allowance made when it is to be used for the estimation of sulphur in ores. Sulphide of Potassium. K 2 S. Sulphide of potassium is made by passing H 2 S into a solution of caustic potassa and filtering from any precipitated alumina or sulphide of iron. It is used instead of the corresponding ammonia-salt when the solution contains copper, as sulphide of copper is slightly soluble in sulphide of ammonium. Bichromate of Potassium. Bichromate of potassium is an orange-colored, anhydrous, crystalline salt, soluble in 20 parts of water at o C., and in I part of water at 1 00 C. It melts below a red heat to a transparent red liquid, crum- bling to powder upon cooling. Heated with strong H 2 SO 4 it gives off about one-sixth its weight of oxygen gas, the reaction being K 2 Cr 2 O 7 -f- 4H 2 SO 4 =Cr 2 K 2 (SO 4 ) 4 -f4H 2 O + 3O. It is readily obtained in a state of purity, but should always be fused to destroy any organic matter before being used to determine carbon in iron or in ores. Chlorate of Potassium. KC1O 3 . Chlorate of potassium is a white, crystalline, anhydrous salt. It is soluble in about 30 parts of water at o C., and in about 2 parts at 100 C. POTASSIUM SALTS. ^ It is readily decomposed by heat, first into a mixture of chloride and per- chlorate of potassium, a portion of the oxygen being set free, and at a higher temperature the perchlorate is decomposed, the remaining oxygen is given off and chloride of potassium alone remains. It is easily obtained in a sufficient state of purity for use in iron analysis. Heated with nitric acid it yields nitrate and perchlorate of potassium, water, chlorine, and oxygen, thus : Heated with hydrochloric acid it gives chloride of potassium, water, and a mixture of peroxide of chlorine and chlorine, called euchlorine, thus : 4KC10 3 + 1 2HC1 = 4 KC1 + 6H 2 + 3 C1O 2 + 9 C1. Bisulphate of Potassium. KHSO 4 . Bisulphate of potassium is a white, crystalline salt, soluble in about one- half its weight of boiling water. A large amount of water decomposes it into sulphate of potassium and free sulphuric acid ; even in the presence of a large excess of sulphuric acid the neutral salt crystallizes out, leaving free sulphuric acid in the solution. Bisulphate of potassium melts at 197 C. ; at higher temperatures it gives off water, leaving the anhydrous salt, and at a red heat it gives -off sulphuric acid, leaving the neutral sulphate. It is difficult to obtain it very pure, but it may be made as follows : Dissolve bicarbonate of potassium in water, filter, and from a graduated vessel add H 2 SO 4 until, after boiling ofT the liberated CO 2 , the solution is neutral, or but very faintly alkaline to test-paper. Filter, if necessary, and to the fil- trate add as much H 2 SO 4 as was added in the first place to neutralize the bicarbonate. Boil the solution down, and finally fuse the mass in a platinum dish. Cool it, and when it is almost ready to solidify pour it into another dish. Break it up, and preserve it in glass-stoppered bottles. Iodide of Potassium. KI. Iodide of potassium is a white, crystalline, anhydrous salt, very soluble in water, and in dissolving it causes a fall of temperature in the solution. It is soluble in about 0.8 part of water at o C., and in 0.5 part of REAGENTS. water at 100 C. It is soluble in 6 parts of alcohol at the ordinary temperature, and, when dissolved, the addition of HC1 does not turn it brown if it is free from iodate. A solution of I part of iodide of potassium in 2 parts of water will dissolve 2 parts of iodine, but upon dilution some of the iodine is precipitated. Permanganate of Potassium. KMnO 4 , Permanganate of potassium is a dark purple-red, anhydrous salt, crystallizing in long needles. It is soluble in 16 parts of water at 15 C. It is easily obtained very pure, but the solution should always be filtered through ignited asbestos, as paper has a strong reducing action on it. Perrocyanide of Potassium. K 4 Pe 2 Cy 6 -f 3H 2 O. 1 Ferrocyanide of potassium is a yellow, crystalline salt, soluble in 4 parts of water at o C., and in 2 parts of water at 100 C. It is used as a reagent to show the presence of ferric salts, which produce a blue coloration, caused by the formation of ferrocyanide of iron (Prussian blue). Ferricyanide of Potassium. K 3 Fe 2 Cy 6 . Ferricyanide of potassium is a blood-red, anhydrous, crystalline salt, soluble in about 3.1 parts of water at o C., and in 1.3 parts of water at 100 C. The dilute solution, like that of the ferrocyanide, is yellow in color. Ferrous salts added to the solution give a blue coloration, due to the formation of ferrous ferricyanide, while ferric salts produce no change of color. The ferricyanide should never be kept in solution. SALTS OF THE ALKALINE EARTHS. Carbonate of Barium. BaCO 3 . Carbonate of barium prepared by precipitation is a soft white powder. It is difficult to obtain it in a state of purity, but it is easily prepared by adding a solution of carbonate of ammonium to a clear boiling solu- tion of chloride of barium, washing the precipitated carbonate of barium with hot water, first by decantation and afterwards on a filter. The car- ALKALIES AND ALKALINE SALTS. ^ bonate of ammonium should, of course, be free from sulphate. The thoroughly washed carbonate of barium should be transferred to a bottle and shaken up with water, in which condition it is ready for use. Car- bonate of barium is very slightly soluble in water, requiring, according to the different authorities, from 4,000 to 25,000 parts of water to dissolve it. It is poisonous. Acetate of Barium. Ba,(C,l B O 2 ) 2 . Acetate of barium may be prepared by dissolving pure carbonate of barium in acetic acid. It crystallizes with I or 3 molecules of water, but dried at o C., or exposed to the air, it effloresces and yields the anhy- drous salt as a white powder. It is very soluble in water, dissolving in about 2 parts of water at o C., and in about I part at 100 C. When heated it decomposes into acetone and carbonate of barium, thus : Ba(C 2 H 3 2 ) 2 = C 3 H 6 + BaCO 3 . Chloride of Barium. BaCl 2 ,2H 2 O. Chloride of barium is a white, crystalline salt, soluble in about 3 parts of water at 15 C., and in about i}4 parts at 100 C. Heated to 100 C. it loses its water of crystallization, yielding the anhydride as a white mass, which melts at a full red heat. Chloride of barium is almost insoluble in strong HC1. It is used almost exclusively for the determina- tion of sulphuric acid, and may be kept in solution for this purpose. 100 grammes of the crystallized salt dissolved in I litre of water is a good proportion to use. Of this solution 10 c.c. will precipitate 1.16 grammes of BaSO 4 , equal to 0.4 gramme SO 3 or 0.16 gramme S. Caustic Baryta. Hydrate of Barium. BaH 2 O 2 ,8H 2 O. Hydrate of barium is a white, crystalline salt, soluble in 20 parts of water at 15 C., and in 3 parts of water at 100 C. The anhydride may be prepared by heating nitrate of barium to redness in a platinum crucible, raising the heat gradually at first to avoid loss from frothing. It attacks platinum, however, at a high temperature. The solution has a strong affinity for carbonic acid, absorbing it readily from the air, the ij 2 REAGENTS. carbonate of barium so formed causing a scum on the surface of the solution. The solution attacks glass very strongly. Chloride of Calcium. CaCl 2 . Crystallized chloride of calcium loses all its water of crystallization at 200 C, yielding the white porous anhydrous chloride, which is very deliquescent. The anhydrous salt fuses at a low red heat, but is partly changed to oxide. For this reason the fused salt should never be used for drying CO 2 in the determination of this gas, as some of it is taken up by the oxide of calcium. A solution of chloride of calcium con- taining 59 parts of the anhydrous salt to 100 parts of water boils at 115 C., a saturated solution at 179.5 C. Carbonate of Calcium. CaCO 3 . Pure carbonate of calcium, for use in Prof. J. Lawrence Smith's method for the determination of alkalies in silicates, is prepared as follows: Dissolve marble or calcite, free from magnesia, in dilute HC1, add an excess of powdered marble, heat the solution, and add some milk of lime to precipitate magnesia, phosphate of calcium, etc. Filter, heat the solution almost to boiling, and precipitate by carbonate of ammonium. The carbonate of calcium formed will be a very dense powder, which will settle readily and be easily washed. Wash thor- oughly, dry, and preserve for use. METALS AND METALLIC SALTS. Metallic Copper. Metallic copper absorbs chlorine gas at ordinary temperatures, and is used in iron analysis to absorb any chlorine that may be given off during the combustion of the carbonaceous matter liberated by the action of sol- vents on iron and steel. It is used in the form of drillings, which should be taken with a perfectly dry drill, and which should be free from oil and grease. The drillings should be kept in a stoppered bottle, and may be used as long as they are perfectly bright and clean. COPPER SALTS. 53 Sulphate of Copper. CuSO 4 ,5H 2 O. Sulphate of copper is a blue, crystalline salt, soluble in 2.7 parts of water at 18 C., and in 0.55 part of water at 100 C. The aqueous solution of the neutral salt is strongly acid to litmus-paper. The crystals of sulphate of copper effloresce on the surface when exposed to the air; heated to 1 00 C. they lose 4 molecules of water, and when heated to 200 C. they lose the remaining molecule. The anhydrous salt is a white saline mass, which is decomposed at a bright-red heat, giving off sul- phurous acid and oxygen and leaving cupric oxide. The anhydrous salt has a strong affinity for water, and also for hydrochloric acid gas. A solution of sulphate of copper dissolves metallic iron, the copper being precipitated from the solution at the same time in a spongy mass. Anhydrous Sulphate of Copper. The property anhydrous sulphate of copper possesses of absorbing hydrochloric acid gas makes it useful in the determination of carbon by combustion, and it is best prepared for this purpose as follows : Heat crystals of sulphate of copper, about the size of a coffee bean, in a porcelain dish until the blue color of the crystals disappears and they become white. Transfer while still hot to a dry, glass-stoppered bottle. Anhydrous Cuprous Chloride. CuCl. To prepare the granulated salt for use as an absorbent of hydrochloric acid and chlorine in carbon determinations, moisten the ordinary powdered salt of commerce in a porcelain dish and rub it up with a glass rod into little lumps about the size of a coffee bean. Heat it gradually until the water is expelled and the lumps, which will be dark brown in color, harden. Transfer to a glass-stoppered bottle. Cupric Chloride. CuCl 2 -J-Aq. To prepare cupric chloride for use in dissolving "iron or steel for the determination of carbon, grind up equal weights of sulphate of copper and common salt in a porcelain mortar, and pour over the mixture a small amount of water heated to 5O-6o C. The liquid becomes emerald-green 54 REAGENTS. in color, and deposits upon evaporation sulphate of sodium. Decant from the deposited salt and evaporate again until the solution is reduced to a very small bulk. Cool, and decant from the remainder of the sulphate of sodium and the excess of chloride of sodium. By further evaporation and cooling the cupric chloride may be obtained in the form of green crystals. These crystals are deliquescent. The solution should be diluted and filtered through asbestos. Double Chloride of Copper and Ammonium. 2(NH 4 Cl),CuCl 2 ,2H 2 O. Double Chloride of Copper and Potassium. 2(KCl),CuCl 2 ,2H 2 O. The double chloride of copper and ammonium is a bluish-green crystal- line salt, quite soluble in water. The double chloride of copper and potassium is bluish-green likewise and more soluble than the ammonium salt. The recent experiments of the American members of the International Steel Standards Committee have shown that the double chloride of copper and ammonium is nearly always impure, from the presence of hydrocarbons in the chloride of ammonium, derived probably from the gas liquor from which ammonia salts are dis- tilled. These hydrocarbons unite with the carbonaceous residue liberated from steel and iron in the process of determining carbon, and of course vitiate the results. Several recrystallizations free the salt to a certain extent from this impurity. The use of the potassium salt is not open to this objection. To prepare these salts proceed as follows: Dissolve 107 parts of chloride of ammonium or 149.1 parts of chloride of potassium and 170.3 parts of crystallized cupric chloride (CuCl 2 ,2H 2 O) in water and crystallize out the double salt. Dissolve about 300 grammes of the double salt in i litre of water, filter through ignited asbestos, and preserve for use in glass-stoppered bottles. Oxide of Copper. CuO. Oxide of copper, both fine and coarse, for combustions is easily obtained. It may be prepared as follows : Dissolve metallic copper in nitric acid, evap- orate to dryness in a porcelain dish, transfer it to a Hessian crucible, and COPPER AND IRON SALTS. ^ heat it in a furnace until no more nitrous fumes are given off. Keep the crucible well covered to prevent any coal getting into it, and avoid raising the heat too high, or the mass will fuse. Stir it from time to time, and when finished the oxide on top will be in a fine powder, while that in the bottom of the crucible will have sintered. Rub it up in a mortar and pass through a fine metal sieve. Keep the two kinds, fine and coarse, separate in glass-stoppered bottles, carefully covered to preserve them from dust. Iron Wire. Very fine soft piano-forte wire is the best form of iron to use when standardizing solutions of permanganate or bichromate of potassium by metallic iron. Wrap one end of a piece of wire, about 2 feet (610 mm.) long, around a lead-pencil, and, using this as a handle, draw the wire several times through a piece of fine emery-cloth, then through a fold of dry filter-paper, then, holding the wire with the paper, wrap it around the pencil. Cut -off the end that has not been cleaned, and the little spiral of wire will be in a convenient form for weighing. Ferrous Sulphate. Ferrous sulphate (green vitriol, or copperas) is a bluish-green crystal- line salt, soluble iru 1.64 parts of water at 10 C, and in 0.3 part at 100 C. It is insoluble in alcohol. The crystals lose 6 molecules of water when heated to 114 C., but retain the last molecule even at 280 C. Heated to a red heat the anhydrous sulphate is decomposed, giving off sulphurous acid and leaving a basic ferric sulphate, which at a higher temperature is entirely decomposed, leaving only ferric oxide. To prepare the crystals for use in volumetric analysis, add alcohol to the aqueous solution of the ferrous sulphate, when the salt is precipitated as a bluish-white powder. Filter, wash with alcohol, dry thoroughly, and preserve in glass-stoppered bottles. The salt prepared in this way remains unaltered for a long time. Double Sulphate of Iron and Ammonium. FeSO 4 (NH 4 ) 2 SO 4 ,6H 2 O. The double sulphate of iron and ammonium is a light green crystalline salt, soluble in 2.8 parts of water at 16.5 C. It may be prepared as 56 REAGENTS. follows : Dissolve 276 grammes of crystallized ferrous sulphate in water, filter, and add to the filtrate a clear solution of sulphate of ammonium ( (NH 4 ) 2 SO 4 , Glauber's Sal Secretum), evaporate down, and allow the double salt to crystallize out. Drain the crystals, wash slightly with cold water, and dry on blotting-paper. When perfectly dry, preserve in a glass-stoppered bottle. The crystals remain unaltered for a long time even in moist air. They contain exactly \ their weight of metallic iron. Mercurous Nitrate. Hg > NO 3 ,H 2 O. To prepare this salt, pour cold, moderately strong HNO 3 on an excess of metallic mercury, and when the violent action has subsided, pour off the acid and allow the salt to crystallize out by the cooling of the acid. The salt is soluble in a small amount of water, but a large amount de- composes it into a basic salt and free acid. Mercuric Oxide. HgO. Mercuric oxide is a light orange-yellow substance when prepared by precipitation from a mercuric salt. To a dilute solution of mercuric chloride add a slight excess of caustic potassa, allow the precipitate to settle, wash it thoroughly by decantation with hot water, and finally wash it into a glass-stoppered bottle. It is used shaken up with water. Chromate of Lead. PbCrO 4 . Fused chromate of lead is a dark brown mass showing a radiated structure, and when powdered it is dark yellow in color, very heavy, and slightly hygroscopic. It is easily obtained very pure, but may be made as follows : Dissolve acetate of lead in water, add a little acetic acid, filter, and precipitate by a solution of bichromate of potassium. Wash by decantation, and finally on linen, dry, and heat in a Hessian crucible until the mass is just fused. Pour on a polished iron slab, grind in a clean mortar, and preserve the powder in glass-stoppered bottles, covered to exclude dust. Chromate of lead heated to a full red heat gives off oxygen and is reduced to a mixture of basic chromate of lead and oxide of chromium. LEAD SALTS. H ? >' Peroxide of Lead. PbO 2 . Peroxide of lead is rather difficult to obtain in a state of purity; it is liable to contain nitrate of lead and oxide of manganese. The latter element interferes materially with its use as a reagent in the determina- tion of manganese by the color test. It should always be carefully ex- amined by boiling with dilute nitric acid, and, if it imparts any color to the solution, must be promptly rejected. It may be readily prepared by digesting red oxide of lead in dilute nitric acid, decanting off the nitrate of lead, and washing the residue thoroughly with hot water. Red oxide of lead by this treatment is decomposed into protoxide of lead, which dissolves in the nitric acid, and peroxide, which remains insoluble. Per- oxide of lead is a heavy brown powder, which, when heated, gives off oxygen and is converted into red lead or protoxide of lead. Oxide of Lead dissolved in Caustic Potassa. Pour a cold solution of nitrate of lead into caustic potassa, 1.27 sp.gr., stirring constantly to dissolve the oxide of lead, which precipitates. Add the nitrate of lead until a permanent precipitate is produced. Allow this to settle, and siphon the clear liquid into a glass-stoppered bottle. It is well to coat the stopper with a little paraffine, to prevent its sticking. Platinic Chloride Solution. Dissolve platinum-foil in HC1, adding HNO 3 from time to time, evaporate to dry ness on the water-bath, redissolve in HC1, and evaporate again to drive off the HNO 3 . Redissolve in water with the addition of a few drops of HC1, filter, and preserve in a bottle the stopper and neck of which are protected by a ground-glass cap to prevent any access of ammonia to the solution. Metallic Zinc. Melt zinc, which should be as free as possible from lead and iron, in a Hessian crucible, and pour it in a thin stream from a height of four or five feet into a bucket of cold water, giving the crucible a cir- 5 8 REAGENTS. cular motion to prevent the zinc from falling in exactly the same place all the time. Pour off the water, dry the granulated zinc, and preserve it in bottles for use. Oxide of Zinc in Water. Emmerton* suggests the following method of preparing this reagent: Dissolve ordinary zinc white in HC1, add the zinc white until there is an excess which will not dissolve, then add a little bromine-water, heat the solution, filter, and precipitate the oxide of zinc by ammonia, being careful to avoid an excess. Wash thoroughly by decantation, and then wash into a bottle. Shake the bottle well, to diffuse the oxide through the water, before using. REAGENTS FOR DETERMINING PHOSPHORUS. Magnesia Mixture. Dissolve 1 10 grammes of crystallized chloride of magnesium (MgCl 2 -f-6H 2 O) or 50 grammes of the anhydrous salt in water, and filter. Dis- solve 28 grammes of chloride of ammonium in water, add a little bro- mine-water and a slight excess of ammonia, and filter. Add this solution to the solution of chloride of magnesium, add enough ammonia to make the solution smell decidedly of ammonia, dilute to about 2 litres, transfer to a bottle, shake vigorously from time to time, allow to stand for several days, and filter into a small bottle as required for use. 10 c.c. of this solution will precipitate about 0.15 gramme P 2 O 5 . Molybdate Solution. Weigh into a beaker 100 grammes of pure molybdic anhydride, mix it thoroughly with 400 c.c. of cold distilled water and add 80 c.c. of strong ammonia (0.90 sp. gr.). When solution is complete, filter and pour the filtered solution slowly with constant stirring into a mixture of 400 c.c. of strong nitric acid (1.42 sp. gr.) and 600 c.c. of distilled water. Allow to settle for 24 hours and filter. A solution prepared in this way will keep for sev- eral months even in hot weather without any deposition of molybdic acid. * Trans. Am. Inst. Min. Engineers, vol. x. p. 201. METHODS FOR THE ANALYSIS OF PIG-IRON, BAR-IRON, AND STEEL. DETERMINATION OF SULPHUR. By Evolution as H 2 S. KARSTEN was the first to suggest dissolving iron or steel in HC1, or dilute H 2 SO 4 , and collecting the evolved H 2 S by ab- sorbing it in a solution of a metallic salt. He recommended CuCl 2 . Absorption by Alkaline Solution of Nitrate of Lead. The apparatus, Fig. 47, shows the usual arrangement for carrying out the process, with the addition of the generating- bottles for supplying hydrogen gas. This is the apparatus described under the head of " Apparatus for Generating CO 2 ," page 42. The wash-bottle A contains an alkaline solution of Description of the ap- nitrate of lead, and is connected with the funnel-tube by the rubber tube B, and a small piece of glass tubing, C, turned at a right angle with one end drawn down and covered with a short piece of rubber tubing. This fits in the neck of the bulb of the funnel-tube and makes a tight joint. The analytical process is conducted as follows : Weigh 10 grammes * of borings or drillings, free from lumps, * A 5-factor weight (6.878 grammes) is a better amount to take, as, when the weight of BaSO 4 found is multiplied by two, each milligramme is one-thousandth of a per cent, of sulphur. 59 6o ANAL YSIS OF IRON AND STEEL. FIG. 47. DETERMINATION OF SULPHUR. 6j into the previously dried flask D, and close it with the rubber Description of the stopper fitted with a funnel-tube and a delivery-tube. The outlet- process, tube from the flask D connects with the tube F t reaching almost to the bottom of the Erlenmeyer flask H. In each of the flasks H are poured about 20 or 30 c.c. of potassium hydrate solu- tion of nitrate of lead* and enough water to fill them two- thirds full. Connect the apparatus, and run a slow stream of , I estmg the hydrogen through until all the air is expelled, then close the ^p^atus. glass stopcock of the funnel-tube, and shut off the supply of hydrogen by closing the small glass stopcock K. If the con- nections are all tight, the liquid will not recede in the tube F. When this is assured, disconnect the tube C, and fill the bulb which should be of about 100 c.c. capacity with a mixture of 50 c.c. of strong HC1 and 50 c.c. of water. Replace the tube C t turn on the hydrogen, and open the stopcock of the funnel-tube, so as to allow the acid to flow into the flask D. When the acid has all run into the flask, regulate the flow of the hydrogen so that the gas shall pass through the solutions in the flasks H, H 1 as rapidly as possible, and heat the flask D. When the solu- tion in the flask D has boiled for fifteen minutes, and all the metal has dissolved, remove the source of heat and continue the current of hydrogen for about ten minutes, regulating its flow by means of the stopcock K, to prevent any reflux of the liquid in H, which might be caused by the cooling of the flask D. Shut off the hydrogen, disconnect the apparatus, and wash the contents of the flask H into a No. 2 Griffin's beaker. Un- less a precipitate of sulphide of lead appears in the second flask Treatment H r , it need not be emptied, but the same solution can be used precipitate. over again for the next analysis. Collect the precipitate in a small filter, wash it once or twice with hot water, and, while still moist, throw the filter and precipitate back into the beaker, in which have been placed just the instant before some powdered See page 57. ANAL YSIS OF IRON AND STEEL. KC1O 3 and from 5 to 20 c.c. of strong HC1, according to the amount of the precipitate of lead sulphide. Allow it to stand in a warm place until the fumes shall have partly passed off, then add about twice its volume of hot water, and filter into a No. I beaker. Wash with hot water, heat the filtrate to boiling, and add NH 4 HO until the solution is slightly alkaline to litmus- paper. Acidulate with a few drops of HC1, add 5 to 10 c.c. of BaCl 2 solution,* boil 15 or 20 minutes, and stand aside for half an hour. Filter the precipitate of BaSO 4 , preferably on a Gooch Baso 4 . perforated crucible, wash with hot water, ignite, and weigh as BaSO 4 , which contains 13.75 P er cent. S. It is -always well to test the alkaline filtrate from the lead sulphide with a few drops of the lead solution, for it might happen that all the lead would be precipitated from the solution as sulphide, and an excess of H 2 S remain in the solution as sulphide of potassium. The entire operation described above can be performed in about two and a half hours, and is, in my opinion, the most ac- curate method known for the determination of sulphur in steel. Absorption by Ammoniacal Solution of Sulphate of Cadmium. f. f. Morrell f passes the evolved gas into an ammoniacal solution of sulphate of cadmium. Prepare a solution of sulphate of cadmium of convenient strength, and add enough ammonia to redissolve the precipitate and give a clear solution. Place this solution in the bottles H, H, and proceed as usual. Filter the precipitate of sulphide of cadmium in a counterpoised filter, wash with water containing a little ammonia, dry at 100 C., and weigh as CdS, which contains 22.25 P er cent - f S. Absorption by Ammoniacal Solution of Nitrate of Silver. Berzelius proposed the use of a dilute solution of nitrate of silver made alkaline by ammonia. The method of procedure is * See page 51. f Chem. News, xxviii. 229. DETERMINATION OF SULPHUR. 63 as follows : Dissolve I gramme of AgNO 3 in a small quantity of Preparation water, and make it strongly alkaline with NH 4 HO ; pour about two-thirds of the solution into the first of the bottles H, and the remainder into the second, and fill up to the proper level silver - with water. Proceed exactly as described above until the sul- phide of silver has been filtered off and washed. Dry this pre- cipitate carefully at a low temperature, say 100 C, and brush it carefully into a small, dry beaker, returning the filter to the funnel. Pour into the bottles H, should any of the sulphide remain adhering to the sides, 20 or 30 c.c. strong HNO 3 , and when it is all dissolved, pour the acid in the filter, allowing it to run into the beaker containing the sulphide of silver, and Details of wash out the bottles with a little HNO 3 , allowing this to run over the filter also. Digest the sulphide of silver until it is all dissolved, then dilute with hot water, add an excess of HC1, and filter off the chloride of silver. Add a small amount of carbonate of sodium, and evaporate nearly dry, dilute, add a few drops of HC1, filter if necessary, and precipitate as before by chloride of barium. Even when the sample contains no sulphur a slight precipitate of carbide of silver may be thrown down by the carburetted hydrogen evolved from the iron or steel by the action of the acid. Absorption and Oxidation by Bromine and HCl. Fresenius * suggested passing the evolved gases through a Advantage solution of bromine in HCl, which has the advantage of oxidiz- method. ing the sulphuretted hydrogen at once, but the disadvantage of filling the room with bromine-fumes unless the apparatus is placed under a hood with a good draft. It is necessary when using this method to avoid bringing the bromine-fumes in contact with rubber stoppers. Instead of the bottles H, attach to the exit-tube Description a bulb-tube of the shape shown in Fig. 48, containing 3 to 5 atus. Pa * Fresenius, Zeitschrift, xiii. 37. 6 4 ANAL YSIS OF IRON AND STEEL. Details of the method. FIG. 48. c.c. of bromine and enough HC1 to fill the bulb-tube to the marks shown in the cut. When the operation is finished, wash the contents of the bulb-tube out into a beaker, heat until the bromine is all driven off, neutralize by NH 4 HO, and precipitate the sulphuric acid exactly as described on page 62. Instead of neu- tralizing by NH 4 HO, the HC1 solution may be evaporated down nearly to dry- ness after adding a little carbonate of sodium or the solution of chloride of barium; but repeated experiments have shown that sulphate of barium is prac- tically insoluble in chloride of ammonium, so that the plan of of BaSO 4 in NH 4 ci. neutralizing by NH 4 HO, being the shorter and less troublesome, is to be preferred. Absorption and Oxidation by Permanganate of Potassium. Drown * suggested the use of permanganate of potassium solu- tion as an absorbent and oxidizer ; the process being carried out as follows : Make a solution of permanganate of potassium, 5 grammes to the litre of water, and fill the bottles H to their proper height with this liquid, using three bottles, however, instead of two, and proceed with the operation as before described, being Avoid rapid careful to avoid a rapid evolution of the gas. Wash the con- evolution of gas. tents of the bottles H into a clean beaker, dissolve any oxide of manganese that may adhere to the sides of the bottles in HC1, add this to the solution in the beaker, and then add enough HC1 to decompose the permanganate entirely. Boil until the solu- tion is colorless, filter if necessary, and precipitate by chloride of barium. Allow it to stand overnight, filter, wash, ignite, and weigh the BaSO 4 . Details of the pro- cess. Journal Inst. Min. Engineers, ii. 224. DETERMINATION OF SULPHUR. & Absorption and Oxidation by Peroxide of Hydrogen. Craig * suggested the use of ammoniacal solution of peroxide of hydrogen in the absorbing-bottles. Attach to the exit-tube of the flask D (Fig. 47) a nitrogen-bulb of the usual form (Fig. 48), in which have been placed 4 c.c. of peroxide of hydrogen and 1 6 c.c. of ammonia, and proceed as before directed. When the operation is finished, wash the contents of the nitrogen-bulb Necessity into a small beaker, acidulate slightly with HC1, boil, add chlo- deter- ride of barium, and determine the amount of BaSO 4 as usual. As peroxide of hydrogen always contains sulphuric acid, the amount must be carefully determined in each fresh lot of the peroxide of hydro- H 2 O 2 , and the proper correction made for the volume used. gen. By Oxidation and Solution. Many chemists still prefer the old method of oxidizing and This method dissolving the metal and precipitating the sulphuric acid in the by many solution by chloride of barium. The details are as follows : Treat 5 grammes of drillings in a No. 4 Griffin's beaker, covered by a watch-glass with 40 c.c. of strong HNO 3 . This requires care, for drillings of bar-iron and low steel are often acted on so violently, even by strong HNO 3 , as to cause the solution to boil over. In this case it is best to place the beaker in a dish con- taining a little cold water and to add the acid gradually. When all the acid has been added and the action has ceased, some small particles generally remain undissolved, and their solution is effected by heating the beaker on the sand-bath and finally by adding a few drops of HC1. With pig-iron and steel there Precautions is usually no action in the cold, and in this case heat the beaker carefully until the action begins, then stand the beaker in a cooler place, and if the action becomes very violent, stand the HN 8 beaker in cold water until it moderates. Very high carbon steels * Chem. News, xlvi. 199. 5 66 ANALYSIS OF IRON AND STEEL. dissolve with great difficulty even in boiling acid ; but the solu- tion may be hastened by adding a few drops of HC1 from time to time. When solution is complete and only particles of graphite and silica remain undissolved, which is shown by the residue being entirely flotant, remove the cover, add a little carbonate of sodium, and evaporate the solution to dryness in the air-bath. The addition of the carbonate of sodium is to prevent any possible loss of sulphuric acid, which might other- wise occur by the decomposition of the sulphate of iron at a Further de- high temperature. Remove the beaker from the air-bath, and when cold add 30 c.c. HC1, and heat until the oxide of iron is dissolved, evaporate again to dryness to render the silica insol- uble, redissolve in HC1, evaporate until the ferric chloride begins to separate out, add 2 c.c. HC1 and a little water. Filter and wash, being careful that the total filtrate and washings shall not excede 100 c.c. in volume. Heat the filtrate to boiling, add 10 c.c. saturated solution of chloride of barium, and allow it to whenig- stand in the cold over night. Filter, wash with a little very dpitate dilute HC1, and finally with cold water; dry, ignite, and weigh as BaSO 4 . If this ignited precipitate is reddish in color, it shows that Fe 2 Q 3 has been precipitated with the BaSO 4 . In this case f use w j t h Na 2 CO 3 , dissolve in water, filter, acidulate the filtrate, and precipitate as before. Or, filter the aqueous solution of the fusion, dissolve in HC1, precipitate by ammonia, weigh the Fe 2 O^ and subtract from the weight of BaSO 4 . Notes and Precautions. The investigations of Phillips* and Matthewmanf have shown conclusively that in many pig-irons, the evolution method fails to give the full sulphur contents. This seems to be due to the formation of organic sulphides, probably of the mercaptan series, and not to the presence of copper or arsenic, as has been sup- * Journal American Chem. Society, vol. xvii. p. 891. f Journal West of Scotland Iron and Steel Institute, vol. iii. p. 27. DETERMINATION OF SULPHUR. posed. As those compounds are quite volatile and very difficult to oxidize, some portions seem to pass through the absorbing solutions, while under certain circumstances other portions remain in the evolution flask with great persistency and are expelled only after long boiling. The only practicable method for pig-irons of this character, therefore, is the oxidation method. There are three precautions to be observed in using this method. I. The sample should be dissolved in strong nitric acid, as, when dilute nitric acid, or even aqua regia, is used, some sulphur seems to escape oxidation. 2. The amount of acid in the solution from which the barium sulphate is precipitated must be most carefully regulated, as well as the absolute volume of the solution. 3. The reagents used must be examined for sulphuric acid. This is best done as follows : Measure into a beaker the total amount of acid, both nitric and hydrochloric, used in the determination, add a little sodium carbonate and evaporate to dryness. Redissolve in 15 c.c. of water and 5 or 10 drops of hydrochloric acid, filter, heat to boiling, add 10 c.c. of barium chloride, boil 10 or 15 minutes, allow to settle, filter, wash, ignite, and weigh as BaSO 4 . The amount found is to be ab- stracted from the total weight of BaSO 4 found in the sample. In the use of the evolution method for steels, the results obtained vary somewhat with the solution used for absorbing the hydrogen sulphide, and I am satisfied that the best absorbent is the alkaline solution of lead nitrate. I have never failed, so far as I know, in getting correct results with this absorbent in any steel. The evolution of the gas should be as rapid as pos- sible, as there seems to be no danger of any hydrogen sulphide passing the liquid in the first flask, and the operation is naturally shortened. If the solution containing the precipitated barium sulphate is boiled vigorously for 15 or 20 minutes, it is not necessary to allow it to stand more than half an hour, so that a 68 ANALYSIS OF IRON AND STEEL. determination can be made in two hours, or two hours and a half, without any trouble. RAPID METHOD. Volumetric Determination by Iodine. This method, suggested by Elliott,* involves the evolution of the sulphur as H 2 S, its absorption in a solution of sodium hy- drate, and titration by iodine in iodide of potassium. It requires a standard solution of iodine, a standard solution of hyposul- phite of sodium, a starch solution, and a standard solution of bichromate of potassium. Iodine Solution. Dissolve 6.5 grammes pure iodine in water with 9 grammes iodide of potassium, and dilute to I litre. Hyposulphite of Sodium Solution. Dissolve 25 grammes hyposulphite of sodium in water, add 2 grammes carbonate of ammonium, and dilute to i litre. The carbonate of ammonium retards the decomposition of the hypo- sulphite of sodium. Starch Solution. Weigh into a porcelain or Wedgwood mortar i gramme of pure wheat starch, and rub it to a thin cream with water. Pour it into 150 c.c. boiling water, allow it to stand until cold, and decant the clear solution. The addition of 10 or 15 c.c. glycerine makes the solution keep better. It is better, how- ever, to make a fresh starch solution every few days. Dr. Waller recommends Miiller's suggestion of grinding the starch with a strong solution of potassium or sodium hydrate and dissolving in hot water for use. It keeps indefinitely. Bichromate of Potassium Solution. Dissolve 5 grammes pure bichromate of potassium in water, and dilute to i litre. * Chem. News, xxiii. 61. RAPID METHODS FOR SULPHUR. g All these solutions should be placed in glass-stoppered bottles and kept in a dark place. Standardizing- the Solutions. Standardize the bichromate solution as directed in the "Anal- ysis of Iron Ores." When bichromate of potassium is added Reaction to iodide of potassium in presence of free HC1, iodine is liber- K 2 cr 2 o 7 is ated, in accordance with the formula K 2 Cr 2 O 7 + 6KI+ I4HC1 Kiwith = 8KCl+Cr a Cl 6 +7H a O + 6I, or i equivalent of K 2 Cr 2 O 7 = e H x ^ sof 294.5 liberates 6 equivalents of iodine =761. 1. Therefore, by adding to a solution of iodide of potassium in the presence of HC1 a known amount of bichromate, we can calculate the ab- solute amount of iodine liberated, and by titrating this solution by the hyposulphite solution we can accurately standardize the latter. The reaction which takes place when a solution of Reaction of hyposulphite (thiosulphate) of sodium is acted on by iodine is P hit e of 2NaHS 2 O 3 + 2! = 2HI + Na 2 S 4 O 6 > or 2 equivalents of thiosul- ^3. phate unite with 2 equivalents of iodine to form hydriodic acid and tetrathionate of sodium. By adding a few drops of starch solution to a solution containing iodine, blue iodide of starch is formed, and colors the solution as long as it contains free iodine. When enough hyposulphite is added to a solution of this kind to combine exactly with the iodine, the blue color disappears. Conversely, upon adding a solution of iodine to a solution containing hyposulphite of sodium and a little starch, the sensitive blue color of the iodide of starch will disappear as fast as formed until all the thiosulphate has been changed to tetrathionate, and then the first drop of iodine in excess will change the solution to a permanent blue. The same thing Reaction be- holds true as regards a solution containing free H 2 S, the reaction being H 2 S+2l = 2HI + S. Proceed therefore as follows: Dis- solve about I gramme of pure iodide of potassium in 300 c.c. iodine - water, add 5 c.c. HC1, and then 25 c.c. of the bichromate solu- tion, which will liberate a known amount of iodine. Drop in 70 ANALYSIS OF IRON AND STEEL. standard- now the hyposulphite solution from a burette until the iodine hyposui- nearly disappears, add a few drops of starch solution, and con- tion. tinue the hyposulphite until the blue color fades out entirely. The amount of iodine being known, the value of the hyposul- phite solution is calculated from the reading of the burette. Now standard- measure into a beaker with a carefully graduated pipette 25 c.c. iodide 1 so- of the hyposulphite solution, dilute to 300 c.c., add a few drops of the starch solution, and drop, from a burette, standard iodine solution until the blue color is permanent. The value of the hyposulphite solution being known, that of the iodine solution is readily calculated. An example will illustrate this : illustration Suppose we find by titration that I c.c. of our bichromate solu- of the cal- culation of tion is equal to .00566 gramme metallic iron; then, as the of e th V e al s U e - S reaction is 6FeCl 2 + K 2 Cr 2 O 7 + I4HC1 = 3Fe 2 Cl 6 + 2KC1 + Cr 2 Cl 6 + 7H 2 O, I equivalent of K 2 Cr 2 O 7 = 294.5 is equal to 6 equiva- lents of Fe=336. Hence 336 : 294.5 = .00566 : .004961, or i c.c. of the bichromate solution contains .004961 gramme K 2 Cr 2 O 7 , and consequently 25 c.c. contain .124025 gramme K 2 Cr 2 O 7 . Then, as we saw by the formula that 294.5 parts bichromate liberate 761.1 parts iodine, we have 294.5 : 761.1 =.124025 : .32052, or 25 c.c. bichromate solution liberate .32052 gramme iodine. We now find that it requires 25.3 c.c. of the hyposulphite solution to decolorize the solution made by adding 25 c.c. bichromate solution to the iodide of potassium ; consequently each c.c. of the hyposulphite contains enough NaHS 2 O 3 to react with .01267 gramme iodine. We now measure out 10 c.c. of the hyposul- phite solution, dilute it to 300 c.c., add a few drops of starch solution, and find that it requires 20.1 c.c. of the iodide solution to give the permanent blue color. Hence 20.1 c.c. = .1267 gramme iodine, or I c.c. iodide solution contains .006303 gramme iodine. As the reaction with H 2 S is H 2 S + 2! = 2HI + S, it requires 2 equivalents of iodine to decompose I equivalent of H 2 S, and the proportion is 2! : S : : 253.7 : 32.06 : : .006303 : .000796, or I c.c. iodine is equal to .000796 gramme sulphur. RAPID METHODS FOR SULPHUR. n } The standard solutions once ready, the actual determination of sulphur in a sample is very simple. Measure 50 c.c. of a solution of caustic soda, i.i sp. gr., free from sulphur, into the first of the bottles D. The second need not be used, but it is a good plan to keep a caustic potassa solution of nitrate of lead Details of in it, and attach it after the other, to be certain that no H 2 S method, escapes the caustic soda solution. Proceed with the determina- tion as directed on page 61, and when finished wash the contents of the bottle D into a beaker, dilute to 500 c.c., acidulate with HC1, add a few drops of starch solution, and titrate with the iodide solution. See exactly how much HC1 is required to acidulate strongly 50 c.c. of the caustic soda solution, and this amount can be added at once, so that no time need be lost in testing the solution with litmus before titrating. Mr. E. F. Wood,* of the Homestead Steel-Works, modifies the method as follows : Pass the evolved gas into an ammoniacal solution of sulphate of cadmium instead of caustic soda. Filter, place the filter containing the precipitate of sulphide of cadmium in a beaker containing cold water, add enough hydrochloric acid to dissolve the precipitate, and titrate with iodine solution as above described. Mr. Wood thinks that this method has several advantages wood's over that in which caustic soda is used to absorb the H 2 S. The J^ 1 c hydrocarbon gases absorbed by the alkaline solution are gotten rid of, and the error which their presence may produce is avoided; the bulk of the precipitate is an indication of the amount of sul- phur and a guide to the proper amount of hydrochloric acid to use for its solution ; and when the sulphide of cadmium is filtered off, only a small amount of hydrochloric acid is required, and the generation of heat from the neutralization of the alkali is avoided. * Communicated to the author. ANAL YSIS OF IRON AND STEEL. DETERMINATION OF SILICON. By Solution in HNO 3 and HC1. Dissolve 5 grammes of drillings in 40 c.c. HNO 3 with the precautions mentioned on page 65 ; although when silicon alone Best strength is to be determined, HNCX of 1.2 sp. gr. may be used, when, in of HN0 8 most cases, the solution of the drillings will be more rapid. Remove the cover, evaporate the solution to dryness in the air- bath, replace the cover, and raise the temperature of the bath until the nitrate of iron is decomposed. Remove the beaker from the air-bath, allow it to cool, add 30 c.c. HC1, and heat gradually until all the ferric oxide is dissolved. Remove the cover, and evaporate again to dryness in the air-bath, redissolve in 30 c.c. HC1, dilute to about 150 c.c., and filter on an ashless filter. Detach any adhering silica from the sides and bottom of the beaker with a "policeman," and wash it out with cold water. Wash the filter first with dilute HC1, and finally with Testing water. Dry, and ignite in a platinum crucible until all the Sio 2 wkh carbon is burned, weigh the residue in the crucible, moisten it with water, add i-io drops H 2 SO 4 , and enough HF1 to dissolve it completely, evaporate to dryness, ignite, and weigh. The difference between the two weights is SiO 2 , which contains 47.02 By fusion per cent, of Si. In the absence of HF1, unless the SiO 2 is per- Na 2 co 8 fectly white, fuse with 5 or 6 times the weight of Na 2 CO 3 , dis- oratioT^" s l ve m water, acidulate with HC1, evaporate to dryness (in a with HCI. platinum or porcelain dish, with the arrangement shown on page 20), redissolve in HCI and water, dilute, filter, wash, ignite, and weigh. When the weight of Na 2 CO 3 taken does not exceed By treating 2 or 3 grammes, allow the crucible to cool after fusion, and then crucible add to it gradually an excess of strong H 2 SO 4 , heating very H*so 4 . slowly, until the mass is quite liquid and fumes of SO 3 come off. Allow it to cool, dissolve in water, filter, wash well, ignite, and weigh. DETERMINATION OF SILICON. By Solution in HNO 3 and H 2 SO 4 . Drown * has suggested a method which, for pig-irons, has Brown's come into very general use, and which is much more rapid than the other method, and quite as exact. Treat I gramme of borings in a platinum or porcelain dish with 20 c.c. HNO 3 , 1.2 sp. gr. When all action has ceased, add 20 c.c. of H 2 SO 4 (equal parts acid and water), and evaporate using the arrangement shown on page 20 until copious fumes of SO 3 are given off Allow to cool, and dilute with 150 c.c. water; heat carefully until all the sulphate of iron has dissolved, filter hot, wash first with dilute HC1, i.i sp. gr., and then with hot water, ignite, and weigh. Treat the contents of the crucible with H 2 SO 4 and HF1, evaporate to dryness, ignite, and weigh again. The difference between the two weights is SiO 2 . By Volatilization in a Current of Chlorine Gas. As almost all steels and irons contain slags of various com- presence of positions, it must be understood that the SiO 2 obtained by the ^onTnd methods above given is the total SiO 2 , comprising any SiO 2 that steeK may be present m the admixed slag, as well as that formed from the Si present in the metal. The volatilization method Separation separates the two. The process suggested by Drown,f and sio^ worked out independently two years later by Watts,! is as fol- lows : Fig. 49 shows the general arrangement of the apparatus. Description The large flask contains binoxide of manganese in lumps. The bottle above it contains strong common HC1, which runs into the flask through a siphon-tube extending almost to the bottom. The flask stands in a dish containing water, which can be heated by the burner under the tripod. The evolution-tube from the flask has a stopcock, and connects with the three bulb-tubes on the stand, the first containing water, the second * Jour. Inst. Min. Engineers, vii. 346. f Ibid., viii. 508. % Chem. News, xlv. 279. 74 ANAL YSIS OF IRON AND STEEL. DETERMINATION OF SILICON. j^ pumice-stone, and the third pumice saturated with strong H 2 SO 4 . The outlet-tube from the latter leads into the porcelain or glass tube in the furnace. This tube contains small lumps of char- Purification coal or gas carbon, kept in position by loosely-fitting plugs of f r0 mo. asbestos,' and occupying about 8 inches (200 mm.) in the middle of the tube. The outlet-tube from this connects with the drying-tubes on the second stand, which contain pumice moist- ened with strong H 2 SO 4 . The outlet from the second drying- tube connects with the glass combustion-tube, which leads through the second furnace, and is bent at a right angle where it is connected with the large tubes, half filled with water. The apparatus being in order, * start a slow current of chlorine Details of through the apparatus by blowing HC1 from the bottle into the method. flask and filling the dish in which the latter stands with water. Light a low light under the dish, and open the stopcock wide enough to allow a very slow current to bubble through the bulbs. Light the burners of the first furnace so that the tube is heated to dull redness. When the apparatus is full of chlorine, weigh i gramme of pig-iron, or 3 grammes of steel, into a porcelain boat about 3 inches long, distributing the drillings evenly along the bottom of the boat. Remove the stopper at the rear end of the second tube and insert the boat to about the centre. Replace the stopper, and continue the current of chlorine in the cold for ten or fifteen minutes to make sure that no oxygen remains in the tube, then light the burner under the forward end of the boat. The heat must be just sufficient to volatilize the ferric chloride, which should condense in the cooler part of the tube, and the current of gas should be slow enough to prevent any ferric chloride from being carried for- ward into the water-tubes or any loss of carbon from the boat. * All the stoppers used should be of rubber coated with paraffine on the ends, or of asbestos, and where glass tubes are joined together with rubber the ends of the glass tubes should be brought into close contact. 7 6 ANALYSIS OF IRON AND STEEL. When the fumes of ferric chloride begin to come off more slowly, light the next burner, and continue until all the burners under the boat are lighted, maintaining the heat until the fumes of ferric chloride cease. The tube for the entire length occupied by the boat should be at a dull red heat. Should the condensed ferric chloride at any time choke the tube so as to prevent the passage of the gas, heat that part of the tube gently with a spirit-lamp, so as to drive the ferric chloride a little farther along the tube. When the fumes of ferric chloride are no longer given off from the boat, the operation may be considered finished. Turn out the lights under the tube containing the boat, remove the stopper, and draw out the boat, which now contains the carbon, the slag, and the greater part of the manganese (as Residue in Mnd 2 ) which were contained in the iron or steel. This residue boat avail- able for may be used for the determination of the carbon or the slag, donofc as will be shown farther on. If another determination is to be >ag ' made, another tube may be substituted for the one which con- tained the boat, and the analysis carried out in the manner described above. If not, put out all the lights, close the stopcock, and withdraw the combustion-tube with the water- tubes. Remove the stoppers from the latter, and pour the con- tents of these tubes into a platinum dish containing a small amount of an aqueous solution of sulphurous acid, to prevent the chlorine in the solutions from acting on the platinum. Rinse the tubes into the dish, and if any silica has separated out and adheres to the water-tubes or to the end of the com- bustion-tube, loosen it with a " policeman" and wash it into the dish. Add 5 c.c. strong H 2 SO 4 , evaporate to dryness, and heat until fumes of SO 3 are given off. Allow the dish to cool, add 100 c.c. cold water, and filter off on a small ashless filter any SiO 2 , which burn and weigh as such. Calculate to Si. The Separation filtrate from the SiO 2 will contain any TiO 2 which may have from TiO 2 . been in the metal and which can be 'determined, as will be shown farther on. Silicon and titanium are volatilized as RAPID METHOD FOR SILICON. chlorides, SiCl 4 and TiCl 4 , under the conditions shown above, and decomposed by water thus: SiCl 4 + 2H 2 O = 4HC1 + SiO 2 and TiCl 4 + 2H 2 O = 4HC1 + TiO 2 . tion by H,0. Rapid Method for Determination of Silicon. (S. Alfred Ford.*) At the Edgar Thomson Steel-Works the molten pig-metal is taken directly from the furnaces to the converters, and it is generally necessary to determine the amount of silicon in the pig-iron as a guide in blowing the metal. To get the sample Method of for analysis, a small ladle is dipped into the iron as it runs from ^f e the furnace, and a small quantity of molten iron is taken. The ladle is then held about three feet above a bucket of water, and the molten metal drooped into the water, at the same time giving the ladle a circular motion over the bucket. This will cause the Appearance of shot de- iron to form in globules, more or less round according to the pending amount of silicon contained in the iron. Thus, with iron which si" contains 2 per cent, of silicon or more, the globules will be almost perfectly round, concave on the upper surface, and gen- erally from j{ inch (6 mm.) to ^ inch (9 mm.) in diameter; while if the iron be low in silicon, the shot or drops will be very small, flat, and irregular in shape, and if the iron be very low in silicon, as is the case with spiegel and ferromanganese, the shot will be elongated and have tails sometimes *^ inch (6 mm.) in length. In fact, a close observer can soon judge very closely as to the amount of silicon from the condition of these shot or drops. The next step in the process is to take the shot from the bucket and place them for a minute in the ladle which has been used to dip up the molten iron. The ladle, being hot, will dry the shot almost instantly. The shot are then placed Pulverizing in a large steel mortar (Fig. 7, page 17) and crushed. The ple . crushed shot are then sifted with a fine sieve, and .5 gramme * Prepared by Mr. Ford for this volume. 78 ANAL YSIS OF IRON AND STEEL. Determina- of the fine siftings are placed in a platinum evaporating-dish, 10 tion of the Si. c.c. HC1, 1.2 sp. gr., are then added, and the dish covered with a watch-glass. The dish is then placed over a light, and the iron dissolved ; as soon as solution takes place, which requires about one minute, as the particles of iron are so small, the watch- glass is removed and the solution evaporated to dryness as rapidly as possible over a naked light ; as soon as dry, not even waiting for the dish to cool, dilute HC1 is dropped on the chloride of iron, and as soon as all the sesquioxide of iron (which may have been formed by the decomposition of the chlo- ride) is dissolved, water is added. The contents of the dish are then poured on a filter, to which is attached a pump, filtered, and washed. The filter and its contents are then placed in a Burning c weighed platinum crucible, placed over a blast-lamp ; as soon of o. as the filter-paper is burned off, the crucible is turned on its side, the lid removed, and a small jet of oxygen is driven very gently into the crucible. As soon as what little carbon there is in the precipitate is burned off, the crucible is cooled and weighed, and the amount of silicon calculated from the weight of the silica in the crucible. Time re- By this method the amount of silicon in a pig-iron can be quired for determi- determined in twelve minutes from the time the ladle is put nation O f si. into the molten iron, and it gives results close enough for prac- tical purposes. DETERMINATION OF SLAG AND OXIDES. Presence of A certain amount of slag and oxide of iron is always present and steel, in puddled iron as a mechanical admixture. It is also found, as a general thing, in basic steel, and the presence of slag in steel made by the acid process, as well as in pig-iron, is not unusual. The easiest method for the determination of these substances is by solution in iodine, as suggested by Eggertz. DETERMINATION OF SLAG AND OXIDES. By Solution in Iodine. Weigh 5 grammes of borings free from lumps into a No. 2 Details of Griffin's beaker. Stand the beaker, carefully covered with a method, watch-glass, in a dish filled with scraped ice or snow, so that the bottom and sides of the beaker half-way up shall be in contact with it. Pour over the iron in the beaker 25 c.c. of ice-cold boiled water, and stir until all the air in the borings has escaped. Add gradually 28 or 30 grammes of resublimed iodine,* stirring occasionally, until all the iodine has dissolved. Keep the beaker constantly surrounded by ice, and add the iodine slowly enough to prevent any rise in the temperature of the solution. Stir the solution frequently until the iron is perfectly dissolved, which will take several hours; then add 100 c.c. cold boiled water, allow the insoluble matter to settle, and decant the supernatant fluid on a small ashless filter. Wash the insoluble matter several times, by decantation, with cold water, then add to it a little insuring total solu- water, with a few drops of HC1, and observe whether any hydro- tionofFe. gen is disengaged. If none can be perceived, the metallic iron may be considered entirely dissolved ; but if gas is given off, the opposite is the case. In either event, quickly decant the acidulated water on the filter, and if any metallic iron remains, add a very little water and some iodine to dissolve the iron entirely. Then transfer the insoluble matter, consisting of graphite, carbonaceous matter, slag, oxide of iron, and some Separation silica, to the filter, wash the filter once with very dilute HC1 (i acid to 20 water), and finally with cold water, until the filtrate is free from iron. Unfold the filter, and with a fine jet wash the insoluble matter off into a small platinum or silver dish. Evaporate almost to dryness, add 50 c.c. solution of caustic potassa, sp. gr. i.i, and boil five or ten minutes. Decant the liquid on a very small ashless filter, repeat the boiling with * Page 41. 3 O ANALYSIS OF IRON AND STEEL. fresh caustic potassa, transfer the insoluble matter to the filter, and wash well with hot water. Wash once with dilute HC1 (i acid to 20 water), and finally with hot water, until the filtrate gives no precipitate with a solution of nitrate of silver. Dry, ignite, and weigh as Slag and Oxide of Iron. Instead of using iodine directly for the solution of the iron, Use of iodine a solution of iodine in iodide of iron, as suggested by Eggertz,* in iodide of iron as a may be used to great advantage, as it affords a ready method for getting rid of the impurities usually present in resublimed iodine. Treat 5 grammes of iron (as free as possible from silicon) with 25 grammes of iodine, and, when the solution is complete, add 30 grammes more of iodine, which will dissolve in the iodide of iron in a few minutes. Dilute to 50 c.c. with cold boiled water and filter through a washed filter. Add the filtrate at once to 5 grammes of the weighed sample, and, after solution is complete, proceed as directed above. By Volatilization in a Current of Chlorine Gas. Proceed exactly as in the method for the determination of silicon (pages 74 et seq.} until the boat is withdrawn from the washing out combustion-tube. Wash the contents of the boat into a small chlorides, beaker with a jet of cold water, and filter on a small ashless filter. The water dissolves any soluble metallic chlorides, MnCl 2 , CaCl 2 , etc., which are not volatile at a low red heat, and the insoluble matter in the filter consists of slag and carbon. Burn off the carbon and weigh the residue as Slag and Oxides. Or, Using coun- if the carbon has been determined by another operation, filter terpoised filters. the carbon and slag on a counterpoised filter j or on a Goocn crucible, dry at 100 C., and weigh as Carbon, Slag, and Oxides; by subtracting the weight of the carbon the difference is Slag and Oxides. * Jern-Kontorets Annaler, 1 88 1, p. 301, and Chem. News, xliv. 173. f See page 27. DETERMINATION OF PHOSPHORUS. OF Q T DETERMINATION OF PHOSPHORUS. For the determination of phosphorus in iron and steel but two methods are in general use, either of which, properly carried out, will give extremely accurate results. Some chemists prefer one method, some the other, while a combination of the two is sometimes used. The two general methods are known respectively as the Acetate Method and the Molybdate Method. Methods in There are innumerable variations in the details, especially of the latter method, but any departure from what might be termed the standard instructions should never be attempted by any but a very experienced analyst. The Acetate Method. The essential parts of this method were suggested by Fre- senius,* the changes and improvements in details being the work of many chemists.t Treat 5 grammes of drillings in a No. 4 Griffin's beaker with Detailsof the acetate 80 c.c. HNO 3 (1.2 sp. gr.), and, when violent action has ceased, method. add 10 c.c. strong NCI. Evaporate the solution to dryness in the air-bath, replace the cover, and heat until the nitrate of iron is nearly all decomposed. Cool, add 30 c.c. HC1, heat gradually until the oxide of iron is dissolved, and evaporate to dryness again in the air-bath. Cool, dissolve in 30 c.c. HC1, dilute, and, in steels or puddled iron, when silicon is to be determined, filter, and treat When si is to be de- the insoluble matter as directed for the determination of Si, page 72. In the case of pig-irons which may contain titanium, filter, and keep the residue of graphite, silica, etc., for treatment, as directed farther on, " when titanium is present." In the case of steels, when silicon is not to be determined when si is not to be in this portion, the solution need not be filtered at all, but may deter- be diluted at once to about 250 c.c. * Jour, fiir Pr. Ch., xlv. 258. f Tenth Census of the U. S., vol. xv. " Iron Ores of the U. S.," p. 523. 6 IS present. 32 ANALYSIS OF IRON AND STEEL. In any case, heat the filtered or unfiltered HC1 solution nearly to boiling, remove the beaker from the light, and add gradually from a small beaker a mixture of 10 c.c. NH 4 HSO 3 * and 20 c.c. NH 4 HO, stirring constantly. The precipitate, which forms at first, redissolves, and when all but about 2 or 3 c.c. of the NH 4 HSO 3 solution has been added, replace the beaker Deoxidiz- over the light. If at any time while adding the NH 4 HSO 3 solution, solution the precipitate formed will not redissolve even after vigorous stirring, add a few drops of HC1 ; and, when the solu- tion clears, continue the addition, very slowly, of the NH 4 HSO 3 . After replacing the beaker on the light, add to the solution (which should smell quite strongly of SO 2 ) NH 4 HO, drop by drop, until the solution is quite decolorized, and until finally a slight greenish precipitate remains undissolved even after vig- orous stirring. Now add the remaining 2 or 3 c.c. of the NH 4 HSO 3 solution, which should throw down a white precipi- tate, which usually redissolves, leaving the solution quite clear and almost perfectly decolorized. Should any precipitate remain undissolved, however, add HC1, drop by drop, until the solution clears, when it should smell perceptibly of SO 2 . If the reagents are used in exactly the proportions indicated, the reactions will take place as described, and the operations will be readily and quickly carried out. If the solution of NH 4 HSO 3 is weaker than it should be, of course the ferric chloride will not be reduced, and the solution, at the end of the operation described above, will not be decolorized and will not smell of SO 2 . In this case add more of the NH 4 HSO 3 (without the addition of NH 4 HO) until the solution smells strongly of SO 2 , then add NH 4 HO until the slight permanent precipitate appears, and redissolve it in as few drops of HC1 as possible. The solution being now very nearly neutral, the iron in the ferrous condition, and an excess of SO 2 being present, add to the solution 5 c.c. * See page 44. DETERMINATION OF PHOSPHORUS. 3^ of HC1 to make it decidedly acid and to insure the complete decomposition of any excess of the NH 4 HSO 3 which may be present. Boil the solution,* while a stream of CO 2 passes Boiling off through it, until every trace of SO 2 is expelled, then pass a ^^ current of H 2 S through it for about fifteen minutes to precipi- FIG. 50. tate any arsenic which may be present, and finally allow the solution to stand in a warm place until the smell of H 2 S has disappeared, or, better, pass a current of CO 2 through the * By passing a current of CO 2 through the boiling solution the SO 2 is soon ex- pelled, and the operation requires no watching. ing the As. 8 4 ANALYSIS OF IRON- AND STEEL. solution, which will expel the H 2 S in a few minutes. The arrangement, Fig. 50, is convenient for this purpose. Filter from any As 2 S 3 , CuS, S, etc., into a No. 5 beaker, wash with cold water, and to the filtrate add a few drops of bromine-water, and cool it by placing the beaker in cold water. To the cold solution add NH 4 HO from a small beaker very slowly, and finally drop by drop, with constant stirring. The green pre- cipitate of ferrous hydrate which forms at first is dissolved by stirring, leaving the solution perfectly clear, but subsequently, drate. although the green precipitate dissolves, a whitish one remains, and the next drop of NH 4 HO increases the whitish precipitate or gives it a reddish tint, and finally the greenish precipitate remains undissolved even after vigorous stirring, and another drop of NH 4 HO makes the whole precipitate appear green. If before this occurs the precipitate does not appear decidedly red in color, dissolve the green precipitate by a drop or two of HC1, and add a little bromine-water (i or 2 c.c.), then add NH 4 HO as before, and repeat this until the reddish precipitate is obtained, and then the green coloration as described above. Dissolve this green precipitate in a very few drops of acetic acid (sp. gr. 1 .04), when the precipitate remaining will be quite red in color, then add about I c.c. of acetic acid, and dilute the solu- tion with boiling water, so that the beaker may be about four- Filtering and fifths full. Heat to boiling, and when the solution has boiled riieVr" 8 one minute, lower the light, filter as rapidly as possible through a 5^-inch (i4O-mm.) filter, and wash once with hot water. The filtrate should run through clear, but in a few minutes it will appear cloudy by the precipitation of the ferric oxide, which has been formed by the exposure of the filtered solution to the Precautions, air. The points to be observed are the red color of the precipi- tate and the clearness of the solution when it first runs through. Ferric phosphate being white, the red color of the precipitate shows that enough ferric salt was present in the solution to form ferric phosphate with all the phosphoric acid, and enough DETERMINATION OF PHOSPHORUS. 35 more to color the ferric phosphate red with the excess of ferric oxide. When the precipitate has drained quite dry, pour about 15 c.c. of HC1 into the beaker in which the precipitation was made, warm it slightly so that the acid may condense on the sides and Solution of the prccip" dissolve any adhering oxide, wash off the cover into the beaker, Hate. add about 10 c.c. of bromine-water, pour this on the filter con- taining the precipitate, allowing it to run around the edge of the filter, and let the solution run into a No. I Griffin's beaker. Wash out the beaker once or twice, and then wash the filter well with hot water. If the acid in the beaker is not sufficient to dissolve the precipitate completely, drop a little strong acid around the edge of the filter before washing it with hot water. The scaly film of difficultly soluble oxide which sometimes forms cause of on boiling the acetate precipitate is caused by the presence of cu i t i y sol . too much acetate of ammonium, but when the instructions given above are carefully carried out it never appears. Evaporate the solution in the small beaker nearly to dryness to get rid of the excess of HC1, add to it a filtered solution of 5 or 10 grammes of citric acid (according to the size of the precipitate of Fe 2 O 3 , etc.) dissolved in 10 to 20 c.c. of water, then 5 to 10 c.c. of magnesia-mixture and enough NH 4 HO to make the solution faintly alkaline. Stand the beaker in cold water, and when the solution is perfectly cold, add to it one-half its volume of strong NH 4 HO and stir it well. When the precipitate of Predpita- Mg 2 (NH 4 ) 2 P 2 O 8 has begun to form, stop stirring, and allow it to thM g , stand in cold water for ten or fifteen minutes, then stir vigorously ^ 4)s several times at intervals of a few minutes, and allow it to stand overnight. Filter on a small ashless filter, and wash with a mixture of 2 parts of water and I part of NH 4 HO containing 2.5 grammes of NH 4 NO 3 to 100 c.c. Dry the filter and precipitate, and ignite them at a very low Filtering and burn- temperature at first so as to carbonize the filter without decom- ingthe posing the precipitate, which may then be readily broken up tate . 86 ANALYSIS OF IRON AND STEEL. Treatment soluble Treatment with a platinum wire. Raise the heat gradually, and finally ignite at the highest temperature of the Bunsen burner. When the precipitate is perfectly white, cool and weigh. Then fill the crucible half full of hot water, add from 5 to 20 drops of HC1, and heat until the precipitate has dissolved. Filter off on another small, ashless filter any SiO 2 or Fe 2 O 3 that may remain, ignite, and weigh. The difference between the two weights is the weight of Mg 2 P 2 O 7 , which, multiplied by 0.27836, gives the weight of P. When Titanium is Present. When a solution of ferric chloride containing TiO 2 and P 2 O 5 is evaporated to dryness, a compound of TiO 2 ,P 2 O 5 and Fe 2 O 3 is formed, completely insoluble in dilute HCL* Iron ores and pig-irons containing TiO 2 require, therefore, a somewhat different method of treatment from that given above. Dry and ignite the residue of graphite, silica, etc., from the solution of the pig-iron, so as to burn off all the carbon. Moisten this residue with cold water, add 5 to 10 drops of H 2 SO 4 and enough HF1 to dissolve the silica, and evaporate until fumes of SO 3 are given off. While this is going on, proceed with the deoxidation of the filtrate as described above, but when the SO 2 has been driven off do not pass H 2 S through the solution, but cool it, and proceed with the acetate precipitation. Instead of dissolving the precipitate, after washing it as described above, dry th e filter and precipitate in the funnel, being careful not to heat it so as to scorch the filter. Clean out any of the precipitate which may have adhered to the sides of the beaker in which the precipitation was made, by wiping it with filter-paper, and dry this paper with the filter and precipitate. When the precipitate is quite dry, transfer it to a small por- celain mortar. The precipitate may be readily detached from * Published in Report on Methods employed in the Analysis of the " Iron Ores," Tenth Census U.S., vol. xv. p. 512. I first noted this fact in 1878. DETERMINATION OF PHOSPHORUS. g* the filter by rubbing the sides of the latter together over a large piece of white, glazed paper, so that any little particles that fall out may be seen. Roll up the filter with the bits of paper which were used to wipe out the beaker, wrap a piece of platinum wire around it, burn it on the lid of the crucible in which the graphitic residue was treated, and transfer the ash to the mortar. Grind the precipitate and ash with 3 to 5 grammes of Na 2 CO 3 Fusion of the precipi- and a little NaNO 3 , and transfer it to the crucible containing tate. the residue which was treated by HF1 and H 2 SO 4 . Clean the mortar and pestle by grinding a little more Na 2 CO 3 , and add this to the other portion in the crucible. Fuse the whole for half an hour or more, cool, dissolve the fused mass in hot water, filter from the insoluble Fe 2 O 3 , etc.,* acidulate the filtrate with HC1, add a few drops of NH 4 HSO 3 , boil off all smell of SO 2 , and pass H 2 S through the hot solution to precipitate any arsenic that may be present. Pass a current of CO 2 through the solu- Precipita- tion to expel the excess of H 2 S, filter off the As 2 S 3 , and to the AS. filtrate add a sufficient amount of Fe 2 Cl 6 solution to combine with all the P 2 O 5 as Fe 2 (PO 4 ) 2 and leave a slight excess. Add a slight excess of NH 4 HO, which should throw down a red precipitate, while- the solution is alkaline to test-paper ; then add acetic acid to slightly acid reaction, boil, and filter off the Fe 2 (PO 4 ) 2 and Fe 2 O 3 , and wash with hot water. Dissolve the precipitate in HC1, allow the solution to run into a small beaker, Predpita- . , t . tion of the evaporate until the solution is syrupy, add citric acid and mag- M g2 nesia-mixture, and precipitate the Mg 2 (NH 4 ) 2 P 2 O 8 as described pj^ above. Unless the amount of phosphorus is very small, a second fusion of the insoluble residue of Fe 2 O 3 , etc., is necessary. The Necessityfor two filtrates can then be added together, acidulated with HC1, and the remainder of the process carried out as directed above. To avoid the fusion of the acetate precipitate with Na 2 CO 3 , which * This Fe 2 O 3 , etc., contains all the titanium that was in the pig-iron as titanate of soda, and must be kept for the estimation of that element when it is to be determined. 88 ANALYSIS OF IRON AND STEEL. is always troublesome, the method for the determination of phosphorus may be modified (in many cases with advantage, and generally when titanium is not to be estimated) as follows : After filtering off the insoluble matter, graphite, silica, etc., ignite it, burn off the graphite, and treat the residue with HF1 and H 2 SO 4 , evaporate down until the excess of H 2 SO 4 is driven off, and fuse with Na 2 CO 3 . Treat the fused mass with water, and filter. Acidulate the filtrate with HC1, and add it to the main Method to solution, which has been deoxidized in the mean time with bisul- phite of ammonium. Expel the last traces of SO 2 from the um ted filtrates by boiling and passing a current of CO 2 through acetate he solution, as previously directed. If the solution remains clear, precipi- tate - pass H 2 S through it, and filter off the precipitated sulphides. Cool the solution, and make the acetate precipitation as directed Tendency of on page 84. The only danger to be apprehended now is the TiO 2 to separate tendency of titanic acid to separate out and carry phosphoric acid with it when in the evaporation of the HC1 solution of the acetate precipitate the liquid becomes concentrated. To avoid this, the evaporation must be watched very carefully, and citric acid added as soon as the titanic acid begins to separate. Then, if the separation has not proceeded too far, the phosphoric acid may be precipitated in the usual way. If, however, the separation of titanic acid is not checked in time, proceed with the evapo- ration as directed on page 85, add 5 c.c. strong HC1, and warm gently. The solution will nearly always clear, but if it does not, then add citric acid and a slight excess of ammonia, and filter. Stand the filtrate aside, burn off and fuse the precipitate with Na 2 CO 3 , dissolve in. water, filter, acidulate the filtrate with HC1, add a little Fe 2 Cl 6 solution, a slight excess of ammonia, and acidulate with acetic acid. Boil, filter off the precipitate of phosphate and oxide of iron, dissolve in a little HC1, allow the solution to run into a small beaker, evaporate down, and add it to the ammoniacal filtrate from the separated titanic acid obtained above. Add excess of magnesia-mixture, and precip- DETERMINATION OF PHOSPHORUS. 8 9 itate the phosphoric acid in the usual way. When the solution other sources of becomes cloudy after deoxidation with NH 4 HSO 3 , and remains error. so after acidulating with HC1, proceed as directed above, but dry, and ignite the filter containing the precipitate by H 2 S and that on which the acetate precipitate was filtered, fuse with Na 2 CO 3 , treat with water, filter, acidulate with HC1, pass H 2 S through the solution, filter, add a little Fe 2 Cl 6 solution, and pre- cipitate by ammonia and acetic acid. Add the solution of this precipitate, after filtering it off, to the solution of the main acetate precipitate, and proceed as before. Instead of adding citric acid and magnesia-mixture to the Removing solution of the acetate precipitate, Fresenius,* and afterwards Fes before Spiller,t advised the method of adding citric acid, excess of ammonia, and sulphide of ammonium, filtering off the precipi- tated sulphide of iron, and, after evaporating to small bulk, adding magnesia-mixture and ammonia. When the bulk of the iron precipitate is not too great, this is quite unnecessary, for Shown to be many determinations have shown that with an excess of mag- sar y- nesia-mixture, ammonium magnesium phosphate is absolutely insoluble in both citrate of iron and ammonium and citrate of aluminium and ammonium. The precipitate is also insoluble in ammonia- water (i part of NH 4 HO to 2 parts of water). The Molybdate Method. Svanberg and StruveJ first discovered the reaction on which this method is based, and Sonnenschein first used it quantita- tively. Weigh 5 grammes of drillings into a No. 4 Griffin's beaker, and add, with the proper precautions (page 65), 40 c.c. strong HNO 3 . Instead of using HC1 to hurry the solution, it solution. is better, when the action slackens, to add water very cautiously * Jour, fur Pr. Chem., xlv. 258. f Jour. Chem. Soc. (2), iv. 148. J Jour, fur Pr. Chem. xliv. 291. g Jour, fur Pr. Chem., liii. 339. 9 o ANALYSIS OF IRON AND STEEL. from time to time until the metal is completely dissolved. Evapo- rate to dryness in the air-bath, replace the cover, and heat for one hour at a temperature of about 200 C. in order to decom- Destroying pose all the carbonaceous matter,* otherwise the precipitation bonaceous of the phospho-molybdate will be incomplete. Allow the beaker to cool, dissolve the precipitate in 30 c.c. HC1, evaporate to dry- ness to render the silica insoluble, redissolve in 30 c.c. HC1, Removal of and evaporate carefully until the excess of HC1 is driven off, shaking the beaker from time to time to prevent the forma- tion of a crust of dry chloride of iron. Cool the beaker, and dilute the solution with twice its volume of cold water. Filter on a small, washed German filter, 3-inch (7 5 -mm.), or on the Gooch crucible. In the latter case the precipitation of the phospho-molybdate may be made in the small flask into which the solution is filtered. The washing should be done with cold water after dropping a little dilute HC1 around the edge of the Volume of filter. The filtrate and washing should not exceed 50 or 60 c.c. aon. in volume. Add to the solution 50 to 100 c.c. molybdate solu- tion,f heat it to 40 C. in a water-bath carefully kept at this ture of the solution, temperature, and allow it to stand in the bath for about four hours. Filter on a small, washed filter, and wash thoroughly with dilute molybdate solution (i part of solution to I part of water) until a drop of the filtrate gives no reaction for iron with ferrocyanide of potassium. Stand the filtrate aside in a warm place to see whether any further precipitation of phospho- Soiutionof molybdate of ammonium takes place; if it does, it must be filtered off and treated like the main precipitate. Pour 2 or 3^ c - c - strong NH 4 HO on the precipitate, stir it up with a fine jet of hot water, and allow the solution to run into the flask or beaker in which the precipitation of phospho-molybdate was * In 1877 I discovered the necessity for destroying the carbonaceous matter, and communicated the fact to Hunt and Peters, who mentioned it in the Metallurgical Review, vol. ii. p. 365. f See page 59. DETERMINATION OF PHOSPHORUS. QJ made. When it has all run through the filter, replace the flask or beaker by a small beaker of a little over 100 c.c. capacity, remove any phospho-molybdate that may have adhered to the sides of the original flask or beaker, by means of the ammoni- acal filtrate, and then pour this back on the filter and allow it to run through into the small beaker. Wash out the beaker or flask with hot water and pour it on the filter with the addition of a little more NH 4 HO. Unless the precipitate of phospho- molybdate is very large, this amount of NH 4 HO should dis- solve it, and a very little more washing should be sufficient. If the precipitate is very large, it may be necessary to use more Volume of NH 4 HO and more wash-water, but under all circumstances the niacaiso- amount of NH 4 HO and of wash-water should be as small as is consistent with perfect solution of the precipitate and thorough washing of the beaker and filter. When the precipitate is small, the filtrate and washings should amount to about 25 c.c. Neutralize the solution with strong HC1 ; if the yellow phospho- ^ molybdate begins to precipitate, add NH 4 HO until it redissolves, and if there should remain a flocculent white precipitate, prob- ably silica, after the solution is quite alkaline, filter it off. Then to the cold alkaline liquid add, very slowly, 10 c.c. magnesia-mixture, stirring constantly, and after the magnesia- mixture is all in, add one-third the volume of the solution of P2 8 ' strong NH 4 HO and stir vigorously. It is well to stand the beaker in cold water and stir the solution several times after the precipitate has begun to crystallize out. After standing about four hours, it may be filtered off on a very small ashless filter and washed with dilute ammonia- water (i part NH 4 HO to 2 parts water) containing 2.5 grammes nitrate of ammonium to the 100 c.c. Dry, ignite very carefully to burn off the carbon- Filtration aceous matter, and finally heat for ten minutes over the blast- lamp to volatilize any molybdic acid that may have been precipitated with the Mg 2 (NH 4 ) 2 P 2 O 8 , cool, and weigh. Fill the crucible half full of hot water, add 5 to 20 drops HC1, and 9 2 ANALYSIS OF IRON AND STEEL. date. heat for a few minutes to dissolve the Mg 2 P 2 O 7 . Pour the contents of the crucible on a small ashless filter, wash, ignite, and weigh the small residue that may remain undissolved. The difference between the two weights is the weight of Mg 2 P 2 O 7 , which contains 27.836 per cent, phosphorus. Direct Many chemists, following Eggertz,* prefer to weigh the of the yellow phospho-molybdate direct instead of dissolving it and precipitating as Mg 2 (NH 4 ) 2 P 2 O 8 . In this event take I gramme of the drillings and proceed exactly as directed above, but use only about one-third the amount of HNO 3 and HC1 for the solution. Before adding the molybdate solution, the volume of the filtrate from the silica should amount to only about 25 c.c. Add 50 c.c. of the molybdate solution, allow it to stand four hours at a temperature of 40 C., and filter off the precipitated phospho-molybdate on a Gooch crucible; wash first with dilute molybdate solution, and finally with water containing I per cent, of HNO 3 , dry in an air-bath heated to 120 C., and weigh as (NH 4 ) 3 uMoO 3 PO 4 (approximate formula), containing 1.63 per cent, of phosphorus. In the absence of a Gooch crucible, use counterpoised filters f for weighing the phospho-molybdate. The points of special importance are : First, the necessity for destroying all the carbonaceous matter by heating the nitric acid solution, after evaporation, to a suffi- ciently high temperature to effect this with certainty. Second, the avoidance of an excess of HC1 in the final solu- tion before precipitating by molybdate solution. Third, when the phospho-molybdate is weighed directly, the necessity for rendering the silica insoluble. Fourth, the danger of heating the solution above 40 C. after adding the molybdate solution, as arsenic, when present, precipitates with the phosphorus if the solution is heated to a higher temperature. Precautions necessary. * Jour, fur Pr. Chem., Ixxix. 496. f See page 28. DETERMINATION OF PHOSPHORUS. 93 Fifth, the danger of causing a precipitation of molybdic acid with the phospho-molybdate by heating the solution to a tem- perature approximating 100 C. Some chemists prefer to drive off the HC1 entirely by adding variations HNO 3 to the hydrochloric acid solution, and boiling down detafli. nearly to dryness once or twice before filtering off the silica. Others, after filtering off the silica, add NH 4 HO until a slight permanent precipitate appears, then the molybdate solution, which is sufficiently acid to redissolve the slight precipitate of ferric hydrate, and leave the solution quite clear, with the exception of the precipitate of phospho-molybdate. Others supersaturate the hydrochloric acid solution with NH 4 HO, and redissolve with the least possible amount of HNO 3 before adding the molyb- date solution. Many of these are matters of personal preference, but the safest plan for the beginner is to follow the instructions first given until he has sufficient knowledge and experience to judge of the value of these variations, or to invent some for himself. The Combination Method. Riley* was the first to suggest the precipitation of phos- . phorus as phospho-molybdate, preceded by a separation of the phosphoric acid from the mass of the ferric chloride by deoxi- dation and precipitation by the acetate method. This method was worked out afterwards by A. Wendel, of the Albany and Rensselaer Steel Company, S. Peters, of the Burden Iron Com- pany, and J. L. Smith.f Proceed as directed for the determination of phosphorus by Details of the the Acetate Method, using I gramme of borings and proper- method, tional amounts of reagents until having dissolved the acetate precipitate in HC1, evaporate to dryness, redissolve in a very little HNO 3 , dilute to 20 c.c. with water, add a slight excess of NH 4 HO, redissolve the precipitated ferric oxide in HNO 3 , * Jour. Chem. Soc., 1878, vol. i. p. 104. f Chem. News, xlv. 195. 94 ANAL YSIS OF IRON AND STEEL. and add 30 c.c. molybdate solution. Heat to 40 C. for an hour, filter, wash with water containing I per cent, of HNO 3 , dry, and weigh. When Titanium is Present. When phosphorus is determined in pig-irons containing tita- nium, burn off the residue of carbon, silica, etc., treat it with HF1 and H 2 SO 4 , evaporate, and heat until the greater part of the H 2 SO 4 is driven off. Fuse with 2 or 3 grammes of carbonate of sodium, dissolve in water, filter, acidulate the filtrate with HNO 3 , add 50 c.c. molybdate solution, and heat to 40 C. for four hours. Filter, wash, and add this precipitate to the one obtained in the filtrate from the carbon, silica, etc. If any slight insoluble matter should remain on the filter upon dissolving in NH 4 HO the phospho-molybdate obtained in the filtrate from the carbon, silica, etc., burn it, fuse it with carbonate of sodium, and test it also for phosphorus. As remarked above, page 92, the formula given for the dried Variable phospho-molybdate of ammonium is approximate only. The composi- don of the composition of the salt seems to vary very much, the percentage moyb-~ f phosphorus in it being given by various authorities from 1.27 to 1.75. It seems to depend upon various circumstances, such as the presence or absence of HC1 in the solution, the degree of acidity, the temperature at which the precipitation is effected, the length of time the solution stands before the pre- cipitate is filtered off, the size of the precipitate, the state of concentration of the solution, and even the amounts of the iron and ammonium salts present. The precau- This fact must be borne in mind when the phosphorus is tions it ne- cessitates, determined by direct weighing of the phospho-molybdate, and every effort must be used to effect the precipitations always under as nearly as possible the same conditions. RAPID METHODS FOR PHOSPHORUS. 95 FIG. 51. RAPID METHODS. Volumetric Method.* This method gives an indirect determination of P by means of the estimation of the MoO 3 in the phospho-molybdate of ammonium, in which form the P is precipitated. The MoO 3 is reduced to a lower state of oxidation by the reducing action of Zn and H 2 SO 4 , and the reduced oxide is titrated with a standardized permanganate solution, MoO 3 being again formed by the reaction. Fig. 51 shows a form of shaking-ma- chine for shaking four flasks at once. The construction and method of use are ap- parent from the sketch. Fig. 52 shows a form of reductor which is most convenient and efficient The tube a is 0.018 m. in inside diameter and 0.300 m. long. The small tube below the contraction with the stopcock c is 0.006 m. in inside di- ameter and o.ioo m. long below the stopcock. The tube is filled by placing at the point of contraction a flat spiral of platinum * This method is the one prepared by the sub-committee on Methods of the Inter- national Steel Standards Committee of the United States. It is by far the best method known, and the results obtained by it are exceedingly accurate when the details are carefully observed. The sub-committee consists of W. P. Barba, A. A. Blair, T. M. Drown, C. B. Dudley (chairman), and P. W. Shimer. 9 6 ANAL YSIS OF IRON AND STEEL. wire which nearly fills the tube and from the centre of which a perpendicular wire extends downward a few millimetres into the small tube. On top of this is placed a plug of glass wool, about 0.008 m. thick, and then asbestos, previously treated with con- centrated hydrochloric acid, thoroughly washed, ignited, and dif- fused in water, is poured into the reductor tube until it forms a coating on top of the glass wool not over o.ooi m. thick. This FIG. 52. FIG. 53. makes a filter which prevents very small pieces of zinc or other materials from being carried through. It is necessary to clean and refill the tube from time to time, as the filter after some use becomes clogged and the liquid passes too slowly. The tube is filled to within 0.050 m. of the top with granulated amalgamated zinc, and a plug of glass wool is placed on top of the zinc which prevents all spattering of the solution on the upper part of the RAPID METHODS FOR PHOSPHORUS. tube. The funnel b, which should be not less than o.ioo m. in diameter across the top, is fitted tightly into the reductor tube by means of a rubber stopper, as shown in the cut. The reductor tube is fixed at such a height that when the block is removed from under the flask /, the latter may be readily detached from the tube and removed without disturbing the apparatus. Fig. 53 shows the burette arranged for running the potassium permanganate directly into the flask and needs no explanation. It should be carefully calibrated. The various beakers, flasks, graduates, etc., required by this method need no special comment. Reagents. Nitric Acid. Nitric acid of 1.135 S P- g r -> made by mixing C. P. nitric acid 1.42 specific gravity with about three parts of distilled water. Strong Sulphuric Acid. The C. P. material of 1.84 sp. gr. Dilute Sulphuric Acid. Sulphuric acid 2j^ per cent., by volume, made by adding 25 c.c. of concentrated C. P. sulphuric acid to i litre of distilled water. Strong Ammonia. The C. P. material of 0.90 sp. gr. Dilute Ammonia. 0.96 sp. gr., made by mixing concentrated C. P. ammonia water of 0.90 sp. gr., with about one and a half times its volume of distilled water. Strong Solution of Potassium Permanganate, for oxidizing the phosphorus and carbonaceous matter in the nitric acid solution of a steel. Made by dissolving 12.5 to 15 grammes of crystallized potassium permanganate in i litre of distilled water and filtering through asbestos. Standard Solution of Potassium Permanganate for titrating the reduced solutions of ammonium phosphomolybdate. Made by dissolving 2 grammes of crystallized potassium permanganate in I litre of distilled water and filtering through asbestos. This solution is standardized as follows: Weigh into 125 c.c. Erlen- 7 98 ANAL YSIS OF IRON AND STEEL, meyer flasks, three portions of thoroughly cleaned soft steel wire, in which the iron has been carefully determined, of from 0.15 to 0.25 grammes each, and pour into each of the flasks 30 c.c. of distilled water and 10 c.c. of strong sulphuric acid. Cover with a small watch-glass and heat until solution is complete. Add a sufficient amount of the strong solution of potassium permanga- nate to oxidize the iron and destroy the carbonaceous matter, being careful to avoid an excess which would cause a precipitate of binoxide of manganese. Should this occur, redissolve it by adding a very few drops of sulphurous acid and boil off every trace of the latter. Allow the solution in the flasks to cool and add to each 10 c.c. of dilute ammonia. Pass through the reductor and titrate in the flask. In all cases the mode of procedure in using the reductor should be as follows : Everything being clean and in good order from previous treatment with dilute sulphuric acid, and washing with distilled water, a little of the wash water being left in the neck of the funnel b (Fig. 52), and the flask being attached to the filter pump, pour 100 c.c. of warm dilute sulphuric acid into the funnel and open the stopcock c. When only a little remains in the neck of the funnel, transfer the solution to be reduced to the funnel. This solution should be hot but not boiling. Pour some of the dilute sulphuric acid into the vessel which contained the solution to be reduced to wash it, and when only a little solution is left in the neck of the funnel as before, add this to the funnel in such a way as to wash it and follow with about 200 c.c. more of warm dilute sulphuric acid and finally with 50 c.c. of hot distilled water. In no case allow the funnel b to get empty, and close the stopcock c when there is still a little of the wash water left in the funnel. This precaution prevents air from passing into the reductor tube. A blank determination is made by passing through the reductor a solution containing a mixture of 10 c.c. strong sulphuric acid, 10 c.c. dilute ammonia, and 50 c.c. water ; preceded and followed by the dilute acid as described RAPID METHODS FOR PHOSPHORUS. above. The amount of potassium permanganate required to give this blank a distinct color is subtracted from the amount required to give the same color to each reduced solution. To get the value of the permanganate solution, multiply the weight of iron wire taken by the percentage of iron in the wire and divide by the number of cubic centimetres of potassium per- manganate used in the titration. This will give the value of I c.c. of permanganate in terms of metallic iron. Multiply this result by 0.88163, the ratio of molybdic acid to iron and the product by 0.01794, the ratio of phosphorus to molybdic acid and the result is the value of I c.c. of the permanganate solution in terms of phosphorus. The ratio of molybdic acid to iron given above is that found when a known amount of molybdic acid in sulphuric acid solution is passed through the reductor in the manner described above and then titrated with potassium permanganate solution whose strength in terms of metallic iron is known. The reduction of the molybdic acid in the reductor in this case is to the form Mo 24 O 37 . The ratio of phosphorus to molybdic acid given above is that found by the analysis of the yellow precipitate of ammonium phosphomolybdate obtained from nitric acid solution of iron under varying conditions. Sulphurous Acid. A strong solution of the gas in water. Siphons of the liquefied gas may be obtained in the market. Acid Ammonium Sulphite. The strong C. P. solution of the reagent diluted with 10 parts of water. Ferrous Sulphate. Crystals of the salt free from phosphorus. These three reagents are for reducing the excess of binoxide of manganese thrown down in oxidizing the carbonaceous matter in the nitric acid solutions of the steels. Sulphurous acid is preferred. Molybdate Solution. Weigh into a beaker 100 grammes of pure molybdic anhydride, mix it thoroughly with 400 c.c. cold distilled water and add 80 c.c. strong ammonia, 0.90 sp. gr. When solution is complete, filter and pour the filtered solution 100 ANALYSIS OF IRON AND STEEL. slowly with constant stirring into a mixture of 400 c.c. strong nitric acid 1.42 sp. gr. and 600 c.c. distilled water. Add 50 milligrammes of microcosmic salt dissolved in a little water, agitate thoroughly, allow the precipitate to settle for 24 hours, and filter before using. Acid Ammonium Sulphate Solution, for washing the precipitate of ammonium phosphomolybdate. To I litre of water add 15 c.c. of strong ammonia, 0.90 sp. gr. and 25 c.c. strong sulphuric acid, 1.84 sp. gr. Amalgamated Zinc. Dissolve 5 grammes of mercury in 25 c.c. strong nitric acid diluted with an equal bulk of water, dilute to 250 c.c. and transfer to a stout flask of about 1000 c.c. capacity. Pour into it 500 grammes of granulated zinc which will pass through a 2O-mesh sieve, but not through a 3O-mesh. Shake it thoroughly for a minute or two and then pour off the solution, wash the zinc thoroughly with distilled water, dry, and preserve in a glass bottle for use. Operation. Weigh 2 grammes, or in case of steels containing over 0.15 per cent, phosphorus, I gramme of the steel into a 250 c.c. Erlenmeyer flask, pour into it 100 c.c. of nitric acid 1.135 sp. gr., and cover with a small watch-glass. Heat until the solution is complete and nitric oxide is boiled off. Add 10 c.c. of the strong potassium permanganate solution, boil until the pink color has disappeared and binoxide of manganese separates. Continue the boiling for several minutes, then remove from the source of heat and add a few drops of sulphurous acid, ammonium sulphite, or a small crystal of ferrous sulphate, repeating the addition at intervals of a minute until the precipitated binoxide of manganese is dissolved. Boil two minutes longer, place the flask in a vessel of cold water, or allow it to stand in the air until it feels cool to the hand, and then pour in 40 c.c. of dilute ammonia 0.96 sp. gr. The precipitated ferric hydrate will redissolve when the liquid is RAPID METHODS FOR PHOSPHORUS. IOI thoroughly mixed. When the solution is about the temperature of the hand, say 35 C., add 40 c.c. of molybdate solution at the ordinary temperature, close the flask with a rubber stopper, and shake it for five minutes, either by hand or in the machine, Figure 5 1 . Allow the precipitate to settle for a few minutes, filter on a 0.090 m. filter, and wash with acid ammonium sulphate solution until 2 or 3 c.c. of the wash water give no reaction for molyb- denum with a drop of ammonium sulphide. Pour 5 c.c. of ammonia 0.90 sp. gr. and 20 c.c. of water into the flask to dis- solve any adhering ammonium phosphomolybdate and then pour it on the precipitate in the filter, allowing the filtrate to run into a 250 c.c. Griffin's beaker. Wash out the flask and wash the filter with water until the solution measures about 60 c.c. Add to the liquid in the beaker 10 c.c. strong sulphuric acid and pass it through the reductor exactly in the manner described for the solutions of ferric sulphate in standardizing the solution of potas- sium permanganate. By adding the strong sulphuric acid to the ammoniacal solution immediately before passing it through the reductor it is heated sufficiently by the chemical action to insure thorough reduction. In washing be careful that no air passes into the reductor, and when the water has been drawn through, leaving a little still remaining in the stem of the funnel, close the stopcock, detach the flask F, wash off the drawn out portion of the reductor tube into it, and titrate the solution with the standard permanganate. The reductor should be so arranged that the whole reduction occupies about 3 or 4 minutes. The solution that passes through should be bright green in color. In adding the permanganate, the green color disappears first, and the solution becomes brown, then pinkish yellow, and ulti- mately colorless. Continue the addition of the permanganate drop by drop, shaking the flask vigorously until the solution assumes a faint pink coloration, which remains after standing one minute. Subtract from the reading of the burette the amount given by a blank determination, obtained exactly as IO2 ANAL YSIS OF IRON AND STEEL. described under the method given above for standardizing the permanganate solution, multiply the number of c.c. so obtained by the value of I c.c. in terms of phosphorus, multiply by 100 and divide by weight taken, and the result is the percentage of phosphorus in the steel. When a large number of analyses are to be carried along at once the following modification is recommended : Obtain the yellow precipitate and dissolve in ammonia exactly as described above, except that the solution is allowed to run into the flask in which the precipitation was made, and the washing of the filter is continued until the solution amounts to 75 c.c. Add now to the flask 5 grammes of pulverized zinc, 100 mesh, pouring it into the flask through a funnel to prevent any zinc clinging to the sides of the flask. Then add to the flask 1 5 c.c. strong sulphuric acid 1.84 sp. gr. This is most conveniently done in practice by letting it run in from a glass-stoppered burette. Close the flask at orfce with a rubber stopper carrying a glass tube bent twice at right angles, the further arm dipping into a beaker containing a saturated solution of sodium bicar- bonate. The flask should now stand undisturbed for about thirty minutes, when, if all action has ceased, it is ready to titrate with permanganate. The solution should be green, not brown. The temperature of the solution at the end of thirty minutes is about 40 C. and the titration succeeds best if done at this temperature. But the flask may stand a couple of hours without reoxidation of the reduced molybdic acid, and may then be successfully titrated. If the solution changes in color to brown the determination should be rejected, as the result will be too low. A blank should be made by adding to another flask 65 c.c. of water, 10 c.c. of dilute ammonia 0.96 sp. gr., 5 grammes of the lOO-mesh zinc, added in the manner described, and 15 c.c. of strong sulphuric acid 1.84 sp. gr. This flask should be treated the same as the others and the amount of permanganate it uses up should be deducted from the amount required by each flask RAPID METHODS FOR PHOSPHORUS. containing a test. When this method is used the reduction is practically complete to Mo 2 O, so that the factor 0.85714 must be used instead of 0.88163. Example. 0.1745 grammes of wire requires 50.0 c.c. of permanganate to give the required color. A blank determination gave o.i c.c., so that the wire actually required 49.9 c.c. permanganate. The wire contained 99.87 per cent, of iron, then 0.1745 X 0.9987 -=- 49.9 equals 0.0034923, or i c.c. of permanganate equals 0.0034923 grammes metallic iron. Then multiplying the value in iron by the ratio of molybdic acid to iron 0.88163 or 0.85714 and the product by the ratio of phosphorus to molybdic acid 0.01794, we have 0.0034923 X 0.88163 X 0.01794 equals 0.000055238, or i c.c. permanganate equals 0.000055238 grammes of phosphorus. Again the precipitated ammonium phosphomolybdate from 2 grammes of steel required 35.6 c.c. permanganate less blank o.i c.c. equals 35.5 c.c.; 35.5 X-O.OOOO55238 X 100 -H 2 equals 0.098 per cent, phosphorus. Notes and Precautions. It will be observed that the method given above oxidizes the phosphorus in the iron by means of nitric acid, completes and perfects this oxidation and possibly neutralizes the effect of the carbon present by means of potassium permanganate, and then separates the phosphoric acid from the iron by means of mo- lybdic acid. The molybdic acid in the yellow phosphomolybdate is subsequently determined by means of potassium permanganate, the phosphorus being determined from its relation to the molyb- dic acid in this precipitate. The method given above applies to steel and wrought iron, but it is not yet recommended for pig- iron. It is hardly necessary to say that all the chemicals and materials used in the analysis are assumed to be free from im- purities that will injuriously affect the result. IO4 ANAL YSIS OF IRON AND STEEL. 1.135 S P- g r - nitric acid apparently oxidizes the phosphorus just as successfully as a stronger one, while by its use solution is sufficiently rapid, and there is less trouble during the subse- quent filtration due to silica. The boiling of the solution to remove nitrous acid and assist the action of the oxidizing permanganate seems to be essential. Some steels may not require 10 c.c. of the permanganate and some, like washed metal high in carbon, may require even more. It is essential that enough should be added to cause a precipita- tion of binoxide of manganese and to give a strong pink color to the solution. This color gradually disappears on boiling. Less is required if the permanganate is added in small successive portions. Boiling two minutes after reducing the binoxide of manganese removes any nitrous acid that may be formed by that operation. In washing the yellow precipitate it shows some disposition to crawl up to the top of the filter. Care should be taken therefore to have the filter fit the funnel so closely that even if the precipi- tate does crawl over the top it will not be lost while washing the filter completely to the top. It is very easy to leave enough molybdic acid in the top of the filter, even though the washings are tested, to cause an error of .005 per cent, in the determina- tion. It is best to make up molybdate solution rather frequently. It is also best to keep it in the dark at a temperature not above 28 to 30 C. Much of the so-called molybdic acid of the market is molybdate of ammonium or molybdate of some other alkali. This fact cannot be ignored in making up the molybdate solution. A series of experiments with various molybdic acids and alkaline molybdates obtained in the market, indicates that if the amount of molybdic acid in the solution is that called for by the formula, irrespective of whether this amount is furnished by pure molybdic acid or by any of the commercial molybdates referred to, the re- sult will be much nearer the truth than if this is not done. Good RAPID METHODS FOR PHOSPHORUS. IO jj molybdic acid is the best, but the alkaline molybdates can be used. The amount of molybdic acid in these molybdates can readily be determined by dissolving o.iooo gramme in 60 c.c. of water to which 10 c.c. of dilute ammonia has been added, filtering, adding 10 c.c. strong C. P. sulphuric acid, and passing through the reductor as above described. The method given in the example above enables the amount of molybdic acid to be determined. If the molybdic acid as obtained in the market, or the ammonia used in dissolving it, contains any soluble sili- cates, the resulting molybdate solution will be yellowish in color and the determinations made with this solution will be high, owing apparently to ammonium silicomolybdate being dragged down with the phosphomolybdate. Treatment of the molybdate solution with microcosmic salt, as described, overcomes this diffi- culty and gives a perfectly colorless molybdate solution. A molybdate solution tinged with yellow should never be used. It will be observed that the molybdate solution recommended above contains much less nitrate of ammonia than is given by many of the formulas now in use. Experience shows that a molybdate solution made on this formula keeps much better than those containing more ammonium nitrate. It will also be observed that the amount used for each determination is less than many methods employ. It is believed that the amount recommended is sufficient and that the ammonium nitrate re- quired to assist the formation of the yellow precipitate is fur- nished by the 40 c.c. of dilute ammonia added to the nitric acid solution of the steel. Of course the molybdate solution recom- mended above cannot be used for other work interchangeably with that made on the older formulas, on account of lack of ammonium nitrate. The directions in regard to the reductor, both as to making and use, should be strictly followed. By the use of the stop- cock, and the amalgamated zinc, and by keeping a little liquid in the neck of the funnel, the same blank can be obtained from IO6 ANALYSIS OF IRON AND STEEL. a reductor almost continuously, even though two or three days of standing intervene between blanks. It is, however, always advisable to treat with dilute sulphuric acid and wash before using, even though only one night has elapsed since the last previous use. If the solution to be reduced does not contain enough acid or is not warm enough, the reduction will not be complete. Care should therefore be taken not to allow too much mixing of the dilute sulphuric acid with the solution to be re- duced, either in the funnel or in the reductor tube itself, The best asbestos to use is the mineral known as actinolite, but any fibrous mineral which will act as a filter and not be dissolved by the acids used may be employed. Glass wool alone will not do, as a good filter is essential in order that neither small particles of zinc nor impurities in the zinc may be drawn down into the flask with the reduced solution. The consumption of zinc is very small. In testing with ammonium sulphide, to see whether the wash- ing of the yellow precipitate is complete, good results are ob- tained by putting two or three drops of yellow ammonium sulphide into a few cubic centimetres of distilled water, and allowing the washings to drop into this solution from the stem of the funnel. If iron is present in the washings it will show while the solution is still alkaline. By allowing the washings to continue running into the ammonium sulphide solution it soon becomes acid, when molybdenum, if any is present, shows by a more or less brownish color. If the acid solution is pure white from separated sulphur the washing is complete. Since the acidity of the solution in which the yellow precipi- tate is formed has an influence on its composition, it is quite desirable that the sp. gr. of the 1.135 nitric acid and of the 0.96 ammonia should be taken with some care. The tempera- ture at which the figures are correct is 15 C. It is best to use the Westphal balance in determining these gravities, but failing this, a sufficiently delicate hydrometer can be employed. RAPID METHODS FOR PHOSPHORUS, In using the reduction with 5 grammes of loo-mesh zinc, it will be observed that as the zinc becomes nearly all dissolved a blackish residue remains. This residue seems to be metallic lead. It disappears slowly during the titration and apparently uses up some permanganate. It takes a little longer to secure a satisfactory end reaction with the loo-mesh zinc, as the pink color fades out several times before it will remain permanent for one minute. It is essential that air should be excluded from the flask after the reduction is nearly complete, and it is for this purpose that the sodium bicarbonate solution is used. A tendency to suck the soda solution back into the reducing flask will be noticed, due to the cooling of the flask. The reduction should be made in a place free from draughts. With the amalgamated zinc in the reductor made as above described the blank generally uses up about O.I c.c. of the standard permanganate solution. The blank when using the reduction by means of 5 grammes loo-mesh zinc usually amounts to 0.6 c.c. of the standard permanganate, and may be higher. Pulverized zinc is rarely free from sulphides, and while this seems not to be a very important matter, it is nevertheless not recom- mended to use, either in the reductor or in the flask reduction, a zinc that gives a high blank. If the amount of sulphurous acid or other reagent added to the nitric acid solution to remove the precipitated binoxide of manganese is insufficient, a brown stain will be left on the filter paper after the yellow precipitate is dissolved in ammonia. This may occur even though the nitric acid solution looks clear, and as no harm can arise from a slight excess of the reducing agent, it is usually more satisfactory to add an excess. It is not de- sirable to add the reducing agent to the solution while boiling, as under such circumstances it frequently boils over. It is rather essential to use the dilute sulphuric acid warm, so that the general temperature of the reductor may be kept up. IO 8 ANALYSIS OF IRON AND STEEL. A good method for cleaning the wire in standardizing the potassium permanganates is as follows : Take a round lead pencil and make a hole in it with a pin near the end. Insert the end of the wire in this hole and revolve the pencil until there are two turns of the wire around it. Hold the turns firmly in one hand and cut the wire so that about 0.75 m. will remain attached to the pencil. Draw this wire through a piece of folded fine sand- paper several times and then several times through a piece of filter paper. Seize the wire near the pencil with the filter paper and cut off the part which was wound around the pencil and remove it. Then insert the end of the cleaned wire in the hole and revolve the pencil with one hand, holding the wire in the filter paper in the other hand, until it is all wound loosely on the pencil. Push the coiled wire off the end of the pencil. It is now in a convenient form for weighing. Direct Weighing of the Phospho-Molybdate. Instead of using the volumetric method, some chemists pre- fer to weigh the yellow precipitate. Mr. Wood's method* is as follows : Wood's Dissolve 1.63 grammes steel in a six-ounce Erlenmeyer flask method. in 30 c.c. warm nitric acid, 1.2 sp.gr., place the flask over a Bunsen flame and evaporate down to 10 or 15 c.c., hastening the evaporation by blowing a gentle current of air into the flask. Heat 50 c.c. of molybdate solution to 5O-55 C, add it to the solution in the flask, and shake well. Complete precipita- tion should take place in from three to five minutes. Filter on the pump in a 7 c.m. Munktell's No. I filter which has been pre- viously washed, dried at 100 C., and weighed. Wash with dilute nitric acid, suck dry, wash once with alcohol and thoroughly with ether, and place the filter containing the precipitate in a funnel in an air-bath heated to 110 C. The funnel in the bath * Communicated to the author. Mr. Wood states that the details adapting this to a " rapid method" were worked out by Mr. J. A. Nichols, of the Homestead Works. DETERMINATION OF MANGANESE. is connected with the exhaust so that the precipitate and filter are thoroughly dried in from one to three minutes, according to the size of the precipitate. Weigh, and I milligramme of precipi- tate will be equal to .001 per cent, of phosphorus in the steel. In the case of pig-iron and spiegel, the metal after solution in nitric acid, 1.2 sp. gr., is diluted with 20 c.c. water, 5 drops of hydrofluoric acid are then added, the solution is boiled for two or three minutes, filtered through asbestos on the pump, and concentrated to 15 c.c. 15 c.c. of chromic acid is added, the solution is boiled down again and precipitated as above. The hydrofluoric acid prevents the separation of gelatinous silica, but does not interfere with the precipitation of the phosphorus. This method will not work with ferro-manganese, as the combined carbon is not completely oxidized to prevent the pre- cipitation of all the phosphorus. The solutions referred to above are prepared as follows: Molybdic acid solution: To 1200 c.c. water add 700 c.c. R eag ents ammonia, sp. gr. 0.88, and I pound molybdic acid ; when the molybdic acid is dissolved add 300 c.c. nitric acid, sp. gr. 1.42, and cool. Pour this solution into a mixture of 4800 c.c. water and 2000 c.c. concentrated nitric acid. Filter for use after standing twenty-four hours. Chromic acid solution: 1.42 sp.gr. nitric acid saturated with chromic acid. DETERMINATION OF MANGANESE. The Acetate Method. Dissolve I gramme of drillings in 15 c.c. HNO 3 , 1.2 sp.gr., in a No. 2 Griffin's beaker. Evaporate to dryness in the air- bath, and heat to decompose carbonaceous matter. Allow the beaker to cool, add 10 c.c. HC1, heat carefully until all the IIO ANALYSIS OF IRON AND STEEL. For steel and iron ultra- Na 2 co 3 . importance of avoid- ing excess Fe 2 O 3 is dissolved, evaporate to dryness to get rid of all the HNO 3 , redissolve in 10 c.c. HC1, and evaporate carefully until the solution is almost syrupy. Dilute with cold water to about IOO c.c., and filter off the insoluble matter, allowing the filtrate and washings to run into a No. 6 Griffin's beaker. In the case f stee l or puddled iron the filtration may be omitted, the solu- ^ on being poured into the large beaker, and the rinsings of the small beaker added. To the solution in the large beaker, which should amount to about 200 c.c., add a solution of car- bonate of sodium very slowly, stirring vigorously. The solution will finally become very dark red in color, and the precipitate formed will redissolve very slowly. Add the solution of car- bonate of sodium 2 or 3 drops at a time, stir well, and allow the solution to stand several minutes, to see whether the precipitate will redissolve or not. When, under these circumstances, a decided precipitate remains, add 2 drops of HC1, stir well, and allow the solution to stand for some minutes ; if the solution does not clear, add 2 drops more, and stir again. If the first part of the operation has been carefully conducted, this amount of HC1 will usually be sufficient, but if, for any reason, too large a precipitate has been formed, it may require a few drops more. It is important, however, that no more HC1 be added than just enough to redissolve the precipitate formed by the carbonate of sodium, and, to insure this, the solution should be well stirred and allowed to stand a sufficient length of time after each addition of HC1. The solution may be so dark in color that it is difficult to see when the precipitate does finally disappear, but by standing the beaker on a piece of white paper the light reflected through the bottom of the beaker will greatly diminish the difficulty. When, under this method of procedure, the solution clears, add 2 grammes of acetate of sodium dissolved in a few c.c. of water, stir well, and dilute the solution to about 700 c.c. with boiling water. Heat it to boiling, and allow it to boil for about ten minutes, then remove DETERMINATION OF MANGANESE. IU it from the tripod, and allow the precipitated hydrate and basic acetate of iron to settle. Decant the clear, supernatant fluid on Filtering off a large washed German filter, throw the precipitate on, and wash it two or three times with boiling water, allowing the filtrate to run into a large beaker or flask, from which it can be transferred to a platinum or porcelain dish and evaporated rapidly. When the precipitate has drained quite dry, by means of a platinum spatula transfer it . to the beaker in which the precipitation was first made ; dissolve the precipitate which remains adhering to the filter, and that which remains on the blade of the spatula, by pouring around the edge of the filter and on the spatula held over it 10 c.c. HC1 diluted with twice its volume of hot water, allowing it to run into the beaker containing the precipitate. Wash the filter free from chloride of iron with cold water, and heat the beaker containing the precipitate until the latter is dissolved. Cool the solution, and repeat the precipitation, filtration, and resolution of the pre- cipitate precisely as in the first case, adding this filtrate to the first one. Precipitate, filter, and wash a third time in the same Evaporation manner, evaporate all the filtrates down together until they are reduced to about 300 c.c. in volume, and transfer this solution to a No. 3 beaker. If during the evaporation any manganese has become oxi- dized by exposure to the air, it forms a hard ring on the side of the capsule, and may be dissolved, after the solution is poured into the beaker, by two or three drops of HC1, and washed into the beaker. Should any oxide of iron separate out, pour the solution in the capsule through a small filter, allowing it to run into the beaker, wash the precipitate with hot water, dissolve it in a very few drops of dilute HC1, and let it run into a No. I beaker. Add just enough solution of carbonate of sodium to precipitate it, make it faintly acid with acetic acid, boil it, and filter into the main solution. This solution now contains all the manganese, nickel, and 112 ANALYSIS OF IRON AND STEEL. Separation of Cu, Ni, and Co from the Mn. Precipita- tion of MnO 2 by Br. Precipita- tion of Mn 2 (NH 4 ) 2 P 2 O 8 +Aq. cobalt and the greater part of the copper which may have been in the metal. Add to it 10 grammes of acetate of sodium and a few drops of acetic acid, heat it to boiling, and pass a current of H 2 S through the boiling solution for fifteen minutes. This will precipitate the copper, cobalt, and nickel. Filter off the black sulphides, boil the filtrate to expel the excess of H 2 S, let the solution cool somewhat, and add bromine-water in excess. If no precipitate forms at first, stand the solution, which should be colored by the bromine-water, in a warm place for an hour or two, to allow the precipitate of MnO 2 to separate out. If a precipitate forms immediately, add bromine-water until, when the precipitate settles, the solution is strongly colored by it, and stand it aside for an hour or two. At the end of this time, the precipitate having settled and the supernatant fluid being still colored by the bromine, heat it carefully, finally to boiling, and expel the excess of bromine; allow the precipitate to settle, filter, wash very carefully, and avoid stirring up the precipitate when it is on the filter, as it has a tendency to go through. Dissolve the precipitate on the filter in sulphurous acid water containing a little HC1; allow the solution to run into a platinum dish, and wash the filter well. A little of the SO 2 water will quickly dissolve any MnO 2 which may adhere to the beaker in which it was precipitated, and this may be poured on the filter. Boil the solution in the dish to expel the excess of SO 2 , add 5 to 20 c.c. of a clear filtered solution of microcosmic salt, heat to boiling, and add, with constant stirring, NH 4 HO drop by drop. When the precipitate of phosphate of ammonium and manganese begins to form, stop adding NH 4 HO, and stir until the precipitate becomes crystalline. When this change occurs, add one more drop of NH 4 HO ; the additional precipitate formed will be curdy, but a few seconds' continued stirring at the boiling temperature will change it to the silky crystalline condition. Continue the addition of NH 4 HO in exactly this manner until the precipitate is all down and further additions of NH 4 HO fail DETERMINATION OF MANGANESE. n ^ to change the silky appearance. Add a dozen drops of NH 4 HO in excess, remove the dish from the light, and stand it in ice- water until perfectly cold. Filter on an ashless filter, wash with Solution of r . f /,- NH 4 NO 3 cold water containing 10 grammes of nitrate of ammonium (dis- f or wash- solved in water made faintly alkaline with NH 4 HO and filtered) Jj^. in 100 c.c. until the filtrate gives no reaction for HC1, dry, tate - ignite, and weigh as Mn 2 P 2 O 7 , which contains 38.74 per cent. Mn. During the precipitation of the phosphate of ammonium and manganese the stirring must not be discontinued for an instant, as the solution has a great tendency to bump when the precipitate is allowed to settle. The crystalline condition of the precipitate, which is absolutely necessary for the success of the determina- tion, can be most readily brought about by the means described above. It can, of course, be accomplished by adding an excess of NH 4 HO at once, but it will require much more boiling and stirring than the method above described. The final precipita- tion as phosphate of ammonium and manganese, due to Dr. Gibbs, is much the most accurate method known. A common practice, however, is to wash the bromine precipitate of hydrated weighing as binoxide of manganese, dry, ignite, and weigh as Mn 3 O 4 , which contains 72.05 per cent. Mn. There are two objections to this objections to this. method of procedure : first, the difficulty of washing the MnO 2 free from sodium salts ; secondly, the uncertainty as to the exact state of oxidation of the ignited oxide of manganese. The first of these objections Eggertz claims to overcome by washing the precipitated MnO 2 with water containing I per cent, of HC1. It may also be overcome, or rather the danger may be avoided, by using no fixed alkalies. By this method, nearly neutralize the HC1 solution of the iron or steel by NH 4 HO, then add a solution of carbonate of ammonium exactly as directed above for carbonate of sodium, and finally, instead of acetate of sodium, Avoidmgus* add acetate of ammonium (5 c.c. of NH 4 HO slightly acidulated alkalies, by acetic acid). Evaporate the filtrates obtained in this way to about 500 c.c., transfer to a flask of about I litre capacity, and 8 114 ANAL YSIS OF IRON AND STEEL. Variable composi- tion of ignited oxide of manga- nese. Weighing as MnS. Source of error in acetate method. Amount of NaC 2 H 3 2 necessary. cool. When perfectly cold, add 3 or 4 c.c. bromine, shake well, and when the solution is strongly colored all through by bro- mine, add an excess of NH 4 HO, and heat to boiling. Filter, wash with hot water, dry, ignite, and weigh as Mn 3 O 4 . The second objection seems, according to Pickering,* to be well founded, the amount of manganese in the ignited oxides varying from 69.688 per cent, to 74.997 per cent., according to the temperature to which they were heated and other undeter- mined conditions. This cause of error may be avoided by weighing the precipitate as MnS, containing 63.18 per cent. Mn. This method, due to H. Rose,f is carried out as follows : Ignite the oxide in a porcelain crucible, allow it to cool, mix it with 5 or 6 times its volume of flowers of sulphur, place the crucible on a triangle, and insert the bowl of a clay tobacco-pipe, which should be large enough to quite fill the top of the crucible and too large to reach to the precipitate. Pass through the stem a current of dry hydrogen until all air is expelled, heat the crucible gradually to as high a heat as a good Bunsen burner will produce, cool in the current of hydrogen, and weigh as MnS. General Remarks on the Acetate Method. The chief source of error in the acetate method, as it is usually practised, is in the addition of too much acetate of sodium, whereby the manganous chloride is changed to manga- nous acetate, which, according to Kessler,J is readily decomposed to manganous oxide and acetic acid. Under these circumstances, a larger amount of manganese is precipitated with the iron than would be the case if a less amount of acetate of sodium were added. When acetate of sodium is added to ferric chloride, the reaction may be written, 6NaC 2 H 3 O 2 ,3H 2 O + Fe 2 Q 6 ==6NaCl-f- Fe 2 (C 2 H 3 O 2 ) 6 +3H 2 O; and to precipitate the iron as ferric acetate * Chem. News, xliii. 226. \ Chem. News, xxvii. 14. f Rose, Quant. Anal. (French ed.), p. 104. DETERMINATION OF MANGANESE. n - in i gramme of metal would necessitate the use of 8 grammes of acetate of sodium. But, as Kessler in the same article remarks, when a solution of ferric chloride is treated with car- bonate of sodium and HC1 exactly as described above, a liquid is formed which contains 14 times its equivalent of ferric hydrate in solution. Consequently ^ gramme of acetate of sodium would be sufficient to precipitate I gramme of iron as ferric hydrate and basic acetate. In order, however, to precipitate the manga- nese as MnO 2 by bromine, it is necessary to convert all the man- ganous chloride into manganous acetate : consequently an excess of acetate of sodium is added before adding bromine. If, when making the acetate precipitation, the solution contains any ferrous chloride, a "brick-dust" precipitate is usually formed, which Brick-dust generally passes through the filter, and is very difficult to dis- ta te. solve or manage in any way. It is usually the shortest and best plan, in this event, to start a fresh portion and throw away the other. The Nitric Acid and Chlorate of Potassium Method. (Ford's Method^ The acetate method is at best very tedious, and when the amount of manganese is very small it is of course desirable to work on larger amounts than I gramme of the sample, but the iron precipitate in this event is so large that it becomes very difficult to manage it properly. With Ford's method, however, there is almost no limit to the amount which can be operated upon, and many experiments have shown that with proper pre- cautions it is an extremely accurate process. The reaction on which the process is based was first noticed by Hannay* in 1878; but Fordt first worked out the method in its present practical Method for form. Dissolve 5 grammes of borings in a No. 3 beaker in steel and puddled 60 c.c. HNO 3 , 1.2 sp. gr., evaporate down until the solution is iron. * Jour. Chem. Soc., xxxiii. 269. f Trans. Inst. Min. Engineers, ix. 397. ANALYSIS OF IRON AND STEEL. Filtering the cold solu- tion. Effect of N 2 O 3 in HN0 3 . Separation from small amounts of Fe 2 3 by NH 4 HO. almost syrupy, then add 100 c.c. strong HNO 3 , 1.4 sp. gr., and 5 grammes KC1O 3 . Stand the beaker on a tripod with a thin piece of sheet asbestos, about I inch (25 mm.) in diameter, in the centre of the wire gauge or on the air-bath, and heat the solution to boiling. Boil the solution fifteen minutes, remove the light, add 50 c.c. strong HNO 3 and 5 grammes KC1O 3 , replace the light, and boil fifteen minutes longer, or until the yellowish fumes from the decomposition of the KC1O 3 are no longer given off. Cool the solution as rapidly as possible by standing the beaker in cold water, filter on the pump, using the cone* or glass filtering-tube with asbestos filter, f and wash two or three times with strong HNO 3 , which must be free from nitrous fumes.J Nitrous acid reduces MnO 2 to MnO, which then dissolves in HNO 3 . Its presence may be recognized by the yellow color it imparts to HNO 3 , and it may be removed by blowing air through the acid. It is always formed in HNO 3 which has been exposed to sunlight, and for that reason this acid should be kept in a dark place. Suck the precipitate dry, and transfer it, with the asbestos filter, to the beaker in which the precipitation was made. Pour into the beaker 10 to 40 c.c. strong sulphurous acid water, which will dissolve the precipitate almost instantly. By pouring it through the cone or filtering- tube, any adhering precipitate will be dissolved and carried into the beaker. As soon as the precipitate is dissolved, add 2 to 5 c.c. HC1, and filter from the asbestos into a No. I beaker, wash- ing with hot water. Heat the filtrate until the excess of SO 2 is driven off, add bromine-water until the solution is strongly colored with it, and boil off the excess of bromine. Add NH 4 HO until the solution smells quite strongly of it, boil for a few minutes, and filter into a No. 3 beaker. Wash several times with * See page 26. f As described under Methods for Determination of Carbon. J It is always well to transfer the filtrate and washings to a No. 4 beaker, add 2 grammes KC1O 3 , and boil again, to see whether any further precipitate of MnO 2 is formed. DETERMINATION OF MANGANESE. hot water, remove the beaker, dissolve the ferric hydrate on the filter in dilute hot HC1 (l part of acid to 3 of water), allowing the solution to run back into the beaker in which the precipitation was made, and wash the filter with hot water. Boil this filtrate for a few minutes to drive off the chlorine which may be present from the solution of any little MnO 2 precipitated with the ferric hydrate, reprecipitate by NH 4 HO as before, filter, and repeat the solution, precipitation, and filtration, allowing all the filtrates from the ferric hydrate to run into the No. 3 beaker. Acidulate this solution, which will be about 300 or 400 c.c. in volume, with acetic acid, heat to boiling, and pass H 2 S through the boiling solution for ten or fifteen minutes. Filter into a Separation platinum dish from any sulphide of cobalt, which is the only baU . metal likely to be present with the manganese ; boil off the H 2 S after adding a little HC1, add microcosmic salt, and precipitate, filter, ignite, and weigh, as directed on pages 112 and 113, as Mn 2 P 2 O 7 . Steels containing much Silicon. In steel high in silicon, 0.2 per cent, and over, the gelatinous silica formed is very apt to clog the filter when operating as described above, and it is better to dissolve the sample in HC1, evaporate to dryness, being careful not to heat it too hot, redis- solve carefully in 50 c.c. strong HNO 3 , boil down until nearly syrupy to destroy all the HC1, redissolve in 100 c.c. strong HNO 3 , and precipitate as directed above. Instead of dissolving in HC1, Mr. Wood suggests adding a few drops of hydrofluoric acid to the nitric acid solution before evaporating. This seems to work extremely well, and saves much time in the case of high silicon steels. It may also be Si - used to advantage in the case of pig-iron instead of the method given below. Pig-iron. Dissolve 5 grammes in 50 c.c. dilute HC1 (i part HC1 to I part water), filter on a washed German filter into a No. 3 beaker, US ANALYSIS OF IRON AND STEEL. evaporate to dryness, redissolve in 50 c.c. strong HNO 3 , and proceed as in the case of " steel high in silicon." Spiegel and Ferro-manganese. It is best to use only I gramme of spiegel or ferro-manganese of 20 to 40 per cent, manganese and .5 gramme of very high, 60 Variation in to 8o per cent, ferro-manganese. In the latter, indeed, it is better methodfor to use the acetate method with NH 4 HO and NH 4 C 2 H 3 O 2 , and, ga^esT*"" omitting the precipitation by bromine, boil off the H 2 S from the nitrate from the insoluble sulphides, after adding HC1, and then precipitate by microcosmic salt as directed above. RAPID METHODS. Volumetric Methods. Volhard's Method* This method is based on the principle announced by Moraw- ski and Stingl,f that when permanganate of potassium is added to a neutral manganous salt all the manganese is precipitated, in accordance with the reaction 4KMnO 4 -j- 6MnSO 4 + 4H 2 O = ioMnO 2 + 4KHSO 4 +2H 2 SO 4 . When all the manganous salt is oxidized, the solution is colored by the permanganate, which thus indicates the end reaction. The permanganate used for titrating iron ores may be used for this determination, and, its value being determined, as directed, in terms of Fe, the cal- Caicuiation culation for Mn is as follows : The reaction, when perman- ofperman- ganate is added to a solution of ferrous sulphate, is ioFeSO 4 -|- ganate " 8H0 or 2 molecules of permanganate oxidize 10 molecules of FeSO 4 . Now, as 2 molecules of permanganate oxidize 3 molecules of man- ganous sulphate, while 2 molecules of permanganate oxidize 10 molecules of ferrous sulphate, the oxidizing power of the per- * Liebig's Annalen, Band cxcviii. p. 318; Chem. News, xl. 207. j- Chem. News, xxxviii. 297. RAPID METHODS FOR MANGANESE. U manganate is only three-tenths as great in the former case as it is in the latter, and its value in Mn is to its value in Fe as 3 is to 10, or |-| X YQ = iro"- Therefore the value of the permanganate Details in Fe multiplied by |-| or 0.2946== its value in Mn. Dissolve method. 1.5 grammes of borings in a platinum or porcelain dish in 25 c.c. HNO 3 , 1.2 sp. gr. When solution is complete, add 12 c.c. dilute H 2 SO 4 (i part concentrated H 2 SO 4 and I part water), and evaporate to dryness, as directed on page 20, heating until fumes of H 2 SO 4 are given off in order to destroy all the car- bonaceous matter. Or dissolve in HNO 3 as above, evaporate to dryness, and heat on the tripod until the carbonaceous matter is destroyed; dissolve in 15 c.c. HC1, add 12 c.c. dilute H 2 SO 4 as above, and evaporate until fumes of H 2 SO 4 are given off. Allow the dish to cool, add 100 c.c. water, and heat until all the ferric sulphate is dissolved. Wash into a carefully graduated 300 c.c. flask, so that with the washings the solution may not exceed 200 c.c. in volume, and add solution of car- bonate of sodium until the precipitate which is first formed dissolves only with difficulty. Then add slowly zinc oxide* suspended in water, shaking well after each addition until the iron is precipitated, which will be shown by the sudden coagu- lation of the solution. The precipitate will then settle, leaving a slightly milky supernatant liquid. Fill the flask exactly to the mark on the neck (300 c.c.), and mix thoroughly by pour- ing the entire contents of the flask into a large, clean, dry beaker, and back again into the flask, repeating this several times. Allow the precipitate to settle for a few minutes, and pour the solution through a large, dry filter. Fill a 200 c.c. pipette with this filtrate, which will, of course, represent exactly I gramme of the sample, run it into a flask of about 500 c.c. capacity, heat to boiling, and add 2 drops of HNO 3 , sp. gr. 1.2. Now add permanganate solution slowly from a burette, shaking * See page 58. 12Q ANALYSIS OF IRON AND STEEL. after each addition to mix the solution and facilitate the collec- tion of the precipitated hydrated peroxide of manganese. When the reaction is nearly finished, the solution will be slightly col- ored by the permanganate, but the color disappears after shaking the flask and allowing it to stand for a moment. Finally, how- ever, a drop or two will give the solution a permanent pink color, which will not disappear for several minutes. The number of c.c. of the permanganate solution used multiplied by the factor found (the Fe factor of the permanganate multiplied by .2946) is the amount of manganese in the sample. If, during the addition of the permanganate, the solution should become cool and the precipitate fail to collect and settle quickly, heat the solution, Applicable but not quite to the boiling-point. This method is applicable except for very for all samples except those containing very minute amounts of TmTunts manganese. In working on spiegel, take .75 gramme, then, using ofMn - two-thirds of the filtrate, the amount will be calculated on .5 gramme. Williams' s Method. This method, which consists in precipitating the MnO 2 by Ford's method, filtering, washing, dissolving in H 2 SO 4 with a measured volume of some reducing agent, such as oxalic acid or ferrous sulphate, and titrating the excess by permanganate, was first used by Williams.* Regarding the precipitate by KC1O 3 in a nitric acid solution as MnO 2 , the reaction in dissolving it might be expressed thus: MnO 2 -f- 2FeSO 4 + 2H 2 SO 4 =MnSO 4 -r- Fe 2 (SO 4 ) 3 + 2H 2 O, or MnO 2 + H 2 C 2 O 4 + H 2 SO 4 = MnSO 4 + 2CO 2 Oxidizing -f-2H 2 O. Therefore I molecule of MnO 2 oxidizes 2 molecules power of MnO 2 . of ferrous sulphate or I molecule of oxalic acid, and, the excess of oxalic acid or ferrous sulphate unoxidized having been de- termined by a solution of permanganate, the difference between this excess and the amount originally added is the amount oxidized by the MnO 2 . * Trans. Inst. Min. Engineers, x. 100. RAPID METHODS FOR MANGANESE. 12 \ We therefore require two standard solutions, one of perman- standard solutions ganate and one of ferrous sulphate, ammonium ferrous sulphate, required, or oxalic acid. The permanganate solution used for iron deter- minations answers perfectly. A solution of ferrous sulphate is perhaps the most satisfactory, and is prepared by dissolving 10 grammes of the crystallized salt, FeSO 4 ,7H 2 O,* in 900 c.c. water and 100 c.c. strong H 2 SO 4 . It will keep perfectly in a glass- stoppered bottle in the dark for a long time. One c.c. of this solution will be equal to about .002 gramme Fe, or nearly .001 gramme Mn, and if the permanganate is of the usual strength, say I c.c. = .007 gramme Fe, I c.c. of the permanganate will equal about 3.5 c.c. of the ferrous sulphate. The permanganate standard- solution having been carefully standardized, measure 50 c.c. of the solutions. ferrous sulphate solution by means of a pipette into the dish,f dilute to about I litre, and run in permanganate solution from a burette, stirring constantly until the first permanent pink tint appears. The reading of the burette will give the value of 50 c.c. ferrous sulphate in permanganate, and consequently by a simple calculation its value in Fe and Mn. Suppose, for instance, I c.c. permanganate solution = .0068 gramme Fe, or (according to the proportion given above, 1 12 : 55 : : Fe : Mn) = .00334 gramme Mn. Then if 14.1 c.c. permanganate = 50 c.c. ferrous sulphate, 100 c.c. ferrous sulphate will be equivalent to 28.2 c.c. permanganate. In using oxalic acid, dissolve 2.25 grammes of the crystallized acid, H 2 C 2 O 4 ,2H 2 O, in I litre of water, and determine its strength by measuring 50 c.c. into the dish, diluting with hot water, adding 5 c.c. H 2 SO 4 , and titrating with permanganate. The details of the method are as follows : Weigh out 5 Details grammes of the sample of puddled iron, pig-iron, or steel, and method. proceed as directed on p. 116 et seq. ; but after filtering and washing the precipitated MnO 2 with strong HNO 3 , suck the pre- cipitate as dry as possible, and then wash out the beaker in * See page 55. f See Determination of Iron in Iron Ores. 122 ANALYSIS OF IRON AND STEEL. which the precipitation was made with cold water. Pour this water on the precipitate, and repeat the operation two or three times to get rid of all the HNO 3 . Suck the precipitate as dry as possible, transfer it with the asbestos to the beaker in which the precipitation was made, measure into the beaker 100 c.c. of the standard ferrous sulphate solution (or TOO c.c. oxalic acid solution and 10 c.c. H 2 SO 4 ), and stir until the MnO 2 is all dis- solved. When using oxalic acid it is necessary to heat gently to about 60 C. Wash the solution and asbestos into the dish, dilute to about I litre (with oxalic acid use hot water), and titrate with permanganate. We will sup- FIG. 54. Example. ^ pose, for example, that it requires 10.2 c.c. permanganate to give the permanent rose tint; then, as 100 c.c. ferrous sulphate 28.2 c.c. permanganate, there would be the equivalent of 28.2 10.2 = 18 c.c. of permanganate in ferrous sul- phate oxidized by the MnO 2 pre- cipitate. One c.c. of permanga- nate being equivalent to .00334 gramme Mn, 18 c.c. = .06012 gramme Mn, and, 5 grammes of the sample having been taken, .06012 -5- 5 = .01202 X ioo 1. 202 per cent. Mn. Fig. 54 shows a very con- Apparatus venient piece of apparatus designed by Mr. E. A. Uehling in for ferrous sulphate 1 884-* It is especially useful when it is necessary to rapidly add a constant volume of a standard reagent, for instance, a measured * Communicated to the author by Mr. A. L. Colby, of the Bethlehem Iron Company. RAPID METHODS FOR MANGANESE. 12 $ excess of ferrous sulphate in volumetric determination of man- ganese after precipitation with potassium chlorate. The burette-tube extends to the bottom of the Wolff bottle, which holds 2 litres. Enough air is supplied, without danger of dust or evaporation of solution, by means of a pin-hole drilled in the neck of the bottle and through the hollow glass-stopper. The bottle may be blackened to preserve the solution from the action of light. Spiegel and Ferro-manganese. When working on spiegel or ferro-manganese, take .5 gramme of the sample and proceed in the same manner as directed for steel or iron ; but it is better to use a standard solution of ferrous sulphate containing 30 grammes of FeSO 4 ,7H 2 O to the litre for very high ferro-manganese. As there seems to be some uncertainty as to the exact com- composition position of the oxide of manganese,* the permanganate solution ideof may be standardized as follows : Determine the absolute amount of manganese in a finely-ground and well-mixed sample of spiegel or ferro-manganese by a gravimetric method, then treat .5 gramme standard- of the same sample exactly as described above, and, having found spiege i of the number of c.c. of permanganate that are equivalent to 100 c.c. of the ferrous sulphate solution, the amount of manganese in the sample divided by the number of c.c. of permanganate equivalent to the ferrous sulphate oxidized by the oxide of manganese in the sample, gives the value of the permanganate solution. Thus, if 100 c.c. ferrous sulphate solution require 28.2 c.c. permanganate to give the rose tint upon titration, the sample of spiegel con- tains 14.50 per cent. Mn, and the ferrous sulphate remaining after the solution of the oxide of manganese in 100 c.c. requires 6.5 c.c. permanganate to give the rose tint upon titration (using * Stone, Trans. Inst. Min. Engineers, xi. 323, xii. 295, 514; Mackintosh, Trans. Inst. Min. Engineers, xii. 79, xiii. 39. 124 ANALYSIS OF IRON AND STEEL. .5 gramme of the sample, of which i gramme contains .1450 Example. gramme Mn), the calculation would be as follows: 28.2 c.c. 6.5 c.c. = 21.7 c.c. = .0725 gramme Mn, or i c.c. permanganate is equivalent to '^jf =.00334 gramme Mn. Deshays's Method* This method is based on the fact that nitrate of manganese, when boiled with excess of nitric acid and peroxide of lead, is oxidized to permanganic acid, which is reduced again by a standard solution of arsenite of sodium. Dissolve .5 gramme of steel or pig-iron in a No. o Griffin's beaker, or in a test-tube, in 30 c.c. nitric acid, 1.2 sp. gr., and boil until solution is complete and the evolution of nitrous fumes ceases. Remove from the burner, and add cautiously 1-3 grammes of dioxide of lead, or red lead, free from manganese, Washing the and dilute with hot water to about 60 c.c. Heat the solution to dpitate. boiling, and as soon as it commences to boil stand the beaker or test-tube aside and allow the lead salt to settle. When tol- erably clear, decant the solution and boil the residue with 50 c.c. nitric acid and water (i part acid to 3 parts water). Decant as before, and repeat the operation until the supernatant fluid is colorless. Filter the decantations through asbestos and titrate with a standard solution of arsenite of sodium. The standard solution may be prepared of a convenient strength by dissolving 4.96 grammes of arsenious acid together with 25 grammes of carbonate of sodium in water and diluting to 2-2^ litres. standard- To standardize this solution, treat a steel containing a known arsenite of amount of manganese, as described above, and calculate the value solution f eacn c - c - f the standard solution by dividing the per cent. of manganese in the steel by the number of c.c. required to destroy the color of the permanganic acid. Or take a measured quantity of a standardized solution of permanganate of potas- * Bull. Soc. Chim. de Paris, June 20, 1878. RAPID METHODS FOR MANGANESE. I2 sium and see how many c.c. of the arsenite of sodium are equal to I c.c. of the permanganate solution. Then the value of the permanganate solution in iron, multiplied by 11/56 is equal to its value in manganese, according to the equation, ioFeS0 4 + 2KMn0 4 + 8H 2 SO 4 = 5Fe 2 (SO 4 ) 3 + K 2 SO 4 + 2MnSO 4 + 8H 2 0, or 10 atoms of Fe correspond to 2 atoms of Mn, or 560 parts by weight of Fe no parts by weight of Mn. From this we get the weight of Mn to which I c.c. of the arsenite of sodium is equivalent, from which the percentage of manganese in the steel is calculated. The details of this method have been very carefully worked out by Mr. H. C. Babbitt, of the Wellman Steel Company, who Babbitt's has used it for many years. He finds that ordinary red lead is t i ons . quite as effective as the more expensive dioxide, and in an inter- esting series of experiments he shows that results obtained by filtering off a portion of the first solution obtained by boiling with red lead and titrating are not accordant, and that the only method of getting thoroughly reliable results is by washing out all the permanganic acid and decanting as described above. Pattinsoris Method (for Spiegel and Ferro-manganese). This method is based on the precipitation of manganese as MnO 2 , from a solution of MnCl 2 , by hypochlorite of calcium and carbonate of calcium in the presence of ferric chloride (the presence of the latter salt or of chloride of zinc being necessary to prevent the precipitation of any manganese in a lower state of oxidation than MnO 2 ).* Dissolve .5 gramme of spiegel or Details ferro-manganese in a No. 5 beaker in 15 c.c. HNO 3 , 1.2 sp. gr., method, evaporate to dryness, and heat to destroy carbonaceous matter. Redissolve in HC1, and boil down to remove HNO 3 , but not * Jour. Chem. Soc., xxxv. 365. 126 ANALYSIS OF IRON AND STEEL. to dryness, add a few drops of HC1, and dilute with 10 c.c. water. Add carbonate of calcium diffused in water, until the solution becomes reddish by neutralization of the free acid, then add 5 or 6 drops HC1 and 100 c.c. of a solution of bleaching powder (hypochlorite of calcium), made by treating 15 grammes of the powder with I litre of water and filtering. Now pour in about 300 c.c. of boiling water, which will raise the temperature of the solution to about 70 C., and add carbonate of calcium, with constant stirring, until all the iron is precipitated. If the supernatant fluid has a pink color, due to the formation of a little permanganate, add a few drops of alcohol, which will reduce it. Filter on a large filter, wash untill the filtrate is free from chlorides, place the filter and its contents in the beaker in which the precipitation was made, and add 100 c.c. of standard solution of ferrous sulphate, made as directed on page 1 2 1. When the precipitate is dissolved, transfer the solution to the dish, dilute to about I litre, titrate the excess of ferrous sulphate as directed on page 121, and calculate the percentage of Mn as there directed. The Color Method (for Steel). This method was first suggested by Pichard,* and was used essentially in its present form by Peters. f It is now in very gen- eral use in steel-works, and takes rank with the color carbon method in its usefulness. It requires one or more standard steels in which the manganese has been most carefully deter- mined by a gravimetric method. When a number of samples are to be tested at the same time, as is usually the case, a bath like the one shown in Fig. 78 is necessary, but for the man- Chiondeof ganese color method it should contain a solution of chloride of bath Um calcium, which boils at 115 C.J It is, of course, very neces- * Comptes-Rendus Hebd. des S6ances de 1'Acad. des Sciences, Dec. 30, 1872. f Chem. News, xxxiii. 35. This latter modification is due to Mr. S. A. Ford. RAPID METHODS FOR MANGANESE. 127 sary in a method of this kind that the operations should always be conducted as nearly as possible under the same conditions, and that the standard should always be dissolved at the same time as the samples to be tested. Weigh out .2 gramme of each sample and of the standard, and place them in 8-inch test- method. tubes properly numbered. Pour into each test-tube 15 c.c. HNO 3 , 1.2 sp. gr., cover each with a small glass bulb or very small funnel, and stand the test-tubes in the holes in the top of the bath, as shown in the sketch, Fig. 78. Heat in the bath at 100 C. until solution is complete. Pour the contents of a test-tube into a 100 c.c. tube, wash the test-tube out with cold water, adding it to the solution in the 100 c.c. tube, and finally dilute to the 100 c.c. mark. Mix thoroughly by placing the thumb over the top of the tube and turning it upside down several times. Draw out 10 c.c. of this solution with a pipette graduated to deliver 10 c.c., and let it run into the test-tube in which the solution was made. Treat each sample in this way, including the standard. The tube is merely washed out with water, but the pipette can be best cleaned by drawing it full from the 100 c.c. tube of the fresh sample, throwing the con- tents away, and -filling it a second time to deliver into the test- tube. Stand the test-tubes in the rack again, add to each 3 c.c. HNO 3 , 1.2 sp. gr., replace the bulbs or funnels, and stand the rack in the chloride of calcium bath, the solution in which should now be boiling. When the solutions in the test-tubes begin to boil, add to each .5 gramme fine peroxide of lead* and boil exactly five minutes. The PbO 2 can readily be meas- ured by a small platinum spoon, made to hold about .5 gramme. It is necessary that the solutions in the test-tubes should boil, and it is easy to assure one's self of this fact by looking down solutions into the test-tubes after the action caused by the addition of the PbO 2 has ceased. Remove the rack from the bath at the * See page 57. I2 g ANALYSIS OF IRON AND STEEL. expiration of the five minutes, and stand it with the test-tubes in cold water, to cool the solutions and allow the insoluble lead salt to settle. The insoluble matter settles to the bottom of the tube in a heavy compact mass, leaving the supernatant fluid perfectly clean. When this occurs, which is usually within the space of half an hour, the solutions are ready to be decanted into the comparison-tubes.* In working on a number of steels we will suppose that we use two standards, one containing 1.2 per cent, of manganese, the other .6 per cent. As we weighed out .2 gramme, diluted the solution to 100 c.c., and took 10 c.c. in which to determine manganese, the amount taken cor- responds to 0.02 gramme of the sample; and if we dilute the solutions of the standards after decanting into the comparison- tubes to 24 c.c., one c.c. will correspond to .05 per cent, in the high, and .025 per cent, in the low, standard. Decant each solution in turn into a comparison-tube, -and dilute it until it Comparing has the exact tint and depth of color of the standard to which the colors. it most nearly approximates when first decanted. The per- centage of manganese is found by multiplying the number of c.c. to which the sample has been diluted by .05 or .025, according to the standard with which it has been compared. If, however, the solution of a sample when first decanted and before dilution should be lighter in color than the lower standard, the latter may, after the other samples have all been finished, be diluted to 30 c.c., when each c.c. will correspond to .02 per cent, manganese, or, if this color is not sufficiently light, to 40 c.c., when each c.c. will correspond to .015 per cent, manganese. When even this color is not sufficiently light, a lower standard must be used for comparison, or a larger amount of the sample taken for solution. The comparison of the colors should be made in a camera or box, as shown in Fig. 8 1. * See Fig. 80. DETERMINATION OF TOTAL CARBON. I2 g The direct rays of the sun should not be allowed to shine on the solutions, and a northern light for the comparisons is preferable to any other. DETERMINATION OF CARBON. Carbon differs from all other elements in iron and steel in The con- . ditions that it is supposed to exist in several conditions, and analytical in which chemistry supplies the means of distinguishing between at least two of these conditions. Until within a few years it was con- and sidered to exist in two forms, as graphite and as combined car- bon. To Karsten is due the recognition of the fact that graphite is a form of pure carbon, and not a compound of carbon and hydrogen. It is always present as a mechanical mixture, and is thus distinguished from the other form, which was supposed to be combined chemically with the iron. Of late years the opinion has been growing that " combined carbon" exists in at least two conditions in steel, but as yet chemical methods for separating and distinguishing between these conditions have failed, so far as quantitative work is concerned. The analytical methods here given are: The Determination of Total Carbon, The Determination of Graphitic Carbon, and The Determination of Combined Carbon. DETERMINATION OP TOTAL CARBON. We may divide the methods for the determination of total carbon in iron and steel into the following classes : A. The direct treatment of the borings or drillings without previous separation of the iron, including : I. Direct combustion in a current of oxygen (Berzelius). 130 ANALYSIS OF IRON AND STEEL. 2. Combustion with chromate of lead and chlorate of potas- sium (Regnault). 3. Combustion with oxide of copper in a current of oxygen (Kudernatsch). 4. Combustion with potassium bisulphate (Bourgeois). 5. Solution and oxidation of the borings in sulphuric, chromic, and phosphoric acids, the volume of the CO 2 being measured (Wiborg, modified). 6. Solution and oxidation of the borings as in 5, the CO 2 being weighed. B. Removal of the iron by volatilization, and subsequent com- bustion of the carbon, including : 1. Volatilization in a current of chlorine (Berzelius, Wohler). 2. Volatilization in a current of hydrochloric acid gas (Deville). C. Solution of the iron, and combustion or weighing of the residue, including: 1. Solution in double chloride of copper and ammonium, filtration, and weighing or combustion of the residue (Pearse and McCreath). 2. Solution in* double chloride of copper and potassium, filtration, and combustion of the residue in oxygen (Richter). 3. Solution in chloride of copper, and combustion of the residue (Berzelius). 4. Solution in iodine or bromine, and combustion with chro- mate of lead, or weighing, of the residue (Eggertz). 5. Solution by fused chloride of silver, and combustion of the residue (Berzelius). 6. Solution of the iron in sulphate of copper, filtration, and combustion of the residue in a boat in a current of oxygen (Langley). 7. Solution of the iron in sulphate of copper, and oxidation of the residue by CrO 3 and H 2 SO 4 (Ullgren). 8. Solution in dilute HC1 by the aid of an electric current, and combustion of the residue (Binks, Weyl). DETERMINATION OF TOTAL CARBON. l ^ l The most accurate method is undoubtedly the solution of the drillings in the double chloride of copper and potassium and combustion of the residue in oxygen gas. A. 1. Direct Combustion in a Current of Oxygen. This method requires the sample to be reduced to a very fine Necessity for pow- state of subdivision, otherwise some of the metal in the centre dermg the of the lumps becomes coated with oxide, and the carbon in 7a is prepared in the same way as directed for the boat, and, after drying the carbonaceous residue, the disk is moved upward in the filtering-tube before inserting the latter in the combustion-tube, to allow the gas to pass through the filtering-tube during the combustion. The boat has several advantages over the filtering-tube, the principal one being that the boat has a much larger filtering-sur- face, and, besides r there is no danger of the felt being disturbed during the filtering, while the disk in the tube may be loosened in its seat and allow some of the carbonaceous matter to pass around it. If the boats when not in use are kept carefully covered, the same felts may be used for a large number of filtrations; but occasionally they become clogged, and then it is better to renew them. Instead of either of these forms of filtering-apparatus, a sim- Glass filter- pie glass tube, as represented in Fig. 71, may be used. The closely-coiled spiral of platinum wire fits in the tube as shown in the sketch. On this is placed a rather thick layer of ignited long-fibre asbestos, and ignited asbestos suspended in water is poured over it to make a solid felt. The tube may be used in a stand, as represented in Fig. 72, or it may be used with the 158 ANALYSIS OF IRON AND STEEL. filter-pump under very gentle pressure. Filter and wash the carbonaceous matter, and while still moist transfer it to the boat FIG. 71. C FIG. 72. (Fig. 73) by opening out the sides of the boat, inverting the tube over it, and allowing the felt and spiral to slide out of the tube. Wipe off any carbonaceous matter that may remain on the sides FIG. 73- Boats of platinum- foil. of the tube, or that may have adhered to the spiral in removing it, with little wads of fibrous asbestos held in the forceps (Fig. 67). Place these wads in the boat, bend the sides of the latter into DETERMINATION OF TOTAL CARBON. 159 their proper shape, dry the boat and contents at 100 C, insert the boat in the porcelain or platinum tube, and burn off the carbonaceous matter as before directed. This boat is made by cutting a piece of platinum-foil in the shape shown in Fig. 74, and bending it up over a brass former into the shape shown in Fig. 73. FIG. 74- Instead of burning the carbonaceous matter in a current of combustion oxygen, it may be burned by H 2 SO 4 and CrO 3 in the arrange- ment shown in Fig. 75. P' is an empty U-tube, O is a tube containing sulphate of silver dissolved in strong H 2 SO 4 , P con- tains anhydrous sulphate of copper, Q granular dried chloride of calcium,* the Liebig bulb and drying-tube R constitute the absorption apparatus, S is the safety-guard tube, and L, L con- stitute the arrangement for passing air through the apparatus. The air is freed from CO 2 in passing through the U-tube M filled with lumps of fused caustic potassa. Transfer the carbo- naceous matter and asbestos to the flask A, insert the stopper carrying the bulb-tube B, close the stopcock C, and connect the apparatus as shown in Fig. 75, including the weighed ab- sorption apparatus. See that the joints are all tight, and then pour into B 10 c.c. of a saturated solution of chromic acid, ad- mit it to the flask A by opening the stopcock C, and then pour of the residue inCrO 8 and H 2 S0 4 . * The bulb of Q contains a wad of slightly moistened cotton-wool, as described on page 137. i6o ANALYSIS OF IRON AND STEEL. DETERMINATION OF TOTAL CARBON. l ^ l into B 100 c.c. strong H 2 SO 4 which has been heated almost to boiling with a little CrO 3 . Let this run into A slowly, connect the air-apparatus by the tube N, and start a slow current of air through. Light a very low light under A, and increase it grad- ually until the liquid is heated to the boiling-point. Gradually lower the light while the current of air continues to pass, and when about I litre of air has passed through the apparatus after the light is extinguished, detach and weigh the absorption ap- paratus, with the precautions mentioned on page 146. The carbonaceous residue may also be weighed directly in- weighing stead of being burned off. In this method, filter on a Gooch residue* crucible or on counterpoised filters,* dry at IOO C, and weigh. Burn off the carbonaceous matter and weigh the residue : the difference between the two weights is carbonaceous matter, which contains about 70 per cent, of carbon f in steel or iron free from graphite. Of course this method of direct weighing is applicable only to samples when all the carbon is in the so-called combined condition. 2. Solution in Chloride of Copper and Chloride of Potassium, Filtration, and Combustion of the Residue in Oxygen. As a solvent this salt has no advantage over the ammonium salt, but the presence of carbonaceous matter in the latter, which can only be removed by repeated crystallizations, has brought the potassium salt into use. Solution is almost, if not quite, as rapid Advantages . of the po- with the potassium salt as with the ammonium salt, and the price is decidedly in favor of the former. The absence of volatile con- stituents is another advantage, for it is quite possible that chlo- ride of ammonium if left in the carbonaceous residue may be decomposed in the red-hot oxide of copper and form some com- pound capable of being absorbed by the caustic potassa in the Liebig bulb of the absorption apparatus. The only satisfactory * See page 27. f Amer. Chem. Jour., iii. 245. II : 62 ANALYSIS OF IRON AND STEEL. way to test a solution of double chloride is to make several deter- minations on a standard steel with each fresh lot of the solvent. 3. Solution in Chloride of Copper, and Combustion of the Residue. The only disadvantage in the use of this reagent is the length of time required to dissolve a sample of steel in it. Even with a strongly acid solution and constant stirring, unless the sample is very finely divided, it may require several days for its complete solution. 4. Solution in Iodine or Bromine, and Combustion with Chromate of Lead, or "Weighing, of the Residue. The determination by this method, when iodine is used, is carried out exactly as directed for the estimation of " Slag and Oxides," page 79, the residue being filtered on asbestos, dried, and burned with chromate of lead or oxide of copper, as directed Weighing in A. 2, page 132 et seq. The residue may also be filtered on du e e resi a counterpoised filter* or Gooch crucible, washed, dried at 100 C, weighed, the carbonaceous matter burned off, and the resi- due weighed. The difference between the weights is the amount of carbonaceous matter, which contains, according to Eggertz,f 59 per cent, of carbon. It also contains about 16 per cent, of iodine, so that the residue cannot be burned in a current of oxygen, nor with CrO 3 and H 2 SO 4 . If bromine is used instead of iodine, great care must be taken in adding the bromine, 10 c.c. bromine for 5 grammes of iron or steel, as the action is very violent, and unless the bromine is added very slowly and the solution kept as near o C. as possible, there will be oxida- tion, and, consequently, loss of carbon. The details of the method when bromine is used are otherwise the same as when iodine is the solvent. * See page 27. f Percy, Iron and Steel, page 891. DETERMINATION OF TOTAL CARBON. 5. Solution by Fused Chloride of Silver, and Combustion of the Residue. Fuse in a porcelain crucible 20 grammes of chloride of silver, Details and see that the button when cold has a smooth, flat surface on method, top. Place the button in a porcelain dish about 6 inches ( 1 5 cm.) in diameter, and pour on the button 3 grammes of drillings. Add 300 c.c. cold distilled water containing 2 drops of HC1, place the dish on a ground-glass plate, and cover it with a bell-glass to exclude the air during the time occupied in dissolving the sample. It is not necessary that the sample should be in drillings, as a single piece will be dissolved in this way. The chloride of silver should weigh at least 6 times as much as the sample of iron or steel. The reaction is a simple substitution, Fe+ 2AgCl FeQ 2 -f- 2Ag, by galvanic action, but secondary reactions occur, including the decomposition of water, both hydrogen and oxygen being taken up by the carbon at the moment of its liberation. A slight excess of oxygen over the amount necessary to form water with the hydrogen is taken up and a little hydrogen is liberated. There is a tendency, of course, for the ferrous chloride when formed to oxidize, consequently the air must be excluded. The decomposition requires several days, as many as ten if the sample of steel or iron is in a single piece and not very thin. The metallic silver is quite cohesive, and is readily separated from the carbonaceous residue. When the action is finished, remove the mass of silver, washing off any of the carbonaceous matter ad- hering to it, add a little HC1 to dissolve any ferric oxide which may have formed, filter off, and burn the carbonaceous matter by one of the methods previously described. 6. Solution of the Iron in Sulphate of Copper, Filtration, and Combustion of the Residue in a Boat in a Current of Oxygen. Weigh 3 grammes of steel into a No. 3 beaker, and add 150 c.c. of solution of sulphate of copper, made by dissolving 200 164 ANALYSIS OF IRON AND STEEL. Prepara- tion of sulphate of copper solution. grammes of the copper salt in water, adding a dilute solution of caustic soda until a slight permanent precipitate appears, allowing it to settle, filtering through asbestos, and diluting to I litre. For pig-iron, spiegel, and ferro-manganese, use I gramme, and 50 c.c. of sulphate of copper solution. Heat the solution gently, and stir well until decomposition is complete. Filter in a glass filtering- tube on asbestos, as described on page 157. Wash well with water, transfer to a boat, as directed on page 158, dry, and burn in a porcelain tube, as directed for A. I, page 131. The results are apt to be a' little low, owing to the difficulty of thoroughly oxidizing the mass of copper mixed with the carbonaceous matter.* Instead of filtering off the mass of copper, carbonaceous matter, etc., decant the clear supernatant fluid through the filtering-tube, wash several times by decantation, and then dissolve the copper in double chloride of copper and ammonium, chloride of copper, or ferric chloride. Filter, wash the residue with a little dilute HC1, and then with cold water, transfer to a boat, and burn as directed on page 142 et seq. 7. Solution of the Iron in Sulphate of Copper, and Oxida- tion of the Residue by CrO 3 + H 2 SO 4 , Treat the sample with solution of sulphate of copper, as in the method just described. Allow the precipitated copper and carbonaceous matter to settle, pour off the clear supernatant liquid, and transfer the residue to the flask A (Fig. 75, page 160) by means of a platinum spatula and a fine jet of water. The water used should not exceed 20 or 25 c.c.f The apparatus is that sketched in Fig. 75, the only difference being that the tube * See report of the U. S. Board appointed to test iron, steel, and other metals, vol. i. p. 284. f The borings may be treated with the sulphate of copper solution in the flask A, and the clear liquid drawn off with a pipette. This will avoid the necessity for transferring the residue. DETERMINATION OF TOTAL CARBON. i6 5 O contains merely a little strong H 2 SO 4 . exactly as described on page 159. Effect the combustion FIG. 76. Description of the ap- paratus. 8. Solution in Dilute HC1 by the Aid of an Electric Current, and Combustion of the Residue. The arrangement shown in Fig. 76 may be used in carry- ing out the details of this method. It consists of a Nc. 3 Griffin's beaker, in which is a piece of platinum-foil, the wire from which connects with the negative pole of the battery; a small basket of very fine platinum gauze is supported from a platinum wire, on one end of which is a clamp connecting with the positive pole of the battery. The battery is usually a single Bunsen or Grove ele- ment, and the intensity of the current should be regulated by varying the distance between the foil and the basket, or by introducing resistance-coils in the connections, so that no gas is given off from the iron. Hy- drogen, of course, is given off abundantly from the surface of the foil, and the iron dissolves in the acid as ferrous chloride. Weigh into the basket from i to 5 grammes of the sample, which should be in pieces and not in powder. Suspend the basket from the wire, having previously connected the rest of Details the apparatus and poured into the beaker a mixture of 200 c.c. water and 50 c.c. HC1, and regulate the intensity of the cur- rent as directed above. When solution is complete, remove the foil from the liquid, wash the carbonaceous matter from the basket with a jet of cold water, and determine the amount of carbon by one of the methods previously given. of the method. 1 66 ANALYSIS OF IRON AND STEEL. DETERMINATION OP GRAPHITIC CARBON. Karsten gave the first information in regard to the existence of graphite in pig-iron, and he suggested dissolving the sample in HNO 3 with the addition of a few drops of HC1, in HC1 alone, or in dilute H 2 SO 4 , boiling the residue with caustic potassa, filter- ing, washing again with HC1, and finally with water, and weighing the residue as graphite. A very interesting comparison of the results obtained by the use of different solvents is given by Drown,* and many experiments seem to show that the amount of graphite found varies with the different acids used to dissolve the sample, and also with the variations of treatment when the same Solution acid is used. The usual method is as follows : Treat I gramme of pig-iron or 10 grammes of steel with an excess of HC1, i.i sp. gr. When all the iron is dissolved, boil for a few minutes, allow the graphite to settle, and decant the supernatant fluid on an asbestos filter, using either the perforated boat, Fig. 66, or the filtering-tube, Figs. 70 and 71. Wash several times with hot water by decantation, then pour on the residue in the beaker 30 c.c. of a solution of caustic potassa, sp. gr. i.i, and, when the effer- vescence ceases, heat the solution to boiling. Filter on the same filter, transfer the graphite, etc., to the filter, wash with hot water again, and finally with alcohol and ether. Burn the graphite by one of the methods given under " Determination of Total Carbon," and from the weight of CO 2 obtained calculate the percentage Comparison of carbon existing as graphite. It frequently happens, when the obtaTntd 5 sam pl e is a high steel, that the residue which remains after treat- by dis- j n g j t as a b ove j s black, and contains carbon, but it is not crystal- solving in HCI line in appearance, and bears no resemblance to graphite. The and HN0 3 . same steel will dissolve completely in HNO 3 , and when filtered will not leave a trace of carbon on the felt. Steels containing graphite give appreciably less carbon when dissolved in HNO 3 than when dissolved in HCI. The method giving probably the * Trans. Inst. Min. Engineers, vol. iii. p. 42. DETERMINATION OF COMBINED CARBON. 167 most accurate and certainly the most uniform results is as fol- lows : Dissolve the weighed sample in HNO 3 , sp. gr. 1.2, using solution in 15 c.c. of acid to each gramme taken for analysis. Filter on the perforated boat or on an ignited asbestos filter, in a glass tube, transfer the residue to the filter, and wash thoroughly with hot water. Treat the residue on the filter with hot caustic potassa solution, i.i sp. gr. (as the Si is all oxidized to SiO 2 there will be no effervescence), wash thoroughly with hot water, then with a little dilute HC1, and finally with hot water. Burn the carbon by one of the methods previously mentioned and calculate the CO 2 obtained to carbon, and call the result graphite* DETERMINATION OP COMBINED CARBON. Indirect Method- Having determined the total carbon and the graphite, by subtracting the latter from the former we obtain the amount of carbon existing in the combined condition. Direct Method. This method was first introduced by Eggertz,f in 1862. It is based on the fact that when steel containing carbon is dis- solved in HNO 3 , 1.2 sp. gr., the carbon, which sometimes at first separates out in flocks of a brownish color, is eventually dis- solved, giving to the solution a depth of color directly propor- tionate to the amount of combined carbon in the steel. To use this in practice it is only necessary to determine accurately the amount of combined carbon contained in a steel, by a combustion method, and to compare the depth of color in a solution of this standard with that of any unknown steel, in order to ascertain the Limitatioll amount of carbon in the latter. There is, however, a limitatation the use of this in the application of this method. Reference was made on page method. * Shimer (Jour. Amer. Chem. Soc., vol. xvii. p. 873, has shown that carbide of titanium is insoluble in dilute hydrochloric acid and that the nitric acid method is the only accurate one for the determination of graphite. f Jern-Kontorets Annaler, 1862, p. 54; 1874, p. 176; 1881, 301; Chem. News, vii. p. 254; xliv. p. 173. ANALYSIS OF IRON AND STEEL. 129 to the fact that combined carbon is now believed to exist in two conditions in steel, or rather that under circumstances a por- tion of the combined carbon changes its condition, and, from a chemical point of view, while it is still combined carbon, in that it is soluble in HNO 3 , it fails to impart so dark a color to its nitric acid solution as it did in its original state. The circumstances under which a change of this kind occurs are quite well known, and are merely those occasioned by the mechanical treatment to which steel is submitted, such as hammering, rolling, hardening, tempering, etc.* It may be stated, then, as a general proposition, that the standard steel for the color-test should be of the same kind and in the same physical condition as the samples to be tested. To obtain the best results samples should be taken from the original ingots that have not been reheated, rolled, or hammered ; Bessemer steel should be compared with Bessemer, crucible with crucible, open hearth with open hearth ; the standard should con- tain approximately the same amount of carbon as the samples to be tested, and should have as nearly as possible the same chem- ical composition. The only elements that seem to have any de- cided effect on the color of the nitric acid solution are copper, cobalt, and chromium. Details Weigh out carefully .2 gramme of each sample, including the method standard, into test-tubes 6 inches (150 mm.) long and ^ inch (16 mm.) in diameter. The test-tubes should be perfectly clean and dry, and each one marked with the number of the sample on a small gummed label near the top. A little wooden rack (Fig. 77) is convenient for holding the test-tubes in the weighing-room, and to avoid all chance of error the tube is not placed in the rack until the sample has been weighed and is ready to be transferred. * Two very interesting papers on this subject will be found in the Chem. News, J. S. Parker, "On the Varying Condition of Carbon in Steel," xlii. p. 88; T. W. Hogg, "On the Condition of Carbon in Steel," xlii. p. 130. In my own practice I have seen one-third of the total carbon changed from the combined form to the graphitic in a high carbon steel by heating and hammering the ingot. DETERMINATION OF COMBINED CARBON. jfo A little platinum or aluminium dish about \y 2 inches (40 mm.) in diameter, with a spout, and furnished with a counterpoise (Fig. 44, page 36), is very convenient for holding the drillings, which are brushed from it into the test-tube with a camel's-hair brush. A very excellent form of water-bath is shown in Fig. 78. It may be pro- vided with a constant level arrangement, consisting of a tubulated bottle, the height of the end b of the vertical tube a Description fixing the level of the water in the bath. A is the bath, and bath!* 6 B the rack. The top of the rack is of sheet-copper, perforated to receive the test-tubes, the bottoms of which rest on the coarse Q C 7 r ^ V r ^ V TJ V V r H ^ i V i I (T\ Jj t j j> i ^ & FIG 78. copper gauze, which is joined to the top by the uprights C. The top of the rack rests on a flange around the top of the bath. Place the test-tubes in the rack B, and stand the rack in the bath which contains cold water. Drop into each test-tube, from ANALYSIS OF IRON AND STEEL. Amount of HNO 8 to be used. Apparatus for de- livering different volumes of HNO 8 . FIG. 79. a pipette, the proper amount of HNO 3 , sp. gr. 1.2. For steels containing less than .3 per cent, carbon use 3 c.c. HNO 3 ; from 3 to .5 per cent, carbon, 4 c.c. ; from .5 to .8 per cent., 5 c.c. ; from .8 to I per cent., 6 c.c. ; and over I per cent, 7 c.c. An insufficient amount of acid gives the solution a slightly darker tint than it should properly have. The apparatus shown in Fig. 79 * is useful for the rapid addi- tion of different measured quantities of nitric acid to the samples. It consists of a glass reservoir holding 750 c.c., communicating below with four bu- rettes graduated to deliver various quantities of acid up to 10 c.c. Each burette is fur- nished with a loose-fitting glass cap. The burettes are fitted with three-way glass stop- cocks, so that a quarter of a revolution con- nects them with the reservoir, and when the proper amount of acid has run in, the stop- cock is turned another quarter, which shuts off the reservoir and completely empties the burette, thus delivering the exact amount of acid measured, into the test-tube contain- ing the weighed sample of steel in which carbon is to be determined. As shown in the cut, each test-tube stands in a bottle of cold water to prevent too violent action of the acid during solution. The whole apparatus is mounted on a rotary stand, and, as used at the laboratory of the Bethlehem Iron Company, is contained in a small hood near the drill and balance described on page 16, so that the operator, seated on a revolving stool, can add acid to one sample of steel while the drillings of the next sample are falling into the balance-pan. * Communicated to the author. DETERMINATION OF COMBINED CARBON. j^j The apparatus, as here shown, is a modification by Mr. Albert L. Colby, chemist of the Bethlehem Iron Company, of an appa- ratus first designed by Mr. E. A. Uehling in 1884. The HNO 3 is made by adding its own volume of water to Proper acid of the usual strength, 1.4 sp.gr. It should be absolutely O f HNO S . free from chlorine or hydrochloric acid, as, according to Eggertz, .0001 gramme Cl in a nitric acid solution of .1 gramme iron in 2.5 c.c. HNO 3 gives a decided yellow color. The HNO 3 should be added slowly, to prevent violent action, and the drillings should not be too fine, for the same reason. Place in the top of each test-tube a small glass bulb * or a very small funnel, and heat the water in the bath to boiling, and boil until all the carbonaceous matter is dissolved, shaking the tubes from time to time to prevent the formation of any little film of oxide. The time required for solution is for low steels about twenty minutes, and for high steels (over I per cent, carbon) forty-five minutes, After entire solution of the carbonaceous matter, prolonged heat- ing tends to make the color lighter ; therefore, as soon as the absence of small bubbles and the disappearance of any brownish flocculent matter show complete solution, remove the rack from the bath and stand it in a dish of cold water. The dish should be about the same size as the bath, so that the top will be covered by the top of the rack, thus excluding the light from the solutions, in which case the color will not fade for a long time. Under all circumstances the solutions should be kept out of the light, and especially out of direct sunlight, as much as possible. If there should be necessarily, in the steels operated on at one time, a wide range in carbon, the test-tubes should be removed from the bath as fast as their respective contents are dissolved and placed in cold water in a dark place. The appearance of the drillings will often give an idea of the approxi- * These bulbs are easily made by sealing one end of a glass tube in the blow- pipe flame, heating it, blowing a bulb of the proper size, allowing it to cool, heating it above the neck, and drawing it out as shown in Fig. 77. 1/2 ANAL YSIS OF IRON AND STEEL. Comparing the colors. Compari- son-tubes. wood's modifica- tions for mate carbon contents of a sample, but when there is no clue whatever, it is best to begin by adding 3 c.c. HNO 3 to the weighed portion in the test-tube, and increase the amount I c.c. at a time as the depth of color of the solution or the amount of flocculent carbonaceous matter indicates a higher carbon percentage. To compare the colors of the solutions, pour the standard into one of the carbon tubes (Fig. 80), wash out the test-tube with a little cold water, add it to the solution in the carbon tube, and dilute to a convenient amount. This dilution should be sufficient to make the volume of the diluted standard at least twice as great as the volume of acid originally used to dissolve the sample, as this amount of water is necessary to destroy the color due to the nitrate of iron. It should not, however, greatly exceed this amount, and should be in some convenient multiple of the carbon contents of the standard in tenths of a per cent. Thus, if a standard contains .45 per cent. carbon, dilute the solution in the carbon tube to 9 c.c.. then each c.c. will equal .05 per cent. The carbon tubes should be about ]/ 2 inch (12 mm.) in diameter, holding at least 30 c.c., and graduated to ^ c.c. The tubes should have exactly the same diameter, and the glass should be perfectly colorless and have walls of the same thickness. They should, of course, be most accurately graduated. Mr. E. F. Wood,* of the Homestead Works, leaves the ... lower ends of the tubes free from graduations to give a clear space for comparing the colors. He considers this especially necessary in low steels, for which he uses I gramme of the sample, dissolves in 25 c.c. of nitric acid, boils for five to seven minutes in a glycerine bath at 140 C, and compares in tubes Y inch (18 mm.) in diameter. FIG. 80. 121 Communicated to the author. DETERMINATION OF COMBINED CARBON. 173 The standard having been prepared, pour the solution of the sample to be tested into another carbon tube, rinse the test- tube into it with a little cold water, and compare the colors. If the solution of the sample is darker than that of the stand- ard, add water little by little, shaking the tube well to mix the solution until the shades are exactly the same. Allow a minute or two for the solution to run down the walls of the tube, and read the volume. If the standard was diluted as above, then, of course, each c.c. will equal .05 per cent, carbon, and if the volume of the sample is 10.5 c.c. it will contain .525 per cent, carbon. If the solution of the sample when first transferred to the tube should be lighter in color than the standard, a lower standard must be used, or this one may be diluted to, say, 13.5 c.c., in which case the number of c.c. divided by 3 will give the percentage of carbon in tenths. The color may be com- pared by holding the two tubes in front of a piece of white paper held towards the light, but a camera made of light wood and blackened inside is most convenient, and at night is quite invaluable. It is shown in Fig. 8 1, and consists of a box 3^ inches (90 mm.) high inside, i^ inches (38 mm.) wide at one end, and 5 inches (127 mm.) at the other. It is 24 inches (610 mm.) long, and is supported on a rod, which can be raised and lowered to suit the convenience of the ob- server. The small end is closed by a piece of ground-glass, which slides in through a slot on top I inch (25 mm.) from the end. Immediately beyond this is an- other slot to receive a thin piece of faintly blue glass, which is inserted when the tests are made at night, using an oil-lamp FIG. 81. Description of camera. 1 y ^ ANALYSIS OF IRON AND STEEL. placed on a stand just beyond the camera. In fact, in many steel-works, to avoid the differences between the colors as seen by daylight and lamplight, all comparisons are made in a dark room, using a box or camera and an oil-lamp. Two holes in the top of the camera just inside the ground-glass screen receive the carbon tubes, the ends of which rest on a piece of black cloth on the bottom of the camera inside. Another piece of black cloth fastened across the top of the camera, covering the top of the ground-glass slide, and having holes just large enough to admit the tubes, excludes all light except that at the back of the tubes. A north light is much the best for com- paring the colors, and, as to most observers the left-hand tube appears a little the darker, the color will be exactly matched when, the tubes being reversed, the left-hand tube still appears a little the darker of the two. Use of per- Instead of diluting the solutions to agree with a standard, as ^ndards. above described, some chemists use a rack of permanent stand- ards, as suggested by Britton.* The principal difficulty hereto- fore attending the use of permanent standards has been the im- possibility of preventing their fading ; but, according to Eggertz,f this is now entirely overcome by the method of preparing them suggested by Prof. F. L. Ekman. The details are as follows : Dis- solve 3 grammes of neutral ferric chloride in 100 c.c. water con- taining 1.5 c.c. HC1; dissolve 2.1 grammes cupric chloride in 100 c.c. water containing .5 c.c. HC1 ; dissolve 2.1 grammes cobaltic chloride in 100 c.c. water containing 5 c.c. HC1, using the neutral Preparation salts in all cases. These solutions will contain about .01 gramme solution, of the metal to the c.c., and by adding to 8 c.c. of the iron solu- tion 6 c.c. of the cobalt solution, 3 c.c. of the copper solution, and 5 c.c. water containing .5 per cent HC1, a liquid is obtained which has a color approximating to that obtained by dissolving .2 gramme of steel, containing I per cent, of carbon, in HNO 3 , and * Chem. News, xxii. 101. f Chem. News, xliv. 173. DETERMINATION OF COMBINED CARBON. ij$ diluting to 10 c.c., or .1 per cent, carbon to the c.c. Prepare a number of test-tubes of the size described on page 168, but in this case it is essential that they should be of exactly the same diameter, and that the glass should be as nearly colorless as pos- sible. By successive dilutions with water containing .5 per cent. Preparation HC1, of the normal solution prepared as above, make solutions of standards. about the proper strength for the series required. The variations should be about .02 per cent, between the differ- ent tubes of the series, corresponding to, say, the even hundredths. There should be about 10 c.c. of solution in each tube, and then the color of each should be compared with a standard steel, diluted to the exact strength required in the permanent standard. For example, if the standard steel contains .4 per cent, carbon, and you wish to get the exact color for the .32 per cent, carbon tube in the permanent series, then dissolve .2 gramme of the standard exactly as directed on page 170, pour the solution into a carbon tube, and dilute it in accordance with the formula, carbon required : carbon of standard : : 10 c.c. : the number of c.c. required, or, in this case, 32 : 40 : : 10 c.c. : 12.5 c.c. Therefore dilute the solu- tion in the carbon tube to 12.5 c.c., pour 10 c.c. into a test-tube exactly like those used for the permanent standards, and compare it with the .32 per cent, carbon tube. If the color of the perma- nent solution is not exactly the same, correct it by adding por- tions of the solutions of the iron, cobalt, or copper salts, or water containing .5 per cent. HC1. The iron salt or HC1 alone gives a yellowish, the cobalt salt a brownish, and the copper salt a green- FIG. 82. ish, tone to the solution. The standards may now be arranged in a rack, as shown in Fig. 82. The colors of the permanent stand- ards once fixed, the samples to be analyzed are treated exactly ANALYSIS OF IRON AND STEEL. Details of method when using per- manent standards. White cast iron. Filtering from graphite, etc. Stead's method. as described on page 170, the test-tubes used being precisely like those containing the permanent standards, and each one carefully graduated to contain 10 c.c. When the samples (.2 gramme each) are dissolved and cooled, dilute each solution in turn with cold water to 10 c.c., mix thoroughly, and compare it with the stand- ards in the rack, by which means the carbon may be estimated to the nearest hundredth of a per cent. In testing white cast iron, use only .05 gramme, dissolve in 7 c.c. HNO 3 , dilute the standard to some convenient amount approxi- mating 20 c.c., and compare as quickly as possible to avoid the precipitation of carbonaceous matter, which is apt to occur under these circumstances. The graphite in ordinary gray pig-iron, and sometimes even in steels, renders filtration necessary. In this case add to the cold acid solution one-half of its volume of water, filter through a small, dry, ashless filter into the carbon tube, wash with as little water as possible, and compare as usual. For steels very low in carbon, the color test, as above described, becomes uncertain, but Stead* has suggested and elaborated a method which gives excellent results. It is based on the fact that the carbonaceous matter liberated from iron and steel is soluble in the caustic alkalies as well as in HNO 3 , while the color which it imparts to the alkaline solution is about 2^ times as great as that which it gives to the acid solution. For this method is required, besides the HNO 3 , 1.2 sp. gr., a solution of caustic soda 1.27 sp. gr. Weigh I gramme of each sample, including the standard, into a No. I beaker, add 12 c.c. HNO S , and heat on the bath until solution is complete, which, in the case of puddled iron or low steel, is in about five or ten minutes. Add to each 30 c.c. of boiling water and 13 c.c. of the soda solution, stirring well. Pour each solution in turn into a glass measuring-jar, dilute to 60 c.c., mix thor- oughly, allow the solution to settle, filter through a dry filter, and receive 15 c.c. of each sample in a carbon tube. Those samples * Jour. Iron and Steel Institute, 1883, No. I, p. 213. DETERMINATION OF COMBINED CARBON. 177 whose solutions are darker than that of the standard contain, of course, more carbon than the standard. Dilute the solutions in turn until the colors agree with that of the standard. The per- centage of carbon is deduced from the equation x^=^, in which a is the percentage of carbon in the standard, 15, of course, the number of c.c. taken of each solution, b is the number of c.c. in the diluted sample, and x is the percentage of carbon in the sample. Take those samples whose solutions are lighter than that of the standard, and dilute the standard until its color is the same as that of the darkest of the samples, read the volume, and dilute it for the next darkest, and so on through the series. The percentage of carbon in each sample is then deduced FIG. 83. a from the equation -, X 1 5 = 13 ITs the letters having the meaning given above. They may also be compared by pouring into measuring-tubes until the colors appear equal when looked at from above. The carbon in this case is inversely as the length of the column. To facili- tate the comparison, Stead (loc. cit.) has devised a very simple instrument based on this last principle. It consists (Fig. 83) of two parallel tubes of any con- venient diameter fastened to a frame. The tube b is open at both ends, but is contracted at the point c. The contracted end passes through the stopper of 12 =L 19 i. 18 1L 17 I. 16 Tl5 ANALYSIS OF IRON AND STEEL. the bottle d, and reaches almost to the bottom of the bottle. A small tube, e t which ends just below the stopper, is connected with a bulb syringe, f. The tube a is closed at the lower end, and contains a small, solid, glazed china cylinder, which rests on the bottom. A similar cylinder rests just above the con- traction in the tube b, and the tubes are so arranged that the upper flat surfaces of the cylinders are on the same level, and exactly the same distance from the open tops of the tubes. The scale g is graduated in .02 up to .20 from the level of the upper surfaces of the cylinders to a point marked on the tube a, 10 inches (254 mm.) above. A solution of a standard steel contain- ing .2 per cent, carbon, prepared as above, is placed in the bottle d, and a similar solution of a sample to be tested is poured into the tube a up to the mark. By squeezing the bulb f a column of the standard solution is forced up the tube b, and when, by looking into the mirror, placed at an angle of 45, the color in the two columns appears equal in intensity, the percentage of carbon is read off on the scale opposite the top of the column in b. The alkaline solution is said to keep its color unaltered for a month when not exposed to direct sunlight. DETERMINATION OF TITANIUM. By Precipitation. Only traces or very minute amounts of titanium are found in steel, but notable quantities exist in some kinds of pig-iron. As pointed out by Riley,* when pig-iron containing titanium is dissolved in HC1 a portion of the titanium goes into solution, while the remainder is found with the insoluble matter. The insoluble portion, as noticed on page 86 et seq., contains P 2 O 5 . It is a curious fact that while TiO 2 interferes with the deter- * Jour. Chem. Soc., xvi. 387. DETERMINATION OF TITANIUM. mination of P 2 O 5 by its tendency to form upon evaporation to insoluble phospho- dryness an insoluble phospho-titanate, so P 2 O 5 interferes with the determination of TiO 2 by partially preventing the precipita- tion of TiO 2 from its boiling sulphuric acid solution. The best Separation method- therefore, for the determination of titanium is to proceed exactly as for the determination of phosphorus when titanium is present, as directed on page 86 et seq., until the residue from the aqueous solution of the carbonate of sodium fusion is ob- tained. Dry this residue, transfer it to a large platinum crucible, preferably the one in which the carbonate of sodium fusion was made, burn the filter, add its ash to the residue, and fuse the whole with 15 or 20 times its weight of bisulphate of potassium. In fusing with bisulphate of potassium it is necessary to begin Fusion with a very low heat, and to raise the temperature very slowly KHSO* and carefully to a low red heat, as the mixture has a strong tendency to boil over the top of the crucible whenever the tem- perature is increased too rapidly. When the lid of the crucible is raised, fumes of SO 3 should come orT, and the fusion should be kept at this point for several hours, or until it is quite clear and the whole of the ferric oxide has been dissolved. Incline the crucible as far as possible on one side while the fused mass is still liquid, and allow it to cool in this position. The mass will harden in a cake on the side of the crucible, and can be readily detached without bending the sides of the crucible. Place the crucible and lid in a No. 4 beaker, and suspend in the beaker a little platinum wire-gauze basket containing the fused mass, as shown in Fig. 76, page 165. Pour into the beaker 50 c.c. of strong sulphurous acid water, and fill the beaker to the top of the fused mass in the basket with cold water. Under Solution of the bisul- these circumstances the fused mass dissolves quite rapidly, as the concentrated solution falls to the bottom, and the iron is at the same time deoxidized. Without the basket, it is necessary to stir the liquid constantly, and the time occupied in dis- solving the fused mass is much prolonged. When solution is ANALYSIS OF IRON AND STEEL. complete, remove the basket, the crucible, and the lid from the beaker, wash them with a jet of cold water, and filter the solu- tion into a No. 5 beaker. Add a filtered solution of 20 grammes acetate of sodium and one-sixth the volume of the solution of acetic acid, 1.04 sp. gr., to the filtered solution, and heat to boiling. The titanic acid is precipitated almost immediately in a flocculent condition, and quite free from iron. Boil for a few minutes, allow the titanic acid to settle, filter, wash with hot water containing a little acetic acid, dry, ignite, and weigh as TiO 2 , which contains 60.00 per cent. Ti. Instead of fusing the residue from the aqueous solution of the carbonate of sodium fusion with bisulphate of potassium, the operation may be hast- ened as follows : Treatment Transfer the residue to the large crucible, as before directed, th and fuse with 5 grammes of dry carbonate of sodium. Allow H 2 so 4 . t k e crucify f- cool, anc j then pour into it very gradually strong H 2 SO 4 . When the effervescence slackens, warm the crucible slightly, and continue the addition of H 2 SO 4 and the careful application of heat until the fusion becomes liquid and the ferric oxide is all dissolved. Heat carefully until copious fumes of SO 3 are given off, allow the crucible to cool, and pour the con- tents, which should be just fluid when cold, into a beaker con- taining about 250 c.c. of cold water. Add to it 50 c.c. of a strong aqueous solution of sulphurous acid, or 2 or 3 c.c. of bisulphite of ammonium, filter if necessary, nearly neutralize by NH 4 HO, allow it to stand until it is entirely decolorized, add 20 grammes acetate of sodium and one-sixth its volume of acetic acid, 1.04 sp. gr., and precipitate the TiO 2 as before. By Volatilization. Drown* suggested the method of determining titanium by volatilizing it in a current of chlorine gas. The details, with * Trans. Inst. Min. Engineers, viii. 508. DETERMINATION OF COPPER. some modifications, are as follows. Treat the sample exactly as directed for the determination of silicon, by volatilization in a current of chlorine gas, page 73 et seq. To the filtrate from the silica, page 76, add a slight excess of NH 4 HO, acidulate with acetic acid, boil, filter, wash, and ignite the precipitate. As this precipitate may contain a little ferric oxide (carried over mechanically as Fe 2 Cl 6 ), phosphoric acid, tungstic acid, etc., fuse it with a little carbonate of sodium, dissolve the fused mass in hot water, filter, wash, dry, and ignite the residue, which will contain all the titanic acid as titanate of sodium, and any iron that may have been present as Fe 2 O 3 . The filtrate will contain the P 2 O 5 , etc. Fuse the ignited residue with a little carbonate of sodium, treat it in the crucible with strong H 2 SO 4 , as directed on page 180, and determine the TiO 2 in the manner there described. DETERMINATION OF COPPER. For the determination of copper the precipitate by H 2 S, ob- tained in the determination of phosphorus, page 84, may be used, but in this case the precipitate must be filtered off before getting rid of the excess of H 2 S, after which, if any additional precipi- tate of As 2 S 3 is thrown down in the filtrate, it must be filtered off before proceeding with the determination of phosphorus. Dry and ignite the filter with the precipitate of CuS, etc., in a porce- lain crucible, burn off all the carbon from the paper, allow the crucible to cool, and digest the precipitate at a gentle heat with HNO 3 and a few drops of H 2 SO 4 , keeping the crucible covered with a small watch-glass. When the CuS is entirely dissolved, remove the watch-glass and evaporate the solution until all the HNO 3 is expelled and fumes of SO 3 are given off. Allow it to cool, add enough water to dissolve all the CuSO 4 , heating gently, 182 ANALYSIS OF IRON AND STEEL. if necessary, and wash the solution into a platinum crucible. - Place the crucible in the little brass holder (Fig. 84), and attach eiectroiy- the weighed platinum cylinder and connect the battery. The battery should consist of three Daniell's 2-quart cells, arranged as shown in Fig. 85. The connectors a, b pass through the sides of the box (which should be kept covered), and, the jars being FIG. 84. Zn connected as shown in the sketch, by simply changing the wire from a to b, three cells are brought into action instead of two. For depositing the small amount of copper found in iron or steel, two cells furnish a sufficiently strong current. The platinum cyl- inder should weigh about 3 or 4 grammes; it is lowered into the liquid until it is just clear of the bottom of the crucible, and the crucible is covered with two small pieces of glass to prevent liquid being carried off by the escaping gas. It is much neater to deposit the copper on the cylinder than in the crucible, as it weighs less, is quite as easy to wash and dry, and there is no danger of any silica or dirt from the solution being covered by the deposited copper. When the copper is all deposited, usu- ally in two or three hours, remove the cylinder, wash it with cold water, then with alcohol, dry at 100 C, cool, and weigh. The increase of weight is Cu. DETERMINATION OF COPPER. ^ In pig-irons containing titanium it is necessary to use a Using solu- tion from separate portion for the determination of copper. In steels, the s, deter- solution in the flask from the determination of sulphur (page 61) sted s n may be used for the determination of copper. In this case, wash the contents of the flask into a No. 5 beaker, nearly neutralize with NH 4 HO, add 5 c.c. HC1, heat the solution to boiling, and pass H 2 S through the boiling solution for fifteen or twenty min- utes, filter, wash with hot water, and treat the precipitate as directed above. In the case of pig-irons, however, it is best to Procedure dissolve in aqua regia, evaporate to dryness, redissolve in HC1, iron. filter, reduce the iron in the filtrate with NH 4 HSO 3 , boil off the excess of SO 2 , and precipitate by H 2 S. Instead of using H 2 S, the copper may be precipitated in a sulphuric acid solution by hyposulphite of sodium. Dissolve 5 grammes of the sample in Predpita- tion by a mixture of 150 c.c. H 2 O and 12 c.c. strong H 2 SO 4 . Dilute to about 500 c.c. with hot water, heat to boiling, and add 3 grammes of hyposulphite of sodium dissolved in 10 c.c. hot water. Boil for a few minutes, allow the precipitate to settle, and filter and wash with hot water. Dry the precipitate, which besides the CuS will consist of the graphite, silica, etc. ; transfer it to a small beaker, burn the filter, and add the ash to the main portion. Digest the whole with aqua regia, dilute with hot water, filter, wash, add a few drops of H 2 SO 4 , and evaporate until fumes of SO 3 are given ofT, cool, dissolve in water, transfer to the platinum crucible, and determine the copper by the battery as directed above. Instead of determining the copper by electrolysis, it may be determined as subsulphide, Cu 2 S, or as oxide, CuO. To deter- GU S S. mine it as Cu 2 S, dilute the sulphate obtained by any of the methods mentioned above with water to about 50 c.c., add an excess of NH 4 HO, filter from Fe 2 O 3 , etc., wash with ammoniacal water, and pass H 2 S through the cold solution. Filter, wash with H 2 S water, dry the filter and precipitate, transfer the latter to a small porcelain crucible, burn the filter, and add its ash to tion as 1 84 Determina- tion as CuO. ANALYSIS OF IRON AND STEEL. the precipitate. Add to the precipitate in the crucible about twice its volume of flowers of sulphur and ignite it in a current of hydrogen, as directed for the determination of manganese as MnS, page 114. Weigh as Cu 2 S, which contains 79.82 per cent. Cu. Instead of igniting the precipitate obtained above as Cu 2 S, the copper may be determined as CuO, as follows : Dissolve the sulphide in aqua regia in a small porcelain dish, evaporate nearly dry, dilute with hot water, heat to boiling, and add a slight excess of a dilute solution of caustic soda or potassa. Filter on a small ashless filter, wash with hot water, dry, transfer the pre- cipitate to a platinum crucible, burn the filter and add its ash to the precipitate, moisten the whole with HNO 3 , and heat very gently at first, but increase the heat slowly to redness. Cool, and weigh as CuO, which contains 79.85 per cent. Cu. Separation from Cu. DETERMINATION OF NICKEL AND COBALT. Treat 3 grammes of the drillings exactly as directed for the determination of manganese by the acetate method, page 103 et seq. The precipitate by H 2 S, page 112, will contain all the nickel and cobalt and a portion of the copper contained in the sample. Filter this precipitate on a small washed filter, wash with H 2 S water containing a little free acetic acid, dry and ignite the filter and precipitate, and transfer them to a No. I beaker. Dissolve in HC1 with a few drops of HNO 3 , evaporate to dryness, redis- solve in 10-20 drops of HC1, dilute with hot water to about 50 c.c., heat the solution to boiling, and pass a stream of H 2 S through the boiling solution to precipitate any copper that may be present. Filter, wash with hot water, evaporate the filtrate to dryness, moisten the dry mass with 4 or 5 drops of HC1, add 20 or 30 drops of cold water, and then 2 or 3 grammes of nitrite DETERMINATION OF NICKEL AND COBALT. 185 of potassium (KNO 2 ) * dissolved in the least possible amount of water, and acidulated with acetic acid. The presence of cobalt separation is shown by the formation of a bright yellow precipitate of the GO. double nitrite of cobalt and potassium, (KNO 2 ) 6 Co 2 (NO 2 ) 6 -f- Aq. Stir the solution, and allow it to stand twenty-four hours, with occasional stirring. Filter on a small ashless filter, wash with water containing acetate of potassium and a little free acetic acid, remove the filtrate which contains the nickel, and wash the precipitate and filter free from acetate of potassium with alcohol. Ignite the filter and precipitate carefully in a porcelain crucible, . r . i i r being careful not to raise the temperature high enough to fuse the precipitate; transfer to a very small beaker, and digest in HCl and a little KClO 3 . Evaporate to dryness, redissolve in 3-5 drops of HCl, dilute with cold water, add about I gramme of acetate of sodium, and boil for an hour to precipitate the small amount of Fe 2 O 3 and Al 2 O 3 that is always present. Filter, to the filtrate add excess of NH 4 HO and NH 4 HS, and heat to boiling. As soon as the precipitate of CoS has settled, filter, wash with water containing a little NH 4 HS, dry and ignite the precipitate and filter, in a platinum crucible. When all the car- bon is burned, allow the crucible to cool, pour in a little HNO 3 , heat carefully, and finally evaporate to dryness. Add a few AsCoSO 4 . drops of H 2 SO 4 , digest until the sulphide and oxide are changed to sulphate of cobalt, drive off the excess of H 2 SO 4 , heat finally to dull redness for a few moments, cool, and weigh as CoSO 4 , which contains 38.05 per cent, of cobalt. Heat the filtrate from the double nitrate of cobalt and potassium to boiling, add a slight excess of caustic potassa, boil for a few minutes, filter, and wash the precipitate of oxide of nickel with hot water. Dis- solve the precipitate on the filter with HCl, allow the solution to run back into the beaker in which the oxide of nickel was precipitated, and wash the filter with hot water. Evaporate See page 47. 1 86 ANALYSIS OF IRON AND STEEL. As Ni 2 S or NiO. Determina- tion by electroly- sis as Ni + Co. Determina- of Co. Determina- of Ni. the solution to dryness, redissolve in 3-5 drops of HC1, dilute with cold water to about 50 c.c., add about I gramme of ace- tate of sodium, boil for about an hour, filter off any Fe 2 O 3 and A1 2 O 3 , and wash with hot water. To the filtrate add an excess of NH 4 HS (a brown color shows the presence of nickel), acid- ulate with acetic acid, heat to boiling, and pass a current of H 2 S through the boiling solution until the precipitated sulphur and sulphide of nickel agglomerate. Filter, wash with H 2 S water, dry and ignite the filter, and precipitate. Allow the crucible to cool, add a little carbonate of ammonium to the precipitate, heat to dull redness, and volatilize any sulphuric acid that may have been formed as sulphate of ammonium, cool, and weigh as Ni 2 S or NiO, which contains 78.55 per cent, of nickel. The nickel and cobalt may also be weighed in the metallic condi- tion by precipitating them by the battery from the ammoniacal solutions of the sulphates. If it is not desired to separate them, evaporate the filtrate from the precipitated sulphide of copper with an excess of H 2 SO 4 until the HC1 is driven off and fumes of SO 3 appear, allow the beaker to cool, add about 5 c.c. water, then an excess of NH 4 HO, filter if necessary, transfer to a plat- inum crucible, and precipitate on the small cylinder (Fig. 84, page 176) in a strongly ammoniacal solution, using three cells of the battery. Wash the cylinder with water, then with alcohol, dry at 100 C, and weigh as Ni -f- Co. To determine the nickel and cobalt separately, precipitate the cobalt as double nitrite of cobalt and potassium, treat the ignited cobalt precipitate with an excess of H 2 SO 4 , heat until fumes of SO 3 are given off, di- lute a little, make the solution strongly ammoniacal, and pre- cipitate the cobalt as above directed. Precipitate the NiO, in the filtrate from the cobalt, by KHO solution, filter, wash, dis- solve on the filter in HC1, evaporate the solution with H 2 SO 4 , add excess of NH 4 HO, and precipitate the Ni by the battery as above. For the analysis of nickel steel, which contains from 2 to 3 per DETERMINATION OF CHROMIUM AND ALUMINIUM. 187 cent, of nickel, use I gramme of the sample, and, after obtaining Nickel steel, the precipitate of NiS as described above, burn it with the filter in a porcelain crucible, allow it to cool, add a little pure powdered sulphur, and ignite in a stream of hydrogen gas as described on page 114. Weigh as Ni 2 S. DETERMINATION OF CHROMIUM AND ALU- MINIUM. Weigh 5 grammes of drillings into a flask of about 500 c.c. capacity, and pour in 20 c.c. strong HC1 diluted with 3 or 4 times its bulk of water. Close the flask with a rubber stopper carrying a valve which is made as follows. Bore a hole through the centre Bunsen of a rubber stopper, and insert a piece of glass tubing long enough to extend from the small end of the stopper to a distance of I inch (25 mm.) beyond the large end. Take a piece of heavy soft rubber tubing 2 inches (50 mm.) long, and cut a longitudinal slit in the middle about ^ inch (12 mm.) long. Close one end of the tube with a piece of glass rod ^ inch (12 mm.) long, and fit the other end over the glass tube in the stopper for a distance of J^ inch (12 mm.). This valve allows the gas to escape from the flask, but prevents air from entering it, so that the iron is not oxidized, but remains dissolved as ferrous chloride. Heat the dilute acid in the flask if necessary, and when the iron or steel is entirely dissolved remove the stopper, drop a small piece of Na 2 CO 3 into the flask, and close it with a solid rubber stopper. Cool the flask with its contents as quickly as possible, and dilute the solution with cold water until the flask is three-fourths full. Add BaCO 3 ,* shaking constantly until the solution appears milky with the excess of BaCO 3 . Loosen the stopper to allow the CO 2 to escape, shake * See page 50. i88 ANALYSIS OF IRON AND STEEL. Cr and Al insoluble in HC1. Separation of Cr and Al from Feby NH 4 HS. Separation of Cr and Alby Dexter's method. the flask at intervals for several hours, and allow it to stand over- night, the stopper being pushed well into the neck. The precipi- tate will consist of all the A1 2 O 3 , Cr 2 O 3 , Fe 2 O 3 from the solution, as well as P 2 O 5 , etc., and the graphite and silica that were insoluble in the dilute acid ; it should be quite white from the excess of BaCO 3 added. Filter as rapidly as possible, wash with cold water, dis- solve on the filter in dilute HC1, allow the solution to run into a small beaker, clean out the flask with the same acid, and wash it and the filter well with hot water. The insoluble matter left on the filter may contain some chromium and aluminium insoluble in dilute HC1, and usually in the form of slag, or in puddled iron as oxides. This may be ignited, treated with HF1 and H 2 SO 4 , evapo- rated to dryness, fused with Na 2 CO 3 and KNO 3 , and the Cr 2 O 3 and A1 2 O 3 determined, or the solution of the fused mass in dilute HC1 added to the filtrate from the insoluble matter. Boil this filtrate, add a slight excess of H 2 SO 4 to precipitate all the barium, allow the precipitate of BaSO 4 to settle, filter, and wash with hot water. Evaporate the filtrate to get rid of the excess of acid, dilute with cold water, add sufficient tartaric or citric acid to hold the iron in solution, add an excess of NH 4 HO, and to the solution, which should be perfectly clear, an excess of NH 4 HS. Allow the pre- cipitated FeS to settle, filter, wash with water containing NH 4 HS, evaporate the filtrate to dryness in a large platinum crucible, heat to redness to volatilize the ammonium salts, and burn the carbon formed from the decomposition of the tartaric acid. Fuse the residue with 6 parts Na 2 CO 3 and I part KNO 3 , dissolve out in water,* transfer to a beaker, add 2 or 3 grammes KC1O 3 , rinse out the crucible with HC1, add it to the solution, and then add a slight excess of HC1. Evaporate to syrupy consistency on the water- bath, adding a little KC1O 3 from time to time to decompose the excess of HCl.f Redissolve in water, add an excess of carbonate * If the fusion or its concentrated aqueous solution is not yellowish in color there is no chromium present. f Dexter, Pogg. Annal., 89, 142. DETERMINATION OF CHROMIUM AND ALUMINIUM. of ammonium to precipitate the A1 2 O 3 , and boil off all smell of ammonia. The alumina will be precipitated as phosphate, wholly or in part, if the sample contains phosphorus, while the chromium is in solution as chromate of potassium or sodium. Filter, wash with hot water, reserve the filtrate and washings, redissolve the precipitate on the filter in HC1, allowing the solution to run into a small beaker, evaporate to dryness to render any silica insoluble, redissolve in HC1, filter, to the filtrate add excess of NH 4 HO and NH 4 HS, boil, filter on a small ashless filter, wash with hot water, ignite, and weigh as A1 2 O 3 , which contains 53.01 per cent. Al. Acidulate the solution containing the chromium with HC1, heat to decompose the excess of KC1O 3 , add a little alcohol, and evaporate to dryness to render silica insoluble. The chromium is now in Determina- the condition of Cr 2 O 3 ; redissolve in HC1, dilute, filter off any silica that may be present, to the filtrate add an excess of NH 4 HO, boil, filter on a small ashless filter, wash well with hot water, ignite, and weigh as Cr 2 O 3 , which contains 68.48 per cent, of chromium. As the precipitates of A1 2 O 3 and Cr 2 O 3 may both contain P 2 O 5 , it is necessary to fuse each of them, after weighing, with a little Na 2 CO 3 , dissolve in water, filter, acidulate with HNO 3 , and determine the P 2 O 5 by the molybdate method, or acidulate with HC1* add a little separation citric acid and magnesium mixture, and determine the P 2 O 5 as Mg 2 P 2 O 7 . Calculate the amount of P 2 O 5 , subtract its weight from that of the A1 2 O 3 and Cr 2 O 3 respectively, and calculate the re- mainder to Al and Cr, as directed above. Instead of separating the aluminium and chromium by HC1 and KC1O 3 , as directed above, the better method suggested by Genth * may be used, which is as follows : Dissolve in water the fusion of the residue from the volatilization of the ammonium salts and the decomposition of the tartaric acid, transfer it to a platinum dish, add a few grammes of nitrate of ammonium, and evaporate down on a water-bath until the solution is syrupy, * Chem. News, vi. 32. ANALYSIS OF IRON AND STEEL. adding NH 4 NO 3 from time to time until the addition fails to produce any further evolution of NH 4 HO from the solution. Add a little carbonate of ammonium towards the end of the operation, and when the solution is syrupy and smells very faintly of ammonia, dilute and filter from the A1 2 O 3 , which treat as directed above. To the filtrate add a strong aqueous solution of sulphurous acid, boil off the excess of SO 2 , and add NH 4 HO to alkaline reaction. Boil, filter, wash, ignite, and weigh the Cr 2 O 3 , which must be tested for P 2 O 5 as above directed. To a- determine chromium alone in iron or steel, treat 5 grammes with alone. HC1, precipitate by BaCO 3 , filter, and wash the insoluble matter and precipitate, as directed above. Place a clean beaker under the funnel, pierce the filter, and wash the contents into the beaker. Clean the flask and filter with hot dilute HC1, and wash them thoroughly with hot water, allowing all the acid and washings to run into the beaker. Add enough HC1 to dissolve the soluble part of the precipitate (Fe 2 O 3 , Cr 2 O 3 , A1 2 O 3 , BaCO 3 ), dilute, boil, and precipitate the Cr 2 O 3 , etc., with NH 4 HO. Boil off all smell of ammonia, allow the precipitate to settle, and wash well with hot water. Dry, and transfer the precipitate to a platinum crucible, carefully separating it from the filter, ignite the filter, and add its ashes to the precipitate in the crucible. Before heating the precipitate, add to it in the crucible 3-6 grammes Na 2 CO 3 and y 2 gramme KNO 3 (with pig-irons it is necessary to add 2-3 grammes KNO 3 to oxidize the graphite), and mix thoroughly. Heat gradually to fusion, and finally raise the heat until all the KNO 3 is decomposed. Cool, treat the fused mass with hot water, filter from Fe 2 O 3 , wash well with hot water, acidulate the filtrate with HC1, and evaporate to dryness with a little alcohol. Redis- solve in HC1, dilute, filter from SiO 2 , and in the filtrate precipitate the Cr 2 O 3 by NH 4 HO. Filter, wash thoroughly, dry, ignite, and weigh as Cr 2 O 3 . This precipitate may contain also some A1 2 O 3 and P 2 O 5 , which must be separated in very accurate determina- tions, and the amounts subtracted from the first weight of Cr 2 O 3 . DETERMINATION OF CHROMIUM AND ALUMINIUM. I Q I Determination of Aluminium, Stead's Method.* Weigh off 6-12 or 24 grammes steel, place in 600 c.c. beaker, cover with watch-glass, dissolve it in HC1 (strong), evaporate to dryness, redissolve in HC1, filter into 1000 c.c. beaker through an ashless filter, wash filter containing silica, nearly neutralize the filtrate with dilute ammonia, and boil filtrate, which should measure about 500 to 600 c.c. Add to the solution I or 2 c.c. of saturated solution of ammonium phosphate, and then a large excess of sodium hyposulphite, boil till all SO 2 has passed off (half an hour's boiling should be sufficient) ; just before filtering add 20 c.c. of a saturated solution of ammonium acetate, stir to mix, and filter through an ashless filter, wash precipitate and filter 5 or 6 times, add to the beaker from which the solution and precipitate had been formed 10 c.c. HC1, heat to boiling, re- move the vessel containing the filtrate, and place instead of it under the funnel a platinum dish, and pour over the filter the boiling acid. Rinse out the beaker and wash all soluble mat- ter on the filter with a fine jet, evaporate the solution to dry- ness in the platinum dish, and heat, to drive off excess of acid, on the sand-bath to a temperature of 300 or 400 F. Add from 2 to 5 grammes pure sodium hydrate made from sodium free from alumina and about 2 c.c. water. Heat gently over a rose-burner for ten minutes, maintaining the mass in a fluid state all the time. Cool and add water, and boil till solu- tion is complete. Make the bulk of the solution to 300 c.c. and note the temperature exactly. Shake well and filter through an ashless filter. Measure off 250 c.c. at the original temperature, equal to 5-10 or 20 grammes steel. If any yellow tint is ob- indication servable chromium may be present. In such a case the phos- mium . phate of alumina must be neutralized with HC1 and precipitated by ammonium carbonate, taking care to boil the solution well to free from excess of ammonia before filtering. Filter off * Prepared by Mr. J. E. Stead, of Middlesboro', England, for this volume. ANALYSIS OF IRON AND STEEL. through an ashless filter, dry, burn off, and weigh, dissolve pre- cipitate in HC1 and determine P 2 O 5 in it, and deduct the weight found from the weight of the original precipitate. If chromium is absent, neutralize the solution with HC1 as before described, boil and add excess of sodium hyposulphite, and boil for half an hour, filter off precipitate, burn, and weigh as pure aluminium phosphate, which contains 22.18 per cent, of aluminium. Carnot's Method.* M. Carnot states that the method is very similar to that pub- lished by Mr. J. E. Stead in the Journal of the Society of Chem- ical Industry, 1889, page 965, but that he has used and taught it at the Ecole des Mines for eight years. It is founded on the reaction that he pointed out in 1881, that aluminium is precipi- tated as the neutral phosphate from a boiling solution faintly acid with acetic acid. The precipitation succeeds equally well when the solution contains iron, if the ferric salt has been pre- viously reduced to ferrous by hyposulphite of soda. Treat 10 grammes of the iron or steel in a platinum dish covered with a piece of platinum-foil with hydrochloric acid, and when solution is complete, dilute and filter into a flask, washing the carbon, silica, etc., on the filter thoroughly with distilled water. Neutralize the solution with ammonia and car- bonate of soda, but see that no permanent precipitate is formed, then add a little hyposulphite of soda, and, when the liquid at first violet becomes colorless, 2 or 3 c.c. of a saturated solution of phosphate of soda and 5 or 6 grammes of acetate of soda dis- solved in a little water. Boil the solution about three-quarters of an hour, or until it no longer smells of sulphurous acid. Filter, and wash the precipitate of phosphate of alumina, mixed with a little silica and ferric phosphate, with boiling water. Treat the precipitate on the filter with hot dilute hydrochloric acid, allow the solution to run into a platinum dish, evaporate to dryness, * A. Carnot, Moniteur Scientifique, 1891, p. 14. DETERMINATION OF CHROMIUM AND ALUMINIUM. 193 and heat at 100 for an hour to render the silica insoluble. Dis- solve in hot dilute hydrochloric acid, filter from the silica, dilute to about IOO c.c. with cold water, neutralize as before, add a little hyposulphite in the cold, then a mixture of 2 grammes of hyposulphite and 2 grammes of acetate of soda, wash, and weigh as A1PO 4 , which contains 22.18 per cent, of aluminium. Determination of Chromium. Volumetric Method for Chromium. Galbraith * has suggested a rapid method for the determina- tion of chromium when it is present in appreciable amounts, as in chrome steel or chrome pig-iron. Dissolve 1-3 grammes of the sample in dilute H 2 SO 4 (i part H 2 SO 4 and 6 parts water), add permanganate of potassium in crystals until the iron is all oxidized and the liquid is quite red in color, then add as much more to oxidize the chromium to CrO 3 . Heat the solution to boiling, and boil until the permanganate is all decomposed and there remains a precipitate of oxide of manganese. Filter, wash with hot water, to the filtrate add a measured volume of stand- ardized ferrous sulphate, and determine the excess of ferrous sulphate by a standard solution of permanganate. From the amount of ferrous sulphate oxidized by the CrO 3 calculate the amount of Cr. The reaction is 6FeSO 4 + 2CrO 3 + 6H 2 SO 4 = 3Fe 2 (SO 4 ) 3 -f Cr 2 (SO 4 ) 3 + 6H 2 O, or I equivalent of chromic acid will oxidize 3 equivalents of ferrous sulphate to ferric sulphate. Therefore, if the value of the permanganate is known in metal- lic iron, and consequently the value of the ferrous sulphate (it being standardized by the permanganate) in metallic iron, the amount of chromium is calculated as follows: 3 equiv. Fe= 1 68 : I equiv. Cr= 52.14 :: the value of the ferrous sulphate oxidized by the CrO 3 in Fe : its value in Cr; or multiply the value of the ferrous sulphate oxidized, in Fe, by 6 f$ 1 g* = .3103. * Chem. News, xxxv. 151. 13 ANALYSIS OF IRON AND STEEL. The titration is effected in the manner directed for the deter- mination of iron in iron ores. Barba * has suggested several modifications which decidedly modifica- tion, improve the method. To avoid the large precipitate of manganese dioxide, he uses nitric acid to oxidize the iron, having found that even a considerable excess of this reagent does not effect the subsequent reactions. He uses, most successfully, ammonia to destroy the excess of potassium permanganate. The method is as follows : Dissolve 1.25 grammes steel in 20 c.c. sulphuric acid 1.2 sp. gr. When solution is complete, add nitric acid drop by drop until the iron is oxidized; 5 c.c. of nitric acid 1.2 sp. gr. is generally sufficient. Boil to remove nitrous fumes and add hot water, to bring the volume to 150 c.c. ; add from a pipette, 5 c.c. of a saturated solu- tion of potassium permanganate and boil briskly for 15 to 20 minutes; remove from the plate, wash down the sides of the beaker to remove all permanganate, and add 25 c.c. strong ammonia down the side of the beaker ; shake well and replace on the cooler part of the plate, to avoid "bumping," of which there is some danger if the heat be raised too rapidly. Shake occasionally and digest for about 15 minutes, or until the per- manganate is all decomposed, then add cautiously 20 c.c. dilute sulphuric acid 1.58 sp. gr. and bring gently to boiling. Cool the solution and pour into a graduated 250 c.c. flask. Make up to mark with cold water, and mix well by pouring into a dry beaker, back and forth a few times. Allow to settle and filter through superposed funnels, with close, hard, dry filters, into a dry beaker ; measure off 200 c.c. (equal to I gramme sample) of the clear filtrate, and titrate by adding a known excess of ferrous sulphate, and determining the excess by standard per- manganate. * The Iron Age, vol. Hi. p. 153. DETERMINATION OF ARSENIC. '95 FIG. 86. DETERMINATION OF ARSENIC. By Distillation. Lundin * has suggested the following method of determining arsenic, which gives very good results: Dissolve 10 grammes of drillings in a large beaker in HNO 3 , 1.2 sp. gr., transfer the solu- tion to a platinum or porcelain dish, add 50 c.c. H 2 SO 4 , and evap- orate down until copious fumes of sulphuric acid are given off. Cool the dish, add 50 c.c. of water, and evaporate again until the excess of H 2 SO 4 is driven off, and the ferric sulphate is so dry that it can be readily trans- ferred to a flask of about 500 c.c. capacity. Add to the mass in the flask 1 5 grammes finely- powdered ferrous sulphate, pour in 150 c.c. strong HC1, and close the flask with a stopper carrying a tube bent twice at right angles and con- nected by a rubber tube with a 50 c.c. pipette, the point of which dips about y 2 inch (12 mm.) into 300 c.c. of water in a beaker, as shown in Fig. 86. Heat the liquid in the flask gradually until it boils, and continue the dis- tillation until the wide part of the burette becomes heated. The arsenic acid in the solution is reduced by the ferrous sulphate, and, in the strong hydrochloric acid solution, is distilled over as AsCl 3 . Remove the light, disconnect the pipette, heat the solution in the beaker to about 70 C, and pass a rapid current of H 2 S through it until it is completely saturated. Remove the excess of H 2 S by a current of CO 2 , and when the solution smells very Reduction to * Jern-Kontorets Annaler, 1883, p. 360; Chem. News, li. 115. j^6 ANAL YSIS OF IRON AND STEEL. faintly of H 2 S, filter off the yellow precipitate of As 2 S 3 in a Gooch crucible 4 or on a counterpoised filter,* wash with water, then with alcohol, then with pure disulphide of carbon, dry at 100 C., and weigh as As 2 S 3 , which contains 60.93 per cent, of As. Or, after filtering the precipitate on the felt in a Gooch crucible, transfer the precipitate and felt to a small beaker, add a little fuming nitric acid, and, when action has nearly ceased, heat gently until the sulphur is dissolved, dilute, filter, and evaporate Determining down to about io c.c. Add 5 c.c. of magnesium mixture and /^ the volume of the solution NH 4 HO. Stir the solution vigor- ously from time to time, keeping it cool by immersing the beaker in ice-water, and allow it to stand twelve hours. Filter on a Gooch crucible, wash the precipitate of Mg 2 (NH 4 ) 2 As 2 O 8 -f- Aq with the ammonia water containing nitrate of ammonium, used for washing the Mg 2 (NH 4 ) 2 P 2 O 8 (page 85), dry at 103 C. for half an hour, then increase the heat very gradually to redness, and ignite strongly for a few minutes. Weigh as Mg 2 As 2 O 7 , which contains 48.30 per cent, of As. DETERMINATION OF ANTIMONY. Antimony is a very rare constituent of iron or steel, but very minute amounts have been found in Spiegel. To deter- mine antimony, treat io grammes of the drillings as directed for the determination of arsenic by precipitation with H 2 S, page 1 88. Evaporate off the excess of NH 4 HO from the filtrate from the Mg 2 (NH 4 ) 2 As 2 O 8 -f Aq, add a slight excess of HC1, dilute to about 300 c.c. with water, and pass a current of H 2 S through the solution. Expel the excess of H 2 S by a current of CO 2 , filter on a very small ashless filter, or on a disk of paper on the bottom of a Gooch crucible, wash with water, and dry the precipitate and filter. Separate the precipitate, and treat the fil- ter in a small weighed porcelain crucible with fuming HNO 3 . * See page 27. DETERMINATION OF TIN. When it is dissolved, evaporate down, add more HNO 3 if neces- sary, evaporate to dryness, and heat to destroy the organic mat- ter. When the residue in the crucible is quite white, allow it to cool, add the precipitate, and treat it with fuming HNO 3 , evaporate to dryness, and finally ignite to drive off the sul- phuric acid formed, cool, and weigh as Sb 2 O 4 , which contains 78.95 per cent. Sb. When tin is present, and the arsenic has separation been precipitated from a sulphide of ammonium solution,* acid- ulate the filtrate from the 'precipitate of Mg 2 (NH 4 ) 2 As 2 O 8 -{- Aq with HC1, and when the solution smells but faintly of H 2 S, fil- ter on a small ashless filter, wash with water, alcohol, and finally with disulphide of carbon, dry the precipitate and filter, and treat them with fuming HNO 3 , evaporate down, but not to dry- ness, add an excess of dry Na 2 CO 3 , transfer the mass to a silver crucible, add some pure fused NaHO, and fuse the whole for some minutes. Allow the crucible to cool, dissolve the fused mass in water, transfer it to a beaker, and add % the volume of alcohol, .83 sp. gr. Stir several times, and allow the precipi- tate of metantimonate of sodium to settle, filter, and wash with a solution consisting of equal volumes of alcohol and water con- taining a little Na 2 CO 3 solution. The filtrate contains the tin, or tin and arsenic. Dissolve the precipitate of metantimonate of sodium on the filter in HC1 containing tartaric acid, allow the so- lution and washings to run into a small beaker, dilute to about 300 c.c., and precipitate the sulphide of antimony by H 2 S. Fil- ter off, and determine the antimony as Sb 2 O 4 as above directed. DETERMINATION OF TIN. Tin is a most unusual constituent of steel or iron, but has been found in the former in cases where scrap from tinned iron, * The precipitated sulphides from acidulated KHS solution may be treated directly in this way without precipitating the arsenic as Mg 2 (NH 4 ) 2 As 2 O 8 + Aq. jgg ANALYSIS OF IRON AND STEEL. from which the tin has been removed by a chemical process, has been melted in the open-hearth furnace as a portion of. the charge. Proceed as in the determination of antimony, until the sulphides from the acidulation of the KHS solution have been filtered on a small ashless filter and washed thoroughly with a solution of acetate of ammonium made slightly acid with acetic acid. It is not possible to wash the precipitate with water, as the sulphide of tin has a strong tendency, under these circum- stances, to pass through the filter. Dry the precipitate and filter, transfer the precipitate to a weighed porcelain crucible, burn the filter, and add its ash to the precipitate, add a little sulphur, ignition m and ignite in a current of H 2 S, as directed for the determina- HgS vola- ... .-, . . ... tion of manganese as MnS, page 114. Any arsenic present will be volatilized, but it is not possible to weigh the tin as sulphide, as its composition is not constant. Heat the crucible carefully, and roast the precipitate with access of air, heat it strongly two or three times with carbonate of ammonium to volatilize any sulphuric acid that may have been formed, cool, and weigh as SnO 2 , which contains 78.81 per cent. Sn. DETERMINATION OF TUNGSTEN. Dissolve i to 10 grammes of the drillings in HNO 3 , 1.2 sp. gr., evaporate to dryness in the air-bath, redissolve in HC1, dilute slightly, and boil for some time. The tungstic acid is deposited as a yellowish powder. Dilute, filter, wash with hot water con- taining a little HC1, and finally with alcohol and water. The pre- cipitate consists of WO 3 mixed with more or less SiO 2 , graphite, and perhaps a little Fe 2 O 3 , TiO 2 , etc. Dry and ignite the filter and precipitate, and burn off the carbon. Allow the crucible to cool, moisten the precipitate with water, add a little H 2 SO 4 and an excess of HFL Evaporate to dryness under a hood, and ignite to drive off the H 2 SO 4 . Fuse the residue with 5 times a- tion as mercurous DETERMINATION OF TUNGSTEN. its weight of Na 2 CO 3 , allow it to cool, dissolve in water, filter from any insoluble matter, and wash with water containing a little Na 2 CO 3 . The filtrate contains all the tungsten, as tungstate of sodium. Nearly neutralize with HNO 3 , and boil off the CO 2 , allow the solution to cool slightly, and add a faint but distinct excess of HNO 3 . Add an excess of mercurous nitrate,* and then mercuric oxide diffused in water,* until the free acid is all neutralized. The tungsten is all precipitated as mercurous tung- Precipit state, and can be washed perfectly free from all sodium salts with hot water. Allow the precipitate to settle, filter on an ashless tungstate. filter, wash with hot water, and dry the filter and precipitate. Separate the precipitate from the filter, burn the filter in a plat- inum crucible, add the precipitate, and heat it under a hood with a good draft, increasing the heat gradually to a bright red. The mercury volatilizes, and there remains only WO 3 . Cool, and weigh as WO 3 , which contains 79.31 per cent, of W. Rapid Method for Tungsten. A rapid method for the determination of tungsten in high tungsten steels and one that gives results sufficiently accurate for ordinary work is as follows : Treat one gramme of the steel in a No. 3 Griffin's beaker with 25 c.c. of aqua regia, evaporate to dryness, redissolve in 10 c.c. strong hydrochloric acid, add I or 2 c.c. of strong nitric acid, heat for a few minutes, dilute with hot water to 100 c.c., and boil for ten minutes. Filter, wash with water containing a little hydrochloric acid, and ignite. Treat the precipitate in the crucible with a few drops of sulphuric acid and some hydro- fluoric acid, evaporate to dryness, ignite, and weigh. Fuse the precipitate with a little sodium carbonate, dissolve in hot water, filter off the ferric oxide, wash it well with hot water, return it to the crucible, ignite, and weigh. The difference between the two weights is WO 3 . * See page 56. 2QO ANALYSIS OF IRON AND STEEL. DETERMINATION OF VANADIUM. Vanadium is occasionally found in pig-iron, and may be deter- mined with great accuracy by the following method : Treat 5 grammes of the drillings with 50 c.c. HNO 3 , 1.2 sp. gr., in a No. 4 beaker. When all action has ceased, transfer the liquid to a porcelain dish, evaporate to dryness, and heat at a gradually in- creasing temperature over a Bunsen burner until the nitrates are nearly all decomposed and the mass separates easily from the bottom and sides of the dish. Transfer the cooled mass to a por- celain or agate mortar, and grind it thoroughly with 30 grammes of dry Na 2 CO 3 and 3 grammes of NaNO 3 . Transfer to a large platinum crucible, and fuse well for about an hour at a high tem- perature. Run the fused mass well up on the sides of the crucible, allow it to cool, dissolve in hot water, and filter. Dilute the filtrate to about 600 c.c., and add nitric acid carefully to get rid of the car- bonic acid. Boil off the latter, but be careful to keep the solu- tion always slightly alkaline. Filter, and to the filtrate add a few drops of nitric acid to make it faintly acid, when the appearance indication of a yellowish coloration is an indication of the presence of vanadic acid. Add to the solution a few c.c. of mercurous nitrate,* and Predpita- then an excess of mercuric oxide in water,* to render the solution mercurous ncutralf and insure the complete precipitation of all the mer- vanadate. curous vanadate. With the mercurous vanadate are precipitated also all the phosphoric, chromic, tungstic, and molybdic acids as mercurous salts. Heat to boiling, filter, and wash the precipitate. Dry it, separate the paper, burn it in a platinum crucible, add the precipitate, heat carefully to expel the mercury, and finally heat to full redness. Fuse the brownish-red mass remaining in the crucible with a small amount of Na 2 CO 3 and a pinch of NaNO 3 , dissolve the cooled mass in a small amount of water, and filter into a small beaker. Add to the solution pure chloride of ammo- nium in excess (about 3.5 grammes to each 10 c.c. of solution), * See page 56. f Am. Chem. Jour., v. 373. DETERMINATION OF NITROGEN. 2OI and allow it to stand for some time, stirring occasionally. Vana- Predpita- date of ammonium, insoluble in a saturated solution of chloride vanadate of ammonium, separates out as a white powder. It is necessary m0 nium. to keep the solution decidedly alkaline, and a drop or two of am- Precautions, monia must be added from time to time. The appearance of the faintest yellowish tint to the solution is evidence that the solution has become slightly acid, and this must be corrected or the result will be too low. Filter on a small ashless filter, wash first with a saturated solution of chloride of ammonium containing a drop or two of ammonia, and then with alcohol. Dry, ignite, moisten with a drop or two of nitric acid, ignite, and weigh as V 2 O 5 , which contains 56.22 per cent, of vanadium. DETERMINATION OF NITROGEN. This method is based on the reaction by which the nitrogen in iron or steel is converted into ammonia by HC1 during the solution of the steel in this reagent. It was first published by A. H. Allen,* with many interest- ing details and results. The modifications of the method as described by Mr. Allen are by Prof. J. W. Langley,f of Pitts- burg, and consist essentially in the use of caustic soda freed from nitrates and nitrites by the copper-zinc couple and subsequent distillation of all ammonia formed, and in a few details of manipulation. The reagents required are: Hydrochloric Acid of i.i sp. gr., free from Ammonia, which p ure HO. may be prepared by distilling pure hydrochloric acid gas into distilled water free from ammonia. To do this, take a large flask fitted with a rubber stopper carrying a separatory funnel-tube and an evolution-tube, fill it half-full of strong hydrochloric * Chem. News, xli. 231. } Communicated to the author. 2Q2 ANALYSIS OF IRON AND STEEL. acid, connect the evolution-tube with a wash-bottle connected with a bottle containing the distilled water. Admit strong sul- phuric acid free from nitrous acid to the flask through the funnel- tube, apply heat as required, and distil the gas into the prepared water. Test the acid by admitting some of it into the distilling appa- ratus, described farther on, and distilling it from an excess of pure caustic soda, or determine the amount of ammonia in a portion of hydrochloric acid of i.i sp. gr., and use the amount found as a correction. Caustic Solution of Caustic Soda, made by dissolving 300 grammes of fused caustic soda in 500 c.c. of water, and digesting it for twenty-four hours at 50 C. on a copper-zinc couple, made, as described by Gladstone & Tribe, as follows : Place 25-30 grammes of thin sheet zinc in a flask and cover with a moderately-con- centrated, slightly warm solution of sulphate of copper. A thick spongy coating of copper will be deposited on the zinc. Pour off the solution in about ten minutes and wash thoroughly with cold distilled water. Nessier Nessler Reagent. Dissolve 35 grammes of iodide of potas- sium in a small quantity of distilled water, and add a strong solution of bichloride of mercury little by little, shaking after each addition, until the red precipitate formed dissolves. Finally the precipitate formed will fail to dissolve, then stop the addition of the mercury salt and filter. Add to the filtrate 120 grammes of caustic soda dissolved in a small amount of water, and di- lute until the entire solution measures I litre. Add to this 5 c.c. of saturated aqueous solution of bichloride of mercury, mix thoroughly, allow the precipitate formed to settle, and decant or siphon off the clear liquid into a glass-stoppered bottle. standard Standard Ammonia Solution. Dissolve 0.0382 gramme of solution chloride of ammonium in I litre of water. One c.c. of this so- lution will equal O.OI milligramme of nitrogen. Distilled Water free from Ammonia. If the ordinary dis- DETERMINATION OF NITROGEN. 203 tilled water contains ammonia, redistil it, reject the first portions Ammonia- free coming over, and use the subsequent portions, which will be distnied found free from ammonia. Several glass cylinders of colorless glass of about 1 60 c.c. capacity are also required. The best form of distilling apparatus consists of an Erlen- Distn- meyer flask of about 1500 c.c. capacity, with a rubber stopper, pa ratus. carrying a separatory funnel-tube and an evolution-tube, the lat- ter connected with a condensing-tube through which a constant stream of cold water runs. The inside tube, where it issues from the condenser, should be sufficiently high to dip into one of the glass cylinders placed on the working-table. The determination of nitrogen is made as follows : Place 30 Details c.c. of the caustic soda, which has been treated with the cop- method per-zinc couple, in the Erlenmeyer flask, add 500 c.c. of water, and distil until the distillate gives no reaction with the Nessler reagent. While this part of the operation is in progress, dissolve 3 grammes of the carefully-washed drillings in 30 c.c. of the prepared hydrochloric acid, using heat if necessary. Transfer the solution to the bulb of the separatory funnel-tube, and when the soda solution is free from ammonia drop the ferrous chlo- ride solution into the boiling solution in the flask, very slowly. The ferrous hydrate formed is apt to stick to the bottom and sides of the flask and cause it to break. When about 50 c.c. of water has been collected in the cylinder, remove it and sub- stitute another cylinder. Dilute the distillate in the cylinder to 100 c.c. with the special distilled water, and add \y 2 c.c. of Nessler reagent. Take another cylinder, pour into it 100 c.c. of the special distilled water, add I c.c. of the chloride of am- monium solution and I j c.c. of the Nessler reagent. Compare the colors in the two cylinders, and add ammonia solution to the contents of the latter cylinder until the colors of the solutions in the two cylinders correspond after standing about ten minutes. When about 100 c.c. has distilled into the second cylinder, re- place it and test it as before. Continue the distillation until 2O4 ANALYSIS OF IRON AND STEEL. the water comes over free from ammonia, then add together the number of c.c. of ammonia solution used, divide the sum by three, and each o.oi milligramme will be o.ooi per cent, of nitrogen in the steel. DETERMINATION OF IRON. The combined carbon in steel and iron interferes with a direct determination of the amount of metallic iron by solution of the drillings in hydrochloric or sulphuric acid and direct titration. It is always necessary to oxidize the iron and carbonaceous matter in the solution, and the process may be carried out as follows: By solution. Dissolve .5 gramme of the drillings in a small flask, as described for the determination of iron in iron ores, in HC1, add KC1O 3 in small crystals until the iron is all oxidized and an excess of KC1O 3 is present, boil until all the yellow fumes have disappeared, and then proceed as in the determination of iron in iron ores, page 207. Instead of chlorate of potassium, permanganate of potassium or chromic acid may be used to oxidize the iron and destroy the carbonaceous matter. In pig-irons the most satisfactory By fusion, method is to fuse .5 gramme of the borings in a large platinum crucible with 10 grammes Na 2 CO 3 and 2 grammes KNO 3 , dissolve in hot water, transfer to a small beaker, allow the ferric oxide to settle, decant on a small filter, and wash several times by decanta- tion. After the last decantation, remove the beaker containing the filtrate and place the beaker containing the ferric oxide under the funnel. Dissolve any adhering oxide in the crucible with HC1, dilute slightly, and pour it on the filter to dissolve the small amount of oxide, allowing the solution to run into the beaker. Wash the filter if necessary, add more HC1 to the solution in the beaker, evaporate down, transfer to a small flask, deoxidize, and titrate as before. In the case of puddled iron, it is necessary to subtract the iron in the " slag and oxides" from the total iron ob- tained as above to get the amount of metallic iron in the sample. METHODS FOR THE ANALYSIS OF IRON ORES. A FEW words in regard to the proper method of taking Method of samples of iron ores may not be amiss, for unless the sample iron ores, truly represents the lot from which it' is taken, the subsequent work of the analyst is useless, if not misleading. In drawing a sample, note carefully the relative amounts of fine ore and lumps in the lot to be sampled, and see that this proportion be observed in the whole amount taken. A small trowel may be used for taking the fine ore, and only about a teaspoonful should be picked up at one time. In taking pieces from the lumps, it will never do to merely chip the outside, but each lump as selected should be broken and chippings taken from both the inside and the outside, and no piece taken should be larger than a cherry. In sampling from cars or wagons these points should be observed in each car or wagon, for it is rarely the case that the ore even from one mine is so uniform as to render this precaution unnecessary. In some cases the lumps are covered with dirt or gangue, making the outside of the lump poorer in iron than the inside, and on the other hand the lumps are merely masses of dirt coated with ore. Then the fine stuff may be much richer than the lumps, or it may be merely dirt or gangue, while it almost always contains more hygroscopic water than the lumps. The sample should be taken in tin cans with close-fitting lids, Preserving and the amount should be proportioned to the size of the lot sampled. Two pounds to ten tons is a good rule for large lots. 205 2O6 ANALYSIS OF IRON ORES. DETERMINATION OF HYGROSCOPIC WATER. Break the sample down quickly to about pea size, mix thor- oughly in a large glazed earthenware or metal dish, and weigh out from y 2 to I kilo, into a copper box about 4^ inches (114 mm.) long, 3^ inches (95 mm.) wide, and ij^ inches (38 mm.) deep, and dry in a water- or air-bath at 1 00 C. for at least twelve hours, or until it ceases to lose weight. Fig. 87 shows a convenient form FIG. 87. Device for constant level. of water-bath. The boxes are numbered, and each one is pro- vided with a counterpoise stamped with the same number as the box, to facilitate the weighing. When a supply of water is not available to run the constant level shown in Fig. 87, the device, on the principle of Marriott's flask, as shown in Fig. 78, page 169, DETERMINATION OF TOTAL IRON. 207 may be used. The position of the end b of the tube a fixes the level of the water in the bath. A balance sensitive to .1 gramme is sufficiently accurate for Balance for weighing these samples. The loss of weight in grammes divided samples. by 5, when j kilo, of ore was originally used, gives the percentage of hygroscopic water in the sample. Grind the dried sample very fine, mix it well, heat as much of it as may be required for the analysis, in the water-bath, and put it while still hot into a per- fectly dry, glass-stoppered bottle. DETERMINATION OF TOTAL IRON. Very few iron ores are completely decomposed by hydro- Residue chloric acid, the insoluble residue usually containing more or less faHca. iron, as silicate, titaniferous iron, etc. The disregard of this fact may occasion grave errors in the determination of iron, and, unless a previous examination has shown the absence of iron in the insoluble residue, it is best to proceed as follows : Weigh I Treatment gramme of the finely-ground sample into a No. I beaker, add 10 c.c. HC1, and digest it on the sand-bath until the residue appears quite white and flotant, or until the acid appears to have no further action. When the ore contains carbonaceous matter, add a little KC1O 3 . Wash off the watch-glass with a fine jet of water, remove it, and evaporate to dryness in the air-bath. Redissolve in about 5 c.c. HC1, dilute with 10 c.c. water, allow to settle, and decant the clear liquid into a flask (B, Fig. 89) of about 50 to 75 c.c. capacity. Transfer the residue to a small filter, fitted in a funnel placed in the neck of the flask, with as little water as pos- Treatment sible, and wash with cold water from a fine jet. Transfer the filter of *? in ' soluble to a small platinum crucible, burn it off, allow the crucible to cool, residue by H 2 S0 4 and pour on the residue 20 or 30 drops of H 2 SO 4 and about twice and HFI. 2o8 ANALYSIS OF IRON ORES. as much HF1. Heat carefully, and, if the residue is dissolved, evap- orate off the HF1, allow the liquid to cool, and dilute slightly, when it will be ready to add to the solution in the flask, which shall have been deoxidized in the mean time by one of the methods explained farther on. Occasionally this treatment fails to decompose the insoluble residue, in which case it is necessary to heat the crucible until the greater part of the H 2 SO 4 shall have been driven off; then Treatment add about .5 gramme KHSO 4 , and heat gradually until the with KHS0 4 . KHSO 4 is quite liquid and fumes of SO 3 are given off whenever the lid of the crucible is raised. When all the black specks have disappeared, allow the crucible to cool, and dissolve the salt in the crucible with hot water and a few drops of HC1. Several methods are used for the deoxidation of the solution of ferric chloride, but the one in general use is by adding metallic zinc to the solution. The iron is deoxidized according to the reaction Fe 2 Cl 6 + Zn = 2FeCl 2 -f ZnQ 2 , while the excess of HC1 is decomposed and hydrogen liberated, 2HC1+ Zn = ZnCl 2 -f 2H. As all zinc contains a small amount of iron, the amount added to the solution should be roughly weighed. Add then to the solu- metallic tion in the flask 3 grammes of granulated zinc,* and, when the evolution of hydrogen has somewhat slackened, heat the flask slightly. The neck of the flask is closed by a small funnel, which allows the hydrogen to escape while the liquid is caught on the funnel and falls back into the flask. It sometimes happens as the solution becomes neutralized that a basic salt of peroxide of iron is thrown down, giving the solution a reddish color ; in this case add a few drops of HC1, and when the solution finally becomes End of the colorless add a few drops more of HC1. If this fails to produce a yellowish coloration, the solution may be considered deoxidized. Final addi- Pour in through the funnel the solution of the residue insoluble in H 2 so 4 . HC1, and add gradually a mixture of 10 c.c. H 2 SO 4 and 20 c.c. * See page 57. DETERMINATION OF TOTAL IRON. 2OQ H 2 O. This addition of H 2 SO 4 is a very necessary part of the operation, for it not only serves to dissolve the remainder of the zinc which is unacted on when the deoxidation is complete, but it supplies the proper amount of sulphate of zinc and iron, which makes the end reaction with permanganate of potassium as sharp as if no HC1 were present in the solution. As soon as all the zinc is dissolved, wash down the funnel inside and out and the neck of the flask with a fine jet of water, filling the flask almost full, cool the flask in water, and when the solution is quite cold transfer it to a large white dish of about 1500 c.c. capacity (see A, Fig. 89, page 214). Wash the flask and funnel well with cold water, pour the rinsing into the dish, and make the solution up to about 1000 c.c. Run in from a burette a standard solution of Titratkm by perman- permanganate of potassium (Marguerite's method), the value of ganate which has been carefully determined by one of the methods de- scribed farther on. At first the color of the permanganate is destroyed almost as soon as it touches the liquid in the dish, which should be stirred carefully with a glass rod. The permanganate should be added more and more slowly until towards the end of the operation it is added only drop by drop. The liquid in the dish gradually assumes a yellowish tint, which is deeper the larger the amount of iron jn the ore. Finally a drop of the per- manganate seems to destroy the yellow color, and the next drop gives the liquid a very faint pink tinge. This is the end of the reaction. Take the reading of the burette, and then add another drop, which will cause the solution to become decidedly pink in color. The number of c.c. of the standard solution used when the reading was taken, less a small correction for the zinc, etc., noted farther on, multiplied by the value of I c.c., gives the amount of metallic iron in the ore. The reductor, Fig. 88, is also useful for reducing ferric salts to Jones's ferrous ; the only disadvantage is that it seems necessary to have the iron present as sulphate, which necessitates evaporating off the hydrochloric acid used in dissolving ores. The description of the 14 210 ANALYSIS OF IRON OKES. reductor and the method of using it in iron determinations is as follows : * The conditions essential to the accurate determination of iron by this method are : That the iron must be in the state of ferric sulphate ; that the solution of ferric sulphate must be dilute; that the least traces of hydrochloric and nitric acids must be absent. There should not be over 50 c.c. sulphuric acid, 1.32 sp. gr., in 300 c.c. of the ferric solution ready for re- duction. For iron ores, and in almost all cases, this ordinarily pre- sents no difficulties. If the solution is in strong sulphuric acid, it must be reduced in bulk, or diluted to such an extent as to avoid violent action in contact with zinc. The volume of the solution should not exceed 350 c.c. Preparing The reductor should now be filled with zinc and washed as ductor. required. If there is still enough zinc remaining in the tube from previous reductions, a single washing will usually suffice. The ferric solution is now brought to the reductor and trans- ferred to one or both of the cups A and B, washing out the beaker or flask three or four times with water. Details of The stopcock G of the reductor is opened, and the two-way stopcock C is set to discharge the solution, which is then filtered through the zinc. The cup is then rinsed out five times with water as described. The stopcock G is then closed to relieve the pressure, and the flask F is detached. The solution has now a volume of about 400 to 500 c.c. In this manner a solu- tion of ferric sulphate is instantaneously and completely reduced in two minutes. The burette is now filled to the zero mark as described, and the solution is titrated in the flask direct. A little practice will enable the operator to give a continuous circular motion to the flask held in the right hand, with the left hand in control of the flow of the permanganate from the burette. * Prepared by Mr. Clemens Jones for this volume. DETERMINATION OF TOTAL IRON. 211 The average time by this means for the reduction and accu- rate titration of a ferric solution is four minutes. The burette Description B (50 c.c. to ^ c.c.), shown in Fig. 88, consists of the gradu- FIG. 88. A ated glass tube proper, and an arm, E, fused to it, below the 50 c.c. mark. At its top are rubber connections with the blast- aspirator, shown in the cut. By means of the stopcock D con- ANALYSIS OF IRON ORES. nection through E is established with the glass reservoir F. The burette is clamped securely to a slide, C, which is coun- terpoised, and moves freely on guides between two parallel sides, L, L, suitably mounted in a frame, and through their whole length. Back of the burette a porcelain scale may be fixed, graduated to correspond with it, and secured to the slide, in front of which the burette may be adjusted. The reservoir F is suspended in a shelf placed within the frame, and is introduced into the side- door K, shown open, and is then encased in a box, which has an annular hole in the top to admit the prong of the tube E, the slide C being previously raised. The reservoir is so placed that when the slide is at the lowest point the inlet-prong has a safe margin from the bottom. If a float is used, it remains in the burette permanently, and is caught on a stage of fine platinum wire supported by a spiral, when it descends within one-half inch of the inlet-tube. In Reservoir operation, the reservoir F, containing about two litres, is filled with the solution of permanganate and placed in position ; the slide C is lowered until the zero marks are brought in the di- rect line of vision; blast is admitted to the aspirator by the brass valve V, and the suction produced is communicated to the burette, both stopcocks, H and D, being closed. When the float is used, the stopcock H is first opened, the suction lifting the float to the zero mark in the burette. Stop- cock H is then closed, and, while the float slowly descends, stop- cock D is opened, admitting the permanganate solution and allowing the float to sink without enclosing any bubbles of air. The burette is then filled exactly to the zero mark. In titration, the blast must, of course, be shut off, and the column of solution connected with the outside atmosphere by turning a suitably- arranged stopcock of the aspirator. If the float is not employed, stopcock H remains closed, and by opening stopcock D the burette is filled in the manner described above. manganate solution. DETERMINATION OF TOTAL IRON. To cleanse the burette, allow the solution partially filling it Method of . , TT . - cleaning to run out. Stopcock H is then closed, suction is again pro- burette, duced by starting the aspirator as described, and a beaker of water is held so that the burette tip is in the water. On open- ing the ' stopcock H, the water rises in the burette. This is then run out by again stopping the aspirator, and the operation is repeated until the burette is perfectly clean. Should the burette require further cleansing, hydrochloric acid may be used in the same manner. This is then washed out with water as before, and the burette may then be dried in a few minutes by turning on the blast gently, and reversing the aspirator by simply closing its main outlet with a rubber cap, allowing the current of air to pass down through the burette and out through the open stop- cock H. By closing the outside doors the apparatus is protected from light. The apparatus is always ready for use. Twenty ac- curate titrations can be easily made in an hour's time. The simple form of reductor, Fig. 52, shown on page 96, may be used for deoxidizing the solution of the ore in which the iron is in the form of sulphate. With amalgamated zinc it is a most excellent and rapid device. The method of reduction is given on page 98 in the description of the method of standard- izing the potassium permanganate solution. Another form of burette which is extremely convenient and Another form of has the great advantage of dispensing with the glass stopcock, burette; which is liable to stick at a critical moment, or break without warning, is shown in Fig. 89. The burette is attached to the wooden stand by bands of German silver or of nickel. The top of the burette is closed by a rubber stopper carrying a glass tube of small bore con- nected by rubber tubing with a small glass tube attached to the back of the burette-stand. To the end of this tube, near the base of the burette-stand, is attached a short piece of heavy- walled gum tubing, a, passing under a compressor fixed to the base of the stand. Fig. 90 shows the form and construction of 214 ANALYSIS OF IRON ORES. FIG. 89. the clamp or compressor. By applying suction at the end of the tube b the standard solution may be drawn up into the burette a little above the zero mark, and the compressor closed down on the tube a, holding the liquid in the burette until the admission of air through the tube a allows the liquid to flow out of the burette. The entire practical value of this burette * depends on placing a drop or two of water in the tube , which, flowing to the point of compression, not only closes the tube hermetically when the clamp is screwed down, FIG. 90. Method of Du t makes it possible, by a slight movement of the clamp, to controlling the flow of admit the smallest quantity of air to the burette, and thus to permit the liquid to flow from the burette at any desired rate. The flow is thus controlled by the left hand while the solution in the dish is stirred with the right. Towards the end of the opera- The suggestion of Mr. Thos. H. Garrett, of Philadelphia DETERMINATION OF TOTAL IRON. 215 tion a single drop may be made to flow from the burette, when the clamp is closed (not too tightly), by compressing the tube a at the point c with the thumb, and forcing a little air into the burette. Even a fraction of a drop may be obtained by touching the point of the burette with the stirring-rod. The scale shown in the sketch is fixed on the wall, so that the eye may always be kept at the proper level in taking the readings of the burette. When usiner a standard solution of bichromate of potassium Thration with bi- (Penny's method), the end reaction is not rendered apparent by a chromate change in the color of the solution, but the presence or absence sium . of ferrous salt in the solution is determined by taking a drop from the dish on the end of the stirring-rod and allowing it to run into a drop of a dilute, freshly-made solution of ferricyanide of potas- sium placed on a white tile or capsule. Dissolve a very small crystal of ferricyanide of potassium in a few c.c. of water, and place a number of drops of the solution on a white tile or on a flat-bottomed capsule. Run the carefully standardized solution of bichromate of potassium from the burette into the deoxidized iron solution previously placed in a white dish. The solution, at first colorless, changes gradually to a decided chrome-green from the reduction of "the chromic acid. Test the progress of the oxi- dation of the iron solution by transferring a drop of it on the end of the stirring-rod to one of the drops of ferricyanide. As the blue color produced becomes less intense, add the bichromate more slowly and make the test more frequently, towards the end of the operation after the addition of each drop of bichromate. When, finally, no color appears in the test-drops, even after the End of the reaction. lapse of several moments, the oxidation of the ferrous salt is complete, and the amount of bichromate used, less a small cor- rection for the zinc, is the measure of the amount of iron in the ore. The ferricyanide of potassium employed must, of course, Purity of ferricy- be perfectly free from ferrocyanide : it may be tested by adding an ide. a drop of ferric chloride solution to one of the drops of ferri- cyanide solution, the absence of any resulting blue color in the 2I 5 ANALYSIS OF IRON ORES. test-drops being proof of the purity of the ferricyanide. As deteranhia- towards the end of the operation the frequent tests become rather tedious, some analysts prefer to make the determinations in dupli- cate, using the first to get an approximate result. Treatment When the ore is completely decomposed by HC1, a separate or ores r completely treatment of the residue is unnecessary, and the ore may be poseTby weighed at once into the flask and treated with 10 c.c. HC1 and a little KC1O 3 when organic matter is present. When the ore is completely decomposed, and any Cl from the KC1O 3 driven off, add 30 c.c. of water, and proceed with the deoxida- tion. Instead of deoxidizing the solution of ferric chloride by zinc, it NH 4 Hso 3 . may be deoxidized by a solution of bisulphite of ammonium. In fact, the deoxidation by zinc is not practicable in ores containing inthepres- much TiO 2 , for the TiO 2 is reduced by metallic zinc to Ti 2 O 3 , im- ence of Tio 2 . parting a purple or blue color to the solution, and acting like a solution of ferrous salt on the standard solution of permanganate. In deoxidizing a solution of ferric chloride by this method it should be placed in a flask of 120 c.c. capacity, and two or three small spirals of platinum wire added to facilitate the subsequent boiling. Add cautiously to the solution (which should not exceed Details of the 40 c.c. in volume) enough ammonia to produce a slight permanent method. precipitate of ferric hydrate, which remains even after vigorous shaking. Add now 5 c.c. of a strong solution of NH 4 HSO 3 ,* shake vigorously, and warm the flask gently. As the color of the solution at first a deep red fades, increase the heat, and finally heat to boiling. When the solution is quite colorless, add to it the solution of the residue and 100 c.c. H 2 SO 4 mixed with 20 c.c. H 2 O. Boil the solution until all the sulphurous acid is driven off. When the escaping steam no longer smells of SO 2 , place the flask in cold water, wash down the funnel and the neck of. the flask, filling the latter quite full of water, and when the * See page 44. DETERMINATION OF TOTAL IRON. solution is quite cold transfer it to a dish and titrate with a standard solution. A third method of deoxidizing the solution of ferric chloride by SnCl 2 . is used, in which the reducing agent is a solution of stannous chloride. The investigations of Zimmerman* and Reinhardtf have made this method of reduction a favorite one, especially when, by the use of phosphoric acid and manganous sulphate, the subsequent titration with potassium permanganate is practica- ble. The details are as follows : Prepare the following solutions : 1. Phosphoric acid solution: Dissolve 200 grammes of crystallized manganous sulphate in I litre of water, add a few drops of sulphuric acid, and filter. Add to this I litre of phos- phoric acid (1.3 sp. gr.), 600 c.c. water, and 400 c.c. strong sul- phuric acid. 2. Stannous chloride solution: Dissolve 120 grammes of granulated tin, free from iron, in 500 c.c. hydrochloric acid (1.19 sp. gr.), dilute to I litre, and filter through asbestos. To the filtrate add I litre of hydrochloric acid (1.124 S P- g r -) an d 2 litres of water. 3. Mercuric chloride solution : Dissolve 50 grammes of mercuric chloride in I litre of water and filter. Dissolve I gramme of the ore in 30 c.c. strong hydrochloric acid (if necessary, ignite, and fuse the residue with a little sodium carbonate, dissolve in water and hydrochloric acid, and add to the main solution), transfer to a 150 c.c. Erlenmeyer flask, heat to boiling, and add, from a burette, stannous chloride solution until the color of the solution fades completely. Pour into the dish (page 214) 600 c.c. of water and add to it 60 c.c. of the phos- phoric acid solution. To the deoxidized solution in the flask add 60 c.c. of the mercuric chloride solution, pouring it all in at once, shake vigorously and wash the solution out into the dish, using plenty of wash water, and titrate with permanganate in * Berichte d. Chem. Ges., 1884, xv. 779. f Chem. Zeit., xiii. 324. 2i 8 ANALYSIS OF IRON ORES. the usual way. The phosphoric acid makes the solution nearly colorless by forming ferric phosphate, and the end reaction is very sharp. The mercuric chloride should not be added until everything is ready for the titration, as the absence of any deoxidizing sub- stance may cause the solution to become slightly oxidized on standing. Mixer and Dubois* give several modifications of the method as used in the Lake Superior region. They use a solution of potassium permanganate of such strength that I c.c. equals two per cent, of iron when one-half gramme of ore is used. They use for standardizing the permanganate an iron ore the amount of iron in which is accurately known, and if the permanganate is not exactly of the proper strength, they use such a weight of the ore, approximating 0.5 gramme, that the reading of the burette multi- plied by 2 gives the percentage of iron. Necessarily this implies the use of the same weight of the ore to be analyzed. They also add to the ore about 2.5 c.c. of a 25 per cent, solution of stannous chloride before adding the hydrochloric acid, as this is said to very much hasten the solution of the ore. Methods for Standardizing the Solutions. It is of the utmost importance that the value of the standard affecting solution employed should be determined with the greatest accu- racv *f t ^ le resu lts obtained by its use are to be anything but mere approximations. To do this, not only should the reagents em- the stand- ployed be pure, but the conditions under which the standard is ard fixed should be, as nearly as practicable, those under which it is employed in actual use. The conditions referred to are not only those of temperature, dilution, etc., but of the actual chemical composition of the liquid acted on by the standard solution by which its value is determined. The best reagent to employ is a solution of ferric chloride * Journal of the American Chem. Soc., vol. xvii. p. 405. DETERMINATION OF TOTAL IRON. 2I 9 of known strength. To prepare this, dissolve 100 grammes of wrought iron (free from manganese and arsenic, and in which the phosphorus has been accurately determined) in nitric acid, evapo- rate to dryness in a capsule, and heat until the nitrate of iron is largely decomposed and the mass separates easily from the bottom and sides of the capsule. Transfer to a piece of platinum-foil with the edges turned up, and heat for some time in a muffle at a very high temperature, or heat it, a portion at a time, in a crucible at the highest temperature obtainable by a blast-lamp. Grind the entire mass very fine in an agate mortar, dissolve in HC1, evaporate to dryness, redissolve in dilute HC1, filter to get rid of SiO 2 , and dilute the solution to about 4 litres. Twenty c.c. of this solution will contain about .5 gramme Fe, and it may be kept indefinitely in a glass-stoppered bottle sealed with paraffine, or after being thoroughly mixed it may be preserved in a number of smaller bottles properly secured. Wash out and dry thoroughly three of the small flasks used for deoxidizing the solutions of the ores, weigh them to within I mg., and measure into each a portion of the ferric chloride solution ranging from 15 to 25 c.c. in volume. Weigh the flasks and their contents ; the differences between the first and second weights are the weights of the ferric chloride solution taken. Transfer the solution carefully from each flask to a platinum dish, dilute, boil, precipitate by NH 4 HO, filter, wash, dry, ignite, and weigh the precipitate with the precautions mentioned farther on. The precipitate is Fe 2 O 3 -f P 2 O 5 . Subtract from this weight the amount of P 2 O 5 in this weight of the material, and the remain- der will be the weight of Fe 2 O 3 in the amount of solution used. Suppose, for example, that the original iron contained .1 per cent. P, this would be equivalent to 0.229 P er cent. P 2 O 5 , but, as the iron has been oxidized to Fe 2 O 3 , the percentage of P 2 O 5 in the iron as oxide would be only ^ as great as in the iron itself, the weight as oxide being ^ as great as it was as Fe. Therefore multiply .229 per cent, by .7 for the percentage of P 2 O 5 in the Fe 2 O 3 , which Preparation of ferric chloride thes strength ' solution. Example JrateThe method - 220 ANALYSIS OF IRON ORES. gives .16 per cent. P 2 O 5 . If we further suppose that the weight of Fe 2 O 3 -hP 2 O 5 obtained was .8131 gramme, .16 per cent, of this would be .0013 gramme, the weight of P 2 O 5 in the precipitate, and .8131 .0013 = . 8118 gramme, the weight of Fe 2 O 3 in the amount of solution taken. Divide this weight by the weight of the solution, and the result is the weight of Fe 2 O 3 in I gramme of the solution of ferric chloride. Take the mean of the three results obtained in this way, and call this result the value of the ferric chloride solution in Fe 2 O 3 , or multiply by .7 for its value in Fe. To standardize the permanganate or bichromate solution, weigh out three portions of the ferric chloride solution into the flasks, reduce them by the method selected, and titrate the re- duced solutions exactly as directed above. Before calculating the strength of the standard solution a small correction must be ap- plied to the burette reading, due to the fact that a definite amount of oxidizing solution is required to produce the end reaction in all cases where permanganate is used, and, when bichromate is used, in those cases where zinc has been the deoxidizing agent. Determina- Treat 3 grammes of zinc in a small flask with 5 c.c. HC1 and tion of the cor- 20 c.c. H 2 O, add gradually 10 c.c. H 2 SO 4 and 20 c.c. H 2 O. When for zinc, the zinc has all dissolved, place the flask in cold water until the solution is cold. Wash it out into the dish, dilute to I litre, add 20 c.c. ferric chloride solution (free from ferrous salt), and drop in the standard solution until the end reaction is obtained. Subtract the correction thus obtained from every burette reading. To calculate the strength of the standard solution, therefore, subtract the correction from the burette reading, and the result is the absolute volume of the standard solution required to oxidize the ferrous salt in the solution operated on. Knowing then the weight of the ferric chloride solution used, the amount of Fe in each gramme of the solution, and the volume of the standard required to oxidize this amount, the value of each c.c. of the DETERMINATION OF TOTAL IRON. 221 standard solution is found by multiplying the weight of ferric Calculation chloride solution used by the value of each gramme in Fe, and value dividing the amount by the number of c.c. of the standard used sta ndard in titrating. The mean of the results obtained in the three por- tions used should be taken as the value of the standard solution. An example will illustrate the method of computation, and, as logarithms very much facilitate these calculations, they will be given in the example as well. Weight of empty flask 22.8817 Example of Weight of flask -f- ferric chloride solution 40.0640 Weight of ferric chloride solution used 17.1823 = ^.1.2350813 Value of ferric chloride solution, determined as on p. 219 i gramme = .03227 gramme Fe = log. 8.5087990 10 Fe in ferric chloride solution used 55448 gramme = log. 9.7438803 IO Burette reading after titration =82.0 c.c. Less correction 0.25 Corrected reading 81.75 c.c. =r log. 1.9124878 I c.c. standard solution .0067826 gramme Fe =log. 7.8313925 10 Of course in calculating the amount of Fe in an ore it is only calculation necessary to get the logarithm of the corrected reading (page 220) Lore" 1 and add it to the logarithm of the standard solution as found above, the number corresponding to the resulting logarithm being the weight of Fe in grammes in the ore. This multiplied by 100 will give the percentage. Very fine iron wire may be used to standardize the solutions, Use of iron instead of a standard solution of ferric chloride. Weigh into the standard- reducing flasks from .4 to .6 gramme of fine iron wire (page 55) which has been carefully rubbed with fine sand-paper and wiped clean with a linen rag. Dissolve in 10 c.c. HC1 and 20 c.c. H 2 O, with the addition of a few small crystals of KC1O 3 . Deoxidize carefully, and titrate as before directed. Multiply the weight of iron wire by .998 to get the absolute amount of Fe used, apply the proper correction to the burette reading, and calculate the value of the standard. 222 ANALYSIS OF IRON ORES. Use of fer- rous sul- phate or ammonio- ferrous sulphate. Degree of concen- tration of standard solutions. Preparation and pres- ervation of solutions. Ferrous sulphate, FeSO 4 ,7H 2 O,* containing 20.1439 P er cent. Fe, or the double sulphate of iron and ammonium FeSO 4 ,(NH 4 ) 2 SO 4 ,6H 2 O,f containing 14.2857 per cent, or almost exactly \ of its weight of Fe, may be used instead of ferric chloride solution or iron wire to determine the value of the standard solutions. The pure salts are generally weighed off, dissolved in water with 10 c.c. H 2 SO 4 , added and titrated direct, but they are not so satisfactory in use as the first and second methods described. It is important to have the standard solutions of the proper strength ; that is, neither too dilute nor too concentrated for convenience in work- ing. As iron ores rarely contain more than 60 per cent, metallic iron, a standard solution 100 c.c. of which are equal to .66 gramme Fe will be found sufficiently concentrated to avoid the necessity of refilling the burette for a determination ; and where ores much poorer than this are habitually used the solutions may be correspondingly more dilute. When permanganate of potassium is added to a solution of ferrous sulphate the reaction is ioFeSO 4 + 2KMnO 4 -f 8H 2 SO 4 = 5Fe 2 (SO 4 ) 3 + K 2 SO 4 + 2MnSO 4 -f 8H 2 O, or 316.2 parts by weight of KMnO 4 will oxidize 560 parts by weight of Fe, or 3.727 grammes KMnO 4 to the litre will give a solution of about the strength required. In the case of bichromate of potassium the reaction is 6FeSO 4 + K 2 Cr 2 7 + 7H 2 S0 4 - 3Fe 2 (SO 4 ) 3 + K 2 SO 4 + Cr 2 (SO 4 ) 3 -f 7H 2 O, or 294.5 parts by weight of K 2 Cr 2 O 7 will oxidize 336 parts of Fe, or 5-7 8 5 grammes of bichromate of potassium dissolved in I litre of water will give a solution 100 c.c. of which will be equivalent to about .66 gramme Fe. To prepare the solutions, therefore, dissolve the above weights, or multiples of them, in pure distilled water, allow the solution to stand for some little time, filter through asbestos, and dilute to the proper volume. Mix thoroughly by shaking in the bottle, * See page 55. f See page 56. DETERMINATION OF FERROUS OXIDE. and standardize as above directed. The solutions should be kept in glass-stoppered bottles in a dark closet, and the bottles should be well shaken whenever the solution is used. DETERMINATION OF IRON EXISTING AS FeO. Many iron ores contain iron in the state of FeO, and this FeO may be either soluble or insoluble in HC1. To determine FeO soluble the FeO soluble in HC1, weigh I gramme of the finely-ground ore into the flask A, Fig. 91, of about 100 c.c. capacity. Close the flask with a rubber stopper fitted with the two glass tubes B and C, and place it in the position shown in the sketch. Connect the tube C by means of a piece of rubber tubing with the bent tube D dipping below the surface of the water in the beaker E. Pass a current of CO 2 through the tube B until all the air is expelled, then remove for a moment the rubber tube connecting B with the source of CO 2 , and by means of a small funnel and rubber connector introduce into the flask A, through B, 10-12 c.c. strong HC1, and establish the current of CO 2 as before. Heat the flask carefully, and when the ore is entirely decomposed, or the HC1 ceases to exert any further action on it, remove the source of heat, stop the current of CO 2 for a moment, cool the flask with the hand, and allow the partial vacuum thus formed to draw the water from E back into A. Turn on the current of CO 2 again, place a dish of cold water under the flask A, and allow the solu- tion to cool. Dissolve in a small flask 3 grammes of metallic zinc in 10 or 15 c.c. H 2 SO 4 , diluted with the proper quantity of water, cool it, and have it ready to pour into the titrating-dish by the time the solution in the flask A is cool. Wash out the solution of the ore from the flask A into the dish, add the zinc solution, dilute to I litre, and titrate with a standard solution. Subtract from the burette reading the proper correction, calculate the percentage of Fe, divide by 7, and multiply by 9. The result is 224 ANALYSIS OF IRON ORES. tion of the percentage of FeO in the ore soluble in HC1. Allow the solu- tion in the dish to stand for a few minutes, when all the undecom- posed particles of ore will settle. Draw off the greater part of in HC1. FIG. 91. Q the clear supernatant fluid with a siphon, wash the sediment into a beaker with a jet of cold water, filter on a thin felt* in a Gooch crucible, and wash the sediment on the felt with cold water. Transfer the felt and sediment to a platinum crucible, pour into the crucible 5-10 c.c. HC1 and about half the quantity of HF1, * The asbestos of which the felt is made must be free from FeO. >.= DETERMINATION OF FERROUS OXIDE. cover the crucible, and place it in the water-bath shown in Fig. 92. The crucible rests on a platinum triangle fixed over the hole in the centre of the tip of the bath. Around this hole is a groove FIG. 92. 225 j.. o NCHES in which a funnel stands as shown in the cut, while the water in the groove forms a tight joint.* Pass a current of CO 2 or coal- gas through the tube in the side of the bath, as figured in the cut, to exclude the air, and heat the bath until the residue and felt are completely dissolved. Wash the crucible out into the titrating- * Avery, Chem. News, xix. 270; Wilbur and Whittlesay, Crook's Select Methods, Page 133- 226 ANALYSIS OF IRON ORES. dish, into which have been poured just previously 3 grammes of zinc dissolved in H 2 SO 4 and enough cold water to make the solu- tion up to nearly I litre. Titrate, and calculate the amount of FeO as before. Separate Of course separate portions of the ore may be used to deter- mine the FeO soluble and insoluble in HC1, but it is more trouble- some, and experience has shown that it is no more accurate, and soluble in - n some cases l ess accurate, than the method just described. Total FeO The total FeO may also be determined in one operation by operation, treating I gramme of the ore direct in the crucible with 20 c.c. HC1 and 20 c.c. HF1, but it is often difficult to get the ore perfectly dissolved even by prolonged heating in the bath, and the ore must be ground very fine in the agate mortar. It is necessary to re-- move the funnel from time to time, raise the lid of the crucible, and stir the contents with a platinum wire. When the ore is completely decomposed by HC1, or when the portion undecomposed contains no FeO, the treatment of the residue is unnecessary. When an ore contains much organic matter, an accurate deter- mination of FeO is often impossible, as the solution of the ore in HC1 reduces some of the ferric salt. DETERMINATION OF SULPHUR. Sulphur exists in two conditions in iron ores, as sulphur in the form of sulphides and as sulphuric acid in the form of sulphates. Total sui- To determine the total sulphur, weigh I gramme of the finely- ground ore into a large platinum crucible, add to it 10 grammes of Na 2 CO 3 and a little KNO 3 (less than I gramme).* Mix * See pages 46 and 48. It is well to make a blank determination, using the same amounts of Na 2 CO 3 , KNO 3 , and HC1, applying the amount of BaSO 4 found as a correction. DE1ERMINATION OF SULPHUR. 22/ thoroughly with a platinum wire, and heat carefully over a large Bunsen burner or blast-lamp until the mass appears perfectly liquid and in a tranquil state of fusion. Run the fusion well up on the sides of the crucible, allow it to cool, and treat it in the crucible with boiling water. Pour the liquid into a tall, narrow beaker, treat the crucible again with boiling water, and repeat the operation until all the sodium salts are dissolved and nothing remains in the crucible except the unavoidable stains. Stir the liquid in the beaker well, and allow the oxide of iron to settle. If the solution is colored red or green, it is proof of the presence Evidence or of manganese in the ore ; add a few drops of alcohol, which will e *" g and precipitate the manganese as oxide, leaving the solution colorless unless the ore contains chromium, in which case the solution will be yellowish. Decant the supernatant liquid on a small filter, allowing the filtrate to run into a No. 4 beaker, fill the small beaker nearly full of hot water, stir well, and allow to settle. Decant again on the filter, and repeat the operation once more. Acidulate the collected filtrates with HC1 (about 20 c.c. will be required), evapo- rate to dryness in the air-bath, redissolve in water with a few drops of HC1, filter into a No. 3 beaker, heat the filtrate to boiling, and add 10 c.c. of a solution of chloride of barium.* Allow to stand for some hours, filter on the Gooch crucible or on a small ashless filter, ignite, and weigh as BaSO 4 , which multiplied by .1376 gives the weight of S. The insoluble portion from the aqueous solu- tion of the fusion may be used to determine the total iron in the ore, and is very convenient for this purpose in ores difficult to dissolve. Pour into the crucible in which the fusion was made about 10 c.c. HC1, place the lid on the crucible, and warm the crucible slightly to dissolve the adhering oxides, dilute with about an equal bulk of water, and pour it on the small filter through which the aqueous solution was decanted, allowing it to run into the beaker which contains the residue of oxide of iron, iron in the fusion ' * See page 51. 228 ANALYSIS OF IRON ORES. etc. Wash out the crucible, pouring the washings on the filter, and wash the filter free from iron with a jet of cold water. Evap- orate the solution in the beaker to dryness, redissolve in 10 c.c. HC1, and transfer the solution of ferric chloride, the silica, etc., to one of the small flasks, deoxidize, and titrate as directed. The sulphur which exists as sulphuric acid in an iron ore is usually combined with either calcium or barium : as sulphate of calcium or of any of the other alkaline earths except barium, of the alkalies, or of the metals, it is soluble in HC1 ; as sulphate of barium it is practically insoluble. We may, therefore, deter- Determi- mine the soluble sulphates as follows : Boil 10 grammes of the soiubie ore with 30 c.c. HC1 and 60 c.c. water, filter from the mass of the sulphates. unc jj sso i vec j ore> evaporate the filtrate to dryness, redissolve in HC1 and water (12), filter into a No. 2 beaker, nearly neutral- ize by NH 4 HO, heat to boiling, and precipitate by BaCl 2 solu- tion. Filter and wash the precipitate, ignite, and weigh as BaSO 4 , which contains 34.352 per cent. SO 3 . Determi- To determine the sulphuric acid which exists as sulphate of sulphate barium, treat 10 grammes of the ore with 50 c.c. HC1 until the um ' ore appears to be decomposed. Evaporate to dryness, redis- solve in dilute HC1 (1-3), dilute, filter, and wash the insoluble matter thoroughly. Ignite and fuse the insoluble matter with Na 2 CO 3 , treat the fused mass with hot water, and filter. In the filtrate is the sulphuric acid as sulphate of sodium, while the barium remains on the filter as carbonate of barium. It is safer to calculate the sulphate of barium from the amount of barium rather than from the amount of sulphuric acid, as the ore may contain sulphides (pyrites, etc.), which are not decom- posed by HC1, but are decomposed and partly oxidized by fusion with Na 2 CO 3 . The other forms of barium besides the sulphate (silicate and carbonate) are readily decomposed by HC1, and are not likely to be found with the barium in the insoluble residue. It is, of course, possible to suppose the coexistence of silicate or carbonate of barium and of sulphate of calcium . DETERMINATION OF PHOSPHORIC ACID. in an ore, and the consequent formation of sulphate of barium when the ore is decomposed by HC1; but, as the soluble sul- phuric acid is determined in one operation and the insoluble in another,* the total amount of sulphuric acid existing as such is determined, and the object of the analysis attained. To deter- mine the barium, then, treat the insoluble matter obtained by the filtration of the aqueous solution of the fusion by dilute HC1, evaporate to dryness to render SiO 2 insoluble, redissolve in water with a few drops of HC1, filter into a No. 2 beaker, heat the filtrate to boiling, and add a few drops of H 2 SO 4 diluted with a little water. Allow the precipitate to settle, filter, wash, ignite, and weigh as BaSO 4 , from which weight calculate the amount of SO 3 in the ore insoluble in HC1. To find the amount of sulphur existing as sulphides, subtract from the total S the amount of S in the SO 3 found as sulphates. DETERMINATION OF PHOSPHORIC ACID. Treat 5 or IQ grammes of the finely-ground ore in 30 or solution of 60 c.c. HC1. (With low phosphorus ores use 10 grammes ; with others, 5 grammes.) When the ore is decomposed, evaporate to dryness, redissolve in 20 or 40 c.c. HC1, dilute, filter, and proceed exactly as directed in the determination of phosphorus in iron and steel, page 81 et seq. The weight of the Mg 2 P 2 O 7 multiplied by .63788 gives the weight of the P 2 O 5 . The weight of the phospho-molybdate of ammonium multiplied by .03735 gives the weight of the P 2 O 5 . Titanic acid is very generally found associated with iron Precautions ores, and may be regarded as one of the usual constituents. * The insoluble matter from the treatment of 10 grammes of the ore with HC1 for the determination of soluble sulphates, page 228, may be used to determine the sulphate of barium. 230 ANALYSIS OF IRON ORES. Means of recogniz- ing titan- iferous ores. Ores con- taining barium. Additional test for titanic acid. As mentioned on page 86 its presence, if overlooked, may lead to serious errors in the determination of phosphoric acid. When an ore contains much titanic acid it may readily be recognized by the peculiar milky appearance of the solution when it is diluted preparatory to filtering off the insoluble matter, and by the strong tendency it shows to run through the filter as soon as the attempt is made to wash the insoluble matter with water. Smaller quantities of titanic acid may be recognized by the clouding of the solution when it is deoxidized by bisulphite of ammonium, as noted on page 89. In the latter case, however, this clouding may be caused by the formation of sulphate of barium when the ore contains the latter element in the form of carbonate or silicate. Silica in the solution may also cause a cloud under those circumstances which closely resembles that caused by titanic acid, while sulphate of barium may readily be distinguished from either by its granular appearance and its tendency to settle to the bottom of the beaker. The insoluble residue from the solution of the ore in HC1 should, therefore, be treated to recover any P 2 O 5 which may have remained insoluble in combination with TiO 2< * An ad- ditional test for the presence of titanic acid, and one that rarely fails even with very small amounts, is to dissolve the insoluble matter from the aqueous solution of the fusion of the residue from the HF1 and H 2 SO 4 treatment of the insoluble residue from the ore, in dilute HC1, allowing it to run into a test-tube and adding metallic zinc. When titanic acid is present the solu- tion becomes first colorless, and then pink or purple, and finally blue from the formation of Ti 2 O 3 . The simplest way is to pro- * When HF1 is not available, fuse the residue with Na 2 CO 3 , treat the fused mass with hot water, filter, acidulate the filtrate with HC1, evaporate to clryness to render SiO 2 insoluble. Redissolve in water with a little HC1, filter, and add the filtrate to the main solution, or add a little Fe 2 Cl 6 , and make a separate acetate precipitation in this portion, adding the solution to the solution of the main acetate precipitation. DETERMINATION OF TITANIC ACID. 231 ceed as directed an pages 88 and 89 when using the acetate method, or on page 94 when using the molybdate method. These methods are not practicable, however, when the ore contains a very large amount of TiO 2 , and recourse must be had to the method described on page 86 et seq., involving the fusion of the acetate precipitate and the residue from the treat- Fusion of ment of the insoluble matter with HF1 and H 2 SO 4 , with and a little NaNO 3 . It is best to pursue this method at any rate whenever TiO 2 is also to be determined, as the same por- tion can be used for the estimation of both TiO 2 and P 2 O 5 , and the aggregate labor involved is much lessened. DETERMINATION OF TITANIC ACID. The determination of titanic acid has always presented many Difficulties difficulties, and its separation from a large amount of oxide of C i P itation iron and alumina has been far from satisfactory, besides being most tedious. The principal sources of error in the estimation of titanic acid in iron ores are the tendency of P 2 O 5 to prevent the precipitation of TiO 2 by boiling, when its sulphuric acid solution contains P 2 O 5 and ferrous sulphate, and the liability of A1 2 O 3 to separate out with the TiO 2 when the latter is precipitated under the circumstances above mentioned. There is also a mechanical difficulty, caused by the adhesion of the precipitated TiO 2 to the bottom and sides of the beaker, from which it can sometimes be removed only by boiling with a strong solution of caustic potassa. The admirable series of experiments carried out by Dr. Gooch * on the separation of aluminium and titanium suggests a method which renders the determination of TiO 2 in iron ores much less troublesome, while adding greatly to the accuracy of the results. * Proceedings Am. Acad. Arts and Sciences, New Series, vol. xii. p. 435. 2 3 2 ANAL YSIS OF IRON ORES. Details of the method. Principles involved. In carrying out the details of the method, dissolve 5 or 10 grammes of the ore in HC1, and proceed exactly as in the deter- mination of P 2 O 5 , by fusing the residue from the treatment of the insoluble matter by HF1 and H 2 SO 4 and the acetate pre- cipitate with Na 2 CO 3 and a little NaNO 3 ,* and then complete the operation exactly as described in the determination of Ti in pig-iron.f The essential points in this method are i. Separation of the TiO 2 from the mass of Fe 2 O 3 by acetate of ammonium in the deoxidized solution. 2. Separation from all the P 2 O 5 and the greater part of the A1 2 O 3 by fusion with Na 2 CO 3 , by which means a titanate -of sodium insoluble in water is formed, and at the same time phosphate and aluminate of sodium soluble in that men- struum. 3. Separation from the last traces of A1 2 O 3 from the iron, calcium, etc., by precipitating the TiO 2 in the thoroughly deoxi- dized solution in the presence of a large excess of acetic acid and some SO 2 , the sulphuric acid being all in the form of sulphate of sodium. The addition of a large excess of acetate of sodium, by which this latter condition is effected, converts all the sulphates of iron, calcium, etc., into acetates, and precipitates the TiO 2 almost instantaneously as a hydrate, which is flocculent, settles quickly, shows no tendency to run through the filter, and is washed with the greatest ease. It sometimes happens that a little FeO is precipitated with the TiO 2 , and the latter, after ignition, appears discolored; in this case fuse with a little Na 2 CO 3 , add H 2 SO 4 to the cold fused mass, dissolve, and repeat the precipita- tion with acetate of sodium in the presence of sulphurous and acetic acids exactly as in the first instance. A number of experiments covering all the points involved in this method show it to be extremely accurate and entirely trust- worthy. * See page 86 et seq. f See page 178 et seq. DETERMINATION OF MANGANESE. 333 DETERMINATION OF MANGANESE. When manganese alone is to be determined in an ore, any one of the methods described under the determination of manga- nese in iron and steel, page 109 et seq., may be used. The most convenient, however, is Ford's method with the modifications Ford>s - f method. necessary in the analysis of pig-iron, page 117. The only change requisite is to evaporate the solution in HC1 to dryness to render silica insoluble before filtering off the insoluble matter. In the determination of manganese in high grade manganese ores, it is best to use a one-tenth factor weight (0.3874 gramme) of the sample, dissolve in hydrochloric acid, evaporate to dryness, redissolve in dilute hydrochloric acid and filter off the insoluble matter. Ignite the insoluble matter in a platinum crucible, fuse with a little sodium carbonate, dissolve in water, acidulate with hydrochloric acid, and evaporate to dryness. Redissolve in dilute hydrochloric acid and filter into the main solution. Or, treat the ignited insoluble matter with sulphuric and hydrofluoric acids, drive off the hydrofluoric and the excess of sulphuric, cool, add water and a little hydrochloric acid, and heat until the residue dissolves, then add the solution to the main solution of the ore. Evaporate the main solution until it is syrupy, add an excess of strong nitric acid and evaporate off the hydrochloric acid. Precipitate by potassium chlorate in the usual way and filter through asbestos. Wash the precipitate thoroughly with cold water to get rid of the calcium nitrate, which, being practically insoluble in strong nitric acid, will remain with the precipitated manganese dioxide, unless this precaution be observed. There is no danger of dissolving the manganese dioxide by this treatment. Proceed with the determination as directed on page 116. Each milligramme of manganese pyrophosphate is a tenth of one per cent, of manganese in the ore. In using the acetate method it is, of course, necessary that The acetate all the iron should be in the form of Fe 2 Cl 6 , and also that there method ' should be no oxidizing agent in the solution. Even a very small 234 ANALYSIS OF IRON ORES. amount of FeCl 2 will cause the formation of a " brick-dust" precipi- tate, which cannot be kept from passing the filter while some of the iron remains dissolved in the acetate solution. When, there- fore, the ore contains FeO, it should be oxidized by HNO 3 or KC1O 3 , and the excess of the oxidizing agent removed by evapo- ration with HC1. Volhard's Method Applied to High Grade Manganese Ores. Volhard's is the most satisfactory volumetric method for high grade manganese ores. Dissolve I gramme of the ore in a small beaker in hydrochloric acid, heat until the chlorine is all driven off, wash out into a platinum dish (Fig. 36), and add 5 c.c. strong sulphuric acid and a little hydrofluoric acid. Evaporate to dry- ness and heat until the sulphuric acid begins to volatilize. Cool, dissolve in water, transfer to a 300 c.c. flask, and proceed as directed on page 116, except that 100 c.c. of the filtered solution representing one-third of a gramme of the ore is used. In running in the permanganate it is necessary to heat the solution in the flask after there appears to be a slight excess. This will make the precipitate settle rapidly and generally show the necessity for adding more permanganate. A large number of comparative analyses have shown that it is necessary to add one one-hundredth of the amount obtained to get the true percentage of manganese ; in other words, the results obtained are always one one-hundredth too low. For instance, if by calculation the ore contains 50 per cent, of manganese by this method, the true result is 50.5 per cent. Pattinson's Method. 1 Dissolve in hydrochloric acid such a quantity of the sample as shall contain not more than 0.25 gramme of manganese. In high manganese ores add enough ferric chloride to the solution to make the iron and manganese contents about equal. Add 1 Society of Chemical Industry, vol. x. No. 4. DETERMINATION OF MANGANESE. 235 calcium carbonate to the solution until it is slightly red in color and acidulate by adding hydrochloric acid until the red color disappears. Add sufficient zinc chloride in solution to give 0.5 gramme metallic zinc. Heat to boiling and dilute with boiling water to 300 c.c., and add 60 c.c. of a solution of calcium hypo- chlorite containing 33 grammes to the litre. To the solution of hypochlorite just before using it, add enough hydrochloric acid to give it a faint greenish tinge after agitation. Finally add 3 grammes of calcium carbonate diffused in 1 5 c.c. of boiling water, and after stirring well 2 c.c. of methyl alcohol. Filter on a large filter and wash with water at 65 until a strip of iodized starch paper gives no indication of chlorine. Measure into a beaker 100 c.c. of a carefully standardized strongly acid solution of ferrous sulphate containing 10 grammes of iron to the litre and place the precipitate and filter in it. When the precipitate has dissolved add cold water and determine the excess of ferrous sulphate by a standard solution of potassium bichromate. When the ore contains much organic matter it should be fil- FCO and tered off before attempting to oxidize the ferrous salt, as it is quite mftterta impossible in some cases to destroy the organic matter, and reso- lution of the evaporated mass in HC1 causes a reduction of some of the ferric salt. Many manganiferous iron ores contain manganese in a higher Ores con- state of oxidation than the protoxide, and the determination of the excess of oxygen is often necessary. All ores of this character when treated with HC1 evolve chlorine gas, which, is easily recog- nized by its yellowish-green color and peculiarly irritating odor. The reaction by which chlorine is liberated is MnO 2 + 4HCl = MnCl 2 -f- 2H 2 O -j- 2C1, or each molecule of MnO 2 = 87 corresponds to 2 molecules of Cl = 70.90. This reaction is the basis of Bun- sen's method for the estimation of the amount of the MnO 2 in manganese ores, which consists in driving the liberated Cl into a solution of iodide of potassium, and determining the amount of 2 3 6 Bunsen's method. ANALYSIS OF IRON ORES. iodine set free, by starch and hyposulphite solution. When the method given on page 68 et seq. for determining sulphur in steel is in use, the solutions employed in carrying out that method (with the exception of the iodine in iodide of potassium) can be used in this, or they may be prepared by the directions there given, for use in this method. Weigh from .5 gramme to I gramme of the finely-ground ore into the flask a, Fig. 93, pour in 10 c.c. strong HC1, connect the FIG. 93. bent tube b quickly by means of a piece of gum tubing, and heat the flask gently at first and finally to boiling to drive all the Cl over into the tube r, which contains a strong solution of pure iodide of potassium free from iodate. This tube is placed in ice- water. When all the Cl has been expelled from the flask a and absorbed in c, detach the latter, wash its contents into a large dish, DETERMINATION OF MANGANESE. 237 add a little starch solution, and run in the hyposulphite until the blue color just vanishes. If, as in the example given on page 70, Example. I c.c. of the hyposulphite solution is equal to .01267 gramme of iodine, and I equivalent of chlorine =3 5. 45 replaces i equiva- lent of iodine = 126.85 in the iodide of potassium, i c.c. of the hyposulphite solution would be equal to (126.85 : 35.45 :: .01267: .003541) .003541 gramme of chlorine; and, as I equivalent of MnO 2 = 87 is equal to 2 equivalents of chlorine = 70.90, i c.c. of the hyposulphite would be equal to (70.90 : 87 : : .003541 : .004345) .004345 grammes MnO 2 . In most laboratories, however, it is generally more convenient to determine the amount of MnO 2 in an ore by determining its oxi- dizing power on a solution of ferrous salt. The reaction is 2FeSO 4 + MnO 2 + 2H 2 SO 4 = Fe 2 (SO 4 ) 3 + MnSO 4 + 2H 2 O, or 2 equivalents of Fe = 1 12 are equal to i equivalent of MnO 2 = 87. Grind in an tion by agate or Wedgwood mortar about 10 or 15 grammes of ferrous means of sulphate or ammonio-ferrous sulphate, and weigh out two portions, S u7phate. one of 2 grammes and one of 3 to 8 grammes, according to the quality of the manganese ore. One gramme of pure MnO 2 would oxidize 1.2874 grammes of Fe, equal to nearly 6.5 grammes of ferrous sulphate, -or more than 9 grammes of ammonio-ferrous sulphate. Transfer the 2-gramme portion to the dish, add a large amount of water and about 5 c.c. HC1, and pour in 3 grammes of zinc dissolved in 10 c.c. H 2 SO 4 diluted with enough water to dis- solve the sulphate of zinc readily. Titrate with the standard solu- tion of permanganate or bichromate of potassium in the usual way, and calculate the amount of iron in i gramme of the ferrous salt used. Weigh into the flask A, Fig. 90, page 218, I gramme of the finely-ground ore, and add to it the larger portion of the ferrous salt previously weighed out. Connect the flask as in Fig. 91, and pass in a current of CO 2 until the air has been driven out. Now pour into the flask A, by means of a small funnel attached to B, 10 c.c. HC1 and 30 c.c. water, reconnect the CO 2 apparatus, and while the current of CO 2 is passing dissolve the ore, heating the 238 ANALYSIS OF IRON ORES. flask, and shaking it from time to time as necessary. When the ore is all decomposed, stop the current of CO 2 for a moment, remove the light, and allow the water in E to flow back into the flask A. Transfer the solution to the dish, add 3 grammes zinc dissolved in H 2 SO 4 , and titrate it with the standard solution. From the titration of the ferrous salt calculate the amount of Fe in the amount used in the solution of the ore, and subtract from this the amount found by this last titration ; the difference is the weight of Fe oxidized by the chlorine liberated from the MnO 2 in the ore. Then, as 112 parts of Fe correspond to 87 parts of MnO 2 , multiply the above weight of iron by 87 and divide by 112, and the result is the weight of MnO 2 in the ore. Calculation The total Mn having been determined by one of the methods of MnO and previously given, subtract from it the amount of Mn as MnO 2 (found by multiplying the weight of MnO 2 by .63218), and cal- culate the difference to MnO by multiplying by 1.2909. DETERMINATION OF SILICA, ALUMINA, LIME, MAGNESIA, OXIDE OF MANGANESE, AND BARYTA. Treatment of iron ores with HC1 leaves a residue which only residue in very rare instances consists of silica alone, being usually sili- ca tes of aluminium, calcium, and magnesium, mixed with an excess of silica. These silicates are often much more complicated, and contain, besides the substances enumerated above, protoxide of iron, soda, potassa, and oxide of manganese. With these sili- cates are occasionally found titanic acid, titaniferous iron, chrome iron ore, sulphate of barium, and ferrous sulphide, besides organic matter, and sometimes graphite. As this residue must be fused with Na 2 CO 3 in order to decompose it, and the introduction of DETERMINATION OF SILICA, ALUMINA, ETC. 239 sodium salts into the main solution is not desirable, the two por- tions of the ore (the soluble and the insoluble in HC1) should be analyzed separately. Weigh i gramme of ore into a No. I beaker, add 15 c.c. HC1, cover with a watch-glass, and digest at a gentle heat until the ore appears to be quite decomposed, add a few drops of HNO 3 , heat until the action has ceased, and then wash off the cover with a fine jet of water, and evaporate to dryness. Redissolve in HC1, and evaporate to dryness a second time to render all the silica insoluble. Redissolve in 10 c.c. HC1 and 30 c.c. water, filter, solution of transfer all the residue to the filter (a small ashless filter) with a fine jet of cold water, using a "policeman" to detach any ad- hering particles from the beaker, and wash the filter with a little HC1 and plenty of cold water. Allow the filtrate and washings to run into a No. 5 beaker, and ignite and weigh the residue as "Insoluble Silicious Matter" Add to the insoluble matter in the crucible about ten times its Analysis weight of pure dry Na 2 CO 3 and fuse it. Run the fusion well up on the sides of the crucible and treat it with hot water. Wash it silicious matter. out into a platinum dish, dissolve any particles adhering to the crucible in HC1, and add this to the solution in the dish. Acidu- late with HC1, evaporate to dryness, moisten with HC1 and water, evaporate to dryness a second time to render silica insoluble, then pour into the dish 5 c.c. HC1 and 15 c.c. water, and stand it in a warm place for some time. Dilute with about 20 c.c. water, filter on a small ashless filter, wash well with hot water, receiving the filtrate and washings in a small beaker, dry, ignite, and weigh. Treat the ignited precipitate with HF1 and a drop or two of H 2 SO 4 , evaporate to dryness, ignite, and weigh again. The differ- SiOa< ence between the two weights is SiO 2 . If the difference between the last weight and the weight of the empty crucible is more than a milligramme or two, the residue must be examined and its nature determined. This residue may consist of titanic acid, sulphate of from HFl and H 2 S0 4 barium, alumina, or sulphate of sodium (from imperfect washing treatment 240 ANALYSIS OF IRON ORES. of the silica). If it is titanic acid or alumina, the weight must be added to the weights of the A1 2 O 3 , etc. Return the filtrate from the SiO 2 to the dish in which it was previously contained, heat to boiling, add a few drops of bromine- Ai 2 o 3 , etc. water and an excess of NH 4 HO, boil until it smells but faintly of NH 3 , filter on a small ashless filter, wash well with hot Possible water, dry, ignite, and weigh as A1 2 O 3 , etc. Besides alumina constit- uents of this precipitate may contain titanic acid, sesquioxide of chro- dpStatT mium, sesquioxide of iron, oxide of manganese, and phosphoric acid. Return the filtrate from this precipitate to the dish, evaporate down to about 100 c.c., add oxalate of ammonium and ammonia, boil for a few minutes, allow the precipitate to settle, filter on a small ashless filter, ignite finally for five minutes over a blast- Cao. lamp, and weigh as CaO. To the filtrate from the oxalate of calcium add microcosmic salt and about one-third the volume of the solution of ammonia, cool in ice-water, stir vigorously several times, and allow to stand overnight so that the precipi- tated Mg 2 (NH 4 ) 2 P 2 O 8 may settle properly, filter, wash with water containing one-third its volume of ammonia and about 100 grammes of nitrate of ammonium to the litre, ignite carefully, and weigh. Dissolve the precipitate in the crucible in a little water containing from 5 to 10 drops HC1, filter through a small MgO. ashless filter, which dry, ignite, and weigh. The difference between the two weights is Mg 2 P 2 O 7 , which, multiplied by .36212, gives the weight of MgO. Analysis of When barium has been shown to exist in the ore, as noted from the on page 222, heat the filtrate from the Insoluble Silicious Matter ^lidous" to boiling, add a few drops of H 2 SO 4 , boil for a few minutes Matter- to allow the precipitate to settle, filter on a small ashless filter, Bao. allowing the filtrate and washings to run into a No. 5 beaker, dry, ignite, and weigh as BaSO 4 , which, multiplied by .65648, gives the weight of BaO. To the cold filtrate from the BaSO 4 add NH 4 HO until the solu- DETERMINATION OF SILICA, ALUMINA, ETC. 24! tion is nearly neutralized, then add a solution of carbonate of am- lion by monium until a slight permanent precipitate is formed which fails acetate to dissolve after vigorous stirring, and redissolve this by the care- ful addition of HC1, drop by drop, stirring well, and allowing the solution to stand for a short time after each addition of HC1. As soon as the solution clears, add a solution of acetate of ammo- nium, made by slightly acidulating 5 c.c. of NH 4 HO by acetic acid, dilute to about 600 c.c. with boiling water, and boil for a few minutes. Allow the precipitate to settle, decant the clear liquid through a large washed German filter, pour the precipitate on the filter, and wash it two or three times with boiling water. With the aid of a platinum spatula return the precipitate to the beaker in which the precipitation was made, dissolving any portion remaining on the filter or adhering to the spatula in dilute HC1, allowing the acid to run into the beaker containing the precipitate. Wash the filter thoroughly with cold water, and evaporate the solution and washings to dryness. Redissolve in dilute HC1, filter into a large platinum dish, dilute with hot water,* heat to boiling, and add a slight excess of ammonia. Boil for a few minutes to make the precipitate granular and expel the excess of ammonia, and filter on an ashless filter (using the filter-pump and cone, page 26, with very slight pressure, if practicable. Dis- solve any of the adhering particles of the precipitate in the dish in a very few drops of HC1, heating the bottom of the dish slightly, wash off the rod and cover, and wash down the sides of the dish with hot water, add a slight excess of ammonia, heat gently until the precipitate of ferric hydrate separates, wash this * The distilled water used in the complete analysis of iron ores should never be heated in glass vessels for any length of time, as glass is sensibly attacked by it. An experiment in which distilled water free from residue was heated for twelve hours in a Bohemian flask showed that the water dissolved 52 milligrammes of solid matter to the litre, of which 26 milligrammes were SiO 2 . The water should always be heated in platinum or porcelain dishes, or in tin-lined copper flasks. For convenience, the water may be poured into the washing-flasks for immediate use. 16 242 ANALYSIS OF IRON ORES. on the filter, and wash the precipitate thoroughly with hot water. Dry the filter and precipitate carefully, transfer the latter to a weighed crucible, burn the filter in a wire, add the ash to the precipitate, and heat the crucible, keeping it carefully covered, and raising the heat very gradually and slowly to expel the last traces of moisture from the precipitate of ferric hydrate. Finally heat the crucible to bright redness, and then to the highest tem- perature of the blast-lamp for about five to ten minutes. Cool, Fe 2 o 3 + ignite, and weigh as Fe 2 O 3 + A1 2 O 3 + P 2 O 5 ( + TiO 2 + Cr 2 O 3 + A1 2 O 3 + p 2 o 6 . As 2 O 5 ). Add the filtrate and washings from the acetate precipitation to those from the precipitation by ammonia, evaporate down to about 200 c.c. in a platinum dish, filter off any slight precipitate of Fe 2 O 3 (which must be ignited, weighed, and the weight added to that of the Fe 2 O 3 , etc.), add 20 to 30 drops of acetic acid, heat to boil- ing, and pass a current of H 2 S through the solution for fifteen or twenty minutes, keeping the solution hot during the passage of the gas. Filter off the precipitated sulphides of copper, zinc, nickel, and cobalt, wash with H 2 S water containing a little free acetic acid, and to the filtrate add excess of ammonia and sul- phide of ammonium. Allow the precipitated sulphide of man- ganese to settle, decant the clear, supernatant liquid through a filter, but before pouring the precipitate on the filter remove the beaker containing the filtrate and substitute a clean beaker, for the precipitate is almost certain at first to run through the filter. Wash the precipitate and filter with water containing a little sul- phide of ammonium, add the clear filtrate and washings together, and stand them aside. Dissolve the precipitate of sulphide of manganese on the filter in dilute HC1, and wash the filter thor- oughly with hot water, receiving the solution and washings in a small beaker. Heat to boiling to expel H 2 S, and, when the excess is driven off, destroy the last traces with a little bromine-water, transfer the solution to a platinum dish, and precipitate by micro- cosmic salt and ammonia as directed on page 112. Filter, wash, DETERMINATION OF SILICA, ALUMINA, ETC. 2 43 ignite, and weigh as Mn 2 P 2 O 7 , which, multiplied by .50011, gives the weight of MnO. Mno. Acidulate the filtrate from the sulphide of manganese with HC1, boil off all the H 2 S, filter from the sulphur deposited by this operation into a platinum dish, add an excess of ammonia and oxalate of ammonium, filter off, ignite, and heat at the highest temperature of the blast-lamp for fifteen minutes, cool, and weigh as CaO. Cao. Precipitate the magnesia in the filtrate as directed on page 232, and determine the weight of Mg 2 P 2 O 7 , which, multiplied by .36212, gives the weight of MgO. M g o. By adding the elements determined in the insoluble portion to the similar ones in the soluble portion, we get the total amounts of each in the ore. Thus, we have from the above analysis Si0 2 ,Fe 2 3 + Al 2 3 +P 2 5 +Cr 2 3 + Ti0 2 + As 2 5 , MnO, CaO, and MgO, and it becomes, of course, necessary to calculate prop- erly the iron in its different states of oxidation and to determine the amount of A1 2 O 3 in the ore. It is much more accurate to determine in separate portions of the ore the amounts of P 2 O 5 , As 2 O 5 , Cr 2 O 3 , Fe 2 O 3 , and TiO 2 than to attempt to make the sepa- ration in the precipitate obtained in this portion. Therefore, knowing the amounts of these substances, the Fe 2 O 3 from the vol- umetric determination of iron, as previously described, and the amount of each of the others as found by one of the methods given, add together the weights of the Fe 2 O 3 , the P 2 O 5 , the Cr 2 O 3 , the TiO 2 , and the As 2 O 5 in one gramme of the ore, and subtract the sum from the weight of the precipitate obtained in the above analysis, the result is the weight of A1 2 O 3 in one gramme of the Ai 2 o 3 . ore. Iron may exist in an ore in several conditions, as Fe-jO^ as FeO, as FeS 2 , as FeAs 2 , etc. While it may not always be possible to determine the exact conditions in which it exists, the rule usually followed is, after subtracting from the sulphur existing as sulphides (page 229) the amount necessary to form sulphide 244 ANALYSIS OF IRON ORES. Fes 2 . Feo. Method for ores con- taining of copper, sulphide of nickel, etc., to calculate the remainder as FeS 2 by multiplying the weight of S by 1.87336. The weight of S subtracted from this gives the weight of iron in the FeS 2 . Now from the weight of FeAs 2 subtract the weight of arsenic, and the result is the weight of iron existing as Fe in the FeAs 2 .* Add the Fe in the FeS 2 to the Fe in the FeAs 2 , and subtract this weight from the Fe found as FeO, the remainder calculated to FeO is the amount of FeO in the ore. Subtract the total amount of Fe found originally by titration to exist as FeO from the total Fe found in the ore, and calculate the remainder to Fe 2 O 3 . When an iron ore contains only a very small amount of man- ganese, the acetate separation may be omitted in the method as gi ven above, which simplifies and shortens the operation very materially. In this event transfer the filtrate from the insoluble silicious matter at once to a large platinum dish, heat to boiling, add a few c.c. of bromine-water and then excess of ammonia, boil, and filter the Fe 2 O 3 , etc., on an ashless filter, dry, ignite, and weigh, as described above. The manganese will be in the pre- cipitate after ignition as Mn 3 O 4 , and the amount calculated from the determination of manganese made in a separate portion of the ore must be subtracted from the weight of the above precipitate in calculating the amount of A1 2 O 3 . The lime and magnesia are determined in the filtrate from the Fe 2 O 3 , etc., providing, of course, that the ore contains only minute amounts of nickel, copper, etc. The same general method described above is applicable when the ore contains quite a large amount of titanic acid, so much, in fact, as to cause the cloudiness in the filtrate from the insolu- ble silicious matter, as noted on page 230. Whenever an acetate separation is necessary in an ore of this character, the precipitate must be filtered on an ashless filter, and this filter, as well as the All the weights, of course, are calculated to i gramme of ore. TITANIFEROUS ORES. 245 filter containing any insoluble matter from the resolution of the acetate precipitate, must be ignited and examined for TiO 2 by treating the residue with HF1 and H 2 SO 4 , heating to redness, fusing with Na 2 CO 3 , dissolving in HC1 and water, and precipi- tating by ammonia. The precipitate so obtained is to be filtered, ignited, and the weight added to that of the Fe 2 O 3 , etc. Ilmenite even, when very finely ground in an agate mortar, is frequently capable of being almost entirely decomposed by HC1, and when this is the case it is of advantage to use this method of analysis. It may be necessary, however, under certain circumstances to decompose the ore at the start by fusing with bisulphate of potas- sium. To carry out this method, weigh I gramme of the ore, Fusion with which has been ground as fine as possible in an agate mortar, into of^aL* a large platinum crucible, add 10 grammes of pure bisulphate of potassium,* and heat the crucible, carefully covered, over a very low light until the bisulphate is melted. It is necessary to watch this operation most carefully, for the bisulphate has a strong tendency to boil over, and only unremitting attention on the part of the analyst will prevent the loss of the analysis. It is well at the start to stand by the crucible and raise the lid slightly at very Precautions short intervals to watch the condition and progress of the fusion. The lid should be held just over the crucible and in a horizontal position, otherwise the particles which have spirted on it from the mass in the crucible may run to the edge of the lid and, when the latter is replaced, down the outside of the crucible. Raise the heat very gradually, keeping the mass just liquid and the tem- perature at the point at which slight fumes of SO 3 are given off when the lid is raised, until the bottom of the crucible is dull red. When the ore is completely decomposed, remove the light, take off the lid of the crucible, and incline the latter at such an angle that the fused mass may run together on one side of the crucible and as near the top as possible. Allow it to cool in this position ; * See page 49. 246 ANALYSIS OF IRON ORES. Solution of the fused mass. SiO 2 . Treatment of impure precipitate of TiO 2 . TiO 2 . Fe 2 O 3 and A1 2 O 3 car- ried down with first precipitate of Ti0 2 . when cold it is easily detached from the crucible. Place the crucible and lid in a No. 4 beaker half full of cold water, and the fused mass in the little basket, as shown in Fig. 76, page 165. Pour into the beaker enough strong aqueous solution of sulphur- ous acid to raise the liquid to the top of the basket, and allow the fusion to dissolve, which may require twelve hours. Wash off with a jet of cold water, and remove the basket, the crucible, and lid, stir the liquid, which should smell strongly of SO 2 , and allow the insoluble matter to settle. Filter on an ashless filter, wash well with cold water, dry, ignite, and weigh. Treat with HF1 and 2 or 3 drops of H 2 SO 4 , evaporate to dryness, ignite, and weigh. The difference between the weights is SiO 2 . If any appreciable residue remains in the crucible, fuse with a little Na 2 CO 3 , treat with H 2 SO 4 , and add to the main filtrate. To the main filtrate, which should be quite colorless and which should smell strongly of SO 2 , add a clear filtered solution of 20 grammes of acetate of sodium and one-sixth of its volume of acetic acid, 1.04 sp. gr., heat to boiling, and boil for a few minutes. Allow to settle, filter on an ashless filter, wash thoroughly with hot water containing one-sixth its volume of acetic acid, and finally with hot water, dry, ignite, and weigh as TiO 2 . This precipitate, however, may not be quite pure, as small amounts of ferric oxide and alumina may be carried down with it. The best plan to pursue is to fuse with Na 2 CO 3 , dissolve in water, filter, wash, dry, and fuse the insoluble titanate of sodium, etc., with Na 2 CO 3 , treat the cooled mass in the crucible with H 2 SO 4 , and precipitate and determine the TiO 2 as directed above. The two filtrates from the treatment of the first precipitate of TiO 2 may contain a little oxide of iron and alumina. To recover this, boil down the last filtrate until the greater part of the sulphurous acid has been driven off, add bromine-water to oxi- dize the iron, acidulate the aqueous filtrate from the carbonate of sodium fusion with H 2 SO 4 , add it to this solution, boil the united solutions down in a platinum dish to a convenient volume, and add a slight excess of ammonia. Boil the solution until it smells DETERMINATION OF SILICA. 247 faintly but decidedly of ammonia, filter off, and wash slightly. Redissolve the precipitate in HC1, and reprecipitate by ammonia, filter, wash, ignite, and weigh as Fe 2 O 3 + A1 2 O 3 , to be added to the main precipitate. Boil the main filtrate and washings down in a large platinum dish after adding enough bromine-water to oxidize all the iron, add HC1 from time to time when necessary to keep the iron in solution, and, when reduced to a convenient bulk, nearly neutralize by ammonia, and boil. Filter off and wash the precipitate two or three times, redissolve and reprecipitate by ammonia, filter, wash, dry, ignite, and weigh as Fe 2 O 3 + A1 2 O 3 + F^OS* P 2 O 5 . Fuse this precipitate for a long time and at a high tempera- P 2 o 6 3 ture with Na 2 CO 3 , dissolve in water, wash by decantation, redis- solve the residue of Fe 2 O 3 , etc., in HC1, and determine the iron by titration. Determine the alumina by difference, the P 2 O 5 being determined in a separate portion. In the filtrate from the Fe 2 O 3 + A1 2 O 3 + P 2 O 5 determine manganese, lime, and magnesia in the MnO.CaO, usual way. DETERMINATION OF SILICA. When silica alone is wanted in an ore a more rapid method is sometimes desirable. In this case dissolve I gramme of the ore in HC1, evaporate to dryness, redissolve in dilute HC1, filter on an ashless filter, wash, dry, ignite, and weigh the insoluble silicious matter. Treat this in the crucible with HF1 and a few drops of H 2 SO 4 , evaporate to dryness, ignite, and weigh. It is evident now that if the insoluble silicious matter contains calcium, magnesium, Lossbyvoi- potassium, or sodium, the loss of weight, which in the absence of W uh HFI these elements would represent the SiO 2 volatilized as fluoride of ^504. silicon, will be decreased by the amount of sulphuric acid which, uniting with these elements, remains as a part of the residue in the crucible. It is a simple operation, however, to fuse this residue 248 ANALYSIS OF IRON ORES. Si0 2 . Separation by citric acid, am- monia, and sul- phide ot ammo- nium. Danger of loss by spirting with Na 2 CO 3 , dissolve in water, acidulate with HC1, heat to boil- ing, add solution of BaCl 2 and filter off, and weigh the precipitated BaSO 4 . This being accomplished, calculate the amount of SO 3 , and add its weight to the loss by volatilization. The result is the weight of SiO 2 . When the ore contains appreciable amounts of sulphate of barium this method is not admissible. Separation of Alumina from Ferric Oxide. Besides the indirect method for determining alumina, it is sometimes necessary or convenient to make a direct separation. The method usually taken, the iron and alumina being in solution in HC1, is as follows : Add to the solution about five times the weight of the oxides, of citric acid (tartaric acid may be used, but, as it is liable to contain alumina, citric acid is preferable) and excess of ammonia. If the solution remains clear, heat to boiling, and add a fresh solution of sulphide of ammonium until all the iron is precipitated. If the solution does not remain clear on the addition of ammonia, acidulate with HC1, add more citric acid, and then excess of ammonia. Allow the sulphide of iron to settle, decant the clear liquid through a washed filter, throw the precipi- tate on the filter, and wash it well with water containing sulphide of ammonium, changing the beaker into which the washings run before each addition of wash-water, and keeping the funnel well covered with a watch-glass. Unite the filtrate and washings, acidu- late with HC1, boil until the precipitated sulphur agglomerates, filter into a platinum dish, and evaporate to dryness. Heat care- fully until the chloride of ammonium is volatilized and there remains in the dish a mass of carbonaceous matter from the decomposition of the citric acid. The expulsion of the last traces of water from the chloride of ammonium nearly always causes loss by spirting, but the difficulty may be entirely avoided by placing the dish in one of the holes of the air-bath overnight, after having lightly coated the upper edge of the dish with paraffine or grease to prevent the chloride of ammonium from creeping over the top. SEPARATION OF ALUMINA FROM FERRIC OXIDE. 249 This long heating expels the last traces of water without the least disturbance, and the dish may be at once placed over a Bunsen burner, and the mass in it decomposed without fear of loss. Transfer the carbonaceous matter to a crucible, wiping out the dish carefully with filter-paper, and placing these in the crucible also. Burn off the carbon in the crucible, fuse the residue with Na 2 CO 3 and a little NaNO 3 , treat with water, transfer to a platinum dish, dissolve any adhering particles in the crucible in HC1, add this to the solution in the dish, with enough HC1 to acidulate it, heat to boiling after diluting, add a slight excess of ammonia, boil until the solution smells but faintly of NH 3 , filter, wash thoroughly, ignite, and weigh as A1 2 O 3 . This precipitate will AiaO 3 . contain any P 2 O 5 , Cr 2 O 3 , and TiO 2 that may have been in the original solution. They may be separated by the methods given impurities, on page 189 et seq. It is liable to contain also a little iron, which is almost invariably held in solution by the sulphide of ammonium. Dissolve the precipitate of ferrous sulphide on the filter in dilute hot HC1, allow the solution and washings to run into the beaker in which the precipitation was made, add a little HNO 3 , evaporate to dry ness, redissolve in as little dilute HC1 as possible, filter into a platinum dish, dilute, precipitate by ammonia, filter, wash, dry, ignite, and weigh as Fe 2 O 3 . Fe 2 o 3 . Rose * suggested the method based on the solubility of alu- separation mina in caustic potassa or soda. When the iron and alumina are poua <* in solution, evaporate until syrupy in a platinum dish, add a strong solution of caustic soda or potassa until the solution is strongly alkaline, and then add a large excess of the precipitant, and boil for ten or fifteen minutes ; or, pour the nearly neutral solution of the chlorides into a boiling solution of caustic soda or potassa in a platinum or silver dish, in a thin stream, stirring continually. Filter, wash with hot water, carefully acidulate the filtrate with * Chimie Anal. Quant. (French ed.), page 148. 250 ANALYSIS OF IRON ORES. Objection method. current of after ^e- Rose's mod- ification. Separation by hypo- sulphite of HC1, and precipitate the alumina by ammonia, filter, wash, dis- solve in HC1, evaporate to dryness to get rid of SiO 2 , redissolve, filter, and determine as usual. As the Fe 2 O 3 precipitated by caus- tic soda or potassa always contains alkali, it must be dissolved in HC1, precipitated by ammonia, filtered, and weighed in the usual manner. Rose also suggested fusing the finely-ground ignited oxides in a silver crucible with potassium or sodium hydrate ; but this method, as well as the other, is open to the objection that it is almost impossible to get caustic soda or potassa that does not con- tain alumina, and generally there would be more in the reagent than in the ore. Rivot suggested the following method : After weighing the ignited oxides of iron and aluminium, grind them very fine, and weigh them into a porcelain or platinum boat. Place the boat in a porcelain or platinum tube, and heat to redness in a cur- rent of hydrogen gas until no more H 2 O appears to come off. Replace the hydrogen by a stream of HC1 gas, reheat the tube, and continue the current as long as ferric chloride is given off. Remove the boat, and, if the residue is not white, repeat the opera- tion. Weigh the remaining A1 2 O 3 , and calculate from the amount of the oxides used the total amount in the ore. Rose modified this method by substituting a crucible and tube for the boat, etc. The apparatus as he used it is the same as that described for the determination of manganese as sulphide, page 114. Wohler suggested the method of separating iron and alumina by boiling the nearly neutral solution with an excess of hypo- sulphite of sodium. The following modification of this method* appears to give excellent results, and has the advantage of doing away with a subsequent separation of P 2 O 5 in those cases in which it has not been determined in another portion. The Fe 2 O 3 and * Communicated to me by Mr. S. Peters in 1879. DETERMINATION OF NICKEL, COBALT, ETC. 251 A1 2 O 3 from I gramme of ore being in solution in HC1, dilute to Peters's 400 or 500 c.c. with cold water, and add ammonia until the solu- tion. tion becomes dark red in color, but contains no precipitate. Now add 3.3 c.c. HC1, 1.2 sp. gr., and 2 grammes phosphate of sodium, dissolved 'in water and filtered; stir until the precipitate formed is dissolved and the solution becomes perfectly clear again. Add now 10 grammes of hyposulphite of sodium, dissolved in water and filtered if necessary, and 15 c.c. of acetic acid, 1.04 sp. gr., heat to boiling, boil fifteen minutes, filter as rapidly as possible on an ashless filter, wash thoroughly with hot water, dry, ignite in a porcelain crucible, and weigh as A1PO 4 , which, multiplied by .41847, gives the weight of A1 2 O 3 . It is necessary in burning off the pre- cipitate to raise the heat very carefully until all the carbon has been burned off, as the A1PO 4 may fuse and make it almost impossible to burn off the carbon. DETERMINATION OF NICKEL, COBALT, ZINC, AND MANGANESE. For the determination of these elements use 3 grammes of Solution of ore, dissolve in HC1, add a little HNO 3 or KC1O 3 to oxidize any FeO in the ore, evaporate to dryness, redissolve in HC1, and evap- orate a second time if necessary to get rid of all HNO. As noted on page 235, when the ore contains much organic matter, dissolve in HC1 (if there is much gelatinous silica, evaporate to dryness or the filtration will be much retarded), filter, add HNO 3 or KC1O 3 , evaporate to dryness, redissolve in HC1, and evaporate a second time if necessary, redissolve in 10 c.c. HC1 and 20 c.c. water, dilute, filter into a No. 6 beaker, and proceed exactly as directed for the determination of manganese in iron and steel, page 1 10 et seq. y until the precipitate by H 2 S is obtained and filtered off. Deter- 252 ANALYSIS OF IRON ORES. mine the manganese, if desired, in the filtrate, as directed on page MnO. 112, and calculate to MnO. Dry and ignite the precipitated sulphides of nickel, cobalt, zinc, copper, lead, etc., in a porcelain crucible, transfer to a small beaker, and dissolve in HC1, with the addition of a drop or two of HNO 3 . Evaporate to dryness, redissolve in 10 to 20 drops HC1, dilute to 50 or 60 c.c., heat to boiling, and pass a current of H 2 S Sulphides through the boiling solution. Filter off the precipitated sulphides of copper, lead, etc. of copper, lead, etc., and wash with water containing H 2 S. Evap- orate to dryness the filtrate, which contains only nickel, cobalt, and zinc. To the dry salts in the bottom of the beaker add 2 drops of strong HC1, dilute to 150 c.c. with cold water, and pass H 2 S through the solution until it is thoroughly saturated with the gas. If a white precipitate forms, it is sulphide of zinc. Allow to stand several hours, filter, wash with H 2 S water (the sulphide of zinc has a tendency to pass through the filter, and consequently the beaker into which the filtrate is received must be changed before the precipitate is poured on the filter), dry, and ignite the precipitate. Heat it several times with carbonate of ammonium to drive off any sulphuric acid that may have been formed by the Zno. ignition, cool, and weigh as ZnO. The precipitate is greenish white while hot and yellowish white when cold. If it should carry down a little cobalt from the solution, the ignited precipitate of ZnO is green when cold. Pass H 2 S through the filtrate from the ZnS again, and, if no further precipitate appears, add a few drops of a solution of .5 gramme of acetate of sodium in 10 c.c. water. If this occasions a white precipitate, filter it off, after standing, as in the first instance; but if the precipitate is black (as it is almost certain to be if the instructions given above are strictly followed), add the rest of the acetate of sodium solution, heat the solution to boiling, while the passage of the H 2 S is con- tinued, allow the precipitate to settle, filter it off, ignite it, and treat it as directed for the separation and determination of nickel and cobalt, page 184 et seq. DETERMINATION OF COPPER, LEAD, ETC. 253 DETERMINATION OF COPPER, LEAD, ARSENIC, AND ANTIMONY. Treat 10 grammes of the very finely ground ore with 50 c.c. HC1, add a little KC1O 3 from time to time, and increase the heat gradually until the ore is perfectly decomposed. Dilute, filter into a No. 5 beaker, deoxidize with bisulphite of ammonium, as directed on page 82, drive off the excess of SO 2 , and pass H 2 S through the solution for fifteen or twenty minutes. Allow the solution to stand for some hours until the precipitate has settled completely and the solution smells but faintly of H 2 S. Filter on a thin felt on the Gooch crucible or small cone, wash with cold water, and suck dry. Transfer the felt and precipitate to a small beaker, using a little asbestos wad in the forceps to wipe off" any adhering precipitate from the large beaker and the crucible or cone, and digest it with a few c.c. of a colorless solution of sulphide of potassium. Dilute to Separation about 100 c.c., filter on another felt, and wash with water contain- ing a little sulphide of potassium. The solution contains the sul- phides of arsenic and antimony dissolved in sulphide of potassium, while the sulphides of copper and lead remain in the felt. Return the felt with the precipitate to the beaker from which they were filtered, and digest with HC1, with the addition of HNO 3 , until all the black sulphides are dissolved, dilute with a little hot water, and filter. Evaporate the filtrate, after adding a few drops of H 2 SO 4 , until fumes of SO 3 are evolved, allow to cool, dilute with 25 c.c. cold water, add one-half its bulk of alcohol, allow to settle, filter the precipitated PbSO 4 on the Gooch crucible, wash with alcohol and water, heat carefully over a low light, and weigh. Treat the precipitate in the felt under a slight pressure with a strongly am- moniacal solution of citrate of ammonium, to dissolve the PbSO 4 , wash with hot water, and weigh. The difference between the two weights is PbSO 4 , which multiplied by .68298 gives the weight of Pb, or multiplied by 78879 gives the weight of PbS. PbandPbs. Evaporate the filtrate from the PbSO 4 until the alcohol is 254 ANALYSIS OF IRON ORES. Cu and Cu 2 S. Solution of sulphides of arsenic and anti- mony by HC1 and KC10 3 . Mg 2 (NH 4 ) 2 As2 Aq. and FeAs 2 . driven off and the solution reduced to a convenient bulk, transfer to a platinum crucible, and precipitate the copper on the small platinum cylinder by the battery, page 182. The weight of Cu multiplied by 1.25284 gives the weight of Cu 2 S. Acidulate the nitrate of sulphide of potassium containing ar- senic and antimony in solution with HC1, and allow to stand in a warm place until all the H 2 S has been driven off and the sulphides of arsenic and antimony mixed with the excess of sulphur have settled completely. Filter on a thin felt, wash with warm water, then with alcohol, and finally with bisulphide of carbon, to dis- solve the excess of S. Transfer the felt and precipitate to a small beaker, add 5 c.c. HC1 and a few crystals of KC1O 3 . Digest at a low temperature for some time, adding occasionally a small crys- tal of KC1O 3 , finally heat a little, but not to a sufficiently high degree to fuse any little particles of separated sulphur, keeping the liquid always full of the products of decomposition of the KC1O 3 . When all the sulphides of arsenic and antimony are dissolved, dilute with about 20 c.c. of warm water, and add a few small crystals of tartaric acid to keep the antimony in solution. Filter from the asbestos, using as little wash-water as possible in order to keep down the volume of the solution, add a slight excess of ammonia to the filtrate, and if it remains clear 5 c.c. of magnesia mixture and one-third the volume of the solution of NH 4 HO. Cool in ice-water, and stir vigorously from time to time to pre- cipitate the Mg 2 (NH 4 ) 2 As 2 O 8 -h Aq. Allow to stand overnight, filter, and determine the arsenic as directed on page 196. If the acid solution above mentioned becomes cloudy upon the addition of NH 4 HO, acidulate care- fully with HC1, and add a little more tartaric acid. Then proceed as above directed. The weight of As calculated from the amount of Mg 2 As 2 O 7 , multiplied by 1.373, gives the weight of FeAs 2 . Acidulate the filtrate from the Mg 2 (NH 4 ) 2 As 2 O 8 -f Aq, which contains none of the washings, with HC1 so that the solution is just acid to test-paper, dilute with hot water to about 250 c.c., DETERMINATION OF THE ALKALIES. 2 $$ and pass H 2 S into the solution, heating it gradually to boiling. Drive off the excess of H 2 S with a current of CO 2 , filter on a felt in the Gooch crucible, wash with water, alcohol, and finally with bisulphide of carbon to dissolve any free sulphur, dry carefully, heat to a temperature slightly above 100 C, and weigh as Sb 2 S 3 . For the very small amounts of antimony that are found in iron ores this method is sufficiently exact. The weight of Sb 2 S 3 mul- sb 2 s 3 and tiplied by .71390 gives the weight of Sb. DETERMINATION OF THE ALKALIES. As a rule, the alkalies in iron ores are found exclusively in the insoluble silicious matter, and when the sum of the weights of the SiO 2 , A1 2 O 3 etc., CaO, and MgO in the insoluble silicious matter falls much below the weight of the latter, it is always well to look for alkalies. Dissolve 3 grammes of the ore in HC1, evaporate to dryness, redissolve in 10 c.c. HC1 + 2O c.c. water, dilute, and filter into a platinum dish. Ignite the insoluble residue, treat it in the crucible Treatment with HF1 and 10 to 30 drops H 2 SO 4 , evaporate down until copious * fumes of SO 3 are given off, dissolve in water with a little HC1 if necessary, transfer to a small platinum dish, dilute to 100 c.c., heat to boiling, and add excess of ammonia. Boil for a few minutes, and filter from the A1 2 O S etc. into another platinum dish. Evapo- rate the filtrate to dryness, and heat until the chloride and sulphate of ammonium are volatilized. Treat the residue with a little water, heat to boiling, and add enough oxalate of ammonium to precipi- tate all the calcium, filter into another platinum dish, evaporate to dryness, and heat to dull redness. Treat the residue with a little water, heat the filtrate to boiling, add enough acetate of barium to precipitate all the H 2 SO 4 , boil, and filter. Evaporate the filtrate to dryness and heat to redness to decompose the acetates. Treat the S " (Tf -NTTVERSIT T 2 5 6 ANALYSIS OF IRON ORES. KC1 + NaCl. K 2 PtCl 6 . K 2 0. KC1. Nad. Na 2 O. Treatment of the por- tion of the ore soluble in HC1. Decompo- sition of insoluble matter by CaC0 3 and HN 4 C1. residue with water, filter from the insoluble carbonate of barium, add a few drops of barium hydrate, and evaporate again to dry- ness. Dissolve in a few c.c. of water, and filter into a weighed crucible. Evaporate very low, and, if nothing separates out, add a few drops of HC1, evaporate to dryness, heat to very dull redness, cool, and weigh as KC1 + NaCl. To the residue in the crucible add a little water, in which the residue should dissolve perfectly, and a solution of platinic chloride. Evaporate down in the water-bath until the mass in the crucible solidifies upon cooling, add a little water to dissolve the excess of platinic chloride, and then an equal volume of alcohol. Filter on a Gooch crucible, wash with alco- hol until the filtrate runs through perfectly colorless, dry at 120 C, and weigh as K 2 PtCl 6 . This weight multiplied by .19395 gives the weight of K 2 O. Then multiply the weight of K 2 PtCl 6 by .30696, which gives the weight of KCL Subtract this from the weight of KC1 -j- NaCl previously obtained, and the difference is the weight of NaCl, which multiplied by .53077 gives the weight of Na 2 O. To the filtrate from the insoluble silicious matter add an excess of ammonia, rub a little grease or parafifine on the edge of the dish, and evaporate the mass to dryness. This will render the Fe 2 O 3 very compact and granular. Dilute with hot water, add a few drops of ammonia, filter into another platinum dish, add a few drops of H 2 SO 4 , evaporate to dryness, and ignite to drive off all the ammonia salts. Then proceed exactly as directed for the determination of the alkalies in the insoluble silicious matter. The alkalies in the insoluble silicious matter may also be deter- mined by J. Lawrence Smith's method of fusion with carbonate of calcium and chloride of ammonium, as directed farther on. The chloride of ammonium, which is so troublesome in alkali determinations, may be decomposed * very easily by evaporating * J. L. Smith, Am. Jour. Sci. and Art, 1871, $d Ser., vol. i. (whole No. ci.) p. 269. DETERMINATION OF CARBONIC ACID. 257 the solution down very low, transferring to a tall beaker or flask, and heating with a large excess of HNO 3 , 3 or 4 c.c. HNO 3 to NH 4 cib y every gramme of NH 4 C1 supposed to be present. The decom- position takes place at a temperature below the boiling-point of water, and when the action seems to be over, transfer to a porce- lain dish, and evaporate to dryness after adding a few drops of H 2 SO 4 . Dissolve in water, filter into a platinum dish, and pro- ceed with the analysis in the usual way. DETERMINATION OF CARBONIC ACID. Weigh 3 grammes of finely-ground ore into the flask A, Description - 93 anc * connect the apparatus in the manner shown in the apparatus, sketch. L, L are tubulated bottles for forcing a current of air through the apparatus. The air is deprived of any CO 2 which it may contain by passing through the tube M, which is filled with lumps of caustic potassa. M is connected with the bulb-tube B by the tube N, a piece of gum tubing over the slightly tapering end making an air-tight connection with B. O is a condenser and serves to condense the steam and acid from the flask A. P contains anhydrous CuSO 4 , and Q contains chloride of calcium. The potash-bulb and the drying-tube R form the absorption apparatus, and S is a safety-tube filled with CaCl 2 to prevent R from absorbing moisture from the atmosphere. Weigh the ab- sorption apparatus with the precautions mentioned on page 146, and connect the apparatus. Close the stopcock C, and draw a Details little air through the apparatus by means of a piece of gum ofthe tubing attached to the end of S. Allow the tension of the air to draw the solution up into the rear limb of the potash-bulb, and if it remains there for a reasonable length of time the con- nections may be considered tight. Pour into the bulb B 10 c.c. HC1 diluted with about 65 c.c. water, connect the tube 17 25 8 ANAL YSIS OF IRON ORES. DETERMINATION OF COMBINED WATER. 2 - g N, and by means of the stopcock C allow the acid to flow slowly into the flask A. When the acid has all run in, by opening slightly the stopcock in L, start a slow current of air through the apparatus. Warm the flask A, gradually increasing the heat until the solution boils, and continue the application of heat until a considerable amount of water has condensed in O. Allow it to cool while the current of air is continued, detach, and weigh the absorption apparatus. The increase of weight is the weight of CO,. co 2 . DETERMINATION OF COMBINED WATER AND CARBON IN CARBONACEOUS MATTER. The ores are very rare indeed in which the combined water can be accurately determined by simply heating them in a cruci- ble and calling the loss by ignition "Water of Composition." LOSS by ignition, Nor is the method of absorbing the moisture, driven off by heat, in a drying-tube much more reliable. The presence of pyrites, of organic matter, of graphite, and of binoxide of manganese serves to complicate the problem. The water of composition may indeed Combustion with chro- be determined with great accuracy by heating the ore in a tube mate of with chromate of lead and bichromate of potassium, exactly as de- scribed for the determination of carbon in iron and steel by direct combustion, page 132^ seq. The increase of weight of the U tube which is attached to the end of the combustion-tube (and which should be filled in this case with granulated dried CaCl 2 ) is the weight of "Combined Water" in the amount of ore used. By Combined attaching the absorption apparatus we likewise obtain the total CO 2 in the ore, or that existing as CO 2 in the carbonates, and that due to the oxidation of any carbon existing as carbonaceous or organic matter or as graphite. By subtracting from the weight of CO 2 thus obtained the amount of CO 2 existing as carbonate and determined by the method last given, and multiplying the 26O ANALYSIS OF IRON ORES. Details of the method. difference by .27273, we get the weight of " Carbon in carbona- When it is necessary to make a large number of these determinations, the matter is very much simplified by using the apparatus shown in Figs. 95 and 96.* Fig. 95 shows the details of a form of tubulated platinum crucible suggested by Dr. Gooch, which consists of the crucible with a flange at d into which fits the cap. This cap consists of a conical cover, H, drawn up FIG. 95. Carbon in carbona- ceous mat- ceous matter." Tubulated crucible. 5 -1 INCHES vertically into the tube I. The horizontal tube J is burned into I, and through the centre of I passes the small tube K, which, expanding at a, is burned into I at this point, sealing it securely. The tubes N and M of glass are fused to K and J at C and b respectively. In analyzing ores containing much water or car- bonic acid, use I gramme ; for others, use 3 grammes. Weigh the finely-ground ore into a small agate mortar, and mix it thoroughly with 7 to 10 grammes of previously fused bichromate of potas- sium, transfer it to the crucible A, Fig. 96, and place it in an air-bath * Tenth Census of the U. S., Mining Industries, vol. xv. p. 519. DETERMINATION OF COMBINED WATER. heated to 100 C. to drive off any hygroscopic moisture. When perfectly dry, attach the cap B to the crucible, and stand the latter in the triangle C. Close the end N .with a piece of rubber tubing in the other end of which is fitted a piece of glass rod. Attach the weighed drying-tube D, filled with CaCl 2 , to the horizontal tube from B, by means of a thoroughly dried velvet cork. Attach the absorption apparatus E and F and the safety-tube G. Fill the outside of the flange d with small pieces of fused tungstate of FIG 96. 26l sodium, and, with a blow-pipe flame, melt them, having previously immersed the lower end of A in a small beaker of ice-water. The expansion of the air in the crucible by the heat applied to melt the tungstate of sodium will force some bubbles through the potash- bulb E, and the subsequent cooling of the air in A will cause the liquid in E to flow back into the rear bulb. If the difference of level thus produced be maintained for some minutes, the connec- tions may be considered tight. Connect N with the bottles L, as shown in the sketch, and start a current of air through the appara- tus. The air is purified from CO 2 and moisture by passing through Q, which is filled with fused caustic potassa. Now, by means of the 2 6 2 ANALYSIS OF IRON ORES. blast-lamp P, heat the crucible just above the top of the mixture, and gradually carry the heat downward, increasing it at the same time. This will keep the mixture from frothing and choking the tube. Finally, heat the bottom of the crucible by the burner O, and continue the application of the heat for ten minutes. During the whole of the operation the air passes through N and K into the crucible and out through J and M (Fig. 95) into D (Fig. 96), and so through the apparatus. The moisture from the ore should not be allowed to condense in the wide part of D at f t but should be driven forward into the CaCl 2 by warming the tube at f with the flame from an alcohol lamp. Allow the apparatus to cool while the current of air is continued, then detach, and weigh the tube D and the absorption apparatus, and calculate the results, as directed on page 259. When detached from the apparatus, the wide end of the tube D may be closed by a short cork, covered with tin-foil to prevent the absorption of moisture from the atmos- cieaningthe phere. To clean the crucible, remove it from the stand, and, hold- crucible. ... . r i ing it in a piece ot asbestos board in an inclined position, melt the tungstate of sodium in the flange d with a blow-pipe flame and detach the cap. Dissolve out the bichromate by placing the cruci- ble in a dish of hot water, clean out the ore, dissolve any adhering oxide in HC1, wash the crucible and cap with hot water, dry them, and they will be ready for another determination. DETERMINATION OF CHROMIUM. The small amount of chromium which is found in some iron ores is generally converted into chromate of sodium very readily by fusion with Na 2 CO 3 and KNO 3 . Fuse I or 2 grammes of the finely-ground ore with 10 times its weight of Na 2 CO 3 and a little KNO 3 . Treat the fused mass with water and wash it out into a small beaker. If the solution is colored by manganese, add a DETERMINATION OF CHROMIUM. 263 little alcohol, which will precipitate the manganese, leaving the indication solution, if chromium is present, slightly yellow. If the solution presence is colorless it may be considered proof of the absence of chro- mium. Otherwise filter, wash the insoluble matter on the filter, dry it, grind it with ten times its weight of Na 2 CO 3 and a little KNO 3 , fuse it, treat with water as before, filter, and add this filtrate to the other. Acidulate the combined filtrates with HC1, evaporate to dryness to render the silica insoluble, and reduce the chromic acid to Cr 2 O 3 . Treat the mass with HC1, dilute, filter, and precipi- tate the Cr 2 O 3 -+- A1 2 O 3 by ammonia. Boil for some minutes, filter, wash well with hot water, dry, and ignite the precipitate. Fuse with as little Na 2 CO 3 and KNO 3 as possible, treat with water, and wash the solution into a platinum dish. Evaporate the solution separation until it is very concentrated, adding from time to time crystals of Ai 2 o 8 . nitrate of ammonium to change all the carbonated and caustic alkali to nitrate. At each addition of the nitrate of ammonium the solution effervesces, and carbonate of ammonium is given off. When the solution is nearly syrupy, the addition of nitrate of am- monium no longer causes an effervescence, and the solution smells faintly of ammonia, add a few drops of NH 4 HO, and filter. By this operation all the alumina, phosphate of aluminium, oxide of manganese, etc., are precipitated, and there remain in solution only the alkalies and the chromate of the alkalies. To the fil- trate add an excess of sulphurous acid in water, which instantly changes the color of the solution from yellow to green. Boil well, add an excess of ammonia, boil for a few minutes, filter on an ashless filter, wash well with hot water, dry, ignite, and weigh as Cr 2 O 3 . Cr s o 8 . Chrome iron ore is best decomposed by Genth's * method of chrome fusing .5 gramme of very finely ground ore with bisulphate of potassium, raising the heat very gradually until finally the highest temperature of the lamp is attained, allowing it to cool, adding * Chem. News, vol. vi. p. 31. 264 ANALYSIS OF IRON ORES. 5 grammes Na 2 CO 3 and I gramme KNO 3 , and heating gradually to complete fusion, allowing it to remain so for fifteen or twenty minutes, treating with water, and proceeding as directed above. DETERMINATION OF TUNGSTEN. Digest from i to 10 grammes of the ore in HC1, adding HNO 3 from time to time. When the ore appears to be perfectly decom- posed, evaporate to dryness on the water-bath (a higher tem- perature is not admissible, as it may render the WO 3 insoluble in NH 4 HO), redissolve in HC1, and evaporate down again. Re- dissolve in HC1, dilute, filter, wash with acidulated water, and finally with alcohol. Treat on the filter with ammonia, allowing the filtrate to run into a platinum dish, evaporate to small bulk, add excess of ammonia, filter, if necessary, into a platinum cru- cible, evaporate carefully to dryness, heat gently to drive ofT the ammonia, and ignite. Weigh as WO 3 . DETERMINATION OF VANADIUM. Fuse 5 grammes of the very finely ground ore with 30 grammes of Na 2 CO 3 and from I to 5 grammes of NaNO 3 , and proceed exactly as in the determination of vanadium in pig-iron, page 199. A second fusion of the residue from the aqueous solution of the first fusion is hardly ever necessary. DETERMINATION OF SPECIFIC GRAVITY. 265 FIG. 97. DETERMINATION OF SPECIFIC GRAVITY. The specific gravity of iron ores is determined with much greater accuracy by using the powdered material than by using lumps of the ore. The little flask shown in Fig. 97 was designed for this purpose by the late Mr. James Ho- garth,* and its use avoids two diffi- culties experienced in the use of the ordinary specific gravity bottle, the expansion and overflow consequent upon transferring the flask at 60 F. to the higher temperature of the bal- ance-case, and the necessity for wait- ing until the finely-divided particles of the ore shall have settled before inserting the stopper. These difficul- ties were overcome by melting a capil- lary tubulus to the lower part of the neck of the flask, and by grinding in a stopper having a small bulb above the capillary, to allow for expansion. The operation is conducted as follows : Transfer a weighed amount of the ore to the flask, add enough water to cover it, and heat it almost to the boiling-point by placing it in the water-bath. Place the flask under a bell-jar connected with an aspirator or air-pump, and expel all the air by allowing it to boil for some time at a reduced pressure. Remove it from the bell-jar, fill it up to the tubulus with cold water, insert the stopper, and cool the flask and its contents to about 60 F. By suction on the stopper draw water through the tubulus until it is slightly above the capillary of the stopper, at which point a mark is scratched. When the flask and its contents are exactly at 60 F., Hogarth's flask. Its advan- tages. * Tenth Census of the U. S., vol. xv. p. 522. ANALYSIS OF IRON ORES. adjust the volume exactly to the mark on the capillary by touch- ing a piece of blotting-paper to the end of the tubulus or by draw- ing a little water in through it. Dry the flask, allow it to acquire the temperature of the balance-case, and weigh it. Now, if W is the weight of ore taken, W the weight of the ore and water at 60 F., and K the weight of the flask and its contents to the mark of water at 60 F., then W Sp - gr ' = W+K-W To obtain I, fill the flask with boiled water, and treat it exactly as described above. METHODS FOR THE ANALYSIS OF LIMESTONE. DETERMINATION OF INSOLUBLE SILICIOUS MATTER, ALUMINA AND OXIDE OF IRON, CARBONATE OF CALCIUM, AND CARBONATE OF MAGNESIUM. WEIGH I gramme of the powdered limestone, previously dried at 1 00 C., into a No. I beaker, cover with a watch-glass, and pour in 5 c.c. of HC1 diluted with 25 c.c. of water and a little bromine-water. Digest on the sand-bath until all the action ceases, wash the watch-glass with a fine jet of water, and evap- orate to dryness. Redissolve in 10 c.c. HC1 diluted with 50 c.c. water, filter on a small ashless filter, wash well with hot water, dry, ignite, and weigh as Insoluble Silicious Matter. Heat the fil- insoluble trate to boiling, add a slight excess of ammonia, boii for a few Matter. 8 minutes, filter, wash once or twice. Dissolve the precipitate on Resolution the filter in a little dilute HC1, allowing the solution to run into ^^ the beaker in which the precipitation was made, wash well with a ' pi A t f t " Of AloOs water, dilute, boil, and reprecipitate by ammonia. Filter on a andFe 2 o 3 . small ashless filter, allow this filtrate to run into the beaker con- taining the first one, wash well with hot water, dry, ignite, and Ai 2 o 3 and weigh as A1 2 O 3 and Fe 2 O 3 . Heat the united filtrates to boiling, Quantity of add enough oxalate of ammonium to convert all the calcium and a m mo . magnesium into oxalates.* Allow the precipitate of oxalate of cessary. 25 c.c. of the saturated solution is about the proper quantity. 267 268 ANAL YSIS OF LIMESTONE. CaO. CaC0 3 Quantity of microcos- mic salt required. MgO and MgC0 3 . Other sub- stances found in lime- stones. calcium to settle for fifteen or twenty minutes, filter on an ash- less filter, wash with hot water, dry, ignite for some time over a Bunsen burner, and finally for fifteen minutes at the highest tem- perature of a blast-lamp. Cool in a desiccator, weigh quickly, ignite again over the blast-lamp for five minutes, cool, and weigh again. If this weight is the same, or nearly the same, as the previous one, call the amount CaO. If the second weight is much less than the first, ignite, and weigh again until the weight is constant. The weight of CaO multiplied by 1.78459 gives the weight of CaCO 3 . Add to the filtrate from the oxalate of cal- cium 30 c.c. of a saturated solution of microcosmic salt (phos- phate of sodium and ammonium), acidulate with HC1, and evap- orate the solution to about 300 c.c. If during the evaporation any precipitate should separate out, redissolve it in HC1. Cool the evaporated solution in ice-water, and add ammonia drop by drop, stirring the solution, but being careful to avoid rubbing the sides of the beaker with the rod, as the precipitate of Mg 2 (NH 4 ) 2 P 2 O 8 -J- I2H 2 O is liable to adhere with great tenacity to those points or lines where the rod has touched the sides or bottom of the beaker. Continue the addition of ammonia until the solution is decidedly alkaline, and then add an amount equal to one-fourth of the neutralized solution. After the precipitate has begun to form, stir vigorously several times, allow to stand over- night, filter on an ashless filter, rub off with a " policeman" any of the precipitate that may adhere to the beaker, wash with a mixture of I part ammonia and 2 parts water, containing 100 grammes of nitrate of ammonium to the litre, dry, ignite with great care, as directed on page 85, cool, and weigh as Mg 2 P 2 O 7 , which multiplied by .36212 gives the weight of MgO, and multi- plied by .75760 gives the weight of MgCO 3 . Limestones, besides the ordinary constituents mentioned above, may contain small amounts of phosphoric acid, sulphur as sulphate or as pyrites, titanic acid, organic matter, combined water, alkalies, manganese, fluorine, and in rare instances nearly DETERMINATION OF PHOSPHORIC ACID. 269 all the metals found in iron ores. For most of these the methods described in the analysis of iron ores may be employed. Very often the amounts of silica and alumina are required in calculating mixtures for the blast-furnace, and, as the matter insoluble in HC1 consists usually of silicates of alumina, lime, and magnesia, it Determina- would be necessary in accurate work to decompose the Insoluble S io 2 . Silicious Matter by fusion with carbonate of sodium and to make a separate analysis of it, as described on page 239. It is, indeed, much better to make the analysis in this way than to add the filtrate from the silica to the main solution, for the oxalate of calcium is sure to carry down some of the sodium salts with it and thus very materially complicate the analysis. After weighing the A1 2 O 3 and Fe 2 O 3 from the Insoluble Silicious Matter and that from the portion soluble in dilute HC1 to deter- mine the Fe 2 O 3 , fuse the two precipitates with a little carbonate of sodium, dissolve in water, acidulate with HC1 in a beaker, add a few small crystals of citric acid to the clear solution, then excess of ammonia and sulphide of ammonium. Allow the precipitate of sulphide of iron to settle, filter, wash slightly, dissolve in HC1, add a little bromine-water, boil the solution, precipitate by ammonia, filter, wash, ignite, and weight as Fe 2 O 3 . The weight of Fe 2 O 3 Fe 2 o 3 . subtracted from the weight of the total A1 2 O 3 -f Fe 2 O 3 gives, of Ai 2 o 3 . course, the weight of A1 2 O 3 . The CaO and MgO in the Insoluble Silicious Matter should not Cao and MgOin be calculated as carbonates, but should be considered as existing insoluble r+ r\ i T\T r\ Silicious as CaO and MgO. Matter. To determine phosphoric acid in limestones, treat 20 grammes Determina- with dilute HC1, filter from the Insoluble Silicious Matter, to the po 6 filtrate add a few drops of ferric chloride solution, then ammonia until the solution is alkaline to litmus-paper,* and acetic acid to decided acid reaction. Boil for a few minutes, filter, wash once * If the precipitate is not decidedly red in color, acidulate with HC1 and add more ferric chloride solution. 2/0 ANALYSIS OF LIMESTONE. Treatment of In- soluble Silicious Matter. Treatment of In- soluble Silicious Matter by direct fusion. Sulphur in limestone. with hot water, dissolve in HC1 on the filter, allowing the solution to run into the beaker in which the precipitation was made, add the solution from the treatment of the Insoluble Silicious Matter mentioned below, dilute, and reprecipitate exactly as before with ammonia and acetic acid. Dissolve this precipitate on the filter in dilute HC1, allowing the solution to run into a No. I beaker, wash the filter with hot water, evaporate the solution down almost to dryness, and precipitate the P 2 O 5 as directed on page 85. Ignite the Insoluble Silicious Matter, treat it with HF1 and a few drops of H 2 SO 4 , evaporate until fumes of SO 3 are given off, fuse with Na 2 CO 3 , digest in water, filter, acidulate the solution with HC1, and add it to the solution of the first precipitate in the soluble portion as mentioned above. Instead of treating the Insoluble Silicious Matter with HF1 and H 2 SO 4 , it may be fused at once with Na 2 CO 3 , the fused mass treated with water, filtered, the filtrate acidulated, evaporated to dryness, redissolved in water slightly acidulated with HC1, filtered, and the filtrate added to the solution of the first precipitate by ammonia and acetic acid as above. To determine sulphur in limestone, fuse I gramme with Na 2 CO 3 and KNO 3 exactly as in the determination of sulphur in iron ores, page 226 et seq. To determine sulphates, proceed as in the analysis of iron ores for these substances, page 228 et seq. METHODS FOR THE ANALYSIS OF CLAY. CLAY is essentially silica, mixed with silicates of aluminium, . . tion of calcium, magnesium, potassium, and sodium. These silicates are c i ay . hydrated, so that clay usually contains from 6 to 12 per cent, of water of composition. Besides these usual constituents, clay may contain oxide of iron, titanic acid, pyrites, organic matter, phos- phoric acid, and occasionally some of the rarer elements, such as vanadium. Clay being practically unacted on by HC1, it is necessary to Method of proceed as follows : Fuse I gramme of the finely-ground clay dried at 100 C. with 10 grammes of Na 2 CO 3 and a very little NaNO 3 . Run the fused mass well up on the sides of the crucible, allow it to cool, and treat it with hot water until thoroughly disin- tegrated, transferring the liquid from time to time to a platinum dish. Treat the crucible with HC1, add this to the liquid in the dish, acidulate with HC1, and evaporate to dryness in the air-bath. Treat the mass with water and a little HC1, evaporate again to dryness, and treat with 15 c.c. HC1 and 45 c.c. water. Allow it to stand in a warm place for fifteen or twenty minutes, add 50 c.c. water, and filter on an ashless filter. Wash thoroughly with hot water acidulated with a few drops of HC1, dry, ignite, heat for three or four minutes over the blast-lamp, and weigh. Treat the precipitate with HF1 and a few drops of H 2 SO 4 , evaporate to dry- ness, ignite, and weigh. The difference between the two weights is 271 2/2 SiO 2 . A1 2 3 + Fe 2 3 . A1 2 3 . CaO and MgO. Determina- tion of alkalies. ANALYSIS OF CLAY. SiO 2 . If any appreciable residue remains in the crucible, treat it with a little HC1, and wash it out into the filtrate from the silica. Transfer the filtrate from the silica to a large platinum dish, heat it to boiling, add an excess of ammonia, boil until the smell of NH 3 is quite faint, filter on an ashless filter, and wash several times with hot water. Stand the filtrate and washings aside, and treat the precipitate on the filter with a mixture of 15 c.c. HC1 and 15 c.c. water, cold. Allow the solution to run into a small clean beaker, replace this by the platinum dish in which the pre- cipitation was made, pour the solution on the filter again, and repeat this operation until the precipitate has completely dissolved. Wash, out the beaker into the filter, wash the latter thoroughly with cold water, dry, and preserve it. Reprecipitate by ammonia, as above directed, filter on an ashless filter, wipe out the dish with small pieces of filter-paper, add these to the precipitate, and wash thoroughly with hot water. Dry, ignite the precipitate and filter, and the filter from the first precipitation, heat for a few minutes over the blast-lamp, cool, and weigh as A1 2 O 3 and Fe 2 O 3 . Fuse the ignited precipitate with Na 2 CO 3 , treat the fused mass with water, wash it out into a small beaker, allow the residue to settle, decant off the clear, supernatant fluid, treat the residue with HC1, and determine the iron volumetrically, or add citric acid and ammonia, and precipitate the iron as sulphide. Filter, wash, dis- solve in HC1, oxidize with bromine-water, and precipitate the Fe 2 O 3 by ammonia. Filter, wash, dry, ignite, and weigh as Fe 2 O 3 . Subtract the weight of Fe 2 O 3 from the A1 2 O 3 -f Fe 2 O 3 found above, and the difference is A1 2 O 3 . As the amounts of calcium and magnesium in clay are very small, the filtrate and washings from the second precipitation of A1 2 O 3 + Fe 2 O 3 may be rejected and the CaO and MgO deter- mined in the first filtrate as directed on page 240. To determine the alkalies in clay, treat 2 grammes of the finely- ground material in a platinum dish with 4 c.c. of strong H 2 SO 4 and 40 or 50 c.c. of redistilled HF1. Stir it from time to time DETERMINATION OF THE ALKALIES. 273 with a platinum wire or rod, heating carefully, until the clay is entirely decomposed and no more gritty substance can be felt HFiand TT C(") under the rod. Evaporate to dryness, and heat until fumes of SO 3 are given off. The entire operation should be carried on under a hood with a good draft, as HF1 is very poisonous, and the evaporation may be safely conducted on the little arrangement shown in Fig. 10, page 20. Allow the dish to cool, add about 50 c.c. water and a little HC1, and heat until the mass is all dis- solved. If any of the clay has escaped decomposition, filter into another platinum dish, wash the insoluble matter on the filter, dry, ignite, and decompose it in the crucible with HF1 and H 2 SO 4 . Dissolve the mass in the crucible after evaporating off the HF1, and add the solution to the main solution in the dish. Dilute this solution to 300 or 400 c.c. with hot water, heat to boiling, add an excess of ammonia, boil for a few minutes, and filter. Allow washing the precipitate to drain well on the filter, remove the filtrate, which delated should be in a platinum dish, to a light, and evaporate it down. Pierce the filter with a wire or rod, and wash the precipitate into the dish in which the precipitation was made with a jet of hot water. Dilute to 300 or 400 c.c., add a little ammonia, heat to boiling, filter, and wash several times with hot water. Add this filtrate to the first one, and evaporate to dryness. Heat until all the ammonium salts are volatilized, and proceed exactly as directed for the determination of alkalies in the Insoluble Silicious Matter from iron ores, page 255. Instead of decomposing the clay by HF1 and H 2 SO 4 , the J. Lawrence method given by J. Lawrence Smith may be used for determining method for alkalies. Weigh I gramme of the finely-ground clay into a por- celain or agate mortar, add an equal weight of granular chloride of ammonium,* and grind the two together to mix them. Add 8 grammes of carbonate of calcium,f and grind the entire mass so as to obtain an intimate mixture of the whole. Transfer to a See page 45. f See page 52. 18 274 ANALYSIS OF CLAY. capacious platinum crucible, cover with a close-fitting lid, and heat carefully to decompose the chloride of ammonium, which is accomplished in a few minutes. Heat gradually to redness, and keep the bottom of the crucible at a bright red for about an hour. Allow the crucible to cool, and if the mass is easily detached from the crucible, transfer it to a platinum dish and add about 80 c.c. of water. Wash off the lid into the crucible with water, heat this to boiling, and wash the crucible out into the dish. Heat the water in the dish to boiling, and, when the mass has completely slaked, filter into another platinum dish and wash the mass on the filter with hot water. If the semi-fused mass in the crucible is not easily detached, place the crucible on its side in the dish, wash off the lid into the dish, add about 100 c.c. water, and heat until the mass disintegrates. Remove the crucible, wash it off into the dish, and filter as above directed. To the filtrate add about i y 2 grammes of pure carbonate of ammonium, evaporate on the water-bath, or very carefully over a light, until the volume of the solution is reduced to about 40 c.c., add a little more carbonate of ammonium and a few drops of ammonia, and filter on a small filter. Evaporate the filtrate carefully after adding a few drops more of carbonate of ammonium to make certain that all the cal- cium has been precipitated. If any further precipitate appears, filter into a platinum crucible and evaporate to dryness. Heat carefully to dull redness to drive off any ammonium salts, and weigh the residue as KC1 + NaCl. Separate the potassium and sodium as directed on page 256. Water of Determine the water of composition by igniting I gramme of rtn lp the clay for twenty minutes at a bright red heat, when the loss of weight will represent the water. In the presence of much organic matter or pyrites the method given for the determination of water of composition in iron ores, page 259, may be used. Determina- To determine titanic acid, treat 2 grammes of the finely- Tio 2 . ground clay in a large platinum crucible with HF1 and 5 c.c. H 2 SO 4 . Evaporate off the HF1, and heat carefully until the DETERMINATION OF TITANIC ACID. 275 greater part of the H 2 SO 4 is volatilized. Allow the crucible to cool, add 10 grammes of Na 2 CO 3 , and fuse for thirty minutes at the highest temperature obtainable by a Bunsen burner. Run the fused mass well up on the sides of the crucible, and allow it to cool. Treat the fused mass with water, transfer it to a beaker, and filter. Wash the insoluble matter slightly on the filter, dry, ignite, and fuse it again with Na 2 CO 3 . Dissolve in water as before, and filter. By this method of treatment nearly all the alumina will be dissolved and separated from the titanic acid. Fuse the insoluble matter left on the filter with Na 2 CO 3 , and determine the TiO 2 as directed on page 179. When alkalies are determined, the precipitated alumina may Determina- tion of be used for the determination of TiO 2 . In this case dry the pre- Tio 2 m cipitate of A1 2 O 3 , etc., separate it from the filter, ignite the two t ion taken filters, add the ash to the dried, not ignited, precipitate of A1 2 O 3 , alkalies. etc., and fuse with Na 2 CO 3 as above. n nof 1 METHODS FOR THE ANALYSIS OF SLAGS. Composition BLAST-FURNACE slags contain silica, alumina, lime, magnesia, of blast- furnace and alkalies always, generally also ferrous oxide, manganous oxide, and sulphur, and occasionally titanic acid, small amounts of phosphoric acid, and such metallic oxides as may exist in the ores, fluxes, or fuel used in the furnace. Sulphur, which is occa- sionally present in considerable amounts, is considered to exist in the slag as sulphide of calcium. The method used for the determination of the principal in- gredients depends upon whether the slag is capable of being entirely or but partially decomposed by HC1. In the first case weigh I gramme of the finely-ground slag into a platinum or porcelain dish, add 20 c.c. of water, and shake the dish until the material is thoroughly disseminated through the siags de- water. Add gradually 30 c.c. HC1, with constant stirring, and by HCI. finally heat the dish carefully. The slag will dissolve completely to a clear liquid, but, after heating for a short time, will suddenly form a solid jelly. Evaporate carefully to dryness, treat with a few c.c. of dilute HCI and a little bromine- water, evaporate again to dryness, and add 15 c.c. HCI and 45 c.c. water. Allow to stand fifteen or twenty minutes in a warm place, add 50 c.c. water, filter on an ashless filter, wash thoroughly with hot water, dry, ignite, and weigh. Treat the material in the crucible with a little water, add 2 or 3 drops H 2 SO 4 and enough HF1 to dissolve it. 276 DETERMINATION OF SILICA, ALUMINA, ETC. 277 Evaporate to dryness, ignite, and weigh. The loss of weight is SiO 2 . Sio 2 . Any residue in the crucible after the volatilization of the SiO 2 Non-voiatiie is to be added to the A1 2 O 3 -f- Fe 2 O 3 . Heat the filtrate obtained above, diluted to 500 c.c., to boiling, add a slight excess of ammo- nia, boil for a few minutes, filter on an ashless filter, and wash two or three times with boiling water. Stand the filtrate aside, and pour on the precipitate in the filter a mixture of 15 c.c. HC1 and 30 c.c. cold H 2 O, allowing the solution to run into the dish in which the precipitation was made. Alumina precipitated in this way seems generally to dissolve more readily in cold than in hot Resolution dilute HC1, but it is often necessary to break up the precipitate on dpitated the filter with a rod, to pour the acid solution back on the filter several times after it has run through, and sometimes to pierce the filter with a rod or wire and wash the precipitate still undis- solved into the dish. Wash the filter well with water, dry it, and Preservation of the keep it to ignite with the A1 2 O 3 , etc. Heat the filtrate and wash- filter. ings to boiling, reprecipitate by ammonia, filter on an ashless filter, clean off any adhering precipitate from the dish with filter-paper, add it to the precipitate on the filter, wash well with hot water, dry, ignite, after adding the filter on which the first precipitation was filtered, and weigh as A1 2 O 3 , etc. Add to this the weight of the residue from the treatment of the SiO 2 by H 2 SO 4 and HF1,* and the sum is the total A1 2 O 3 + Fe 2 O 3 + P 2 O 5 + TiO 2 . Ai 2 o 3 ,etc. Evaporate down to about 300 c.c. the two filtrates obtained above, transfer to a No. 3 beaker, add a few drops of ammonia and enough sulphide of ammonium to precipitate the manganese. Filter off, and determine the manganese as directed on page 234, in the " Analysis Mno. of Iron Ores." To the filtrate from the sulphide of manganese add a slight excess of HC1, boil until all the H 2 S is driven off, filter from any precipitated sulphur, and determine the CaO and MgO CaOand as directed on page 259 et seq., in the " Analysis of Limestone." * This residue should be examined for CaO. ANALYSIS OF SLAGS. Determi- nation of FeO. Slags con- taining no manga- nese. Slags that are not entirely decom- posed by HC1. Reprecipi- tation of the CaO. Determi- nation of sulphur in slags. Alkalies, TiO 2 , etc. Converter slags, etc. To determine the FeO, fuse the ignited precipitate of A1 2 O 3 , etc., obtained above, with 5 grammes of carbonate of sodium, at a very high temperature, for at least thirty minutes. Allow the crucible to cool, treat the fused mass with water, transfer to a beaker, allow the insoluble matter to settle, decant the clear, supernatant liquid through a filter, and treat the residue with HC1. Pour the solution through the filter to take up any iron that may have been suspended in the liquid decanted through it, and deter- mine the iron volumetrically or by precipitation as sulphide in the solution to which citric acid and an excess of ammonia have been added, as on page 248.' When the slag contains no appreciable amount of manganese, the precipitation by sulphide of ammonium, page 277, may be omitted and the CaO precipitated at once from the concentrated solution. For the analysis of slags that are not entirely decomposed by HC1, recourse must be had to fusion with Na 2 CO 3 and a little NaNO 3 , exactly as described for the analysis of clay, page 271 et seq. After filtering off the SiO 2 as directed, page 271, proceed with the analysis as described for slags decomposed by HC1, page 277 et seq. As, however, the oxalate of calcium is very liable to carry down sodium salts with it, it is always well, after igniting the oxalate of calcium, to dissolve it in dilute HC1, transfer the solution to a platinum dish, dilute to 300 c.c. with hot water, add an excess of ammonia, and precipitate boiling by 30 c.c. of a saturated solution of oxalate of ammonium. Filter, wash, ignite, and weigh in the usual manner. For the determination of sulphur in slags, fuse I gramme with Na 2 CO 3 and a little KNO 3 , and proceed exactly as directed for the determination of sulphur in iron ores, page 226 et seq. Calculate the total sulphur as CaS and the remainder of the calcium as CaO. For the determination of alkalies, titanic acid, etc., proceed as directed for the determination of these substances in clay. Converter slags, open-hearth slags, refinery slag, tap cinder, mill cinder, etc., are analyzed by the methods described for the DETERMINATION OF PHOSPHORIC ACID. analysis of iron ores. In the case of slags obtained from the Analysis of manufacture of steel by the basic process, which usually contain very large amounts of phosphoric acid, proceed as follows : Treat I gramme of the finely-ground slag in a small beaker with 1 5 c.c. HC1 and a little HNO 3 until it is decomposed. Evaporate to dry- ness, redissolve in 10 c.c. HC1 and 20 c.c. H 2 O, dilute, filter off, and weigh the SiO 2 . To the filtrate diluted to 500 c.c. add a solu- siO 2 . tion of ferric chloride and a slight excess of ammonia, if the pre- cipitate is not decidedly red in color, acidulate carefully with HC1, add more ferric chloride solution, and then a slight excess of ammonia. Add acetic acid to slight acid reaction, heat to boiling, filter and wash slightly with boiling water, stand the filtrate aside, and dissolve the precipitate on the filter in HC1, allow the solution to run into the beaker in which the precipitation was made, wash the filter thoroughly with cold water, dilute the filtrate to about 400 c.c., add a slight excess of ammonia, and then acetic acid, boil, and filter as before. Add this filtrate to the first, evaporate down, and determine the manganese, calcium, and magnesium, as directed in the case of blast-furnace slags, page 277. Dissolve the Mno, Cao, precipitate on the filter in HC1, dissolving any iron that may adhere to the beaker in a few drops of the same acid, pour it on the filter, and wash the beaker and filter well with water. Allow the solution and washings to run into a No. 3 beaker, add about 10 grammes of citric acid and an excess of ammonia. To this solution, which should be cold, and should measure about 300 c.c. add, drop by drop, 50 c.c. of magnesia mixture, stirring carefully, without touching the sides of the beaker with the rod. Add about one-third the volume of the solution of ammonia, allow the beaker to stand in ice-water for some time, stir vigorously several times, and after a few hours filter (preferably on a Gooch crucible), wash with ammonia-water of the usual strength, ignite carefully, and p ^ weigh as Mg 2 P 2 O 7 . Any alumina in the slag will be in the fil- trate from the phosphate of ammonium and magnesium, and may be determined by the method on page 248. Determine the iron 2 80 ANALYSIS OF SLAGS. Feo. volumetrically in a separate portion, and calculate to FeO. Deter- mine any other elements present by the methods under " Analysis of Iron Ores." Phosphoric acid cannot well be determined in basic slags by fusion with Na 2 CO 3 , as phosphate of calcium is not readily decom- posed by this method, and its employment may lead to error. METHOD FOR THE ANALYSIS OF FIRE-SANDS. As sand contains comparatively very small amounts of alumina, lime, and magnesia, and a very large amount of silica, it is best to proceed as follows in the analysis : Weigh 2 grammes of the Treatment finely-ground sand into a large platinum crucible, moisten it Tnd with cold water, add 6 or 8 drops of H 2 SO 4 , and then gradually H2S 4 ' enough HF1 to dissolve it. Evaporate to dryness (under a hood, of course), and heat to redness to drive off the H 2 SO 4 . Allow the crucible to cool, add a little Na 2 CO 3 , and fuse. Dissolve the cold fusion in water, add an excess of HC1, evaporate to dryness, redissolve in HC1 and water, filter from SiO 2 , and determine the A1 2 O 3 , CaO, and MgO as usual. Ignite i gramme of the sand ALA, Cao, and MgO. and determine the loss, which will be water and organic matter (if Water present). It is well to note that in the presence of A1 2 O 3 it is almost impossible to drive off all the SiO 2 by treatment with HF1 and H 2 SO 4 , and the small amount of SiO 2 remaining after this treat- ment must be separated as directed above. Add together the percentages of water, A1 2 O 3 , CaO, and MgO, subtract the sum from 100, and call the remainder SiO 2 . Sl - 281 METHODS FOR THE ANALYSIS OF COAL AND COKE. PROXIMATE ANALYSIS. A PROXIMATE analysis affords a very rapid and comparatively simple way of classifying and valuing coal. From the nature of the material, the determinations cannot be absolute, but infer- ences may be drawn from the relative proportions of Moisture, Volatile Combustible Matter, and Ash. Therefore it is essential that the analysis should be performed in such a way as to obtain the most concordant results. The series of experiments carried out by Prof. Heinrichs,* of the Iowa State Geological Survey, show very clearly that by following a definite course of procedure and taking a few simple precautions the method may be made suf- ficiently accurate to accomplish satisfactorily the desired object. The details, which should in all cases be closely adhered to, are as follows : Weigh from i to 2 grammes of powdered coal into a crucible, heat for exactly one hour in an air-bath from 105 to 110 C, allow the crucible to cool, and weigh it. The loss of weight divided by the weight of coal taken and the result multiplied by Moisture. ioo gives the percentage of Moisture in the coal. Weigh from I Volatile to 2 grammes of the powdered coal into a small platinum crucible, bustibie heat the crucible with the cover on by means of a Bunsen burner for three and a half minutes, then, without allowing the crucible * Chem. News, xviii. 53. 282 ANALYSIS OF THE ASH OF COALS. 283 to cool, heat it for three and a half minutes more at the highest temperature obtainable by means of a gas blast-lamp. Cool and weigh. Divide the loss of weight by the amount of material used, multiply by 100, subtract the percentage of Moisture ', and the remainder is the percentage of Volatile Combustible Matter. This determination should always be made on a fresh portion of coal, Fresh p r - tion to be and never on the portion used for the determination of Moisture. used. After weighing the crucible for the determination of Volatile Combustible Matter as above, place it over a light in the position shown in Fig. 12 or Fig. 13, page 22, and burn off the carbon. This operation, which is liable to be tedious, may be hastened by breaking up and stirring the mass from time to time with a platinum rod or a piece of stiff wire. It is necessary to avoid pro- ducing too strong a draft in the crucible, as by this means par- Precautions in burning tides of the ash may be carried out and a fictitious value given to off car. the coal or coke by the apparent increase of Fixed Carbon and corresponding decrease of Ash. When no particles of carbon are apparent in the ash, allow the crucible to cool, and weigh it. The difference between this weight and the last, divided by the weight of coal taken, and multipled by 100, gives the percentage of Fixed Carbon. - ^ n The difference between the sum of the percentages of Water, Volatile Combustible Matter, and Fixed Carbon and 100 is the per- centage of Ash. The sum of the percentages of Fixed Carbon and Ash. Ash is the percentage of Coke which the coal will yield. The Coke - appearance of the coke before burning off the Fixed Carbon, its hardness, etc., are often valuable indications of the coking qualities of the coal, and should be noted. The appearance, color, etc., of the Ash should likewise be noted. ANALYSIS OF THE ASH. The ash may be analyzed by the method given for the analysis of the Insoluble Silicious Matter in Iron Ores, page 239. 284 ANALYSIS OF COAL AND COKE. DETERMINATION OF SULPHUR. Fusion with Weigh out I gramme of the finely-ground coal or coke, and Na 2 CO 3 and mix it thoroughly, by grinding in a large agate or porcelain mor- tar, with 10 grammes of dry Na 2 CO 3 and 6 grammes of KNO 3 . During the mixing it is well to have the mortar on a large sheet of white glazed paper, to catch any particles that may be thrown from it. Transfer the mixture to a large platinum crucible, clean the mortar by grinding a little Na 2 CO 3 in it, transfer this and any particles that may be on the paper to the crucible, cover the latter with a lid, and place it on a triangle over a Bunsen burner. Heat the crucible very carefully, and raise the heat very slowly, cautiously removing the lid of the crucible from time to time to see that the fusion does not boil over. It is very necessary that none of the fused sodium or potassium salts be allowed to get on the outside of the crucible, for they will certainly absorb sulphuric or sulphurous acid from the burned gas, and thus vitiate the analy- sis. When the mass in the crucible is in a tranquil state of fusion, run it up on the sides of the crucible, allow it to cool, treat it with hot water, and wash it out into a small clean beaker. Filter from the insoluble matter, acidulate the filtrate with HC1, and evaporate to dryness. Redissolve in water with a few drops of HC1, filter, dilute the filtrate to about 500 c.c., heat to boiling, and add 10-20 c.c. solution of chloride of barium.* Allow the precipitated sulphate Washing the of barium to settle, decant the clear, supernatant fluid through a of barium, filter or through a felt on a Gooch crucible, heat the precipitate with a solution of acetate of ammonium,t transfer it to the filter, wash well .with hot water, dry, ignite, and weigh as BaSO 4 , which, Method of multiplied by .13756, gives the weight of S. The time of the ingthe operation may often be very much shortened by adding an excess lon> of ammonia to the acidulated filtrate of the aqueous solution of the fusion, and boiling the solution while passing through it a rapid current of carbonic acid gas. This precipitates the silica, * See page 51. f See page 45. DETERMINATION OF SULPHUR. 285 alumina, etc., and, after filtering this off, acidulate by HC1, and precipitate the sulphate of barium as above directed. A blank determination, using the same amount of Na 2 CO 3 , correction KNO 3 , and HC1, should always be made with every new lot of reagents, reagents, and the amount of BaSO 4 found, subtracted from the amount of BaSO 4 in every analysis before calculating the amount of S in the coal or coke. Besides the method given above, Eschka's* method is very Eschka's often used. It is essentially as follows : Weigh out I gramme of the finely-ground sample, and mix it thoroughly in a mortar with I gramme of calcined magnesia and .5 gramme of dry carbonate of sodium, transfer the mixture to a crucible, and heat it over a Bunsen burner, having the crucible inclined in such a way that the flame may be applied to the bottom of the crucible, so that the heat, a dull red, shall extend only about one-third up from the bottom. Stir the mixture every few minutes with a platinum wire until the carbon is burned off and the ash is a dull yellow. This will gen- erally require about one hour. Allow the crucible to cool, add to the mixture about I gramme of nitrate of ammonium, mix it in thoroughly with a glass rod, place the lid on the crucible, and heat it cautiously until the nitrate of ammonium is decomposed and the crucible is raised to a bright red heat. Allow it to cool, treat it with hot water, and transfer the contents to a beaker. Filter from the insoluble matter, acidulate the filtrate with HC1, and determine the S by precipitation as BaSO 4 in the usual way. In reporting the results of a coal analysis the S should Method of always be reported as a separate matter, and no attempt should [ngThe be made to distribute it between the Volatile Combustible Matter, Fixed Carbon, and Ash. The reason for this is obvious when we coal - consider the conditions in which S exists in coal, and the diffi- culty which attends any attempt to determine the amount existing in any one condition. * Chem. News, xxi. 261. 2 86 ANALYSIS OF COAL AND COKE. Condition Sulphur is known to exist in coal in three conditions, as a s exists metallic sulphide, such as pyrites ; as sulphate of calcium or barium ; and as a sulphuretted hydrocarbon. In a proximate analysis of coal about one-half the sulphur in any pyrites present and all the sulphur existing as a sulphuretted hydrocarbon are probably driven off with the Volatile Combustible Matter. The rest of the sulphur from the pyrites is oxidized and driven off during the burning of the Fixed Carbon (sulphate of iron being easily decomposed at a bright red heat) unless the sulphuric acid formed is taken up by an alkali or alkaline earth. Determina- The nearest approach we can make to a determination of the conditions, conditions in which the sulphur exists in any coal is to make a determination of the total sulphur by fusion, and a determination of the sulphuric acid in the ash. By subtracting the S found by the latter determination from the total S the difference may be taken to represent the amount existing as S (in the form of sul- phide), and the amount found in the ash as that existing as SO 3 (in the form of sulphate). These results will be correct if the coal contains no carbonates of the alkalies or alkaline earths. DETERMINATION OF PHOSPHORIC ACID. Burning off Burn off io grammes of the coal or coke in a crucible, or, the coal or coke, as in anthracite coal or coke this is a very tedious operation, burn it off in a large platinum boat in a tube in a current of oxygen. A boat 4 inches (102 mm.) long, and wide enough to fit in a tube y^ of an inch (19 mm.) in diameter, will hold io grammes very easily, and by its use this amount of coke or anthracite coal may be burned off in a current of oxygen in about one and a half hours. Treat the ash with HC1 to dissolve any phosphate of cal- cium, filter, and wash well with water. Stand the filtrate aside, dry, ignite, and fuse the insoluble matter with Na 2 CO 3 . Dissolve DETERMINATION OP PHOSPHORIC ACID. in water, filter from the insoluble matter, acidulate the filtrate with HC1, and evaporate to dry ness. Redissolve in water and a little HC1, filter, add this filtrate to the HC1 filtrate from the first treat- ment of the ash, add a little ferric chloride solution and a slight excess of ammonia. Acidulate with acetic acid, heat to boiling, boil for a few minutes, filter, and wash the precipitate once or twice with boiling water. Dissolve the precipitate in HC1, evaporate nearly to dryness, add citric acid, magnesia mixture, and ammonium, and precipitate as directed on page 85. Filter off, ignite, and weigh the Mg 2 P 2 O 7 as there directed. Or, after dissolving the acetate precipitate, as above, in HC1, evaporate down, and pre- cipitate the P 2 O 5 by molybdate solution, as directed on page 89 et seq. METHODS FOR THE ANALYSIS OF GASES. THE technical analysis of gases is of growing importance, and a knowledge of the methods of analysis and of the manipulation involved is now generally necessary to the iron chemist. For ease of manipulation, and for the accuracy of the results obtained by its use, Hempel's form of apparatus is generally to be preferred. apparatus. It consists essentially of a burette for holding and measuring the gas B, Fig. 101 (the modified Winkler's gas-burette), and a pipette, G, Fig. 101, which holds the reagent. By means of the level-tube A, filled with water, the gas is forced into the pipette, where it is brought in contact with the reagent and afterwards returned to the burette and measured. By the use of a series of these pipettes, each filled with a separate reagent, the various constituents of the gas under examination are absorbed and their volumes estimated. COLLECTING SAMPLES. Fig. 98 shows a very simple method for taking a sample of gas for analysis. The porcelain tube A passes through the brick-work into the flue through which the gas is carried. In the sketch a portion of the porcelain tube is cut away, to show the loose fila- ments of asbestos with which the tube is filled to keep dust or tarry matter from entering the burette. This asbestos must be put in very loosely, or else it will pack and interfere with the free pas- 288 COLLECTING SAMPLES. 289 sage of the gas. Where the gas, as from a producer, etc., is constantly examined, it is very convenient to have a valve fitted permanently to an iron pipe screwed or cemented into the flue, into which the porcelain tube may be fastened by means of a rubber or asbestos * stopper. A glass tube of about ^ inch (6 mm.) diameter is fitted into the outer end of the porcelain tube FIG. 98. A. )a A, Fig. 98, by means of a rubber or asbestos stopper, and this glass tube is connected by means of the rubber tube C with the opening at the lower end of the burette d. If the gas is under Taking the pressure (as is rarely the case), it is only necessary to open the In**:* stopcocks and allow it to pass through the burette until the air is entirely displaced. Usually, however, it is necessary to draw the gas through ; and the little india-rubber pump D attached to * See page 144. 19 2 9 ANALYSIS OF GASES. Aspirator for draw- ing gas through the bu- rette. Compress- ing the gas in the bu- rette. Other ves- sels for collecting samples. FIG. 99. the capillary tube at the upper end of the burette is very useful for this purpose. It is fitted with a simple valve at each end, so that by compressing the bulb in the hand its contents are dis- charged through the outer end while the pressure closes the valve at the burette end. When the bulb is released it resumes its shape, the tension closing the outer valve and opening the one towards the burette, through which the contents of the latter are drawn into the bulb. A bulb of the usual size will empty a 100 c.c. burette in about three strokes. In taking a sample of gas, turn the 3-way stopcock b so that the passage is open through into the burette, open the stopcock a at the upper end of the burette, and pump the gas th-rough slowly for five or six minutes. Close the upper stopcock #, compress the rubber tube C between the thumb and fingers of the left hand, and, holding the tube with the other hand, slide the left hand towards the burette. This will com- press the gas in the burette, and by closing the stopcock b while the tube C is thus held the gas in the burette will be under pressure. In closing b, it must be turned so that the passage is open from d out through c, as shown in Fig. 99. Remove the burette to the laboratory, attach the rubber tube C of the level-tube A, Fig. 101, to the end of the burette, loosen the pinchcock E, and allow the water to run through until it comes out through the rubber tube on the end of the stopcock. Close E, and allow the burette and gas to attain the temperature of the laboratory. Samples of gas for analysis may also be taken in glass tubes drawn out at the ends and closed by rubber tubes and pinchcocks or pieces of glass rod. When the sample is to be taken to a distance, it may often be col- lected in a metal vessel with conical ends and tubes with well- ground stopcocks. Glass vessels of the proper shape, holding from half a litre to one litre, and fitted with glass stopcocks and METHOD OF FILLING PIPETTES. 2 g r capillary tubes made for this purpose, may be purchased from dealers in chemical glass-ware. From these vessels or tubes the gas may be transferred to the burette by attaching to one outlet a Transfer- tube filled with water and joined to the burette, likewise filled with burette.' " water, placing the other end of the vessel in water, lowering the level-tube, and drawing the gas into the burette. REAGENTS FOR THE PIPETTES. Blast-furnace gas, producer gas, and, in general, gases made Composition by drawing or forcing atmospheric air through coal or coke, con- tain varying amounts of carbon dioxide (CO 2 ), oxygen (O), carbon monoxide (CO), hydrogen (H), methane, or marsh gas (CH 4 ), and nitrogen (N). The best absorbents are caustic potassa for CO 2 , Absorbents, pyrogallol for O, and cuprous chloride in HC1 for CO. Hydro- gen is determined by ignition with excess of oxygen over palla- dium sponge, and marsh gas by ignition in a tube filled with cupric oxide. The pipettes required, therefore, are a simple pipette (G, Fig. 100) filled with caustic potassa, 1.27 sp. gr., for absorbing CO 2 , which is readily filled by placing in the large tube of the Method of pipette a small glass tube, which extends down to the bottom of sim pf e a the bulb and is connected outside with a small glass funnel by P'P ette - means of a piece of gum tubing. Pour the caustic potassa in caustic through the funnel until the large bulb of the pipette and the tube JJJ^T connecting the two bulbs are filled with the liquid. Draw the liquid into the capillary tube until it reaches to within a very short distance of the rubber tube on the end of the capillary, and close the rubber tube with a piece of glass tubing or a pinchcock, as shown in the sketch of the composite pipette, Fig. 100. A composite pipette (Fig. 106) containing pyrogallol for ab- Method 01 filling a sorbing oxygen is filled as follows : Dissolve 30 grammes of pyro- composite gallic acid in 75 c.c. of water, attach a funnel to the capillary tube 20/ 2 ANALYSIS OF GASES. of the pipette by a piece of rubber tubing, and fill it with the solu- tion. Attach a piece of rubber tubing to the other tube of the pipette, and by gentle suction exhaust the FIG. loo. air ; this will cause the liquid to run rap- idly through the capillary tube into the pipette. Keep the funnel full until the liquid which is drawn through the large bulb into the second bulb fills the latter to an inconvenient extent, then stop the suction, and very carefully blow the liquid back into the large bulb. Fill the funnel again, and exhaust the air gently as before. Repeat this until all the solution of pyrogallic acid has been drawn in, and then with the same precautions draw in a solution of caustic potassa, 1.27 sp. gr., until the large bulb and the tube connecting the large bulb and the second bulb are filled with the liquid, which is now an alkaline solution of pyrogallate Pyrogaiioi of potassium. Close the capillary tube as directed for the caustic potassa pipette, page 291. Insert the small tube and funnel in the large tube of the composite pipette, as directed on page 291 for filling the simple pipette, and pour a little water into the last bulb of the composite pipette. The amount of water poured in should not be sufficient to fill the third bulb, for the pyrogallol rapidly absorbs the oxygen of the air in the second bulb, and this contrac- tion causes the water poured into the last bulb to rise in the third bulb. Therefore the amount of water should be small enough to permit small bubbles of air to pass through to supply the contrac- tion in the second bulb, and large enough to avoid emptying the third bulb when the gas during an analysis is forced through the capillary into the large bulb of the pipette. The amount of pyro- gallate of potassium from 30 grammes of pyrogallic acid is suffi- Absorbing cient to absorb nearly 1 500 c.c. of pure oxygen, so that a com- of^yr^ posite pipette filled in this way, and securely sealed by the water in the third and fourth bulbs, will last for almost an indefinite number of analyses. DETAILS OF THE ANALYSIS. 293 Another composite pipette for absorbing carbon monoxide is cuprous filled, as above described, with a saturated solution of cuprous pipette 6 chloride in HC1, i.i sp.gr., and sealed with water. Each pipette Marking pipettes. should be distinctly labelled with the name of the reagent, so that no mistake can be made in using them. It is worthy of note that the absorption of CO by cuprous Absorption chloride is purely mechanical, and is never absolutely perfect, so cuprous that a small amount of CO invariably remains in the gas after never treatment in the cuprous chloride pipette. Moreover, whenever P erfect - a gas absolutely free from CO is treated in a cuprous chloride pipette (which has been previously used to absorb CO) and re- turned to the burette, it will be found to have increased in volume, and subsequent combustion in a palladium tube will yield an amount of CO 2 corresponding to this increase counted as CO. If this fact is overlooked, the CO left in the gas will be counted as methane if a determination of this gas is made in the usual course of the analysis. A composite pipette filled with bromine-water to absorb Bromine ethylene (C 2 H 4 ) is sometimes used, as this gas has been found in the gases from blast-furnace and producers using bituminous coal. But the amount of ethylene is very small, and a separate determination is rarely made, any small amount being absorbed and determined as CO. ANALYSIS OF THE SAMPLE. The burette containing the gas, with the level-tube filled with water attached, as mentioned on page 290, having attained the temperature of the laboratory, raise the level-tube and open the 3-way stopcock so that the passage is open for the water to enter the burette. If the gas is shown to be under a slight pressure, by raising or lowering the burette bring the water just to the stop- cock (if the burette is graduated to read 100 c.c. from stopcock to stopcock, otherwise bring the water to the o mark), and close the 294 ANALYSIS OF GASES. Reading the volume of gas in the burette. FIG. 101. Method of connect- ing the burette and the pipette. stopcock. Then open the upper stopcock for an instant to allow the gas to assume the pressure of the atmosphere. Now open the 3-way stopcock to allow the water to enter the burette, hold the level-tube so that the water in the tube and that in the burette are at the same level, and observe the reading of the burette. It is a very simple matter in this way to get exactly 100 c.c. of gas, which very materially simplifies the calculations. Connect the burette with the pipette containing caus- tic potassa by means of the capil- lary connecting-tube, as shown in Fig. 101. Some little skill is neces- sary in making this connection ; the best way to arrange it is as follows : Attach one end of the capillary connecting-tube to the top of the burette by a piece of gum tubing, wiring it if neces- sary, then compress between the thumb and forefinger of one hand the rubber tube on the capillary of the pipette for its entire length above the pinch- cock (as shown in Fig. 100), then carefully introduce the end of the capillary connecting-tube into the end of the rubber tube, and release the rubber tube. If this is carefully done, the walls of the rubber tube between the pinchcock and the end of the capillary will remain in contact, showing that no air has been admitted. Force the end of the capillary tube down to the pinch- cock, and open the latter, allowing it to remain over the capil- DETERMINATION OF ETHYLENE. 295 lary, as shown in Fig. 102. The apparatus will now be in the position shown in Fig. 101. Open the upper stopcock of the burette, and then turn the 3 -way stopcock D carefully to admit the water from the level-tube into the burette. As the water enters the burette the gas is forced over into the pipette G. Allow the water to fill completely the burette B and to enter the capillary tube F and fill it as far as the rubber connection between it and the capillary tube of the pipette G. Close the upper stop- Determina- cock of the burette, place the pinchcock on the rubber tube be- co> 2 tween the capillary connecting-tube and the pipette, and remove the capillary connecting-tube F from the rubber tube of the pipette, leaving it attached to the burette. Take the pipette from the stand and shake it, to promote the absorption of the CO 2 , which will require only a minute or two. Replace the pipette, attach the capillary connecting-tube F as before, remove the pinchcock, place the level-tube A on the floor, open the upper stopcock of the burette, and allow the water to run from the burette B into the level-tube A, drawing the gas from the pipette G into the burette B. When the caustic potassa solution has run back so as to fill the large bulb and the capillary of the pipette almost to the rubber connection, close the upper stopcock of the burette B quickly, replace the pinchcock on the rubber tube of the pipette G, detach the capillary connecting-tube F from the pipette, hold the level-tube A and the burette B together to get the water on an exact level, and take the reading of the burette. The differ- ence between this reading and the original reading will be the number of c.c. of CO 2 absorbed ; and if the original reading was 100 c.c., each c.c. absorbed will be one per cent, of CO 2 in the gas. If any other volume of gas was originally used, divide the number of c.c. absorbed by the number originally used, mul- tiply this by 100, and the result is the percentage of CO 2 in the gas. If ethylene is to be determined, pass the gas into the bromine- Determina- tion of water pipette, back into the burette, then into the caustic potassa c 2 H 4 . 296 ANALYSIS OF GASES. Determina- tion of O. Determina- tion of CO. Determina- tion of H. Description of the apparatus. Transfer- ring a portion of the unab- sorbed gas. pipette to absorb any bromine fumes, finally back into the burette, and take the reading as before. The contraction is ethylene. Now pass the gas into the pyrogallol pipette, shake the latter gently for four or five minutes to promote the absorption of the oxygen, return the gas to the burette, and note the reading. The contraction from the last reading is O. Pass the gas in the same manner into the cuprous chloride pipette, detach and shake the latter gently at short intervals for five or six minutes to promote the absorption of the CO, return the gas to the burette, and take the reading. The contraction from the last reading is the CO absorbed by cuprous chloride. To determine the remaining CO and the H, the gas is mixed with oxygen and burned over spongy palladium. Fig. icy shows the arrangement of the apparatus. A is the palladium tube, B the burette, C a pipette filled with water, D a small gas-burner for heating the palladium tube, and E the gas-pipe attached to the wood-work of the pipette and connected by a rubber tube with a supply of gas. Instead of a gas-burner for heating the palla- dium tube a small brass spirit-lamp may be used, which is fastened to the pipette-stand by a clamp in such a position as to bring the flame under the palladium tube. With any ordinary furnace or producer gas which con- tains 50 per cent, and upwards of nitro- gen, the best plan is to attach an oxy- gen-cylinder to the top of the burette, using a capillary tube and rubber con- nections, and fill the latter with oxygen gas. With water-gas, or when a supply of oxygen is not available, it is necessary to transfer a portion of the unabsorbed gas in the burette to another burette, and then to admit air to the first burette until it is nearly filled. Of course it makes the calculation a little more complicated to change the volume of the gas in this way during the progress of an analysis, but in the case of nearly pure FIG. 102. DETERMINATION OF HYDROGEN. 297 water-gas the use of oxygen alone would probably lead to an explosion, while with other gases, in the absence of a supply of oxygen, simply filling the burette with air without letting out any of the gas might not admit enough oxygen to burn the hydrogen. After transferring a portion of the unabsorbed gas, read the burette carefully to get the volume of gas taken for combustion, and then Divide the volume of gas taken for combustion by the total Calculating volume unabsorbed, and multiply by the amount originally taken for of gas analysis ; the result is the number of c.c. of the original gas , to which the amount taken for combustion corresponds. After admitting air to the burette, which is done by standing the level-tube on the floor while the burette is on the table, opening the 3-way stopcock so that the water may run into the level-tube, and opening the upper stopcock of the burette until the proper amount of air has been drawn in, take the reading of the burette with care. Connect the apparatus as shown in Fig. 102, light the gas-jet D, open the upper stopcock of the burette B, and by opening very carefully the 3-way stopcock of the burette cause the gas to pass very slowly into the pipette C. The palla- dium tube should not be heated to redness, but to a temperature just below a dark-fed heat. It is very necessary to avoid carrying precautions over any water into the hot palladium tube, as it would be certain "oa^old 7 to crack it, and for this reason it is well to see that the capillary breaki "s ' the pal- tube above the stopcock of the burette and both capillary ends of ladium the palladium tube are dry before making the connections. Any little moisture may be removed by means of a very fine wire wrapped with thread. As the water from the combustion of the H in the palladium is liable to condense in the end of the tube near the pipette, it is always well to warm this gently with the flame of a small spirit-lamp or a piece of glowing charcoal, so as to drive all the moisture into the pipette, and thus prevent its being carried into the hot part of the palladium tube when the gas is returned into the burette. When the water has risen in the burette just above the upper stopcock, lower the level-tube and draw the gas 2 gS ANALYSIS OF GASES. back very slowly into the burette. When the water in the pipette has risen to the usual position in the capillary, replace the pinch- cock on the rubber connection between the palladium tube and the capillary tube of the pipette, extinguish the light under the palladium tube, and, when the latter is cold, close the upper stop- cock of the burette, detach the apparatus, open the 3-way stop- cock fully, and take the reading of the burette. Now, if there were no CO present in the gas before the com- bustion, the contraction would be due to the condensation of the H 2 O formed by the combustion of the H, and, as 2 volumes of H unite with I volume of O to form H 2 O, f of the contraction would be H. In the presence of CO, however, there is an additional con- traction beyond that caused by the formation of H 2 O, due to the fact that 2 volumes of CO uniting with I volume of O form 2 volumes of CO 2 . By absorbing the CO 2 in the caustic potassa pipette, and then reading the burette, the second contraction is the Calculating volume of the CO 2 , which is the volume of the CO. The first con- co. traction, then, is f of the H -f \ the CO, and the 'second contrac- tion being the volume of the CO, it may be stated thus : first contraction = |-H -f- \ second contraction, or -|H = first contraction -^ second contraction; multiplying by |-, H=f first contraction -J second contraction. Divide the number of c.c. of H and CO respectively as found above by the number of c.c. of the original gas to which the amount taken for combustion is equivalent, multiply by 100, and the result is the percentage of H and CO. This percentage of CO is to be added to the percentage found by absorption in cuprous Total co. chloride, and the result is the total CO. Determina- There remain now in the burette only nitrogen and methane. CH 4 . The latter can be properly burned only at a red heat in contact with oxide of copper, forming H 2 O and CO 2 . By absorbing the CO 2 in a solution of caustic baryta, standardized by a normal solu- tion of oxalic acid, and then titrating the caustic baryta, the volume DETERMINATION OF METHANE. of CH 4 is at once indicated. As the normal solution of oxalic acid indicates the volume of CH 4 at 760 mm. of barometric pressure and o C. of temperature, the thermometer and barometer must be noted, and the correction made according to the table (Table V.). Dissolve 5.6314 grammes of crystallized oxalic acid in I litre of water. I c.c. of this solution indicates i c.c. CO 2 , or I c.c. CH 4 , at 760 mm. barometric pressure and o C. Dissolve 14.0835 grammes of crystallized hydrate of barium in I litre of water. I c.c. of this solution is equal to about I c.c. of the oxalic acid solution. The apparatus for the determination is shown in Fig. 103. It consists of a porcelain tube, EE, in the combustion-furnace F ; the FIG. 103. 2 99 porcelain tube is nearly filled with coarse oxide of copper between loose plugs of asbestos, or with a roll of oxidized copper wire (see page 142). The forward end is connected with two absorption- bottles, G, G, containing caustic baryta solution. These bottles are of such a size that 25 c.c. will fill them, so that the gas in bubbling standard acid and caustic baryta. 3 ANALYSIS OF GASES. through forces a little of the solution up into the bulb-tube, thus prolonging the contact. If they are a little too large, the solu- tion of caustic baryta may be diluted, after it is measured in from the pipette, with a little distilled water to bring it to the proper Description volume. A is a cylinder containing oxygen under pressure, or, of the ap- paratus, if this is not available, a couple of bottles for forcing air through the apparatus may be substituted (such as those shown in Fig. 57, page 134). The cylinder and the burette B are connected, as shown in the sketch (Fig. 103), by means of capillary tubes with the bottle C, containing caustic potassa, 1.27 sp. gr. The bottle C is connected with the bottle D, containing H 2 SO 4 , and from D a capillary tube passes to the rubber stopper in the end of the por- Description celain tube EE. Start a current of oxygen or air through the of the process. apparatus (before attaching the absorption-bottles G, G), light the burners of the furnace, and raise the temperature gradually until the tube is red-hot. Continue the passage of the oxygen until a bottle containing a solution of caustic baryta attached to the end of the tube shows that no CO 2 is given off. Measure out 25 c.c. of the caustic baryta solution into each of the bottles G, G, and attach them as shown in Fig. 103, open the upper stopcock of the burette B, and by means of the 3-way stopcock let water into the burette from the level-tube, so that the gas from the burette is made to bubble very slowly into the bottle C. About three or four bubbles should pass into C from the oxygen cylinder to one from the burette. When the water completely fills the burette and the capillary tube in C, close the upper stopcock of the burette, and continue the passage of the oxygen from A until it is certain that all the gas has been carried through the porcelain tube and the absorption-bottles. In the mean time measure out 25 or 50 c.c. of the caustic baryta solution into a porcelain dish, dilute with water, add a drop of phenolphtalein solution (made by dissolving phenolphtalein in alcohol), and from a burette run in the standard solution of oxalic acid until the pink color of the solution just vanishes. This will give the value of the caustic DETERMINATION OF NITROGEN. ^ OI baryta solution in terms of the normal oxalic acid solution. When the combustion is finished, detach the absorption-bottles, wash their contents into the dish, add a drop of phenolphtalein solution, and titrate with the oxalic acid solution. The difference between the calculation value of- 50 c.c. baryta solution and the value of the 50 c.c. from result, the absorption-bottles, in terms of the oxalic acid solution, is the number of c.c. of CH 4 in the gas burned at 760 mm. barometric pressure and o C. Divide this by the number of c.c. burned, reduced to 760 mm. pressure and o C., multiply by 100, and the result is the volume per cent, of CH 4 . Add together the percent- ages obtained of CO 2 (ethylene, C 2 H 4 ), O, CO, H, and CH 4 , sub- tract the sum from 100, and the remainder is the percentage of N Determina- , j-rr tionofN. by difference. An example will illustrate the method of analysis, thus : EXAMPLE OF ANALYSIS. Siemens' Producer Gas. Volume of gas employed, 99.7 c.c. KHO pipette ...... 93.5 c.c. Contraction, 6.2 c.c. Pyrogallol pipette .... 93.3 " " 0.2 " CuCl " .... 74.0 " " 19.3 " = 19.36 Transferred a portion. 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