I GIFT OF MICHAEL REE^E NOTES ON ASSAYING AND ASSAY SCHEMES; BY PIERRE DE PEYSTER RICKETTS, E. M., PH. D Professor of Assaying, School of Mines, Columbia College. FIFTEENTH EDITION. UNIVERSITT SEVENTH THOUSAND NEW YORK JOHN WILEY & SONS LONDON CHAPMAN & HALL, LTD. 1895 i l-C ft Entered according to Act of Congress, in the year 1876, by PIERRE DE P. RICKETTS, E. M , Ph. D., in the office of the Librarian of Congress, at Washington. Press of J. J. Little & Co., Astor Place, New York- PEEFACE. WHEN I first published this little Manual in 1876, I en- deavored to prepare it in such a way that it would prove serviceable to the practical as well as the scientific student, and for that reason avoided all chemical names as far as possible, giving them, when necessary, with the formulae in parentheses, and in the Appendix for reference. x y 1 "" ' # The same arrangement has been retained in the present enlarged and revised edition, the success of the first having led me to believe that the plan is a good one. As I stated in my first preface, the work embodies the system of assaying practiced in the School of Mines of Columbia College, organized and developed by Prof. C. F. CHANDLER and by G. M. MILLEE, E. C. H. DAY, F. PRIME, JR., T. M. BLOSSOM, E. M., and the author of these notes, who have successively had charge of the assay labo- ratory. The system of assay weights employed, was de- vised by Prof. CHANDLER, and will be found superior to any others in use, in the saving of time and calculation. The chapters on gold, silver, and iron, are founded on the excellent papers published by Mr. BLOSSOM, in the Ameri- can Chemist for 1870, modifications and additions having been made when deemed necessary. Most of the methods 6 PEEFACE. given have been tested in the laboratory, and the results appended under the head of ' ' REMARKS ; ' ' much attention having been paid to the various details peculiar to the West. For the processes for testing and assaying tellu- rides, and the cupel furnace for the use of soft coal, I am indebted to Mr. W. A. HOOKEE. Mr. S. G. SACKETT and Captain C. B. DAHLGEEN have also favored me with much useful information as to Western methods, which will, I think, be found useful both in the laboratory and field. In the Appendix, the chapter on blowpipe analysis has been revised and enlarged, and an outline scheme for the assay of ores added, also a number of methods for testing gold ores and alloys. The advertisements in the back of the book have been retained for the purpose of furnishing a guide to those who wish to procure assay apparatus, chemicals, etc. ; while the lists of apparatus have been revised, prices and esti- mates being given. PIERRE DE P. RICKETTS. ASSAY LABORATORY, SCHOOL OF MINES, NEW YORK, June 1st, 1879. CONTENTS, PART I. INTRODUCTION. APPARATUS. REAGENTS AND OPERATIONS. PART II. DRY OR FIRE ASSAYS. PART III. WET ASSAYS OR ANALYSES. PART IV. TABLES AND REFERENCES. APPENDIX. MANIPULATION. BLOWPIPE ANALYSIS. APPARATUS AND REAGENTS. SPECIAL SCHEMES, ETC. PART FIRST. INTRODUCTION. BALANCES AND WEIGHTS. FURNACES AND FUELS. CRUCIBLES, SCORIFIERS, AND CUPELS. LUTES, CEMENTS, AND WASHES. TOOLS AND APPARATUS. REAGENTS AND CHEMICALS. PRELIMINARY TESTING OF ORES. SAMPLING AND PULVERIZING. WEIGHING ORE AND REAGENTS. CALCINATION AND ROASTING. REDUCTION AND FUSION. DISTILLATION AND SUBLIMATION. SCORIFICATION AND CUPELLATION. INQUARTATION AND PARTING. WEIGHING BEADS AND BULLION. TABULATING RESULTS AND REPORTING. PART SECOND. ASSAY OF LEAD. " " ANTIMONY. u " GOLD AND SILVER. " " PLATINUM. " " ZINC. " MERCURY. " " BISMUTH. " " COPPER. " " IRON. " " NICKEL AND COBALT. " u CARBON. PART THIRD. SILVEE BULLION. GOLD BULLION. CHLOEINATION ASSAY. LEAD SCHEME FOE WET ASSAY. PLATINUM " " " " ZINC BISMUTH " " " " TIN u u u " COPPEE " " " {< IEON " u " " MANGANESE " " " u NICKEL " " " " SULPHUR " " PART FOURTH. PEECIOUS STONES. SCALE OF HAEDNESS. METALS CHAEACTEEISTICS. OEES CHAEACTEEISTICS. TJ. S. COINS COMPOSITION AND VALUE. MEASUEES OF WEIGHT AND VOLUME. SPECIFIC GEAVITY. THEEMOMETEES. TABLE OF VALUES FOE GEAIN WEIGHTS. MULTIPLICATION AND CUPELLATION TABLES FOE GOLD. BLANK REPOETS. PEOBLEMS AND QUESTIONS. REFEEENCES ON ASSAYING. APPENDIX. MANIPULATION, FORMULAE, AND CALCULATION. BLOWPIPE ANALYSIS, APPARATUS, AND EEAGENTS. CHEMICAL APPARATUS AND REAGENTS. ASSAYER'S OUTFIT. SPECIAL METHODS FOR GOLD ORES AND ALLOYS. OUTLINE EXAMINATION SCHEME FOR THE ASSAY OF ORES. RULES FOR THE EXAMINATION OF A MINE. SCHEME FOR QUALITATIVE ANALYSIS ZETTNOW. PART I. INTRODUCTION, APPARATUS, REAGENTS AND OPERATIONS. /*& C,,H F -, > (UNIVERSITY \^^lb~- INTRODUCTION. Assaying has for its object the determination and extrac- tion of the metallic elements from their various compounds. The rules are empirical, and a knowledge of chemistry is not absolutely necessary, although the assay er will find that a familiarity with chemical laws and reactions will greatly facilitate his work. The following is a list of the elementary bodies with the exception of one or two recently discov- ered, and their atomic weights and symbols. An element is a body which chemical research has failed to reduce to a more simple form, or separate into constituent parts. The symbol of an element is generally the first letter or letters of its Latin name ; and its atomic weight is the smallest amount of that element which will enter into com- bination with other elements ; the first column of figures being the old and the second the new system of atomic weights. Hydrogen is taken as unity in both systems. 14 INTRODUCTION. TABLE OF ATOMIC WEIGHTS. Revised by C. F. CHANDLER, Oct., 1881. Aluminium, Al. IV. 27-0 Manganese, Mn. VI. 55-0 Antimony, 8b. V. 120-0 Mercury, Hg. II. 200-0 Arsenic, As. V. 74-9 Molybdenum, Mo. VI. 96-0 B mum, Ba. II. 136-8 Nickel, Ni. VI. 59-0 Bismuth, BL V. 210-0 Nitrogen, JV. V. 14-0 Boron, B. III. 11 -0 Osmium, Os. II. IV. 199-0 Bromine, Br. I. 79-7 Oxygen, 0. II. 16-0 Cadmium, Cd. II. 112-0 Palladium, Pd. IV. 106-0 CcBsium, Ga. I. 133-0 PJiosphorus, P. V. 31-0 Calcium, Ca. II. 40-0 Platinum, Pb. IV. 197-0 Carbon, C. IV. 12-0 Potassium, K. I. 39-0 Oerium, Ge. III. 141-2 Rhodium, Ro. IV. 104-0 Chlorine, Gl. I. 35-4 Rubidium, Rb. I. 85-4 Chromium, Cr. VI. 524 Ruthenium, Ru. II. IV. 104-0 Cobalt, Co. VI. 59-0 Selenium, Se. II, 79.0 Columbium, Gb. V. 94-0 Silicon, Si. IV. 280 Copper, Cu. II. 63-1 Silver, Ag. I. 108-0 Davyum, Da. 154-0 Sodium, Na. I. 230 Didymium, D. III. 147-0 Strontium, Sr. II. 87-5 Erbium, E. III. 169-0 Sulphur, S. II. 32-0 Fluorine, F. I. 19-0 Tantalum, To. V. 182-0 Gallium, 0a.III. 69-9 Tellurium, Te. II. 128-0 Grlucinum, Gl. II. 9-2 Thallium, Tl. I. 204-0 Gold, Au. III. 196-2 Thorium, Th. IV. 231-5 Hydrogen, H. I. 1-0 Tin, Sn. IV. 118-0 Indium, In. III. 113-4 Titanium, Ti. IV. 50-0 Iodine, Z I. 126-5 Tungsten, W. IV. VI. 184-0 Iridium, Ir. II. 198-0 Uranium, IT. VI. 240-0 Iron, Fe. VI. 56-0 Vanadium, V. V. 51-2 Lanthanum, La. III. 139-0 Yttrium, Y. III. 60-0 Lead, Pb. 11. 207-0 Zinc, Zn. II. 65-0 Lithium, Z I. 7-0 Zirconium, Zr. IV. 90-0 Magnesium, Mg. II. 24-0 NOTE. The Artiads are printed in Roman, the Perissads in italics. The above table of the atomic weights of the elements was prepared for the use of the students of the School of Mines, and contains the latest values as given by reliable authorities. INTRODUCTION. 15 The various methods for the determination of the metals in their compounds may be classed under two heads : 1st. " Dry way, ' ' or assaying proper. 2d. ' ' Wet way, ' ' or analysis. The first includes all determinations by the direct action of heat, the various operations being performed in furnaces. The second head embraces the estimation and separation of the elements by the action of solvents aided or unaided by heat, the use of furnaces not being essential. There are many cases, of course, where the first class merges into the second, and vice versa. It was originally intended to give in the following pages only a few concise methods for the estimation of the metals in their ores by fire assay ; but, as in many ores the precious metals are associated with others which are either of value or detriment, and whose determination is often necessary, a few schemes for the treatment of such ores in the wet way have been added. The various operations which may take place in making an assay proper, are 1st. Preliminary testing of the ore. 2d. Preparation of the ore, sampling, pulverizing, etc. 3d. Weighing out the ore and reagents. 4th. Calcination and roasting. 5th. Reduction and fusion. 6th. Distillation and sublimation. 16 INTRODUCTION. 7th. Scorification and cupellation. 8th. Inquartation and parting, including solution. 9th. Weighing beads and bullion. 10th. Tabulating results and reporting. All of the above will be described further on ; but as some of the operations require great care in their performance, a few rules and hints for the guidance of the beginner may not be out of place. 1st. Sample well and carefully, for without a fair sample the assay is useless. 3d. Weigh carefully, and adjust the balance before and after weighing. 3d. Always weigh an ore before calcining or roasting, and always roast thoroughly. If the ore be wet, weigh both before and after drying. 4th. Never fill a crucible or scorifier more than three- quarters full, and when a crucible is removed from the fire, tap it on the floor to settle the metal, unless otherwise di- rected, and keep the same covered. 5th. To break a crucible, hit with a middle-sized hammer near the centre, so as to break off the top at one blow. Then lay the bottom on the anvil, and crack it through to get the button out whole. Never break until perfectly cold. To break a scorifier, lay it bottom up on the anvil ; en- circle with the hand, and then strike the bottom. The button will generally come out free from slag. 6th. Never take a scorification or cupellation from the furnace to finish at a future time, but complete the operar INTKODUCTION. 17 tion at once. When buttons are to be scorified or cupelled, be sure that they are free from moisture. 7th. Be certain that all reagents used in an assay are dry and pure, especially when testing for the precious metals. 8th. In reporting results, recollect that a fire assay does not always give the exact amount of metal contained, but often shows only what the yield of an ore would be in smelt- ing, and that the assay of a small piece of ore can not represent the value of the bed or vein from which it may have been taken, and word your report accordingly. 9th. Always observe the color and character of the slag produced in an assay, as the nature of the ore treated may often be determined in this way. 10th. Never accept the results of an assay where the fusion has been incomplete, the button formed being small or brittle. BALANCES AND WEIGHTS Four balances will be found useful in an assay labora- tory. a. A rough scales for weighing large samples of ores, metals, fluxes in bulk, &c. An ordinary grocer's scale will do for this purpose. b. A balance for weighing out ore for assay, and the but- tons of the base metals. (Fig. 1.) This balance should FIG. 1. take ten ounces in each pan, turn with one-twentieth of a grain, and be provided with movable pans, level, and set- screws for adjusting. It is generally placed on a box, fur- nished with a drawer for weights. c. Hanging scales for fluxes. The pans should be made of horn, and supported by threads to a brass beam. It should carry at least ten ounces, and turn with one-half grain. BALANCES AND WEIGHTS. 19 d. The button or bullion scale. (Fig. 2.) This balance should be used for nothing but gold and silver beads, or bullion, and must be accurate and extremely sensitive. FIG. 2. When loaded with one gramme, it should turn with one one-twentieth of a milligramme, and requires to be han- dled with the greatest care. It is provided with steel knife- edges, agate bearings, spirit level, and set-screws. To ADJUST THIS BALANCE. First turn the set-screws, two at a time, until the bubble is in the centre of the level, and the balance is firm. Then note the number of divisions the needle indicates on the scale when vibrated, counting from the second swing. If it shows equally on both sides of the centre line it is correct. Never leave the rest down, or raise it when the needle is not near the centre line, as the knife- edges are likely to be thrown off their bearings and the balance injured. To clean, an artist' s blending-brush is very convenient, as it is soft and 20 BALANCES AND WEIGHTS. THE WEIGHTS employed by the assayer are a. Avoirdupois for ores, base metals, and fluxes. &. Troy for gold, silver, &c. G. The French system based upon the gramme as a unit. These weights can be used for weighing ores, fluxes, and re- sults ; and will always be found convenient, as they are on the scale of ten. d. The assay weights, which is a system made up from a comparison of the three foregoing, will be found ex- tremely simple and useful, saving a vast amount of calcu- lation and labor (see table, page 149). The unit of the system is the assay ton=29.166 grammes. Its derivation will be seen at a glance. One Ib. Avoirdupois =7, 000 Troy grains. 2,000 Ibs. = one ton. 2,000 x 7,000=14,000,000 Troy grains, in one ton Avoirdu- pois. 480 Troy grains \ oz. Troy. 14, 000, 000^480^29,166 + Troy ozs. in 2,0001bs. Avoirdu- pois. . There are 29,166 milligrammes in one assay ton (A. T.) ; hence 2,000 Ibs. is to 1 A. T., as 1 oz. Troy is to 1 milligramme. EXAMPLE. Weigh an A. T. of ore, and if on assay it yields 1 milligramme of gold or silver, the result reads one Troy oz. in 2,000 Ibs. Avoirdupois, without further calcula- tion. Should the assayer desire to make quantitative determi- nations in the wet way, he will require, besides the above, an analytical balance, which will carry 100 grammes in each pan, and turn with one-twentieth of a milligramme. This balance should be provided with apparatus for taking spe- cific gravities, rider, and weighing-tubes. FURNACES AND FUELS. . FURNACES AND FUELS. 1st. FURNACE FOR CALCIN- ING OR ROASTING. Fig. 3 represents two sections. The rireplace is made shal- low ; and, as a high tempera- ture is not required, it may be made of red brick, or only lined with fire-brick, and the body of the furnace bound with strap-iron. It should also have a cast- iron top-plate. The grate-bars may be in one piece or separate, and draw out. The ash-pit should be provided with a door, which may be closed or opened in order to regulate the draft. A hood of sheet-iron will FIG. 3. scale i^-inch to the foot. also be f ound necessary in many cases, as the fumes given off in roasting are often in- jurious. It is an excellent plan to have the hood of gal- vanized iron to prevent rusting. The chimney may be of brick, iron or clay. 2d. FURNACES FOR FUSION OR MELTING (Figs. 4 and 4a). These furnaces should be deeper than the preceding one, and like it, may be built of red brick, but it is better to line them with fire brick. For heavy work the furnaces should be low, to facilitate the lifting in and out of crucibles. Sometimes a crane is added for this purpose. FUENACES AND FUELS. The chimney ought to be of brick, and the larger and higher it is, the stronger the draft. This may be regulated by a damper as well as by the ash-pit door. c The tops should be of cast-iron, and the cover lift or slide easily. An iron shelf can be placed in front to hold in- got moulds when metals are to be poured, as shown in Fig. 4a, which shows in section the furnace used FlG. 4. Scale ^-inch to the foot. for deposit melting in the United States mints. 3d. MUFFLE FURNACES FOE SCOEIFICA- TION AND CUPELLA- TION. Fig. 5 shows ' sections of a porta- ble cupel furnace. FIG. 5. Scale %-inch to the foot. FlG. 40. Scale FURNACES AND FUELS. The same furnace may be used for both operations, but generally it will be found convenient to have a larger muffle for scorifi- cation and higher heat. The muffles are made of refrac- tory clay, and in one piece ; and should be thor- oughly dried be- fore using. The draft of the furnace ought to b e sufficient t o carry off lead fumes, which are injurious. The construction o f the furnace will vary with the fuel used and work to be done. Fig. 6 shows the vertical and hori- zontal sections of a double muffle scorification fur- nace, for works where a large number of scorifications are required. It has been in use in the assay laboratory of the School of Mines, New York, for two years, and its value has been _ FIG. Scale %-inch to the foot. 24 FUKNACES AND FUELS. proved. The muffles are larger than usual, and can be drawn out. The whole furnace is lined with fire brick, as is indicated by the fine shading. By placing a damper at the top, one-half may be used to the exclusion of the other. Fig. 6a is an assay furnace for the use of soft coal. This furnace has the following advantages : 1st. Economy of fuel. A furnace containing 8xl4-inch muffles may be run for eight hours with not more than 100 Ibs. of coal. Any free- burning coal may be used (the Canon City coal of Colorado a lignite gives very excellent results). 2d. Economy of construction. Yery few fire brick and other material are required, and the furnace may be built, exclusive of stack, for from $25 to $50. 3d. Saving in muffles. The muffle not being in contact with the fuel, and subjected only to the action of the flame and gases, does not become covered with slag, but always remains clean and is easily heated. When two muffles are employed, the upper one is suffi- ciently hot for cupellation, but not for scorification. The coal should be broken to the size of the fist, or smaller. The muffles are sufficiently hot for charging in from thirty to sixty minutes after the fire is lighted. The heat is easily regulated by means of the damper closing the ash pit. THE FUELS employed are coke, anthracite, bituminous coal, and charcoal. Sometimes oil and gas are used for small laboratory furnaces. The coke should be about egg size and free from sul- phur. It is chiefly used in calcining and fusion fur- naces. Charcoal, coke, anthracite, and bituminous coal may Section through L. M. Section through E. F* Section "through G. K FIG. Qa. ASSAY FURNACE FOR BURNING SOFT COAL. Muffles 8x15 inches. Bind with lx| inch iron. Ash pit and coaling hole closed by sheet iron door, the latter resting on the binders. 26 CKUCIBLES. be employed for the muffle furnace. Bituminous coal should have, however, a special furnace. (See Fig. Anthracite coal, stove size, is best adapted for the assay- er's purpose, but charcoal may be used as a substitute for either coke or anthracite, when it can be had more cheaply ; it gives a hot fire, and is easily regulated ; but requires constant attention, and the pieces used should be of me- dium size. Oil and gas furnaces are used with varying results, but the limits of this work will not permit a description of them. See "Mitchell's Manual of Practical Assaying," pages 71 to 107 inclusive. Also circular of the Buffalo Dental Manufacturing Company. In lighting a fire it will be found convenient to use pieces of cork or corncobs saturated with rosin, which burn well, are cheap, and save much trouble, as they give no dirt. To use, it is only necessary to light a piece and lay it upon a little kindling-wood placed in the bottom of the fur- nace, then put a few pieces of wood on top and add the coal after the wood has kindled. CKUCIBLES. A good crucible should stand sudden changes of tempera- ture, be infusible, impermeable, and not attacked by fused substances. The crucibles in use may be arranged in the following order. 1. Black lead or graphite for fusing metals. CRUCIBLES. 2. French clay. (Fig. 7.) 3. Hessian sand crucibles, round and tri- angnlar. (Fig. 8.) FIG. 8. FIG 7. 4. Charcoal-lined crucibles. The most refractory crucibles are cut out of quick lime, or can be moulded from magnesia, and chloride of magne- sium, but the latter, however, are soft and not very strong. The composition of the black lead crucibles is generally one to seven parts of refractory clay, and three to ten of graphite ; but sand is sometimes used. If the crucibles contain too much silicious matter they are liable to be acted upon by the melted charge, or the bases contained in the coal around them, when in the fire. These crucibles run in sizes from 1 to 400. The smallest holding from two to three ounces of metal. The next, four to six, and so on. The demand is for two kinds, " steel" and "brass;" but they can be employed for melting all substances which are not oxidizing in their action. French crucibles are made of Paris clay and fine sand, and rank among the best, but are more expensive than the Hessian. For melting charges which can be poured, they are superior as the crucible can be used again. The sizes run from 1 to 20, with covers to match. The composition of the ordinary Hessian crucible is about chree-quarters clay (German), and one -quarter sand. They 28 CRUCIBLES. are round and triangular, and run in regular sizes, viz: Small fives, large do., up to eights. Halves, holding one- half gallon, and ones, holding one gallon, with covers to match. The charcoal crucible is made by lining an ordinary clay or Hessian crucible with a mixture of charcoal and molasses. The charcoal employed should be very fine, and only just enough molasses used to hold it together. The mixture is then packed into the crucible as tightly as possible, dried slowly, and bored out to any extent desirable. Sometimes water and gum are substituted for molasses. Fig. 9 represents three kinds of charcoal lined crucibles. Alumina crucibles for some operations are very satisfac- . 9. tory when intense heat is re- quired, but lime will answer as well. The choice of a crucible depends upon the nature of the substance to be treated in it, the temperature of the fire, and the time it is to remain exposed to the action of heat. If a charge be basic the crucible should be basic also, and vice versa. The grain and appearance of the crucible should be taken into consideration. Much iron will render the crucible fusible. To test a crucible for fusibility, heat a piece of the cru cible and see if the corners are rounded, or if it is fused on the edges. For corrosive action fuse litharge in the crucible. For permeability fill two crucibles with water and note the time required for it to run out, the one which holds the best be- ing preferable. As a rule, crucibles resist permeation and corrosion in the proportion of the fine/less and regularity CUPELS. of grain, but their tendency to crack is increased in the same ratio. The action of sudden changes of temperature may be as- certained by heating suddenly, and cooling first in air and afterwards by plunging in cold water. ROASTING DISHES, (Fig. 10), and SCOKIFIERS, (Fig. 11.) Both dishes and scori- fiers are made of re- FIG. 11. fractory clay the same FIG. 10. as crucibles. They should resist the action of litharge and not be too deep. Painting with water and oxide of iron prevents, to some extent, the cutting by strong bases. Scorifiers may be bought or made, but as a rule it is better to buy them, as they will stand transportation and it requires some care to make good ones. A section of a good scorifier is uniform in character. It is close, and should show no flaws or cracks. (Fig. lla.) FIG. lla. CUPELS. These vessels are generally made of the ashes of burnt bones, freed from organic matter, ground and washed. Horses' or sheep bones are said to be the best. It is better to make cupels than to buy them, especially when they have to be carried some distance. The prepared bone-ash can be obtained in bulk, and is mixed with just sufficient warm water to cause it to hold together without 30 CUPELS. being moist. Sometimes in mixing the bone-ash a little wood ashes is added, or a spoonful of "pearl-ash," (car- bonate of potash), by dissolving it in the water used for moistening the bone-ash. Too much bone-ash should not be mixed at once, as it dries quickly. If the bone-ash is too fine or too coarse it works badly ; as in the first case the cupel will crack upon drying, and in the second, be too porous, absorb silver with the litharge and occasion loss. The cupel is formed by filling and driving the prepared bone-ash into a mould made for the purpose. The right degree of compression should be used, as other- wise the cupel will be either too hard or too porous. A little experience will tell the operator when he has reached ^J| the proper point. When completed it presents the FIG. 12. appearance of Fig. 12. Care should be used in drying, plenty of time being -Y PLAN OF PORTION -A* SECTION ON LINE X. Y. FIG. I2a. ENGLISH SQUARE CUPEL. LUTES. 31 allowed, and all moisture and organic matter expelled pre- vious to using, by heating in a furnace. Sometimes a cupel is made of coarse bone-ash, and the surface finished off with fine washed material. Cupels dried in the sun are better than those dried arti- ficially. They are not so liable to crack. In the Royal Mint, London, England, an improved form of cupel is in use. It is square, with four depressions for holding the same number of buttons, enabling the operator to run two assays in duplicate in the same cupel. Fig. I2a represents the method of making, and the cupel when fin- ished. Iron-bound cupels are sometimes used when the amount to be cupelled is large, especially in treating sweeps. LUTES, CEMENTS AND WASHES. GOOD FIEE LUTES. 1. Fire clay, two parts. Sharp sand, eight parts. Horse dung, one part. Mix well and temper the same as mortar, until fche de- sired consistency is reached. 2. Fire clay, one part. Sand, three parts. Mix with a little hair and weak borax water. 3. Zinc cement. Dissolve three per cent, of borax in water to about 1.49 specific gravity and then add calcined oxide of zinc to suit. OTHER LUTES. Plaster of paris mixed with water, milk, glue, or starch water makes a good lute, and will stand a red heat. Wax or paraffin is useful for bottles, stoppers, etc., also tallow 32 TOOLS. or stearic acid. Faraday's cap cement is made by melting together rosin five parts, yellow beeswax one part, and stir- ring in one part of red ochre. A fine lute for iron vessels is porcelain clay (kaolin) mixed with a solution of borax in water. A good lute for glass vessels, is quicklime slaked in the air and then beaten into a liquid paste with white of egg. Where corrosive vapors are liable to escape, a lute made of fire clay and boiled linseed oil should be applied, and covered with slips of linen spread with the lute of lime and To LINE CRUCIBLES. Fine sifted charcoal mixed with gum water, borax water, or molasses enough to hold when pressed together in the hand, without being wet or sticky. It should contain no lumps. WASH FOR CRUCIBLES AND SCORIFIERS. 1st. Finely pulverized chalk and water. 2d. Sesquioxide of iron (hematite) and water. TOOLS. The tools required by the assayer are regulated more or less by the work to be done. The following are the principal : Crucible tongs (Fig. 13.) They should be made with long FIG. 13. handles for taking crucibles out of the fire, etc. TOOLS. 33 Scorification tongs. (Fig. 14.) The spring should not be FIG. 14. too strong, and the horse shoe part should just fit the scorifier. Cupel tongs. (Fig. 15.) These should be made of steel FIG. 15. and about two and one-half feet long with an easy spring. Three hammers are useful. One large for hammering metal, one medium for breaking crucibles and scorifiers, and one small for marking lead buttons. A set of small steel dies from to 9 inclusive, and large and small alphabet for marking buttons and bullion will be found useful, but are not necessary. Three pokers are convenient, small, large, and medium. One or two small hoes or scrapers for cleaning out the bottom of the cupel muffle. (Fig. 16.) / ^ tg FIG. 16. A pair of cutting shears and nippers for cutting wire for lead assay, etc. A small vise and anvil, medium size, with a suitable bench for the same. Wooden mallets, light and heavy, for packing crucibles, making cupels, etc. Files and cold chisels for sampling and cutting metals. Charcoal saw for blow-pipe charcoal, and crucible tops. Two iron mortars and pestles, and if much ore is to be pulverized, a grinding plate and rubber, as shown in Fig. /^ O.THP nOTNIVERsiTY ^^ c 34 TOOLS. 17, will be a great convenience and save labor. The plate is a flat iron casting 18x24 inches, and 1 inch thick. The sur- face used being planed smooth. The rubber or grinder is a piece of cast iron, 4x6 inches FIG. 17. square, 1J inches in the middle, by | of an inch thick at the ends ; thus giving a slightly convex surface, which should be true on the board at all points. To conduct the operation place the left hand upon the rubber, throwing the weight of the body upon it, and then grasping the handle with the right hand, move the iron rubber back and forth, depressing the handle when pushing forward and raising it in drawing back. For laboratories where large quanti- ties of ore are to be pulverized, the size of the plate, and the weight of the rubber should be increased ; but for ordinary use the dimensions given will be found suffi- cient. The operation is much more rapid than in the ordinary mortar and pestle style, and the manipulator after a little practice has complete control over the ore treated. Should it not be convenient to use the plate and rubber, a long handled pestle coming up to the chest will be found an improvement, as the mortar can be placed on the floor and the pestle worked while the operator is in a standing position. A series of sieves, from twenty to one hundred mesh, will be useful for sifting ores and fluxes. The box sieve, (Fig. 18), is a simple arrangement, and consists of a round tin TOOLS. 35 FIG. 18. box with a sieve fitting into it as represented in the engraving. The sieve is a tin frame with any desired mesh gauze soldered to it, and fits tightly in the box. The advantage gained by its use is that in sifting the pulverized ore there is no dust. The fine material being passed through the sieve is kept from flying around. The size most convenient is 8 inches in di- ameter, the box 2 inches deep, and the rim of the sieve 2 inches, fitting about inch into the box. A tin cover can be placed over the whole. Open and closed ingot moulds for casting lead and silver bars, ingots, etc. Hand button-rolls for gold and silver only. They should be kept covered and free from dust. Cupel mould, (Fig. 19.) This consists of two parts, an iron ring and a steel pestle or FIG 19 driver, just fitting into the ring. A mould for pouring the assay charge in scorification. 9 (Fig. 20. ) This should be of heavy sheet iron or copper. It saves much time, and by employing it, the scorifiers can be used again. Larger moulds of the same style will be found convenient for pour- ing crucible charges, but are not neces- sary, unless crucibles are scarce. Shovels for coke and coal, and a small hatchet for splitting kindling wood. The coke shovel should be ribbed or perforated so that the fine coke or dust may fall through. ooo ooo ooo , 20. TOOLS. Mixing scoops of Russia sheet iron 3J by five inches, with straight sides and back about | inch high. They are convenient for mixing lead or silver crucible charges in, and owing to- the high finish of the iron, the assay on being poured out does not cling to the scoop, a few sharp taps detaching everything. A tin sampler, shown in Fig. 21. will be found very useful. It consists of a series FIG 21. f troughs arranged in a row and fastened together at equal distances by a tin strip soldered on their ends. A shovel full of ore emptied by a series of shakes upon them, is just half caught by the troughs ; one-half going through the openings between. By repeating this operation, the size of the sample can be reduced to any ex- tent desired. A laboratory desk, as shown in Figs. 22 and 23, will be o FIG. 22. Section. Scale }& inch to the foot. FIG. 23. Elevation. Scale ^3 inch to the foot. APPARATUS. 37 found a very suitable and compact arrangement. It con- sists of four parts, shelves for bottles, closet for ore- scales, drawer for cupels and apparatus, and double closet for crucibles, scorifiers, etc. The illustrations being made to a scale, the desk can be constructed from them without trouble. This style of desk has been in use in the School of Mines, New York, for some years, and has been found most convenient. The lower closet should be provided with a shelf and the drawer with partitions. If gas can be had, each desk in a laboratory should have a burner above for lighting purposes, and two or three large jets to which rub- ber tubes can be fastened so that Bunsen burners can be employed on the desk. These jets are best placed next the scale closet. APPARATUS. The amount and kind of apparatus required by the assayer varies, but the following list will be found about all that will be needed for ordinary work : About three dozen quart bottles for reagents, glass stop- pered. One dozen glass-stoppered parting bottles, for bul- lion assay. Eight oz. is a good size. The stoppers should be square-topped and fit exactly, so that the bottles will not leak when shaken. An assortment of corked bottles of different sizes for samples. Two or three ring stands and the same number of Bunsen burners or alcohol lamps. The former are preferable, if gas can be had, and should be provided with two or three feet of rubber tubing for each burner. 88 APPARATUS. Two wash bottles, one small and one large, say one-half pint and quart. One half-dozen horn spatulas or spoons for mixing ore. Some iron pans for roasting. The ordinary long handled frying pan is suitable, and should be about the size of the furnace top. Before roasting it should be lined with chalk or oxide of iron. One dozen parting flasks, (Fig. 24,) for gold bullion assay ; also annealing cups for the same purpose. These are of clay and made thin. (Fig. 25.) Brushes for ores and fluxes made of FIG 25 came l' s narr 5 a large feather trimmed, makes an excellent substitute. A few dozen sheets of glazed paper, or stout manilla paper when glazed paper cannot be had, for mixing ore upon. Black is preferable, and when held up to the light, there should be no holes. Hessian and French crucibles and covers of various sizes and shapes. Scorifiers, large and small. Scorification and cupel muffles to suit furnaces. Cupels from f to 1J inches in diameter. These should always weigh more than the button to be cupelled. Glass beakers and rods. Funnels for filtering. Gum labels, note book, towels, large and small porcelain mortars, balances, scales and weights, as have been described. For volumetric work, silver bullion, etc., graduated flasks, pipettes and burettes, will also be necessary. See bullion assay, page 112. Should the assayer wish to be prepared for all kinds of work, it would be well for him to provide himself with the BEAGENTS AND CHEMICALS. 39 complete list of tools and apparatus, given on pages 188 and 191, Appendix, or at least in addition to the articles which have been described, with iron, clay and glass re- torts, agate mortar (large), one or two platinum crucibles and dishes, and a couple of Bunsen battery cells. The prices of the various articles are given in the list, so that an estimate can be made of the probable cost of starting an assay laboratory. REAGENTS AKD CHEMICALS. These may be divided into seven classes. a. Reducing. To this class belong those bodies which have the power of removing oxygen from its combinations. b. Oxidizing. All bodies which give up oxygen with facility. c. Desulphurizing. This class includes all substances which possess a strong affinity for sulphur, and will decom- pose its compounds under the action of heat or in solution. d. Sulphurizing. Sulphur and such of its compounds as give up their sulphur easily upon elevation of temperature or in solution. e. Fluxes. Under this head, we include a large class of bodies, but generally they are substances which render others to which they are added more fusible ; either by acting as a solvent or as a decomposing agent. Fluxes are either acid, basic, or neutral in their action. f. Solvents include solutions which are used in the wet way only. Such as distilled water, nitric, sulphuric and hydrochloric acids, etc. g. Precipitants in the wet way. As the salt solution used in the bullion assay. The following are the principal reagents and chemicals 40 REAGENTS AND CHEMICALS. employed by the assayer in his work. There are, however, many others which might be used, but they can all be classed under the heads just given. Dry BICARBONATE or SODA (sodic bicarbonate, JNa HC0 3 ) or the corresponding potash salt. These act as desulphur- izing agents, and in some cases as oxidizing agents. The latter action is due to the carbonic acid contained. Some- times they act as basic fluxes. They should be free from moisture and lumps. On account of their easy fusibility they can retain in suspen- sion, without losing their fluidity, a large proportion of finely powdered infusible substances. LITHARGE (PbO), is a basic flux, oxidizing arid desul- phurizing agent, and supplies the lead in the gold and silver crucible assay . It should be dry, and free from red oxide of lead, as the latter has the power of oxidizing silver, and thus causing loss of that metal during the assay. To free litharge from the red oxide, fuse the same in a crucible, and pour the mass into a cold ingot-mould, keep- ing it from the air while cooling. All litharge before using should be well sampled, and assayed for silver. To do this, charge in a crucible- Litharge 4 A.T. Soda 2 " Charcoal 0.7 gm. and cover with a layer of dried salt, one-quarter of an inch thick. Fuse in a hot fire until completely liquid, then withdraw, and proceed as in the assay of a silver ore (p. 71). White lead (carbonate of lead plumbic carbonate, PbCO 3 ), is sometimes employed instead of litharge ; also, acetate of lead for delicate experiments. BORAX, CRYSTALLIZED (2NaBO 2 .B 2 O 3 -10H 2 0). This acts KEAGENTS AND CHEBl. H S I T Y ) 41 \^Jps N . A . y as an acid flux ; but, on account of the water contained, it is generally employed in a vitrified condition, or boras; glass (2NaBO 2 .B 9 O,), which has a more intensified effect. It has neither an oxidizing or desulphurizing action. It is sometimes used as a cover in place of salt. To prepare Fuse the commercial borax in a chalk^ lined crucible, pouring the fused mass out on a clean sur- face to cool. Pulverize, and keep in a glass-stoppered bottle. As borax, when heated, loses its water of crystal- lization, and undergoes an immense increase in volume, only a little should be added at a time in fusing. Boracic acid (H 3 B0 3 ) is also sometimes employed. SILICA (Si0 3 ), acts as a good acid flux, and can often be used with advantage. A good substitute is glass (]STa 2 Si 3 7 +CaSi 3 7 +Si0 2 ), a s it is easily fusible, and forms a good slag. It should be powdered and free from moisture. Lime glass is the best. BLACK FLUX, SUBSTITUTE. A mixture of three parts flour and ten parts of bi-carbonate of soda acts as a flux and reducing agent, and is especially useful in the lead assay. Black Flux, proper =1 of nitre and 3 of argol deflagrated. CYANIDE or POTASSIUM (potassic cyanide, KCy=KCN), as a flux for reducing and desulphurizing is invaluable. It should be prepared with care and kept in a tight bot- tle, as it absorbs moisture. Take the ordinary commer- cial article and pulverize in an iron mortar as fine as possi- ble. Never sift, as the dust is poisonous. To protect your- self, cover the mortar with a towel, or a board having a hole in the centre for the pestle. FERKO -CYANIDE or POTASSIUM (yellow prussiate of pot- ash) (potassic ferrocyanide, K 4 FeCy 6 +H 2 O), will often be found useful as a flux for reducing and desulphum- 42 REAGENTS AND CHEMICALS. ing. The crystallized material should be powdered in a porcelain mortar, and dried over a slow fire until it is almost white. If the heat is too high it will carbonize and turn brown. AEGOL (KHC 4 H 4 O 6 ), crude bitartrate of potash, acts as a basic flux and reducing agent. It should be pulverized and dry, and its reducing power determined. For this purpose we charge Argol 2 gms Litharge 1 A.T. Soda i " in a crucible, fuse in a hot fire, cool, extract the button and weigh in grammes. Dividing by two gives the amount of lead one gramme of argol will reduce from litharge. CHAECOAL, acts as a reducing agent and desulphurizer. It- should be finely powdered and its reducing power deter- mined, as in the case of argol. Using charcoal one gramme, and litharge, 2 A. T. Ordinary wood charcoal will reduce twenty-eight grammes of lead from litharge. STAECH, flour, sugar, and gum, may also be used for re- ducing agents, but are not so convenient. Dried starch reduces thirteen parts of lead. Common starch about eleven and one-half parts. Sugar fourteen and one-half, and gum arabic eleven parts. For some pur- poses pure hydrogen gas will be found essential as in the assay of oxide of tin. It is the strongest and best reduc- ing agent, but requires care in its preparation. It is made by dissolving zinc in dilute sulphuric acid, and passing the gas evolved through oil of vitrol, to dry it before using. One part of hydrogen will reduce about one hundred and four parts of lead from litharge. METALLIC IEON (Fe), is a desulphurizing agent, and is in KEAOENTS AND CHEMICALS. 43 dispensable, especially in the assay of lead ores. The best form is iron wire about inch in diameter. Nails and filings may also be used. PUEE LEAD (Pb), in sheet or granulated form, is used prin- cipally in the assay of silver ores. It acts as a basic flux, and a solvent or wash for the precious metals. The sheet form is useful in cupelling gold and silver beads, and in the bullion assay. The granulated is essential in the scorifica- tion assay. It can be obtained pure by decomposing the best white lead by charcoal, and granulating or fusing in bars, as the case may require. In sections where granulated lead free from silver, or white lead, cannot be obtained, the assayer can make his own granulated lead from pig lead, poor in silver, by the following method : Melt about fifty pounds of lead in an iron pot or crucible, and keep it just at the melting point. Then pour a ladleful of the melted lead into a wooden bread-tray which has been well chalked on the in- side. Keep this agitated by gently rocking the tray to prevent solidification, and when the mass begins to get pasty, throw it into the air and catch it again repeatedly until cold, when the metal will be found to be nearly all granulated. Sift through a twenty -mesh sieve, and what does not go through re-melt. The whole fifty pounds can be granulated in this way in two hours. After granulation sample well and test about thirty to fifty grammes for silver, by the scorification assay. In using the lead, the silver contained in it must be deducted from the results obtained in assaying an ore. NITRE (potassic nitrate, KNO 3 ), acts as a basic flux and oxidizing agent. It should be finely powdered, dry, and assayed for its oxidizing power. Charge : 44 REAGENTS AND CHEMICALS. Nitre : . . . 3 gms. Charcoal 1 " Litharge 2 A.T. Soda 1 " Place in a Hessian crucible and cover with salt. Fuse in a hot fire, remove, cool and weigh. The difference between the weight of the button obtained and that given in the assay of charcoal, divided by three, gives the oxidizing power of nitre per gramme. POWDERED LIME (CaO), (dry), and fluor spar (CaF 2 ), will often be found useful as basic fluxes, especially in the assay of iron ores. Magnesia (MgO), and alumina (A1 2 O 3 ) or kaolin (Al 2 O 3 .2SiO 2 ) are also used, and cryolite (3NaF. A1F 3 ) for tin ores. As SULPHURIZING AGENTS powdered sulphur (S), pure galena (PbS), or sulphide of antimony (Sb 2 S 3 ), are employed. CARBONATE OF AMMONIA (ammonic carbonate, (NH 4 ) 2 C0 3 ), as a desulphurizing agent, is used in the decomposition of some sulphates, as sulphate of copper, in roasting. It should be powdered and kept in a close vessel. COMMON SALT (sodic chloride, NaCl), as a cover and wash, and as a reagent in the bullion assay, should be al- ways kept on hand. The purer it is the better, and it must also be fine and dry. As SOLVENTS AND PEECIPITANTS distilled water (H 2 O), sulphuric acid (H 2 SO 4 ), nitric acid (HNO 3 ), hydrochloric acid (HC1), chloride of sodium (Nad), nitrate of silver (ar- gentic nitrate, AgN0 3 ), and sulphuretted hydrogen (H 2 S), are most frequently employed. The acids may be purchased pure. Nitric acid should be free from chlorine, which can be separated by the addi- tion of nitrate of silver, drop by drop, until a precipitate ceases to form. The clear acid, after settling, being drawn THE PRELIMINARY TESTING OF OKES. 45 off with a syphon. Any excess of nitrate of silver should be carefully avoided. Mtrate of silver may be made by dissolving pure silver in nitric acid free from chlorine ; evaporate to dry ness and dissolve one part of the salt in twenty parts of distilled water. Sulphuretted hydrogen is best prepared from powdered sulphide of iron (ferrous sulphide, FeS) and dilute sul- phuric acid. The gas being passed through a second bot- tle filled with water to wash it. Fig. 26 shows the appara- tus in position for use. The glass tubes are connected with small pieces of rubber tubing. The gas may be passed into the solution to be pre- cipitated, or a water solution may be saturated, and used at pleasure. The sulphide of iron can be made by heating scrap iron or borings to a FIG. 26. red heat in a crucible and throwing in sulphur. The sulphide produced may be then fused or broken up; complete fusion is unnecessary. OTHER CHEMICALS and reagents will often be found neces- sary if assays in the wet way are to be made, but the reader must be referred to the list on page 189. The most important are arsenic (As), arsenide of iron (ferrous ar- senide, Fe 2 As), hyposulphite (Na 2 H 2 S 2 O 4 ), and sulphide of sodium (Na 8 S). PRELIMINARY TESTING OF ORES. Before breaking up a sample it should be thoroughly examined to determine, if possible, its inineralogical char- 46 SAMPLING AND PULVERIZING. acter, and if this is impossible it should be tested with the blowpipe, by the scheme of table pp. 177-184, Appendix. By the result of the blowpipe assay, the assayer can set-- tie upon what method he will pursue, and often save much time. The determination of the presence of gold will de- cide the question of crucible or scorification assay. Arsenic, antimony or sulphur, that of roasting, etc. With a lit- tle practice the assayer will seldom have to use the blow- pipe when the specimen is in lump, the color, hardness, weight and general appearance indicating the nature of the ore, and consequently the method of assay ; all powdered samples should, of course, be examined under a magnifying glass and tested by the blowpipe. SAMPLING AND PULVERIZING. The selection and preparation of the sample for assay may be called the ' ' secret of success. ' ' It is the most im- portant operation which the assayer has to conduct ; and unless the sample be well taken his work will be useless. No matter how large or how small the amount of ore he may be called upon to treat, the same care is necessary in the sampling ; for one portion may be very rich and another portion valueless, so far as the metal sought for is concerned. The sample, therefore, taken for an assay, must always be an average of all the ore. The method of sampling an ore depends upon its consti- tution : a. The ore contains no metallic particles. . The ore contains metallic particles. In the first case the operation is comparatively easy. If there is a large quantity of ore to be sampled, it is broken SAMPLING* AND PULVERIZING. 47 up more or less finely, the degree of fineness depending upon the amount of ore from which the lot for assay is to be taken ; and is then either thrown upon a sampler, page 36, or divided by piling it in a heap and cutting it in quarters, one of which may be selected to be again broken up and quartered, and so on, until a sample sufficiently small for assay is obtained ; or an equal portion of each quarter may be taken, and the four portions well mixed, broken up, thrown in a heap, and the operation repeated until the required sample is reached. If there is only a single specimen or lot obtained by sampling as above, it is better to crush it, and pass it all through a sixty or eighty-mesh sieve ; the finer the better. The pulverized ore is then well mixed with a spoon or spatula on glazed paper, and the amount for assay weighed out by taking a little here and there, or dividing into quarters and taking some from each quarter. Various mechanical devices are employed for sampling down large quantities of ore, but for most purposes the tin sampler described will be founiA sufficient. The size of this may be increased if desira- ble. The fine ore should never be shaken to mix it, or poured upon the scale pan directly from the vessel in which it is contained. b. The ore contains metallic particles. The sample may be selected from the heap of ore in the same manner as described under a, but a larger lot must be taken for assay and the whole pulverized and passed through an eighty-mesh sieve, which will divide the ore into two portions : 1st. Sif tings. 3d. Metallic residue. 48 SAMPLING AND PULVERIZING. The siftings must be well mixed and sampled upon glazed paper, as just described. The metallic residue must be tested as a whole and not sampled, or if the amount is large, can be fused with pure lead, and a weighed portion of the resulting alloy as- sayed. The method of making the assay and calculation of re- sults will be given hereafter. Care must be taken in preparing a sample that all appa- ratus employed is clean, especially the mortars and sieves. The first can be cleaned by pulverizing a little sand in them, or using a pumice-stone pestle, and the latter by rub- bing with a clean towel or rapping upon a bench. The box sieve, (page 35), will be found very convenient, and better than the ordinary kind, as it prevents the loss of dust which would alter, more or less, the value of the sample. The sieve should be used for nothing but ores, and carefully cleaned after each operation. To sample gold or silver bullion, chip from alternate cor- ners above and below ; or else melt and take the first and last pouring. To sample coins : for silver, stamp out small pieces from the center and edge ; for gold coins, cut slips running from the center to the circumference. Sometimes lead chips or granulated alloys are submitted to the assayer, which call for great care in sampling. Lots of this kind should be weighed and melted in a clean cru- cible, carefully poured so as to save all the scum ; the bar weighed and sampled by chipping or boring, and the scum weighed and scorified. The value of the original alloy per ton can then be calculated in the same way as an ore which contains metallic particles. WEIGHING OKE AND EE AGENTS. 49 WEIGHING ORE AND REAGENTS. The ore, litharge, test lead, oxidizing and reducing agents, should be weighed accurately. The ordinary fluxes may be weighed approximately, still it is better to weigh close, as more uniform results are ob- tained. The same pans of either the flux or ore balance should always be used for the weights, and the latter must be handled with the pincers provided for that purpose. The ore scales should be kept free from dust, and be adjusted before each weighing, for next to the sampling, the weigh- ing of the ore is most important. When a number of charges of the same ore are to be weighed, weigh out the fluxes first, and then add the ore in order. In this way the work will be greatly facilitated. Instead of weighing the pure granulated test lead, it can be measured. A very simple and good test lead measure is a glass tube about of an inch in diameter, in which a cork is fitted to slide up and down ; the tube being graduated for known weights. As far as possible glazed paper or watch glasses should be used in weighing, to prevent substances from touching the scale pan, especially in employing the quantitative analytical balance. If the substance is one w^hich is liable to absorb moisture from the air it should be weighed between watch glasses, fastened with a clip. Cyanides must never be weighed upon the pan direct. The balance pans of the bullion and quantitative balance should never be handled with the fingers or set upon a rough surface. 50 CALCINATION AND BOASTING. CALCINATION AND ROASTING. In calcination the object is to drive off moisture, while in roasting the operation is conducted in such a manner as to ensure oxidation, and the elimination of sulphur, arsenic, antimony, etc. To calcine a substance it is not necessary that the air should have free access, or that the material treated be constantly stirred. For calcination a high tem- perature is seldom necessary, 212-220 F. being sufficient. To conduct the operation, crucibles will be found the most convenient vessels. For roasting, combustion must take place, and conse- quently the vessels employed must be open and flat to allow the oxygen of the air to act freely. The ore must be stirred continually, and when easily fusible, be mixed with some substance to prevent agglutination. Charcoal, graphite, or sand may be used for this purpose. The heat should be low at first, and. raised toward the end of the operation, and in some cases chemicals mixed with the mass hasten the pro- cess, and render it more complete, as in the addition of carbonate of ammonia in roasting copper ores, which de- composes any sulphates which may have been formed. The operation may be performed on a crucible furnace in an iron pan lined with chalk or oxide of iron ; or in an open vessel like a scorifier, (Fig. 10) in a muffle furnace. In any case tbe draft of air should be strong, as the fumes are inju- rious ; the ore, however, must not be blown out. A very nice stirrer for this operation can be made from a piece of ordinary wire, by doubling it and bending down the loop like a small hoe, the ends of the wire being twisted together to form a handle. REDUCTION AND FUSION. 51 REDUCTION AND FUSION. Reduction is simply the removal of the oxygen from the body acted upon ; generally by the action of substances having a stronger affinity for it. The operation of reduction is usually accompanied by fusion, which is simply melting, although they may act in- dependently of each other. Reduction and fusion are car- ried on in crucibles, scorifiers, etc. The heat required is higher than that necessary for the foregoing operations, consequently the draft should be stronger, and for this reason wind furnaces are employed. Fusion is sometimes a preliminary step to oxidation and sublimation. To perform the operation of reduction in a muffle fur- nace, the muffle must be partially filled with charcoal, and the mouth closed. DISTILLATION AND SUBLIMATION. Distillation may be divided into two cases : a. When a solid is acted upon. b. When a liquid is acted upon. The product is generally liquid. Sublimation is similar to distillation, but the product is solid. Both operations may be conducted in flasks, retorts, or crucibles ; but usually in the operation of distillation a cooled condenser is necessary, as in the process of making distilled water. The term "destructive distillation" is used where the body acted upon undergoes decomposition. SCOKIFICATION AND CUPELLATION. SCORIFICATTON AND CUPELLATION. Scorification and cupellation include a combination oi fusion, roasting and sublimation, the difference being, that in the latter case the volatile compounds formed are absorbed by the cupel, while in the former they form a slag. Both will be described in detail hereafter. (See assay of silver ores.) INQUARTATION AND PARTING. Under this head comes the separation of alloys, and the treatment of the buttons from the gold and silver assay. Inquartation is the process of alloying gold with silver to form a more soluble alloy, while parting is the separation of the metals by treatment with acids. WEIGHING BEADS AND BULLION. This operation must be conducted with the greatest care, and the balance adjusted both before and after weighing. Before weighing, the bead or bullion should be well cleaned with a small brush. To weigh the buttons of the base metals the ore scales are sufficiently accurate ; but for weigh- ing silver and gold, the bullion balance must be employed. The weights should be counted on the pan, also the vacant spaces in the box as a check. It is best to keep the bullion balance in a separate room from the laboratory, where it will be free from dust and fumes. It should also stand upon a firm shelf, to prevent shaking. In weighing a substance do not use the weights TABULATING RESULTS. 53 at random, but find the nearest single weight, and add the others in regular order, until the required combination is reached. In duplicate assays the buttons should balance each other, or very nearly so. To facilitate the weighing out of pure silver in the bul- lion assay, Mr. W. S. Ward of the U. S. Assay Office, in the city of New York, has devised a series of standard disks, which run from fifty to five hundred milligrammes, and by combining one or more almost any desired weight can bo obtained, thus saving labor and time. When obtain- ing a weight, the door of the balance should be kept closed, and the number of divisions marked by the needle observed, and on which side of the centre-line they are. Each division counts 1-10 of a milligramme on the second swing, and the total can be either added or deducted from the weights in the pan, as the case may be ; if the button is heaviest, add ; if lightest, subtract. On the quantitative balance the rider indicates milligrammes and fractions of the same, so that in obtaining the final weight after the pans are nearly bal- anced, the door can be closed and the rider adjusted by means of the rod from the right-hand side. Never lean on the balance shelf or leave the rider on the beam. The first may throw the balance out of adjustment ; the second, cause error in the next weighing. TABULATING RESULTS. REPORTING. In making an assay each result should be noted as obtained, and nothing left to memory. Care should also be observed in arranging and reporting. To facilitate this, a series of blanks will be found on pages 155-162, from which a choice can be made. 54 TABULATING RESULTS. The report should be made as simple and comprehensive as possible, and written in terms which a business man can understand. It should also indicate in the case of gold and silver, the ounces Troy to the ton Avoirdupois, and the value, in gold, per ton of ore. Gold being taken at $20.67 per oz. Troy. Silver variable ; the value by the old U. S. standard being $1.29 per oz. Base metals, such as lead, antimony, copper, etc., are re- ported in percentage. Gold and silver alloys are reported upon as to fineness, or the number of parts of each metal in a thousand of alloy. PART II. BEY OR FIRE ASSAYS, ERSITY LEAD. 57 LEAD. Symbol- Pb. SOTJECES. The principal ores of lead are : Galena, sulphide (PbS) Pure=86.6 lead Minium, oxide (Pb 3 O 4 ) " =90. " Cerussite, carbonate (PbCO 3 ) " =77.52 " Anglesite, sulphate (PbSO 4 ) " =68.31 " Pyromorphite, phosphate and chloride (3Pb 3 PA + PbCl 2 ) " =76.36 " Lead also enters into the composition of many other min- erals, but they do not occur in sufficient abundance to be classed as workable ores. ASSAY. The assay of lead may be performed either in the crucible or muffle furnace. The methods of treating varying with the ores. The object of the assayer being in all cases to decompose the ore treated, and obtain a button of lead by slagging off the gangue and other impurities. Methods applicable to sulphides, sulphates, etc. : 1ST. 3D. 3D. Ore lOgms. Black Flux ) - (e Substitute } ' 3 Loops Iron Wire, Points down. Salt Cover. Ore 10 gins. Soda, Bi-Carb. ...30 " Argol 2 " 2 Iron Nails / Points down. \ Salt Cover. Ore lOgms. Ferrocyanide of Potassium dry 10-15 " Cyanide of Potas- sium 5-10 " Salt.. ..Cover. The charges should be well mixed, transferred to a cru- cible, and covered with salt. The wires or iron nails being placed in such a manner that they can be drawn out quickly after fusion. A little carbonate of soda in addition to the 58 FIKE ASSAYS. fluxes given in the third method, sometimes gives a better slag. The crucible must be covered while in the fire and dur- ing the process of cooling. In the first and second methods a double sulphide of soda and lead is formed, which is acted upon by the iron present ; the carbon acting also as a reducing agent. In the third method the ore is desulphurized and reduced by the action of the cyanide and also by the iron in the ferrocyanide. 4TH. Ore 10 gms. SodaBi-Carb 20 " Argol 5 " Flour 2 " Borax (fused) 1 " The ore and first three fluxes are mixed and placed in a small Hessian crucible, which will go into the muffle of the cupel furnace. The borax is then added, and three nails or two pieces of iron wire bent into the form of hairpins stuck into the mass ; after which a cover of salt J-inch thick, is packed upon the whole charge, and the crucible covered. Several assays can be run in a muffle at once, but care in heating should be observed. The muffle should be at a bright cherry-red when the assays are introduced, and the heat raised until the salt cover fuses. This will take about twenty minutes, after which the muffle is made white hot for about ten minutes, when a perfectly fluid fusion is obtained. The assays are then withdrawn, the wires care- fully taken out, the crucibles tapped gently, and the contents poured into a mould. This operation must be performed carefully and quickly, to prevent solidification of the slag. The iron and carbonaceous material act as explained in the preceding methods. LEAD. 59 STH. Ore 10 gms. Cyanide of Potassium 25 to 30 " Salt cover. Fuse in a moderate fire twelve to fifteen minutes, keep ing the crucible covered while in the fire and cooling. The cyanide of potassium takes the sulphur from the lead forming a sulpho-cyanide of potassium. Methods applicable to oxidized ores, carbonates, etc. 1ST. Ore 10 gms. Argol 5 " SodaBi-Carb 20 " Salt cover. Mix well and heat slowly for about twelve minutes, and then strongly until in complete fusion. Remove from the fire, cool and break. The argol in this case acts as the reducing agent, owing to its carbon. For treatment of cupel bottoms add ten grammes borax glass. 3D. Ore 10 gms. Black Flux Sub... 35 " Argol 2 " Salt cover. Fuse in a hot fire, and in all cases where the material treated contains substances fusible with difficulty, borax glass must be added to facilitate the fusion. The lead assay is not accurate for several reasons, chiefly because of the volatility of the lead, and the presence of substances which alloy with the button. Antimony and zinc in an ore interfere with the as- say ; as the first will generally be found with the lead, 60 FIEE ASSAYS. while the zinc, though partially driven off, carries lead with it. When much antimony is present, the following method may be employed, (Mitchell, pages 379-380), with approxi- mate results. Ore 10 gms. Carb. of Potash or Soda.. 35 " Saltpetre 1 " Salt cover. The assay is performed in a muffle furnace, and requires about thirty minutes for fusion, then ten minutes slow cool- ing, which is done by opening the door of the muffle, and decreasing the heat. Finally finishing with closed muf- fle, and a high heat for ten minutes, when the crucibles are removed, cooled and broken. Most of the antimony re- mains in the slag. This method requires care and practice. Very often in making an assay in the muffle the crucibles, being small at the bottom, fall over. To avoid this, make a little platform of clay for each crucible. Lead slags can be assayed by fusing the pulverized slag with soda and charcoal charge : Slag 20 gms. Argol 10 " Soda, Bi-Carb 40 " 2 Iron Nails, points down. Salt cover. The assay is conducted in the same way as in the treat- ment of ores. REMAKKS. Pure galena, treated by the foregoing meth- ods, for sulphides, gave the following : ANTIMONY. 61 METHOD. RESULT. No. 1 78.4 and 78.6 " 2 73. " 73.4 " 3 78.5 " 79.1 The assay by cyanide gives lower results, but cleaner buttons, and is to be recommended. The yield by muffle assay is high, duplicates agreeing within two per cent, and the button being clean and malle- able. The first method for carbonates gives results varying from 1 to 2 per cent., but is better than the second. The method by ferrocyanide, although given, is not re- commended, as the buttons nearly always contain iron. A loss of lead is sustained in all the above processes, by the volatility of this metal and its oxide ; for this reason all assays of lead ores, should be made at as low a tempera- ture as is compatible with perfect fusion, and the assay should not be left in the furnace longer than is actually necessary. ANTIMONY. Symbol Sb. SOURCES. The principal ore of antimony is the sul- phide called stibnite, or grey antimony ore (Sb a S 3 ) which contains, when pure, 71.80 per cent, of metal. Antimony is also found native alloyed with other metals, and in com- bination with oxygen. ASSAY. In the assay of antimony ore, the assayermay be required to determine one of two things. a. The pure sulphide of antimony (antimonium crudum), which the ore may contain. 62 FIBE ASSAYS. b. The metallic antimony (regains of antimony), which the ore may yield. a. Determination of the snlphide. As sulphide of anti- mony fnses at a low red heat, it is not changed in its char- acter if the air is excluded, so that the following method may be adopted : Charge the broken ore into a crucible the bottom of which is perforated, and just fits into a second crucible about half its depth. Then cover and lute the lid and the joint be- tween the two crucibles with fire clay and sand. The upper crucible only should be heated, and to effect this the lower can extend into the ash-pit of the furnace, being supported by an inverted crucible or a brick. The sulphide of antimony will melt and collect in the lower crucible, while the silicious and earthy matter re- mains in the upper. b. Determination of metallic antimony. 1st. The ore is in the state of oxide. Ore 10 gms. Black Flux Sub.... 25 " Argol 2 " Charcoal and salt . . . cover. This assay is conducted in the same manner as for lead, only the heat must be regulated with more care, and the assay taken from the fire as soon as finished ; the cover be- ing left on the crucible while cooling. The flour in the black flux substitute, and the argol, act as the reducing agents, metallic antimony being pro- duced. 2d. The ore is a sulphide. ANTIMONY. 63 Ore 10 gms. Cyanide of Potassium, 35-40 " Salt cover. The charge should be well mixed, the heat low, and the operation performed quickly ; observing the same pre- cautions in cooling as in the preceding method. REMARKS. The result obtained in assaying for antimony cannot be accepted as the correct amount of metal in the ore ; it only represents the possible yield, as the button often contains some other metals, which have been reduced with the antimony in the ore, when the latter is not pure. It should, therefore, be tested for iron, etc., alloyed with the antimony. The button should be cleaned by washing, and not hammered, to detach the slag, as it is brittle. When much iron and silicious matter is contained in the ore, the method for the determination of the sulphide does not give good results. Two assays of impure stibnite gave 44.5 and 44.2 per cent. To separate from foreign metals, break the button and dissolve in concentrated nitric acid, which converts the an- timony into antimonic acid, which is insoluble. Filter, wash, dry, and ignite in a porcelain crucible ; the weight found multiplied by 0.7922 gives the metallic antimony. Practically it is not necessary to treat the buttons from the fire assay, as the loss by volatilization more than counter- balances the impurities in the button. For some impure ores a very large charge of cyanide (say 50-60 gms.), and a quick, hot fire has been found to give good results. 64 FIEE ASSAYS. GOLD AND SILVER. Symbols An. and Ag. SOURCES. All substances containing gold and silver may, for the purposes of the assayer, be divided into two classes : Class 1st. Minerals or ores, including incidental indus- trial products. Class 2d. Metallic gold and silver, and alloys, native or artificial. Metallic gold occurs in nature in sufficient abundance to have great commercial value. It is found com- monly in a quartzose gangue, and nearly always associated with one of the following minerals : Iron and copper py- rites, mispickel or arsenical pyrites, blende, and galena. There are also compounds with tellurium, and native alloys. (See pages 146-147.) The principal sources of silver are silver glance, stephanite, pyrargyrite, kerargyrite, native silver, galena and argentife- rous copper ores. But as many minerals contain silver in greater or less quantity, for the convenience of the assayer, a complete list has been arranged on pages 145-146. The assay for gold and silver therefore comprises : a. Assay of ores. b. Assay of alloys. According as we have material of the 1st or 2d class. a a. ASSAY OF OEES. Assays of gold and silver ores are made in almost the same manner, so that a general descrip- tion will answer for both. They embrace the following steps : 1st. Preparation of the sample. 2d. Collection of the gold and silver in a lead button. 3d. Cupellation of the lead button. 4th. Weighing the bead. 5th. Inquartation, parting, and annealing or cupelling of the gold residue. 6th. Weighing the gold. GOLD AND SILVER. 65 PREPARATION OF THE SAMPLE. Extra care must be ob- served in sampling. (See page 46.) THE COLLECTION OF GOLD AND SILVER IN A LEAD BUTTON Is effected in a crucible or scorifier, whence two methods of assay: (a.) Crucible assay, (b.) Scorilication assay. The former is applicable to nearly all ores. The latter to rich silver ores and telluride gold ores ; it is not safe to use this method for all gold ores, as a very slight error may make a great difference in the results, because of the small quantity of ore necessarily employed. (a.) Crucible Assay. An ore of gold or silver is com- posed of precious metals, gangue, oxides, sulphides, etc. To collect the precious metals the ore is mixed with lith- arge, suitable fluxes and oxidising or reducing agents, and fused in a crucible. The litharge is reduced to metallic lead, seizes upon the precious metals, and collects at the bottom of the crucible, while the foreign materials form with the fluxes, a fusible slag above. The crucible is poured, or broken when cold, and the button detached from the slag by hammering it on an anvil. The charge : The weight of ore taken depends upon its probable richness or poverty, since it is required to obtain finally a bead of precious metal for weighing. As a rule it is usual to take one-third to one assay ton for silver, and one, two, or even four assay tons for gold ores. All ores re- quire the following reagents : Argol, charcoal, or an oxidiz- ing agent (nitre), with invariably a cover of salt. Borax, silica, and other reagents are useful at times, but their employment must be left to the judgment of the assayer, guided by the properties of the reagents, and the com- position of the ore. It is well to bear in mind that for basic impurities, an acid flux is used, and for an acid gan- 66 FIRE ASSAYS. gue a basic flux. Unless the charge of ore be very large, as a rule, employ 50 grammes of litharge, and the same amount of carbonate of soda as of ore. These propor- tions may be modified according to the composition of the ore. The amount of nitre depends upon the reduc- ing power of the ore. It is added to lessen the size of the button. Size of the lead button : There are two limits to the size of the button. (1st.) It must be large enough, or sufficient litharge must be reduced throughout the mass to collect all the precious metals. (3d.) There should not be an excess of lead, which would occasion a loss of sil- ver in cupellation. A button of fifteen or twenty grammes is the best size for a weight of ore from one- third to four assay tons, and is convenient for cupellation. A button too large for cupellation can be made smaller by scorify- ing. The reducing power of an ore is due to the presence of sulphur, arsenic, antimony, zinc, etc. PRELIMINARY ASSAY OF ORES. Warm the crucible be- fore placing it in the fire, which should be bright, and effect the fusion in the shortest possible time. When the the contents of the crucible are in quiet fusion, withdraw, 'tap, cool and break. The charge of ore is as follows : Ore 2 gms. Litharge 25 " SodaBi-Carb 10 " Salt cover. Three cases may arise here. Two grammes may yield : 1st. No lead, or less than three grammes. 2d. Three grammes of lead. 3d. More than three grammes. GOLD AND SILVEE. 67 Let us suppose we take for assay A. T. of silver ore, and the reducing power of two grammes of ore is 1.5 gms. lead, i A. T., or ten grammes of ore, (about), will reduce 7.5 of lead, and as the required button is fifteen grammes, we must add enough argol or charcoal to reduce 7.5 gms. in addition ; taking argol as 8.5, we shall require 7.5-^-8.5 =0.882, say one gramme, or charcoal 7. 5-^28 =0.268 say i of a gramme. If the reducing power corresponds to the third case, divide the excess of lead by the oxidizing power of nitre, the quo- tient will show how much nitre is needed. In the second case, ten grammes of ore would reduce a button of fifteen. Experience will often enable the assayer to judge of the reducing power without extra assay, by noting the approxi- mate amount of sulphides contained in the ore before pul- verizing the same. After preparing a charge from the data obtained by this assay, it should be fused, and the slag carefully examined before running a duplicate, so that silica or borax may be added if the slag is basic, or any mistakes as to reducing power corrected. ROASTING. Ores containing a large amount of sulphur, arsenic, antimony, or zinc, should be roasted. In the former case, if the ore is not roasted there will be danger of the formation of oxysulphurets, which, though fusible, are not decomposed at a white heat, and enter the slag carry- ing silver with them. A large quantity of nitre is lia- ble to boil over ; even should this not occur, the evolu- tion of vapors puffs up the mass, and lead may be left adhering to the sides of the crucible. Arsenic and anti- mony produce arseniates and antimoniates, which carry 68 FIKE ASSAYS. silver into the slag. Zinc also increases the loss of silver by volatilization, and in the slag. The ore may be roasted conveniently in a cast-iron pan over the furnace. The pan should be coated with red ochre, or chalk, which protects it and prevents loss of ore. The weighed sample must be spread over the pan, and stirred until all danger of fusion is past. The ore must be heated gradually, not above a dull red for some time, and finally to a full red or higher heat. Too high a temperature at the outset causes the fusion of sulphides and the formation of matter troublesome to roast. A rapid disengagement of arsenic, antimony, or zinc will also causo a mechanical loss of silver. Should fusion occur, it is better to weigh out a fresh portion of ore and roast it again. The operation may be considered finished when, after keeping the pan at a full red heat for some time, no fumes can be perceived. If copper pyrites be present after roasting, cool and mix some carbonate of ammonia with the ore. Cover and heat the pan until fumes have ceased. The sulphates are con- verted into volatile sulphate of ammonia, which passes off. Arsenic and antimony require the addition of fine char- coal to reduce arseniates and antimoniates formed in roast- ing ; care being taken to burn out all the charcoal. If the ore contains a fusible sulphide, as antimony glance or gale- na, mix with some fine sand before roasting. Ores may be roasted in the muffle, in the earthen saucer already men- tioned, page 29. FUSION. The prepared charge is thoroughly mixed and placed in a crucible. A hot fire is employed, and the cruci- ble removed when complete fusion has taken place. This requires from thirty to forty-five minutes. The crucible is tapped on the floor, poured, or broken when cold. GOLD AND SILVER. 69 (b ) Scarification Assay. The reagents for scorification assay are pure granulated lead, and borax glass. The ore is mixed with these, the mixture put in a scorifier, and fused in a muffle. An alloy of lead with the precious metals, and a slag composed of litharge with tie impurities and gangue of the ore is formed. The proportions of lead and borax will vary and should be greater as the gangue and metallic oxides are more difficult of fusion. The following table shows the proportions found by experience to be adapted to the different gangues. They are referred to one part of ore : PARTS PARTS CHARACTER OF GANGUE. TEST LEAD. BORAX GLASS. Quartzose 8. Basic 8. 0.251.00 Galena 5.6 0.15 Arsenical 16. 0.100.50 Antimonial 16. 0.101.00 Fahlerz. 1216 0.100.15 Iron pyrites 1015 0. 10 0.20 Blende 1015 0.100.20 In most cases one-tenth of an assay ton of ore and thirty to forty grammes of lead will be found to work well. The ore and one-half the lead are mixed in the bottom of the sco- rifier, and the rest of the lead poured over the mixture so as to form a cover. Two or three lumps of borax glass the size of a pea being placed on top. The charge of ore varies from one-third to one-twentieth of an assay ton according to its richness, and if one scorifier will not contain it, weigh equal fractional parts for the number required, rather than to weigh the whole charge and roughly divide it between the scorifiers. 70 FIKE ASSAYS. Three distinct periods may be noted in the working of an assay. (1.) Roasting. (2.) Fusion. (3.) Scorification. A strong heat is maintained at first to melt the lead. This is effected by closing the muffle and increasing the draft. As soon as the lead is fused the muffle is opened, and the ore is seen floating upon the surface of the lead. In a large muffle it is sufficient to place the scorifier in the back part first, and move it forward when the lead is fused. (1). The roasting commences and is continued at a mod- erate heat until no more fumes are seen, and the ore has disappeared. (2). The heat is raised in order to fuse all the material. When the fusion is complete, clear white fumes of lead arise from the scorifier, there is a play of colors across the surface of the lead, and the slag encircles the metallic bath like a ring. The borax glass plays an important part just here, by giving liquidity to the slag, so that it can be thrown to the side as fast as formed, exposing the lead for oxida- tion. If borax glass is not added and the ore contains much gangue and is not easily fusible, the scorige will float in masses over the lead, impeding the oxidation. (3). When fusion is complete the heat is lowered to a constant point, until the ring of slag, which is continually growing smaller, closes over the lead. Then the heat should again be raised to liquify the slag, and allow the lead to settle, after which the scorifier is removed from the furnace, cooled or poured. Hammer the button as usual. The whole assay occupies from thirty -five to fifty minutes. Too much borax should not be added at first ; it is better to mix only a portion with the ore, and to introduce the rest as needed during the operation, wrapped in a small piece of paper. N TJK GOLD AND SILVEK." 71 GALENA SPECIAL METHOD. It is best to make a scor- ification assay of galena. If, however, it is desirable to make a crucible assay, a charge of nitre and carbonate of soda is employed, instead of roasting the ore. Twenty grammes of nitre per assay ton are required for pure gale- na, this amount diminishing as the gangue increases in quantity, or the sulphur is lessened. Employ the same weight of carbonate of soda as of ore. Make a prelimi- nary assay with an assumed charge, and modify the reg- ular charge according to the result. THE LEAD BUTTON. The lead button for cupellation must be malleable and of the proper size. A good cupel will absorb its own weight of litharge, but it is better to use a cupel one-third as heavy again as the button. The cupels in ordinary use weigh about eighteen grammes. If a button be too large it may be reduced in size by scorification ; there is less loss in this opera- tion than in cupellation. A brittle button may be due to arsenic, antimony, zinc, or litharge, and must be scorified before cupellation, with lead if necessary. If the button contains copper, it must be scorified until no more copper can be seen on hammering. If nickel is present the button cannot be cupelled ; this, however, will rarely occur. CUPELLATION. This operation differs from scorification in that the scoriae formed are absorbed by the cupel, leav- ing a pure bead of the precious metals. It is thus that we get rid of small amounts of copper, iron, arsenic, etc., in the lead button. The proportion of lead required to carry off impurities varies according to cir- cumstances. The operation of cupelling is conducted as follows : A cupel is wiped out with the fingers carefully, 72 FIKE ASSAYS. all extraneous matter blown out, and then placed in the muffle and heated until of the same temperature as the latter, when the button is gently placed in the cupel with a pair of forceps. The muffle is then closed by a door or a piece of lighted charcoal, to melt the lead. This done, the muffle is opened and the button, which at first appears bright and uncovered, is soon coated with a film of oxide moving in luminous patches over its surface, and being con- tinually thrown toward the edge Avhere it is absorbed by the cupel. The button gradually diminishes in size by oxidation and absorption and becomes more convex ; the patches be- come larger and move more quickly ; the last of the lead is absorbed, and the residue appears to revolve rapidly, becomes very brilliant, and is suffused with the tints of the rainbow ; then presents the appearance of the precious metals. The latter part of the operation is called the ' ' brightening ' ' of the button. Should the bead be large and composed of silver, it must be removed slowly from the furnace to pre- vent " spitting," by which portions of the metal are thrown off and lost. In case the bead is very large, say one hun- dred to three hundred milligrammes, it is well to cover it with a hot cupel. If the bead is not larger than the head of an ordinary pin the danger of spitting is slight and no great precaution need be taken in its removal. Two causes have been assigned for this spitting. First, That the molten silver absorbs oxygen from the atmosphere and gives it up at the moment of solidifying. Second, That by rapid cooling a crust is formed upon the outside which contracts upon the liquid interior. It has been suggested, that as the sprouting is caused by the giving out of the oxygen absorbed when the last traces of lead are being driven off, a piece of charcoal laid over the cupel during GOLD AND SILVEK. 73 this period would act as a preventive, and not interfere with the cupellatior,. It is well to raise the heat of the muffle just at the time of brightening, or to push the cupel into the hotter part to remove the traces of lead. Silver is sensibly volatile at a high heat, and the loss increases with the temperature. We must avoid the two extremes of a high heat and quick work, and a low heat and prolonged work. Of the two the latter is worse. The following are indices of favorable working : The muffle is reddish-white, the cupel red, the fused metal luminous and clear, the lead fumes rise slowly, and the litharge is com- pletely absorbed by the cupeL The heat is too great when the cupels are whitish, when the fused metal is seen with difficulty and the scarcely vis- ible fumes rise rapidly. The heat is too low when the fumes are thick and fall, and when the unabsorbed litharge forms lumps and scales about the button. The degree of heat may be greater according as the lead is poorer in silver. By bearing this in mind the assayer can often hasten the operation without detriment. Too strong a current of air cools the cupel and oxidizes the lead faster than it can be absorbed. Too slow a cur- rent prolongs the operation and increases the loss by volati- lization. Sometimes the material in. a cupel becomes solidified in the midst of an operation, stopping further action. This is called "freezing," and is occasioned by a production of litharge more rapidly than it can be absorbed by the cupel, infusible scoriae due to a cold furnace, or an excess of foreign oxides. It can sometimes be remedied by rais- 74 FIKE ASSAYS. ing the lieat of the muffle ; or if the accident be due to foreign oxides, an addition of pure lead may be made to the assay. In either case the results are unreliable. An assay that has passed well, furnishes a bead well rounded, crystalline below, and readily detached from the cupel. If the bead contains lead it is brilliant below, and does not adhere at all to the cupel. If it exhibits rootlets, the results are inaccurate, and must be rejected. WEIGHING THE BEAD. The bead of gold and silver is detached from the cupel with pincers, thoroughly cleansed with a small brush and weighed. INQUARTATION AND PARTING. The separation of gold from silver is termed parting. It is effected by means of nitric acid, which dissolves the silver and leaves the gold. It is essential that a certain relation should exist between the amount of gold and silver in the alloy. If there be too little silver it win not dissolve completely, but Avill be so enveloped in the gold as to escape the action of the acid. If too much silver be present, the gold obtained will be so fine and light as to occasion loss in washing. The amount of silver added should be from two to three times the weight of the gold. The assayer must judge by the color of the bead as to the proportion of silver contained, and if it be too small he must supply the deficiency with pure silver, which is kept on hand in thin foil. The bead and silver are well fused together to effect complete distribution of the silver. The fusion may be made on charcoal by the blowpipe, or by wrap- ping the bead and silver in a cornet of lead foil, and cupel- ling it. GOLD AND SILVER. 75 The bead is then flattened on an anvil, and treated in a porcelain capsule (Fig. 27), with nitric acid, C. P. FIG. 27. 1.16 sp. gr. (21 Beaume). Enough acid is added to cover the bead and heated gently. The acid must be free from chlorine, which would precipitate the silver. When all action of the first acid has ceased, decant, and care- fully add some fresh acid of 1.26 sp. gr. (32 Beaume). Heat for several minutes, pour off the acid and wash thor- oughly with distilled water, and dry the residue of gold. It is well to apply a high heat before attempting to remove the gold, to render it adherent. The gold residue is de- tached with a knife, transferred to a cornet of lead, cupelled and weighed. Or if perfectly clean and yellow, weighed without cupellation. WEIGHING THE GOLD. The gold obtained is weighed as described, and the assay is completed. CALCULATION OF RESULTS. The milligrammes, of pre- cious metal obtained per assay ton of ore, correspond to Troy ounces in the ton of two thousand pounds Avoirdu- pois. There is therefore no trouble save in the case of an ore which contains metallic scales, and the method em- ployed when such is the case, can be shown by an example. The sample presented for assay weighs 485 gms. Pulver- ized and sifted in a box sieve (Fig. 18) it gave : A. Sifted ore 480. gms. B. Metallic scales 5. " There will be a little loss in sifting, but if the operation be done carefully it need not be taken into account. A. SIFTED ORE. 10 grammes gave by crucible assay : Gold 4. mgs. Silver, after deduction of the silver in the litharge, 14.3 " 76 TIKE ASSAYS. Hence, the total precious metal in the sif tings is : Gold ................................... J X48()=:192 Silver ................................. X480= 686>4 B. METALLIC SCALES. These melted with lead gave a button of, say 60 gms., which was rolled out and 10 gms. taken for cupellation, which yielded : Gold .................................. 2.6 mgs. Silver ................................ 500.0 " Hence, the total precious metals in residue must be : Gold ............................. _jyL x60 = 15.60 mgs. Silver ...................... - Total : Gold in sif tings ............................... 192.00 mgs. " " residue ............................... 15.60 " " " ore taken ............................ 207.60 " Hence : J 4S^ X 29. 166 (value of an assay ton) = gold per assay ton of original ore. Silver in total siftings ........................ 686.40 mgs. " "residue .............. ............... 3000.00 " " " ore taken ........................... 3686.40 " Hence : ~AQK~~ X 29. 166 (value of an assay ton) = silver per assay ton of original ore. REMARKS. All ores or minerals of gold or silver can be GOLD AXD SILVER. 77 assayed by 3ither (a) crucible, or (5) scorification. The latter is preferable whenever it can be used, as it yields higher results and requires no preliminary assay. No oxy- sulphurets are formed, or if formed, are decomposed during the operation ; whereas, in the crucible assay they may es- cape decomposition even at a white heat. It is better for zinc and copper ores, the action of scorification being oxidizing, that of the crucible reducing ; in the latter case much copper will enter the lead button that, in the former, would be oxidized and enter the slag. Instead of roasting, another method for arsenical and antimonial ores is, ore 1 A. T., litharge 2 A. T., soda 1 A. T., ferro- cyanide of potassium 35 gms., and a cover of salt. The button must be scorified. The matte over the button should be saved and put in the scorifier as it may carry silver. In scorifying mattes of this kind, and ores which contain much sulphide of iron and copper, the addition of a little nitre and soda bi-carb. (mixture of equal parts of each) will sometimes make the scorification work better and give a good slag. The mixture should be added to the scorifier in the furnace if the slag seems thick and lumpy, care be- ing taken not to slag the scorifier over by adding too much. Instead of the above mixture, a little litharge might be added with good results, but as it is likely to contain sil- ver it should be weighed beforehand. After roasting an ore for crucible assay, if much iron is contained, add more charcoal than is necessary for a fifteen gm. button, as the ore has an oxidizing action. Sometimes, to avoid roasting, just sufficient litharge may be added to give the required button of lead, but this is not always safe. 78 FIKE ASSAYS. For ores containing, say 80 oz. of silver to the ton, the fol- lowing crucible charge has been recommended : Ore i A. T. Litharge | " Flour 6 gms. Soda, Bi-Carb 50 " Five or six Iron Nails. Borax . . cover of about 10 " If much copper is present in the ore, use more litharge ; if the sample contains lead, use less. Gold ores containing an excess of sulphide of iron and copper can be satisfactorily assayed by the following method : Ore 2 A. T. Soda, Bi-Carb 4 " Litharge 2 " Black Flux Sub 1 " Silica 2 " Iron Wire 12 loops. Salt cover. Mix the charge well and fuse in a hot fire. The slag should be glassy and the button malleable. If any matte is formed, collect and scorify down with the button, adding to the scorifier a little test lead and borax glass. Alloys which contain gold and silver may be fused in a scorifier with pure lead, and the button scorified down and cupelled, the resulting bead being carefully parted with nitric acid in the usual way. In weighing the gold which has been parted, if not previously cupelled, it can be trans- ferred to the scale-pan by means of a piece of pointed wood, great care being observed not to lose any. Ores of gold or silver containing tellurium can be assayed GOLD AND SILVEE. 79 by scorification or crucible, all difficulty arising from the presence of this metal being overcome by the use of plenty of lead or litharge (a cover of litharge has also been recom- mended). The amount must be increased in proportion to the richness of the ores. In the case of very rich ores, sixty to one hundred parts of lead may be employed in scorification with advantage. In such cases it will be found more advisable to use the larger sizes of scorifiers rather than to divide the charge up into several smaller ones. If an insufficient quantity of lead is used, the result will be a flat and ragged button after cupellation, and loss of precious metal owing to its failure to collect in one button. The tellurium must be driven off before the lead button is cupelled. There is probably no loss of gold from volatili- zation with tellurium, but the loss when it occurs, is from the subdivision of the gold button into minute particles on the cupel. The assay of gold and silver, if conducted carefully, is one of great accuracy. Duplicates of silver should agree to within one-half ounce Troy per ton of two thousand pounds, and for gold there should be no difference. This is true of all ores, though some are more difficult than others. Where the difference is greater than the above and accuracy is required, a third assay should be made. Tests made in duplicate of type ores gave : ORE. SILVER. GOLD. Gold ore, quartzose. . . .29. and 29.2 ozs. 10.4 and 10.4 ozs. Poor Galena 5.4 " 5.4 " none Zinc Blende 4.3 " 4.3 " Arsenical 55. " 55. " trace Antimonial 57. " 57. " none Impure mixture 28. 6 k ' 28. 6 " 2.4 and 2. 4 ozs. 80 FIEE ASSAYS. PLATINUM. &ymbol'Pt. SOURCES. Platinum is found native and associated with a variety of metals, such as palladium, iridium, osmium, copper, iron, gold, silver, etc. It occurs in alluvial deposits in grains, and sometimes in masses. ASSAY. The assay of platinum ores may be performed in two ways : (a) By fusion with lead. (&) By solution and precipi- tation. (See scheme, p. 121.) (a) Fusion with lead : Weigh and pulverize the sam- ple as finely as possible, then sift ; the metallic residue will contain most of the metal sought for. Weigh the residue and sif tings separately. 1. Sif tings charge 10 gms. in a small crucible with Litharge 50 gms. Borax glass 15 " Soda 30 " Charcoal 1 " Part of the soda should be mixed with the charge and part used as a cover. The proportion of fluxes may be varied to suit the gangue, so as to render the slag as fusible as possible. The litharge is reduced by the charcoal and alloys with the platinum and foreign metals, save irid-osmium, which will be found principally under the lead button. The lead button is then broken out, scorified with a little borax glass if too large, and cupelled at as high a temperature as pos- sible in an ordinary bone-ash cupel until it solidifies. The residue will be platinum, with a little silver, gold, etc. It may be purified by fusing in a crucible of cut lime, which PLATINUM. 81 is heated by coal gas, the combustion being supported by a current of oxygen. The lead retained in the unpurified button is about one- eighth to one-sixth of its weight. 2. Residue Fuse directly in a scorifier with pure lead and borax glass, cupelling the whole or a weighed portion of the resulting button if it be too large, as in 1. REMAKKS. In place of the method used for the sif tings, pure galena and iron wire might be employed, as in the assay for lead, other fluxes being added to suit. In the charge given for sif tings, twenty to thirty grammes of granulated lead in addition to the litharge can be used with advantage. Instead of cupelling the lead button containing the plati- num, alone, add four to five times the weight of the button in silver. This gives a result free from lead. The silver can afterwards be deducted in the calculation of the platinum. To determine the constituents of the ore which are of no value, charge two gms. of ore and ten gms. of granulated silver, well mixed, in a small crucible, the sides of which have been glazed with borax (melt some borax in it), over the mixture of borax and silver put ten gms. borax glass and one or two pieces of char- coal. Fuse and keep hot for some time ; cool, break, and weigh the button of alloy, after carefully removing the borax glass. Subtract the weight of the button from the sum of the weights of the ore and silver. The dif- ference equals the impurities in the ore. The button uan then be treated as an alloy of platinum. (See page 121.) 82 EIEE ASSAYS. ZINC. Symbol- -Zn. SOURCES. The principal ores of zinc are : Blende, sulphide (ZnS) Pure =67. 7 zino Smithsonite, carbonate (ZnCO 3 ) " =52. " Calamine, silicate (Zn,Si0 4 +H 2 0) " =53.8 " Willemite, silicate (ZnSiG 3 ) " =58.3 " Zincite, oxide (ZnO) " =80.26 " The last two occur associated with Franklinite. The first three are found alone or associated with the ores of other metals ; this being especially true of the sul- phide which often contains silver and is found with galena. ASSAY. The assay for zinc is attended with considerable difficulty, and is not accurate save when done in the wet way (See scheme, p. 122) ; zinc being volatile and easily oxidized. The amount of zinc may be estimated pretty closely by the following method, when no lead or antimony is present. Weigh out 10 gms. of the finely pulverized ore and roast it carefully, with the addition of a little carbonate of am- monia to decompose any sulphates formed. Weigh and mix the residue with Kaolin, or china clay (dry) 1.0 gm. Lime, " 0.5 " and charge the mixture in a charcoal-lined crucible, as in the iron assay, 'but not luting on the cover tight. Fuse at as high a temperature as possible for about two and one- half to three hours. Cool, and break the crucible open. The zinc will have been reduced and expelled. The residue, consisting of slag, and metallic globules if much iron was present in the ore, should be weighed and powdered. Sepa- rate the globules with the magnet, weigh them, and MEKCUKY. 83 add three-sevenths of their weight to that of the total resi- due for the oxygen lost by reduction. The total weight thus obtained deducted from that of the roasted ore and fluxes 1 (\ Q charged, and the difference multiplied by ^'^ gives the yield of metallic zinc. REMARKS. The kind and amount of fluxes used depend upon the character of the gangue of the ore treated ; fusi- ble ores not requiring any. The factors used to calculate the amount of oxygen and the metallic zinc are deduced from the table of atomic weights. (Page 14). The method given is not applicable to ores where zinc blende is associated with sulphide of lead, antimony, arsenic, etc., and carries gold and silver. The latter metals would be reduced and go into the buttons of iron, causing error in the calculation of the oxygen to be added. The method for practical purposes may prove sufficiently close, but where accuracy is required the wet method for zinc is preferable, and is recommended. MERCURY. Symbol-Hg. SOUKCES. The principal ore of mercury is cinnabar, sulphide (HgS 2 ). Pure =86. 27. It also occurs in the me- tallic state, alone and amalgamated with silver, gold, etc., and is sometimes found combined with chlorine. ASSAY. The determination of mercury is made by distil- lation. 1. Ore, sulphide or chloride. Charge Ore, finely pulverized 10 gms. Black flux, substitute 15 " MJNIVERSITY 84 FIEE ASSAYS. This should be mixed by rubbing together with water and drying. The dried mixture being charged in an iron, glass or clay retort, with a bent neck, the end of which is plunged in a glass vessel to collect the distilled metal. It is better also to wrap the neck of the retort with a damp cloth. The retort may be heated over a small charcoal furnace, or in any way by which the heat can be applied slowly, and the whole body of the retort heated, to prevent condensation of the mercury on the top. When after heating sometime, no more mercury comes over, the end of the neck should be lifted out of the water to prevent its being drawn over into the retort. The latter is allowed to cool slowly, and all adhering particles of the metal are brushed with a feather into the glass receiver, where they can be collected by boiling the water for a moment. The water is then decanted, and the mercury dried at the ordinary tempera- ture or with blotting paper and weighed on glass. Some- times lime or iron filings are used in place of an alkaline flux ; the object being, however, in any case to decompose the mercurial compound, freeing that metal, the substance used taking up the sulphur and chlorine. The determina- tions must be made in duplicate, and for very poor ores the pulverized sample should be first digested in muriatic and nitric acids (aqua regia), the solution filtered off and evaporated to dryness, and the dried mass which will con- tain all the mercury as chloride, treated by distillation, as described. 2. Metallic mercury and amalgams. Distill without the addition of any decomposing agent, otherwise conducting the operation as above. The heat used need not be so high, mercury being very volatile. For the treatment of amalgam, small iron crucibles, with an BISMUTH. 86 escape tube for the mercury, can be purchased of almost any apparatus dealer. REMAKKS. For all distillations the retort should be tight. For this reason glass or iron retorts are the best. Earthen retorts should be glazed. The operation should be conducted under a hood, care being taken not to inhale any of the fumes. The wet method is preferable for mercury ores. See Mitchell page 453, and Goody ear's translation of Bodemann and Kerl, page 207. BISMUTH. Symbol E\. SOUKCES. This metal is found principally in the metallic state, but it also occurs in combination with sulphur, oxygen, and tellurium, associated with lead and silver. Bismuth, like lead, possesses the property of causing the absorption of the metallic oxides in cupellation, and may be used in place of the latter, but is not recom- mended. ASSAY. In the assay for bismuth three cases may occur. a. The sample contains native bismuth. b. The sample is composed of bismuth with other sub- stances, or bismuth residue. c. The sample is an alloy. a. Determine as in the assay for ' ' antimonium crudum, " the bismuth being collected in the same way. b. Pulverize finely and charge : 86 FIKE ASSAYS. Ore 10 gms. Borax glass 30 " Soda 10 " Cyanide of Potassium 6 " Salt cover (See Mitchell, page 642). Fuse in a moderate fire in the same manner as for anti- mony. The resulting button must be tested for other met- als, and if any be present treated as an alloy. c. Determine by the wet assay. (See scheme, page 124). REMARKS. Bismuth melts at 268 C., and is volatile at a higher temperature. The assay for bismuth may also be made by fusing the pulverized and sintered ore (prepared by heating alone in a closed crucible) with a known weight (five to ten gms. ) of fine silver, black flux, and three to five gms. of iron wire, covering with salt. The button can afterward be treated as an alloy. Plattner's Manual of Blowpipe Analysis, page 459. Cyanide of potassium can be used alone for assaying bismuth ore, as in the assay for antimony, with good re- sults. A button of bismuth should not be hammered, as it is brittle. TIN. Symbol Sn. SOUECES. The most abundant ore is cassiterite, binox- ide (SnO 3 ), =78.67 per cent, when pure. It is found in veins and in the washings from the same under the name of stream tin ; sometimes it is associated with tungsten, tantalum, 87 or molybdenum. Tin also occurs as a sulphide in stannite, tin pyrites SnS 2 ), and rarely in the native state. In the United States, tin has been found only in small quantities, the ore not being rich enough to pay for work- ing. ASSAY. The treatment of tin ores in the laboratory is a matter of some difficulty for several reasons : 1st. The ore is often associated with a gangue, the con- stituents of which either form salts with the oxide of tin or alloy with the reduced metal from the same. 2d. The majority of the basic fluxes at the disposal of the assayer, combine with the tin and oxygen which may be present, forming stannates which go into the slag. 3d. Acid fluxes, especially silica, form compounds with the oxide of tin, and carry it into the slag. The influence of silica can be seen by the following table, given by Mitchell. The last line shows the yield of metal : Ore ........ 10. 00 10. 00 10. 00 10. QO 10. 00 gms. Silica ...... 2.50 6.60 10.00 15.00 30.00 " Tin ........ 52^ 43% 28% 10 fo none The fusion being made in each case with an equal quan- tity of black flux. 4th. Binoxide of tin is extremely difficult to fuse; it is insoluble even in concentrated acids, and although it is reducible by ignition with hydrogen, charcoal, etc., there is always danger of loss if the temperature be too high, as tin boils at a white heat, air being excluded to prevent oxida- tion. The various methods adopted for the assay of tin may be divided into four classes : a. For pure binoxide of tin. 88 FIKE ASSAYS. 5. For ore containing silica only. c. For very impure ores, sulphides, etc. d. For alloys from the dry assay or tin buttons. a. Treatment of the pure binoxide. 1. Charge ten gms. of ore finely pulverized, into a char- coal-lined crucible, lute the cover well on, then heat for twenty-five minutes, raising the heat gradually until it is almost white. Remove the crucible from the fire and tap it gently. If the tin be in small globules, flatten in a mortar, and pass through a fine sieve to separate from the charcoal. This method gives good results if the ore be per- fectly pure, but not otherwise. 2. Ore 10 gms. Cyanide of Potassium 40 " Use a small chalk-lined crucible, half of the cyanide be- ing placed in the bottom of the crucible, and the rest mixed with the ore. Cover with cyanide and then with salt ; fuse for fifteen minutes in a good fire, cool, break, and weigh. For binoxide and pure ores containing little silica, this method gives excellent results. Foreign metals may be removed before fusion by the process given on page 125, or the button may be treated as an alloy. b. Ores containing silica only. 1. Ore 10 gms. Fluor spar or cryolite. .. .10 to 20 " Mix well and charge in a charcoal-lined crucible, which is first covered with charcoal and then luted with clay. Heat- strongly for about one hour. Remove carefully from the fire and tap gently. Treat the button as an alloy after- wards. TIN. 89 2. Ore 10 gms. Hematite 3 to 8 " Cyanide of Potassium 40 " Mix and charge in a charcoal-lined crucible, cover with cyanide, and then with charcoal, lute and heat strongly from one-half to one hour ; remove, tap carefully, cool, and break. If the tin be in small buttons, collect by wash- ing with water to separate the charcoal, dry and weigh. Treat the button as an alloy of tin and iron. 3. Ore 10 gms. Oxide of Copper 10 " Black Flux Substitute 30 " Argol..... 2 " Borax glass 5 " Mix, and cover with salt and charcoal, in a chalk-lined crucible. Heat gradually, and finally to a white heat for one hour. Tap, cool and weigh. Treat the button as an alloy of copper and tin. Mitchell, page 411. 4. Ore 10 gms. Fluor spar 10 " Powdered charcoal 2 " Salt and charcoal cover. Mix well and charge in an ordinary chalk-lined crucible and use a hot fire. Treat the button as an alloy if it is not soft and malleable. This method is used in Cornwall with success. c. Yery impure ores, sulphides, etc. Weigh out and roast carefully, first alone and then with a little charcoal, to remove arsenic and antimony, adding finally carbonate of ammonia to decompose sulphates ; then treat by any 90 FIKE ASSAYS. method for ores containing silica. Testing the button foi iron, etc., or after roasting separate all associated metals by the method on page 125, and then fuse for tin. d. Alloys. As tin fuses at 228 C., it may be roughly separated from iron and metals of a less degree of fusibil- ity, by simply heating the alloy so that the melted tin can drain off. The only true way, however, is to treat by the wet method, page 127. REMARKS. - - The method by fusion with cryolite or fluorspar can be performed in a small charcoal-lined cruci- ble, with two gms. of finely pulverized and well mixed ore ; the crucible being luted and placed in a cupel muffle. The time required is about one-half hour, the muffle being filled with charcoal the last fifteen minutes, the door closed, and as high a heat obtained as possible. Assays of Durango tin ore containing silica by the above methods, gave the following average results : METHOD. TIN FOUND. a 2 67.0 to 76.0 per cent. 61 75.4 " " 62 74.0 " " b 3 67.1 " " b 4 74.0 " " b 1, b 2, and b 4 seem to be the only methods by which the tin is entirely reduced. If any foreign metals be present in the ore, they are likely to enter the buttons also, making them hard. COPPER. Symbol Cu. SOUKCES. The substances containing copper may be di vided into three classes : COPPEE. 91 1st. Pure or oxidized ores. 3d. Impure ores, or compounds of copper and otliei metals, with sulphur, arsenic, antimony, etc. 3d. Native copper and alloys. The most abundant ores of copper are : Native copper and its silver alloy Pure =100. copper. Cuprite, red oxide (Cu 2 O) " = 88.7 " Malachite, carbonate (CuCO 3 + CuH,O 2 ). " =67.3 " A ., ( carbonate and hydrate ) KK < Azunte, { (2CuC o 3+ CuH 2 O,). p" Chalcocite, copper glance (Cu 9 S) " = 79.8 " Chalcopyrite, copper pyrites (CuFeS 2 ) . " 34.6 " Erubescite, purple copper (FeCu 3 S 3 ). . . " =55.7 " Compounds with arsenic, antimony, lead, mercury, etc., the chloride, atacamite, and the silicate, chrysocolla. ASSAY. Copper can best be determined in the dry way, by roasting the ore with carbonate of ammonia and then fusing with arsenic and slagging off the other ar- senides combined with it. This method is exact but requires practice. It serves to determine be- sides the copper : lead, bismuth, cobalt, and nickel. The crucible used for the fusion is shown in Fig. 28. The assay can be conducted in the muffle fur- FIG. 28. nace, and involves the following operations : a. Roasting with carbonate of ammonia. b. Treatment of the roasted ore with metallic arsenic. c. Fusion with fluxes to collect arsenides in a button, and to separate lead and bismuth. d. Separation of the arsenide of iron, etc., from the arsenides of nickel, cobalt and copper. 9^ FIEE ASSAYS. e. Removal of the excess of arsenic and the separation of arsenide of cobalt. f. Fusion with gold and separation of arsenide of nickel. For details of the assay see method for nickel and cobalt, pages 99 to 102 ; also Watts' Dictionary of Chemistry Yol. II. , page 63. Other methods for assaying copper ores are in use, bul are not recommended on account of the liability of loss of copper in the process of refining ; one or two of them are, however, given below. Weigh out ten gms. of the ore and roast it carefully, if it contains sulphur, arsenic, etc., with three times its volume of fine charcoal or two or three grammes of fine, pure graphite. If the ore be very fusible, add five grammes of powdered hematite, mix the charge well before roast- ing, and line the pan or vessel with chalk or oxide of iron. Add carbonate of ammonia toward the end to decom- pose sulphates. After roasting mix the ore with Black Flux Substitute 20 gms. Borax glass 3 " Hematite (peroxide of iron) 10 to 20 " Cover with a mixture of ten gms. black flux substitue and three gms. charcoal, then with salt. Fuse in an ordinary chalk-lined crucible for twenty minutes. When perfectly fused, pour carefully into a mould. The resulting copper button must be refined by fusing it as quickly as possible in a shallow dish in the cupel muffle, with an equal weight of borax or less, and a little pure lead ; one to two grammes will generally be sufficient, and if the ore contains lead, its addition is unnecessary. When the copper is nearly refined it brightens somewhat like silver, only less distinctly, showing a peculiar green color. If COPPER. 93 the button is small, the assay is considered finished when it no longer fumes. Instead of the above, the following charge may be used in fusing. Ore 10 gms. Black Flux Substitute 25 " Argol 2 " Borax Glass 5 " Litharge 6 " Mix well and cover with salt and charcoal. Then refine as described. The action in the crucible is reducing. An alloy of copper and other metals, if present, being formed which must be refined. REMARKS. A good refining flux is Nitre 3 pts. Argol., 2J- " Salt 1 " Fuse together, pulverize, sift through a thirty-mesh sieve, and test its action on an alloy of copper before using. Iron prevents loss of copper in the slag, which is always the case when the latter has a red color, due to the sub- oxide of copper. If the button from the crucible is small the best way is to refine it before the blowpipe on charcoal, with a little boracic acid, blowing on the slag only, after the assay is once fused. If many ores are to be tested, the wet method will be found the most convenient and accurate, especially if the ores contain silver and gold, which, as they go with the copper, would materially affect the results by tending to increase the percentage. 94 FIKE ASSAYS. IRON. Symbol Fe. SOUECES. The following is a list of the principal ores of iron. Magnetic iron ore, oxide (Fe 3 O 4 ) Pure=72.41 iron. Red hematite or specular iron, oxide (Fe 2 O 3 ) " =70.00 " Brown hematite or limonite, oxide (2Fe 2 O 3 . 3H 8 0) " =59.92 " Spathic iron ore, carbonate (FeC0 3 ) " =48.22 " Ilmenite, titaniferous ore (FeTi0 3 + nFe 2 O 3 ) " =36.82 " Franklinite (Fe, Zn, Mn)(Fe. 2 Mn 2 )O 4 " = 48. 00 " Chromite (FeCr 2 O 4 ). Also Sulphides, as Pyrite, Pyrrho- tite, etc. ASSAY. It is required in the assay for iron not only to reduce the oxide to cast-iron, collect the latter in a button, and to form a fusible slag that will not retain any of the iron in combination or in pellets, but also to use such fluxes and adjust them, so the results will indicate the character of the ore, quality of iron it will yield on smelt- ing, etc. The oxide is reduced by carbon, and we employ for this purpose crucibles lined with, brasque, which is a composition of four parts finely pulverized charcoal to one of molasses. (To prepare this, see page 28.) The lining serves as a support for the crucible, which under the high heat, is apt to soften. In making up the charge we may have, (1) Ores of unknown composition, and (2) Ores previously an- alyzed. The assay in both cases gives a clue to the na- ture of the slag, the iron that may be obtained from the ore, and the character and proportion of the fluxes to IKON. 95 be added in the blast furnace. In the first case we obtain the additional information of the approximate percentage of iron. 1. Ores of unknown composition. In the assay of an ore the composition of which is un- known, we make several preliminary assays, and if satis- factory results are obtained we make another assay with a charge modified according to the indications of the best pre- liminary assay. Preliminary assay charges : 1. 2. 3. 4. Silica 2.5 1. 4.0 2.5 to 0. gms. Lime 2.5 4. 1.0 2.5 to 3. " Ore 10.0 10. 10.0 10.0 " 1 is employed for the purer ores containing very little gangue ; 2, for ores containing silica ; 3, for ores contain- ing the carbonates of lime, magnesia, protoxide of man- ganese, etc., calcareous hematites and spathic iron ; 4, for ores containing silica and alumina, clay iron stones, black band, etc. The principle involved is that of furnishing a base for an acid, and vice versa. The charge, therefore, depends upon the acid or basic nature of the gangue of the ore. Ores containing titanium require the addition of fluor- spar to the charge in quantity varying from 0.5 to 10 gms* 2. Ores previously analyzed. Good results are obtained from a charge proportioned to yield a slag corresponding to a blast furnace cinder, hav- ing the composition R S O 3 . SiO 3 + 2(3RO. SiO 3 ), as given by Percy. E, 2 O 3 represents alumina, and EO, lime, magnesia, and other bases. Its approximate percentage composition is as follows : 96 FIKE ASSAYS. Silica 38. j / 2J parts. R,O 3 (alumina) 15. > or about Formulae. 154 TABLES AND KEFEKENCES. TABLE OF VALUES FOR GRAIN WEIGHTS. sg>s 5-0 O sg>s g-0 O 2. 5>S 5 -o g TO ^ Jf 1-3 CD p' OQ CD g ngfc QT5 CD JfO k^CD (o z O o H j p & O o "~3 ^ P ^ ^ A S" ^ dQ 3 o M 3* ^ T3 *< o ^< C* CtJ QTQ *S QD p *"* To' |a pT CD r!' i o ^ s o 3 ,-K CD QG 50^3 c 3 P? o> fa 1 Is, So 1 i r CD 1 o II i"a o o o II 3 i a O 3 || :^ o s. Ore Assay No. 1. Gold oz. Silver oz. Total oz. Gold $5 Silver Total No. 2. Average oz. oz. oz. $ $ 1 oz. oz. oz. $ $ $ Sample Averaged on Ore Dated No. Signed 160 TABLES AND REFERENCES. SILVER AND GOLD SCORIFICATION ASSAY. Ore Marked Mineral Character Charge Ore Test Lead Borax Glass Silica or Glass No. of Scorifiers Scorification Slag Color Appearance Button Character Weight " after 2nd Scor. " " 3rd " " 4th " " 5th " Cupellation Gold in Ore Silver Silver in Test Lead Silver in Ore Eemarks No. 1. No. 2. A. T. A. T. Gms. Gms. Gms. Gms. < i Mgs. Mgs. " " REPORT. Contained in 2,000 ft>s. Ore. Assay- Gold Silver Total Gold Silver Total No. 1. oz. oz. oz. $ $ $ No. 2. oz. oz. oz. $ $ $ Average oz. oz. oz. 8 I 8 $ Sample Averaged on Ore Dated No. Signed BLANK EEPOETS. GOLD BULLION ASSAY. 161 Alloy Marked Copper Assay Bullion Lead Gold and Silver Base metal Assay proper Cupellation Bullion Silver Lead Copper Parting Cornet Silver retained Gold No. 1. Mgs. Gins. Mgs. a No. 2. Mgs. Gms. Mgs. a Mgs. Gms. a Mgs. a Gms. a Mgs. u Mgs. a u a Remarks EEPOET. Assay No. 1. No. 2. Average Dated No. Gold. Silver. Base Metal. Fine Thds. Thds. a u u u u u Signed 162 TABLES AND KEFEKENCES. SILVER BULLION ASSAY. Alloy Marked Cupellation Bullion Lead Silver Correction for Loss Fineness Volumetric Assay Bullion Normal Salt solution Decimal " " Total Decimal Silver solution Total Salt Equivalent in Silver Fineness Kemarks No. 1. Mgs. Gms. Mgs. Gms. 100. c.c. Gms. Thds. No- Mgs. Gms. Mgs. Gms. 100. c.c. Gms. Thds. Assay No. 1. No. 2. Average Dated No. EEPOET. Silver. Copper, &c Fine. Thds. Signed PROBLEMS AND QUESTIONS. 163 PROBLEMS AND QUESTIONS. 1 . What would be the best method of assaying a poor argentiferous sulphide of antimony for the silver ? 2. Explain the derivation of the assay ton, and calculate its weight for England and the United States. 3. An iron ore contains by analysis Silica 6.61 per cent. Alumina. . . .0.55 Calculate the charge for Percy's slag. Lime 4.68 Magnesia 1.37 " Answer : Silica 0.894 Kaolin 1.890 Lime 2.395 4. What is the theory of the lead assay ? 5. Describe the operations, and the theory of the scorifi- cation assay for silver ores. 6. What would be the best method of treating a pure iron pyrites containing gold ? 7. Mention the reagents employed in the crucible assay of silver ores, and the action of each. 8. Given an ore containing, gold 0.0925 grains in 6 Troy oz.; silver, 0.046 grains in 6 Troy oz.; which has a reducing power of 2=14 of lead. Calculate the best charge for assay, and give the value in ounces per ton. Answer : Roast. Charge of ore, 4 A. T. Silver 0.466 oz. Gold 0.936 " 9. 50 gms. of an ore, sifted, gave 2.59 scales and 47.40 gins, siftings. The scales, melted down with lead, gave a button of 35 gms. 10 gms. of this button yielded, silver 164 TABLES AND REFEKENCES. 4.5 mgs. ; gold 1.3 mgs. J A. T. of the sif tings yielded silver 6.95 mgs. ; gold 1.85 mgs. Required the value of the original ore in ounces per ton. Answer : Silver ............................... 28.96 oz. Gold ................................ 7.92 " 10. An alloy cupelled, gave 0.9848 gms. of silver in one gramme. Added in the volumetric test : Normal salt, 100 c.c. ; decime salt, 5 c.c. ; decime silver, 2 c.c. : 99.7 c.c. normal salt 1 gm. of pure silver. Calculate the weight of the alloy taken for volumetric assay, and the fineness. Answer : Weight taken for assay =1.01 54 gms. Fineness ..................... 994.71. 11. Calculate the charges for the following reducing powers, the charge of ore being one assay ton : (2 gms. = 16.5), (2 gms. =0.42), (2 gms. =5.2), (2 gms. =1.2). Answer : 1. Roast. 2. Argol, 1.5 gms. 3. Nitre, 11.5 " 4. Right size. 12. An ore contains : Lead ....................... 15 per cent. Also sulphur, antimony and iron in quantity. How should it be assayed ? 13. One gramme of an alloy, cupelled and parted, gave silver, 984.2 mgs. ; gold, 8.4 mgs. Wet assay. PEOBLEMS AND QUESTIONS. 165 Added normal salt 100 c.c. Decime salt 13 " " silver 3 " Strength of normal, 101.2 c.c.=l gramme pure silver. Cal- culate the fineness of the bullion. Answer : Fineness =983. 28. 14. Describe the reactions that take place in the nickel and cobalt assay, arsenide method. 15. Name eighteen principal reagents used in the various assays, giving composition of each. 16. Describe the advantages and disadvantages of the tin assay, lead assay, iron assay, etc. 17. Mention the ores of lead, tin, iron, silver and gold. 18. A sample presented for assay gave, on being pulver- ized and passed through a sieve of 80 meshes to the linear inch, the following weights : A. Sifted ore 1458.32 gins. B. Scales of metal 40.75 " C. Total 1499.07 gins. It being known from the mineralogical composition of the sample that it was a rich ore, J A.T. was taken for an assay of the sifted portion (A). The residue of metallic scales, etc. (B), was scorified with test-lead, and yielded a button weighing 60.35 gms. This button was rolled out, and two average samples of 10 gms. each, were cupelled. The following results were obtained from the complete assays : 166 TABLES AND REFERENCES. A. SIFTED ORE. CRUCIBLE ASSAY. One-third assay ton, 9.722 gms. yielded : 1. 2. Average. Au + Ag 0.19355 0.19275 0.19315 Au (by parting) 0.00025 0.00025 0.00025 0.19330 0.19250 0.19280 Agin litharge 0.00067 0.00067 0.00067 Ag in ore 0.19263 0.19183 0.19213 The litharge yielded one milligrm. silver per assay ton, and two-thirds assay ton were employed. B. METALLIC SCALES. 10 grammes of the scorified button yielded. 1. 2. Average. Au + Ag 5.0625 5.0620 5.0622 Au (by parting) 0.0020 0.0020 0.0020 Ag 5.0605 5.0600 5.0602 Ag in test lead none none none A -i 09-1 q A. Sifted ore 1458.32x^^0 =28.819 Ag. y. i & B. Metallic scales.. 40.75, ^^x 60. 35 =30. 538 Ag. C. Total ore ....... 1499.07 59.357 T'l Ag. 29166.66 x ^' B ^I =1154.71 oz. per 2000 Ibs. A. Sifted ore ..... 1458.32 x ' 05 =0.0375 Au. B. Metallic scales.. 40.75, x 60. 35=0. 0121 Au. C. Tofca] ore 1499.07 0.0496 T'l Au, 29166.66 x ^^=0.9707. per 2000 Ibs. PROBLEMS AND QUESTIONS. 167 EESULT PEE 2000 LBS. ORE. Silver 1154.71 oz. at $1.29 $1489.58 Gold 0.97 oz. at $20.67. . . 20.04 Total bullion 1155.97 oz. $1509.62 19. An ore of nickel, cobalt, and copper gave the fol- lowing results from five gins, of the original sample : a. Weight of arsenides from fusion 2.467 gins. b. " arsenide of cobalt, nickel, and copper 1.246 " c. " arsenide of nickel and cop- per 0.542 " d. " " button of copper and gold . . 0. 421 " e. " " gold added 0.150 " Calculate the per cent, of nickel, cobalt, and copper in the original ore. Answer: Cobalt 8.659 per cent. Nickel 1.993 " Copper 5.420 " 20. Given, an ore of zinc : 10 gms. of crude ore gave of calcined ore 8.33 gms. ^ (Kaolin 1.00 " Fluxes added... Lime>> 0.40 Total 9.73 Weight of iron buttons from fusion 4.53 " " slag " " 1.63 Total 6.16 Calculate the oxygen for the iron, the oxide of zinc con- tained in the ore, and the equivalent per cent, of zinc. Answer : Oxygen 1.94 per cent. Oxide of zinc... 16.60 Zinc.. 13.32 " C? THE UNIVERSITY 168 TABLES AND KEFEREISTCES. 21. Given an ore of iron which contains more than is required of one of the ingredients of the slag, or the silica introduced with the kaolin, when added to that already present, increases the quantity beyond the necessary amount. Required to make up a new slag with the excess : The ore 10 grammes ore T? or mi,wi Difference to contains p. c. contain be added. Silica 25.96 2.596 2.50 0.096 Alumina 6.92 0.692 1.00 0.308 Lime, MgO, etc. 7.59 0.759 3.00 2.241 Kaolin (A1,O,, SiO 2 i) required to furnish 0.308 A1 2 O 3 0.616 Silica contained in 0.616 kaolin 0.308 Silica in excess in ore . . . . 0.096 Total excess of silica 0.404 Add fluxes to make up with this excess more slag of com- position as above : -RAmiir^ Difference to Kequned. be added Silica 0.404 2.50 2. Alumina 1.00 1.000 Lime, mag., etc 3.00 3.000 Kaolin required to furnish 1.00 A1 2 O 3 2.00 Silica contained in 2.00 kaolin 1.00 Silica to be added, 2.096-1.00 1.096 Total material to be added to the charge : Silica 1.096 Kaolin . . . .0.616 + 2.00 2.616 Lime 2.241 + 3.00.. 5.241 22. a. How much water should be added to 6 litres of a salt solution to make it normal, when 98.6 c.c. of the solu- tion precipitates 1 gm. of pure silver 3 b. How much salt should be added to 6 litres of a salt REFEBENCES ON ASSAYING. 169 solution to make it normal, when 100.6 c.c. precipitates 1 gin. of pure silver ? Answers : a. 85.09 c.c. b. 0.1938 gins. REFERENCES ON ASSAYING. Barstow, Wm. : "Sulphurets; treatment, etc.;" San Francisco, 1867. Bodemann, Th., n. Bruno Kerl : " Anleitung zur Berg, und Huttenmannischen Probirkunst ; " Clausthal, 1857; 3d edition. Bodemann, Th., and Bruno Kerl : " Treatise on the As- saying of Lead, Copper, Silver, Gold, and Mercury ; " trans- lated by W. A. Goodyear ; New York, 1865. Blossom, T. M.: "On Gold, Silver, and Iron ;" see Amer- ican Chemist for 1870. Budge, J. : "Practical Miner's Guide ;" London, 1866. Byland, A. : "Assay of Gold and Silver Wares." Kerl, Win. : "A Practical Treatise on Metallurgy ; " ed- ited by Wm. Crooks and Ernst Rohrig. Kerl, Bruno: " Metallurgische Probir-kunst ; " Leipsic, 1866. Lieber, O. M. : "The Assay ers' Guide." Mitchell, John: "Manual of Practical Assaying;" ed- ited by William Crooks ; New York, 1872. Mitchell, John : " Manual of Practical Assaying ; " Lon- don, 1868. North, Oliver: " Practical Assay er ;" London, 1874. Overman, Frederick: "Practical Mineralogy, Assaying and Mining ; " Philadelphia, 1863. 170 TABLES AND REFERENCES. Silversmith, Julius: " Handbook for Miners, Metallur- gists and Assay ers." Knapp, F. : " Chemical Technology." Watts, Henry: " Dictionary of Chemistry;" London, 1866-72. See under the heads of the different metals. See also the annual reports of the directors of the English and United States mints, which contain much valuable in- formation. Besides the above, almost all works on the chemistry of the metals treat more or less of the assay of the same. The books mentioned have been given independent of any merit ; there are doubtless many others equally good. APPENDIX. f OF THE ( "O l^T I V E R S T T ~V I MANIPULATION, FORMULAE, >TCU 173 ^^LgAjJFORNJ^^^ MANIPULATION, FORMULA AND CALCULATION. The various operations of weighing, mixing, charging, etc., have already been described under their appropriate heads ; and it only remains to give a few hints on opera- tions peculiar or necessary in the performance of assays in the wet way, or analyses. PRECIPITATION. This operation is the sudden conversion of a dissolved body into the solid state, either by a modi- fication of the solvent, or decomposition with the formation of a new compound. The separation of a precipitate is generally aided by the action of heat and agitation. Porcelain and glass vessels will be found the best. In adding the necessary reagent pour in carefully until the precipitate ceases to form ; unless otherwise directed, an excess of the precipitant should generally be avoided. FILTRATION. This operation has for its object the sepa- ration of the solid particles suspended in a fluid, from the same. Various substances might be used as a filter, but the best is unsized paper, which is prepared for the purpose by cutting a circular form and then folding it into halves and quarters, so that it will just fit into a funnel and not project above the rim. For quantitative work, the prepared Swedish filter paper will be found the best ; it should be cut into circular pieces as described, which should be of a constant size to suit the funnels ; and the ash left by burn- ing one of the same carefully determined. As a rule, it will be found best to moisten the paper with water before filter- ing, and to pour on first the fluid portion of the substance to be filtered. DECANTATION. This is simply a substitute for filtration, the clear liquor being poured off from the precipitate. To effect this the liquid is permitted to run down a glass rod 174 APPENDIX. held against the spout of the vessel, which should be in- clined gently, so as not to shake up the precipitate. WASHING. This is best effected by using a glass flask, fitted with a cork, in which is inserted two glass tubes, one reaching to the bottom of the flask, and bent to any desired angle on the outside, the end being drawn to a point. The second tube reaches to just below the cork, and is also bent on the outside, but not drawn to a point ; by blowing in this tube the water is expelled through the first. Warm water will be found the most effective. The completeness of the washing may be tested by evaporating a small por- tion of the filtrate on platinum foil, and noting the residue. EVAPORATION. Porcelain dishes are the best for this operation ; but if the solution is to be evaporated to dry- ness it should be conducted over a water bath. A sand bath may be used, but care should be taken to prevent loss by spattering. IGNITION. The washed precipitate, after being dried, is ignited to completely expel all moisture, or convert it into a constant or weighable substance. This is best conducted by transferring to a weighed porcelain crucible, and burning the filter paper over it, either on the inverted cover, or by wrapping it in a coil of platinum wire and holding it over the crucible. The ash should be heated until white, or nearly so. The whole operation must be conducted over a piece of glazed paper until the filter paper is burnt, after which the crucible and contents should be heated over a burner or lamp ; gently at first. After ignition the crucible and con- tents should be cooled in a desiccator, to avoid absorption of moisture from the air. FORMULAE AND CALCULATION. The general methods of calculation have been given under the various assays, but it will be well to bear in mind the following : BLOWPIPE ANALYSIS, ETC. 175 1st. The equivalent of the compound found is to the equivalent of its constituent which is sought as the weight of the compound is to the weight of the constituent. 2d. The weight of the substance taken for assay is to the weight of the constituent sought as one hundred is to the per cent, of thp same. The equivalents (atomic weights) will be found in the table on page 14. The equivalent of a compound being equal to the sum of the equivalents of the constituents of the same. Thus, H 2 SO 4 (sulphuric acid) is equal to 2 + 32 + 64=98. The equivalent of hydrogen (H) being 1, sulphur (S)= 32, oxygen (O)=16. Two parts of hydrogen being 2, four parts of oxygen =64. BLOWPIPE ANALYSIS, APPARATUS AND REAGENTS. The assayer will find that a knowledge of the proper use of the blowpipe will prove a great saving of time and labor, by enabling him to more fully understand the char- acter of many substances presented for assay, which he could not otherwise determine, save by qualitative analysis. The first and most important thing in blowpipe analysis is to learn to blow and breathe at the same time, without removing the mouth from the instrument or interrupting the blast ; this can be done by filling the mouth with air and breathing through tlia nose, expelling some of the air into the mouth at each breath. The blowpipe flame consists of two distinct portions. 1st. The outside or oxidizing flame. 2d. The inner blue cone, the point of which is the hottest part of the flame' its action is reducing. This flame is obtained by putting the point of the blowpipe about one-quarter of the way into the lamp flame. The true reducing flame is entirely yellow, the blowpipe point being held just outside of the lamp flame. 176 APPENDIX. The substance to be tested should be finely powdered and treated : 1st. On charcoal, in both flames. This is best done by making a small hole in the right- hand corner of the coal, nearest the lamp, placing a little of the substance in the same, and testing first with the oxi- dizing and then with the reducing fiame, noting the action of each, the formation of fumes, their odor, the fusibil- ity of the substance, and the color of the coating formed, its distance from the assay piece, etc. The holes in the charcoal should be bored on the edge of the grain to avoid splintering. Blow across the coal. 2d. If the substance treated gives off fumes on charcoal, test a little of it in a closed and open tube successively, first alone, and then in the closed tube with a little carbo- nate of soda. Note the coating or mirror formed, the color and odor of the fumes ; also decrepitation, change of color, etc. Heat over an alcohol lamp. 3d. Test the substance with the borax, salt of phos- phorus, and soda beads successively ; this may be done on platinum wire or, if the substance be metallic, on charcoal. To make the proper sized bead, bend the end of the wire into a loop on the point of a sharp pencil, dip it into the reagent and melt before the blowpipe until a clear, good bead is formed, then add the substance and heat, first in the oxidizing and then in the reducing flame, observing the color and appearance of the bead in each flame. 4th. Apply special tests, as the color of the flame, the action of nitrate of cobalt on the coat formed on charcoal ; adding the cobalt solution and then heating. If the sub- stance is not metallic, its fusibility and the color of the flame can best be noted by testing in the platinum-pointed for- ceps. By moistening the material with hydrochloric acid, and bringing it into the tip of the blue cone of the blow- pipe flame, the coloring power is heightened. To get the methods of performing the above operations the following substances will serve as type examples : BLOWPIPE ANALYSIS, ETC. 177 To test blowing and flames : oxide of manganese and molybdic acid, binoxide of tin on charcoal. To test on charcoal : lead and antimony. To test in the matrass or closed tube : cinnabar and ar- senic. To test in the open tube : stibnite, sulphur, and arsenic. To test with the beads : Borax bead, oxide of copper. Salt of phosphorus bead, oxide of copper and sesqui- oxide of iron. Soda bead, manganese and chromium compounds. CHAEACTERISTIC TESTS. Potassa, colours the flame violet ; best seen through a blue glass, which shuts off the soda flame. Soda, reddish-yellow flame ; solution colors red litmus paper blue. Lithia, carmine-red flame. Ammonia, colors red litmus-paper blue, pungent odor. Baryta, burnt with alcohol gives a yellowish -green flame ; enamel- white bead with borax. Strontia, crimson flame ; reaction with borax bead, same as baryta. Lime, colors the flame feebly red, becomes caustic and glows when heated. Magnesia, gives with nitrate of cobalt a pale flesh-color, after long blowing ; best seen in platinum-pointed forceps. Alumina, gives a fine blue color with nitrate of cobalt. Silica, in S. Ph. bead gives a semi-transparent skeleton floating in the glass. Oxide of antimony, on charcoal, is reduced and gives white fumes and coat, also greenish-blue flame. The fused metal smokes after the removal of the blowpipe. Arsenious acid, with soda on charcoal, gives white fumes and garlic odor. In the closed tube, a metallic mirror. Oxide of bismuth, on charcoal, is reduced to metal, and 178 APPENDIX. gives an orange-yellow color. A compound of bismuth treated with a mixture of sulphur and iodide of potassium, on charcoal, gives red sublimate of iodide of bismuth. Oxide of cadmium, coats the coal with a reddish-brown powder and variegated tarnish. Oxide of chromium, with soda in the O. F. gives a yel- low glass; in R. F., green on cooling; with S. Ph. bead, emerald-green. Oxide of cobalt, on charcoal, becomes magnetic. With borax and S. Ph. beads, smalt-blue glass. Oxide of copper, metallic button on charcoal. With borax bead, green glass, blue when cold ; red in R. F. ; with salt, chloride of copper is formed, which gives blue flame. Oxide of gold, with borax on coal, easily reducible to metal. Protochloride and bichloride of tin, when mixed, pro- duce, even in very dilute solutions of gold, a purple pre- cipitate, known as purple of Cassius, which is insoluble in dilute acids, and may therefore be produced in very acid solutions. The gold solution should first be mixed with bichloride of tin, and the pro to chloride then added drop by drop. " A very delicate method of making this reaction is as follows : Sesquichlo- ride of iron is added to protochloride of tin, until a permanent yellow color is produced ; the solution is then considerably diluted. The gold solution hav- ing been likewise very much diluted, is poured into a beaker, which is placed on a sheet of white paper ; a glass rod is dipped into the tin-iron solution, and afterwards into the gold solution, when, if even a trace of the precious metal is present, a blue or purple streak will be observed." (Abel and Bloxam.) Oxide of iron, on coal, becomes magnetic. Borax bead, red to yellow on cooling ; in R. F., bottle-green ; with tin on charcoal, vitriol-green. Oxide of lead, reducible to metal on charcoal with sul- phur-yellow coat and blue flame. Oxide of manganese, with soda, on cooling, bluish- green. With borax, amethyst bead, colorless in reducing flame. BLOWPIPE ANALYSIS, ETC. 179 Oxide of mercury, volatile on charcoal, metallic mirror with soda in closed tube, which unites with gold-leaf, giv- ing it a white color. Molybdic acid, with S. Ph., yellowish green, and color- less when cold. The bead on coal becomes green on cooling. Oxide of nickel, on charcoal, yields a magnetic powder. Borax bead, reddish -brown in 0. F. Gray and cloudy in R. F. Oxide of silver, on charcoal, reducible to metal. With borax, opalescent or milk-white glass. In O. F. on char- coal, brown coat. Oxide of tin, reducible on charcoal to metal. Gives yellow coat, white when cold. With cobalt solution on charcoal in 0. F., gives a bluish-green color. Titanic acid, with salt of phosphorus bead in R. F., a fine violet color. Oxide of zinc, yellow coat on coal, white when cold. With cobalt solution, green in 0. F. Chlorine, with oxide of copper in borax bead, a fine azure-blue flame. Iodine, with soda, or better, bi-sulphate of potash in matrass, violet fumes, which turn starch paper blue. Green flame with oxide of copper. Bromine, with bi-sulphate of potash in matrass, reddish- yellow vapors ; turns starch paper yellow. Fluorine compounds, etch glass, when mixed with a little sulphuric acid and warmed, the glass being placed over the mixture. Carbonic acid, acid reaction, turns lime-water white. Sulphur, burns on charcoal with a blue flame with odor of sulphurous acid ; better in open tube. A sulphide, when fused with soda, and the mass moistened with water, gives a black stain when placed on clean silver foil. Boracic acid, yellowish-green flame, fusible. Selenium, in O. F., gives odor of decaying horse-radish. Tellurides and Tellurium. The following is a most delicate and conclusive test for tellurium : Treat a small 180 APPENDIX. portion of the mineral in 0. F. on a clean piece of porce- lain (a broken bit of an evaporating dish or other fragment will answer). If tellurium or a telluride be present, a coat- ing will form, but may not be seen on the white porcelain. If, however, it is moistened with a drop of pure concentrated sulphuric acid, the presence of tellurium is revealed by a brilliant carmine tint (sulphate of tellurium). The same reaction may be obtained on charcoal, but when this mate- rial is used, it becomes necessary, after moistening the coat- ing with the acid, to play upon it gently with the flame. In this case, the brilliant coloring appears but for an in- stant, whereas, in the first case, the porcelain has already become heated, and the carmine tint remains for some time, and only fades gradually away. SCHEME FOE BLOWPIPE ANALYSIS. The substance may contain As, Sb, S, Se, Te, Fe, Mn, Cu, Co, M, Pb, Bi, Ag, Au, Hg, Zn, Cd, Sn, Cl, Br, I, CO 2 , SiO 2 , HNO,, H.,O, &c. 1. Treat on Ch. in the O. F., to find volatile substances, such as As, Sb, S, Se, Te, Pb, Bi, Ag, Zn, Cd, &c. a. If there are volatile sub- stances present, form a coat- ing, and test it with S.Ph. and tin on Ch. for Sb ; or to distinguish between Pb and Bi, using the R. F. 1). If there are no volatile substances present, divide a part of the substance into three portions and proceed as in A. Sb gives gray bead, clear on long blowing ; with tin the bead becomes gray or black. Bi clear and colorless when hot, blackish-gray and opaque on cooling ; with tin the glass becomes clear ; Pb cloudy and dark, but never quite opaque ; by continued blowing the oxide is reduced and the glass becomes clear. In testing for Bi the antimony must be driven off first. BLOWPIPE ANALYSIS, ETC. 181 If Sb is present it is not necessary to look for Bi, and vice versa. These two substances are very rarely found together. The same is true of Pb and Bi. 2. If As, Sb, S, Se 5 and Te are present, roast a large quantity thoroughly on Ch. in the O. F. Divide the sub- stance into three portions, and proceed as in A. A. TREATMENT OF THE FIRST PORTION. Dissolve a very small quantity in borax, on platinum wire in the O. F., and observe the color produced. Various colors will be formed by the combination of the oxides. Saturate the bead and shake it off into a porcelain dish. a. Treat the bead on Ch. with a small piece of silver or gold, in a strong R. F. Lead can be used instead. b. Fe, Mn, Co, &c., re- main in the bead. If the bead spreads out on the Ch., it must be collected c. M, Cu, Ag, Au, Sn, Pb, Bi are reduced, and collect- ed by the silver or gold but- ton. to a globule by continued Remove tlie bntton from blowing. !tlie bead wMle hot> or by Make a borax bead on pla- tinum wire and dissolve in it breaking the latter when cold on the anvil between a , -i a , i~l > 1/V/JLVI. \JJ-L UJ-Lyj c*-iu. -i-i- KJ^J u 1 1 \s^s*-m. some of the fragments of the | care fully preserving bead, reserving the rest f or , ^^ fra accidents. d. If Co is present, the bead will be blue. If a large amount of Fe is e. If only Fe and Mn and no Co be present, the bead will be almost colorless. present, add a little borax to f^ Look here for Cr, Ti, prove the presence or absence M o , and W. Mo will give a of Co by diluting the bead, ] cloudy-brown or black with the cobalt color being more the borax bead in the R. F. intense. If Mn is present, the bead me uuictx ueiiu. .in m<^ * ? owing to the molybdic acid being reduced. Cr gives when treated on platinum yellowish-green with borax wire in the O. F. will become i bead ; yellow with soda bead ; dark violet or black. emerald-green with S. Ph. 182 APPENDIX. Ti in S.Ph. bead, gives fine violet color ; best seen with tin on charcoal. W, a fine bine color, under the same con- ditions. g. Treat the button on Ch. in O. F. with S.Ph. bead, removing it while the bead is hot. n. If M and Cu are present, the bead will be green when cold. If Ni only yellow. If Cu only blue. Prove Cu by treating the S.Ph. bead with tin on Ch. in the R. F., the bead becomes red on cooling. M and Cu may be separated by fusing them with a gold button of equal weight and oxidizing with borax or S.Ph. The M is dissolved first in the borax glass. i. For Ag and Au make the special test No. 8. B. TREATMENT OF THE SECOND PORTION. Drive off the volatile substances in the 0. F. on Ch. Treat with the R. F., or mix with soda, and then treat with the R. F., for Zn, Cd, Sn. If a white coating is formed, test with cobalt solution and observe the color. Tin gives greenish-blue, zinc, green. If Zn is found, it is not necessary to look for Sn, and vice versa, as they very rarely occur together. Cd. gives a brown coat and variegated tarnish. C. TREATMENT OF THE THIRD PORTION. Dissolve some of the substance in S.Ph. on platinum wire in O. F., observe whether Si0 2 is present or not, and test for Mn with nitrate of potassa, and soda. If Mn be present the bead will be bluish-green. 3. Test for As with soda on Ch. in the R. F., or with dry soda in a closed tube. On charcoal it gives garlic odor ; in the tube, a metallic mirror. 4. Dissolve in S.Ph. on platinum wire in the O. F. (if the substance is not metallic and does not contain any S) and test for Sb on Ch. with tin in the R. F. See 1, a. BLOWPIPE ANALYSIS. ETC. 183 5. Test for Se on charcoal in O. F. ; it gives a horse- radish odor. 6. In the absence of Se, fuse with soda in the R. F. and test for S on silver foil. By moistening the fused mass and letting it stand on the foil the latter turns black if S be present. In the presence of Se, test in open tube, as it would interfere with the reaction. 7. Test for Hg with dry soda in a closed tube ; a me- tallic mirror is formed. 8. Mix some of the substance with test lead and borax glass and fuse on Ch. in the R. F. Cupel the lead button for Ag. Test with nitric acid for Au, dissolving the silver ; cupel the residue with a little pure lead. 9. Test for Cl and I with a bead of S. Ph. saturated with oxide of copper. Cl gives blue flame ; I, intense green. 10. Test for Br with bi-sulphate of potassa in a matrass, gives brownish-yellow fumes. Turns starch paper yellow. 11. Test for H 2 O in a closed tube ; drops collect on the interior. Test these with blue and red litmus paper. 12. Test on platinum wire, or in platinum -pointed for- ceps, for coloration of the flame, moistening with hydro- chloric acid first. 13. Test for C0 2 with hydrochloric acid, passing the gas evolved over lime-water. 184 APPENDIX. 14. Test for HNO 3 with bi-sulphate of potassa in a ma- trass ; yellow-colored fumes, and acid reaction. 15. Test for Te in an open tube ; forms a grayish-white sublimate which fuses to clear, transparent drops when strongly heated. Te burns with a bluish-green flame. Try also special test with sulphuric acid. The above scheme is essentially the same as the one used by the students of the School of Mines, New York, pre- pared by Prof. Thos. Egleston. A few additions and changes have been made so as to obviate reference to works on blowpipe analysis. The abbreviations 0. F., R. F., Ch., and S. Ph., stand respectively for oxidizing flame, reducing flame, charcoal? and salt of phosphorus. BLOWPIPE APPAEATUS. Blowpipe with platinum jet, in three pieces, with cylin- der to catch the moisture. Trumpet mouth-piece. Lamp, for blowpipe, with swivel and stand, four pieces. Lamp, alcohol, with brass cover ground to fit ; for light- ing large lamp and heating open tubes, etc. Forceps, steel, nickel plated (Raynor's), for testing color of flames, cleaning platinum blowpipe tip, etc. Forceps, brass, to handle small buttons, beads, etc. Forceps, steel, for lamp to raise wick. Plyers, cutting, for clipping minerals, sampling, etc. Plyers, flat nose (nippers) for quantitative work, handling lead buttons. Holder, cupel with two cups and one mould, for cupel- ling lead buttons. BLOWPIPE ANALYSIS, ETC. 185 Holder, charcoal, with platinum ring and shield, gene- rally employed for quantitative work, but useful for fusing samples of ore with fluxes, etc. Holder for evaporating dish, with triangle, for parting, making solutions, etc. Holder for chimney, to concentrate the flame of alcohol lamp, when heating capsules, etc. Holder for platinum wire, with six wires, for making bead tests, or flame tests, if the substance is very fusible. Holder for matrass, to hold tubes, etc. Hammer, for breaking slag, pounding buttons, etc. ; for chipping minerals it should have a sharp back. Anvil, for breaking slag, pounding buttons, etc. Borer, charcoal, club shape, to make holes in charcoal for the assay piece, etc. Borer, charcoal, four-cornered, to enlarge coal crucibles for quantitative work or fusions. Borer, charcoal, with spatula, for quantitative work, use- ful in boring out coals. Capsule, mixing, brass, gilded, to mix charges for quan- titative work. Spatula, mixing, steel, for preparing charges. Spoons, ivory, two, for measuring out reagents, etc. Brush, assay button, for cleaning buttons before weighs ing. Charcoal saw, to shape charcoal. Tray, for coal, arranged to hold the various sizes em- ployed. Tray, for dirt, made of japanned tin. Scissors, for lamp, to trim, etc. Knife, small, with long thin blade. Magnifier, with two lenses, to examine minerals. Magnet, bar with chisel edge, to test for iron, nickel and cobalt. Form for paper cylinders, for quantitative work. Test lead measure, Small camel' s hair brushes, for cleaning. 186 APPENDIX. Moulds, for making crucibles, coals, and capsules. Steel mortar, for crushing minerals ; should be well ten> pered. Agate mortar and pestle, for pulverizing. A small glass wash-bottle. Small platinum spoon for fusions. Porcelain streak plate, for testing minerals. Scales for quantitative work, a bullion balance will do as well ; also a measuring scale for buttons (Plattner's). Glass matrasses, closed and open tubes, porcelain dishes and cap- sules, and clay cylinders to support the coal crucibles. Test tubes, one or two funnels, glass rods, and filter papers, will also be found serviceable. For quantitative work the assayer will also require : Coal crucibles and capsules. Clay Square coals and covers. Total cost of complete outfit $75.00. BLOWPIPE KEAGENTS. Carbonate of soda, pure, dry, and free from sulphur. Neutral oxalate of potassa or ammonia, crystals. Cyanide of potassium, pulverized. Not absolutely neces- sary. Iodide of potassium, crystals. Borax and borax glass, pulverized. Salt of phosphorus (phosphate of soda and ammonia). Bismuth flux, one-half sulphur and one-half iodide of potassium, powdered and mixed. Mtre, crystals. Bisulphate of potassa, pulverized. Vitrified boracic acid, in small fragments. Nitrate of cobalt, in solution. Test lead, finely granulated. Tin, in foil best. BLOWPIPE ANALYSIS, ETC. 187 Iron. Wire in pieces of J" to 1" long. Gold, pure, and in foil. Arsenic, metallic, powdered. Test papers, blue and red litmus ; cut in strips. Salt, pulverized and dry. Sulphur, flowers of sulphur best. Fluorspar, fine and dry. Silica, ground and ignited. Oxide of copper, pure and fine. Chloride of silver, in paste ; also nitrate of silver. Starch meal. Graphite, fine and pure, or powdered charcoal. Concentrated sulphuric, nitric, and muriatic acids. Acetic acid and ammonia. Carbonate of ammonia in powder. Charcoal cut in blocks 3" x |" x J". Sifted and washed bone-ash. Starch paper, to test for Br, I, etc. Citric acid, tartaiic acid, and iodine, may prove useful in testing minerals ; as they can be carried in the dry state, and the acid solutions made when required. GENEKAL EEMAEKS. To clean a dirty platinum point hold it in the flame of the alcohol lamp with the platinum-pointed forceps. To clean platinum wires, heat, and plunge into muriatic acid while hot. To break small pieces of mineral, wrap in paper, tin foil, or cloth, before hammering. To trim the wick of blowpipe lamp, cut even with the lamp and raise with one point of the steel forceps ; never pull the wick up with the forceps, To light the usual blowpipe lamp, where a heavy oil is used, direct the flame of an alcohol lamp against the wick until it ignites. 188 APPENDIX. CHEMICAL APPARATUS AND REAGENTS. (Qualitative and Quantitative.) APPARATUS. GLASSWARE. Lipped Beakers, nests of six. Plain " " Flasks, 1 oz. " 16 " (pint) u 24 " 3 Litres. " 50 c.c. (measured) " 100 " " i Litre, a -i u u " Specific Gravity. Pipettes, 10 c.c. 100 " Gay Lussac Burettes. Carb. Acid Apparatus (We- therelTs). Carb. Acid Apparatus (Geis- sler' s). Wash Bottles, 4 oz. u u g u " u 16 " (pint) u u 24 " Wash Bottle Tubes. Funnels, No. 1 (1^ inch) No. 2 (2f u ) No. 3 (3i u ) No. 4 (4 " ) No. 5 (5 u ) " No. 6 (6 u J Watch Glasses. Convex Covers, 3 inch. " " 3A u Convex Covers, 4 inch. 6 ( Flat Covers, 3 < u u 4 ' " 5 ' " u (thick)5 ' Pieces Blue Glass. Desiccators (covered) Bottles, corked, 1 oz. u u 2 " 3 u 4 u 6 u u Glass stoppered, -J oz, u Ito6 " Reagent Bottles for desk. Glass Rods and Tubes. Calcium Chloride Tubes. Funnel Tubes. " u (stop cocks) Ignition Bulb Tubes. U Tubes, set of four. " u No. 1(5^ inch) " " No. 2 (6 " ) " u No. 3 (12 u ) Test Tubes, 4 inch. Specimen Tubes. Retorts, J Litre. i. .REAGENTS. PORCELAIN. Porcelain Mortars, 4^ inch. " Ex. Pestle for. Evap. Dishes, nests of 6. 12 inch. Casseroles, a a a n Crucibles, a a If 2 PAPER. Packages Cut Filters, 3 inch. Sheets Swedish Paper. " Glazed Paper. Note Books. Gum Tickets. METAL. Ring Stands. Files, Triangular. Steel Forceps. " (bent) | Wire Triangles. '' " (covered) 2 inch, u u u o u Scissors. Pieces Wire Gauze. Bunsen Burners or Lamps. W^ater Baths. Watch Glass Clips. Sand Baths. Set Filter Patterns. Platinum Foils, H inch. < i ti O U Wire, 10 feet. Crucible, f oz. Gas Stoves. Blowpipes. Clamps. SUNDRIES. Filter Stands. Test Tube Racks. Rubber Tubing, black, inch. u " white,i " it U U 1 U Corks. Sponge Probangs. Horn Spatulas, 4 inch. r? Towels. Test Tube Brushes. Clay Chimneys. Reagent Bottles (extra). Total cost of apparatus, say $60.00. REAGENTS. Hydrochloric Acid (concent.), HC1. Hydrochloric Acid (dilute), HC1. Mtric Acid (concent.), HJSTO 3 . Mtric Acid (dilute), HNO 3 . Sulphuric Acid (concent.), H 2 SO 4 . Sul- phuric Acid (dilute), H 2 S0 4 . Hydrosulphuric Acid, H a S. 190 APPENDIX. Potassic Hydrate, KHO. Sodic Carbonate, Na 2 CO 3 . Am- monic Hydrate, (NH 4 )HO. Ammonic Carbonate, (NH 4 ) 2 C0 3 . Ammonic Chloride, (NH 4 )C1. Ammonic Sulphide, (NH 4 ) 2 S. Ammonic Oxalate, (NH 4 ) 2 C 2 O 4 . Baric Chloride, Bad,. Hy- dro-Di-Sodic Phosphate, Na 2 HP0 4 . Potassic Ferrocyan- ide, K 4 Cf y = 4KCy . FeCy 2 . Potassic Ferricyanide, K 6 Cf dy = 6KCy.Fe 2 Cy 6 . Ferric Chloride, Fe 2 Cl 6 . Acetic Acid, HC 2 H 3 O 2 . Calcic Sulphate, CaS0 4 . Mercuric Chloride, HgCl 2 . Stan- nous Chloride, SnCl 2 . Sodic Acetate, NaC 2 H 3 O 2 . Am- monic Sulphate, (JNH 4 ) 2 SO 4 . Potassic Bichromate, K 2 Cr0 4 . Cr0 3 . Magnesic Sulphate, MgSO 4 . Lime Water, CaH 2 2 . Calcic Chloride, CaCl 2 . Plumbic Acetate, Pb(C 2 H 3 O 2 ) 2 . In- digo Solution, C 8 H 5 NO.SO 3 . Argentic Nitrate, AgNO,. Pla- tinic Chloride, PtCl 4 . Ammonic Molybdate, (NH 4 ) 2 MoO 4 -(-Nitric Acid. Ammonic Sulphocyanide, (NH 4 )CNS. Ba- ric Carbonate, BaCO 3 . Sodic Carbonate (dry), Na 2 C0 3 . Borax (crystallized), 2NaBO 2 .B 2 3 +10H 2 O. Phosphorus Salt (crystallized), Na(NH 4 )HPO 4 +4H 2 O. Sodic Nitrate (crystals), NaN0 3 . Potassic Cyanide (powder), KCy^KCN. Cobaltic Nitrate, Co(NO 3 ) 2 . Ferrous Sulphate (crystals), FeSO 4 . Test Papers (blue, red and yellow). Common Sul- phuric Acid, H 2 SO 4 . Common Hydrochloric Acid, HC1. EXTRA REAGENTS. Alphabetical order: Alcohol (absolute), C 2 H 5 .OH. Alcohol (common), C 2 H B . OH. Ammonic Fluoride, (NH 4 )F. Arsenic (metallic), As. Battery Acid (dilute), H^O^. Battery Fluid, 10 parts H 2 O ; 3 parts H 2 SO 4 ; 1 part K 2 Cr 2 O 7 . Benzol (pure), C 6 H 6 . Benzol (common), C 6 H 6 . Bromine Water, Br+H 2 0. Chlorine Water, C1 + H 2 O. Chloroform, CHC1 3 . Distilled Water, H 2 O. Iron (wire and plate), Fe. Lead (bar and foil), Pb. Mer- cury, Hg. Nitro-Hydrochloric Acid (aqua regia), HNO 3 -f- 3HC1. Oxalic Acid (crystals), H 2 C 2 O 4 . Potassic Iodide (crystals), KI. Potassic Carbonate (dry), K 2 CO 3 . Potassic Nitrate, KNO 3 . Potassic Nitrite, KNO 2 . Potassic Chlorate, KC1O 3 . Potassic Permanganate (crystals), K 2 Mn 2 O 8 , Silver (foil), Ag. Sodic Acetate (crystals), NaC 2 H 3 O 2 . Sulphur (roll), S. Sulphur (flowers), S. Zinc (bar and sheet), Zn. ASSAYEE'S OUTFIT. 191 ASSAYER'S OUTFIT, INCLUDING THE MOST NECESSAEY AETICLES. ARTICLE. APPROXIMATE COST Ore Balance $22.00 Bullion Balance 65.00 Weights, Assay Ton and Gramme 18.00 Muffles, J doz., at 75 cents each 4.50 Hessian Crucibles, 50 nests, small- fives 1.50 Scorifiers, 500 at 2 cents each 10.00 Cupel Mould 3.50 Scorification Mould 1.00 Crucible, Scorification, and Cupel Tongs 3.00 Hammers, 2 at 75 cents 1.50 Pokers and Scrapers 1.50 Cutting Shears, Vise and Anvil 5.00 Files, Chisels ? Saw, Hatchet, etc 2.50 Iron Mortars, large and small 3.25 Plate and Rubber 10.00 Box Sieve 2.00 Tin Sampler 2.00 Sieves, wood frames, 80-mesh 1.50 Mixing Scoop 40 Reagent Bottles, glass stoppered 8.00 Parting Bottles 90 Bottles for Samples, corked 2.00 Ring Stands and Alcohol Lamps 1.40 Wash Bottles, two, one large, one small 90 Horn Spatulas, Spoons, etc .75 Parting Flasks, Annealing Cups, etc 1.50 Porcelain Mortar 1.00 Glass Rods, Tubes, Funnels, Beakers, etc 2.00 Note Book, Towels, Brushes, etc 1.50 Extra Apparatus, such as Iron Pan for mechanical assay, Pipettes, etc 5.00 Blowpipe, Blowpipe-lamp, etc 6.50 192 APPENDIX. Hammer and Anvil, small $1.65 Button Brush 45 Scissors, Knife, Magnifier, and Magnet 2.20 Forceps, steel and platinum 1.75 Test Tubes and Specimen Tubes 1.00 Filter Papers, Test Papers, etc 1.50 Platinum Wire, Foil, etc 2.00 Bone- Ash, for making cupels 5.00 Litharge 1.80 Soda, Borax, etc. 1. 50 Test Lead 6.00 Nitre, Argol, Potassium Cyanide 4.00 Nitric, Muriatic, and Sulphuric Acids 6.00 Extra Reagents, not mentioned ; . . 5.00 Total $219.45 NOTE. The preceding estimate is based on the assump- tion that the ores to be assayed will be those of gold and silver, and that the method of assay will be, as a rule, the scorification process. No allowance has been made for labo- ratory fittings or furnaces. An ordinary mason can build with brick and clay all that is necessary at a very small cost ; cupel furnaces can, however, be purchased for about $35, packed for shipment. The prices given are, of course, somewhat approximate, and the list a little full, but if it serves as a guide for the beginner it will answer its purpose. SPECIAL METHODS FOR GOLD ORES AND ALLOYS. a. MECHANICAL ASSAY. Crush 4 to 5 pounds of the sample, and pulverize in a mortar until it will pass through a 40-60-mesh sieve ; then wash in a " Batea," which is a conical pan, about 20 inches in diameter and 2^ in depth ; or in a Russia sheet-iron pan. SPECIAL METHODS FOR GOLD ORES AND ALLOYS. 193 The latter should be 18-20 inches at the top, 14 inches at the bottom, and sides 5 inches, sloping at an angle of 30-40. The material to be washed should first be stirred up with water in the pan, and the sand and dirt removed by a slight circular jigging motion, the operation being conducted under water ; to hold which a small tub will be found con- venient for laboratory purposes. The gold and heavier particles of the ore will collect in the bottom of the pan, and can sometimes be separated by drying, and then blowing off the sand, better than by continued washing. A mag- net may prove of service here. If the ore is very poor, a " color" of gold only may be visible at the end of the operation. b. AMALGAMATION ASSAY. The amount of free gold present in an ore can be deter- mined by grinding say 18-20 pounds of the finely pulve- rized ore with about 2 to 3 oz. of mercury and a little sodium- amalgam. If mercury alone is employed, the addition of a small piece of cyanide of potassium will be found bene- ficial. The ore should be ground up with water first, so as to form a thin pulp, and the mercury added by squeezing it through chamois skin. This serves to break the mercury up, and facilitates its dissemination through the mass of the ore. The whole should then be ground for 2 or 3 hours ; this can be done on a concave plate, with an iron rubber, or in a hand " Arrastre." To separate the amalgam formed, thin the mass with water, and shake in a pan or small settler of some kind. The lighter particles of dirt and ore float off, and the amalgam finds its way to the bottom of the vessel, where it can be collected. To separate the gold, etc., squeeze through chamois skin or fine leather, and heat the residue in a small iron retort, condensing the mercury which passes off. Scorify and cupel the gold. 194 APPENDIX. c. CHLOEINATION PEOCESS FOE THE ASSAY or SULPHU- EETS CAEEYING GOLD. Weigh out 6 oz., and roast in an iron pan coated with chalk or clay, until no smell or fumes can be perceived ; cool, grind, and roast again at a strong red heat, then moisten slightly, and transfer into a glass cylinder 8 to 10 inches high, and 2 to 3 inches in diameter, which is pro- vided with a side-opening near the bottom, through which the chlorine gas can be introduced. The top of the cylinder should be fitted with a rubber cork and glass escape tube, which passes into a second cylinder, containing blotting paper or shavings moistened with alcohol. The ore is placed in the first cylinder, on a bed of broken glass or quartz, which should be deep enough to prevent the fine ore from choking up the opening through which the gas enters. The chlorine is generated in a Florence flask, from a mixture of binoxide of manganese (pulverized), salt, and sulphuric acid, then passed through a wash bottle, as in the case of sulphuretted hydrogen (see Fig. 26), to wash it, and into the cylinder containing the ore by the lower side-open- ing already mentioned. The flask containing the mixture for the generation of chlorine should be gently heated, to facili- tate the evolution of the gas, and the process continued for about two hours ; after which the generating flask can be disconnected, the rest of the apparatus being allowed to stand for some time, especially if the ore treated contain galena, zinc blende, etc. To extract the chloride of gold : lixiviate with warm water, acidulate the solution with a little muriatic acid, and precipitate with sulphate of iron ; warm and allow to stand until clear. Filter, wash, and dry the gold. Scorify filter and gold together, and cupel button. d. TOUCH-STONE ASSAY OF ALLOYS. Alloys of gold can be examined for their approximate fineness by means of the touch-stone and nitric acid. The SPECIAL METHODS FOE GOLD OEES AND ALLOYS. 195 touch- stone is a piece of black smooth, stone (Basalt or Slate), on which the alloy to be tested can be rubbed. The streak left is then tested with nitric acid in comparison with the streak left by an alloy of known fineness. Test acid is sometimes employed instead of nitric acid ; this is a mixture of nitric acid (sp. gr. 1.34) 98 pts., muriatic acid (sp. gr. 1.17) 2 pts., and distilled water, 25 pts. The standard alloys are called touch-needles, and consist of pure gold, alloyed in various proportions with copper, silver, or both metals. They are much employed by jewel- ers, and can be purchased ready for use. Where the amount of gold is small, the touch-stone method is less accurate ; but for rich alloys and prelimi- nary work, it may prove useful. A sharp eye and practice is, however, required to arrive at anything like good re- sults. e. SPECIFIC GEAVITY METHOD FOE THE DETEEMINATION OF GOLD IN AN ALLOY. This method is based upon the principle that, in the French system, the volume of a solid is equal to its weight divided by its specific gravity, and that since one cubic centimetre is equal to one gramme, the volume of a solid in cubic centimetres is equal to the weight in grammes of the water it displaces, when weighed in water. Weigh the given alloy in air, and then in water. (See method for taking specific gravities, page 151.) Let a = Weight of alloy in air, in grammes. " b= " " " " water, in grammes. " c = Specific gravity of gold. " d= " " " the other metal. " x Weight of gold in the alloy. Then, a x= the weight of the other metal. - = the weight of water displaced by the gold in the c alloy, when weighed in water. 196 APPENDIX. o v g = the weight of water, displaced by the other metal in the alloy, when weighed in water. jr- Q v- - -1- -5 = a b = the total water displaced by the c ci alloy, or, to put the equation in another form : -, -, , dca deb ac (d-c) x = dca-dcb ac, orx = ^ . . Knowing the numerical values of a, b, c, and d, substi- tute in the equation, multiply, subtract, and divide as indi- cated, and find the value of x. By applying this method to a sample of gold quartz con- taining no impurities, such as pyrites, etc., the approxi- mate amount of gold in the specimen can be determined without crushing the same. The specific gravity of gold can be taken as 19.2, and quartz as 2.6, f. ASSAY OF SPECIAL ALLOYS OF GOLD. 1. Auriferous Tin. Oxidize in muffle. Scorify with Pb, 16 pts., Bx. Glass, 2J to 3 pts., and cupel button. 2. Auriferous Mercury. Distil if possible, and then sco- rify residue at low heat with say 10 pts. of pure lead. It is best to place the scorifier with charge in the muffle when the latter is cold, and let it heat up with the furnace. 3. Palladium-gold. Alloy with 4 times its weight of silver, and part with nitric acid. The palladium dissolves with the silver. 4. Rhodium-gold. Alloy with 4 parts of silver ; part with nitric acid, and fuse residue with bisulphate of potash ; treat with distilled water, and dry and weigh the gold resi- due from the fusion. If this is not pure, the fusion should be repeated. 5. Iridium-gold. Dissolve in nitric acid and hydrochlo- ric mixed (aqua regia) ; wash and weigh the iridium, which remains as a black powder. OUTLINE EXAMINATION SCHEME FOR ASSAY. 197 6. Gold containing platinum. Alloy with excess of silver, and part. See Platinum Scheme, page 121. 7. Gold Sweeps, etc. Burn, and if any particles of metal are apparent, sift, and assay scales and siftings separately. See Assay of Gold and Silver Ores. The pre- cious metals can also be separated by amalgamation, the tailings from amalgamation being assayed by the crucible method for gold and silver. The buttons from cupellation may contain platinum. OUTLINE EXAMINATION SCHEME FOR THE ASSAY OF ORES. The ore may contain : gold, silver, lead, antimony, bis- muth, tin, mercury, zinc, platinum, copper, iron, nickel, cobalt, sulphur, arsenic, tellurium, selenium, etc. Required to determine gold, silver, and useful metals. a. Inspect with magnifying glass. Test with blowpipe. Sample, pulverize and sift. If scales remain on sieve, test with magnet, as they may come from mortar ; if not mag- netic, weigh residue and siftings, and assay separately. Calculate value as directed, page 75. 5. Treat scales by scorification for gold and silver. For other metals, treat as an alloy, by wet methods. c. Charge: ore 10 gms., cyanide of potassium 30 gins., in No. 5 crucible, and fuse in a quick fire ; cool, break, and weigh. The button may contain lead, antimony, bismuth, tin, iron, etc. Test by blowpipe. If lead, determine by muffle method, page 58. If tin, antimony, or bismuth, duplicate by cyanide fusion. If iron, run charges for un- known ores, page 95. If tin is present, it will not be neces- sary, as a rule, to look for other metals. The button from the cyanide fusion should, however, be treated as an alloy. 198 APPENDIX. d. Run preliminary assay (see page 66) ; weigh lead button to determine reducing power (R. P.) ; cupel the lead button to determine approximate richness of ore. Notice the color of cupel, to decide as to presence of copper. The reducing power may be : No. 1. None. Ore probably poor, no S, As, Sb, etc. Charge : Ore 1 A T No. 2. Low. Ore rich or poor, little S, As, Sb, etc. x. Bead from pre- liminary cupella- tion large. No. 3. High. Ore rich or poor, much S, As, Sb, etc. x. Bead from pre- liminary cupella- Litharge. 50 gms. Soda.... 2 A.T. Run scor. assay : Ore i A.T. tion large. "Rl1H SsPAVlfi Pfl "I"! ATI Argol ... 2 gms. Bx. Gls..lO " Silica...! 15 " Salt . . . . cover. Use Hessian cruci- ble. Cupel button from fusion, or else run scorification as- Lead 40 gms. Borax Glass as required. y. Bead from pre- liminary cupella- tion small. Charge : Ore 1A.T. assay : Ore. 4 to ^ A. T. Lead ... 40 gms. Borax Glass as required. y. Bead from pre- liminary cupella- tion small. Qttj) Lcilvlll^Jj O feOUll- fiers, A.T. of ore in each. Combine and cupel buttons. Observe color of cupel after cupella- tion to detect pres- ence of copper, also JlTl'nPflT'ilTIPP O"f Litharge. 50 gms. Soda .... 1A.T. Silica .... 15 gms. Bx.Gl. 5-10 " Argol or nitre ac- cording to calcula- tion from reducing power. See page Roast 2 A.T. of ore, and charge with Litharge. 50 gms. Soda .... 1 A.T. Silica.... 1 " Charcoal. J-l gm. Salt cover bead, which may contain platinum, or non - oxidizable metals, if any were present in the ore. 67. Can run num- ber of scoriliers, % A. T. of ore each, and cupel united buttons, as in the case of No. 1. In Hessian cruci- ble, or use special methods, accord- ing to character of the ore. See pages 77-79. Can run number of scoriliers, as in No. 2. EULES FOR THE EXAMINATION OF A MINE. 199 e. If button freezes in process of cupellation, the furnace being hot, and the cupel unsaturated, copper, cobalt, nickel, tin, or platinum may be present ; cupel dark brown or red after cupellation, probably copper. 1. Determine cobalt, nickel and copper by arsenide method, pages 91, 99-102. 2. For platinum, treat button as an alloy, page 121. 3. Tin : run special assay, section c. f. If the preliminary blowpipe test indicates the pres- ence of mercury, zinc, or tellurium, etc., the ore should be run by scorification method for gold and silver. For ores containing mercury the heat should be very low, at first, and increased gradually. For tellurides, see page 79. The zinc and mercury may be determined by the meth- ods given on pages 82 and 84 ; or, if the ores are impure, by the wet way. NOTE. The above scheme is designed as a guide for be- ginners. The experienced mineralogist and assayer will generally be able to foretell the character of the ore, and select his method. RULES FOR THE EXAMINATION" OF A MINE. The following suggestions are taken from an article pre- pared by Mr. C. B. Dahlgren, and as an outline guide may prove useful. 1. THE HISTORY OF THE MINE (TRADITIONS) AND PERFECT TITLES. All existing data of the mine, as pamphlets, maps, ores, assays, records of work done, traditions, etc., should be collected and carefully studied. The mining laws of the district should be fully under- 200 APPENDIX. stood, so that a perfect title may be given to the pur- chaser. Usually this branch of the business goes through a lawyer's hands. In the United States, the usual transfer of a U. S. Patent or Recorder's Titles are sufficient. But, in Mexico (while well enough to have the former owner or worker's transfer), as no "fee simple" to mines exists, a mine must be worked and transferred in accordance with the " Mining Ordinances." 2. GEOGRAPHICAL POSITION MAP OF ROADS TO AND DISTANCES FROM RAILWAYS, STEAMERS, FREIGHT, ETC. Accurate maps should be prepared of the county, and mining district, giving the roads and distances to the near- est railway, steamers, or stages, or other lines of communi- cation or transportation. Statistics may be made out of freights, fares, time-tables, etc., from the proper relia- ble sources. 3. CLIMATE, WATER, FUEL, TIMBER, CHARCOAL, SALT, BUILDING MATERIALS (LIME, CLAY, STONE), SULPHUR, AGRICULTURAL RESOURCES, ETC. Careful observations should be made as to the climate, acres of fuel or timber, number of inches of water for mill- ing purposes, salt, sulphur, lime, building materials, agri- cultural resources, and supplies. Extravagant terms should be avoided, and precise and concise statistics alone taken and offered to the interested parties. 4. GEOLOGICAL STRUCTURE OF COUNTRY ROCK. The capitalist usually cares very little whether the mine is in diorite, quartzite, Silurian limestone, or is a contact vein, as long as pay ore is found in sufficient quantities to declare dividends. Do not, therefore, indulge in theories as to the formation of lodes, etc., but allude only to plain practical "facts" in a clear, concise manner. Sketches EULES FOR THE EXAMINATION OF A MINE. 201 and photographs will be very appropriate, usually convey- ing quicker and clearer impressions of the subject under examination than any amount of words. 5. SIZE AND STRUCTURE OF YEIN, WITH MAP OF ALL WORK DONE, IN PLAN, ELEVATION, AND SECTION, GIVING COURSE, DIP, WIDTH OF, AND CHARACTER OF WALLS, FAULTS, BREAKS, HORSES, SLIDES, CROSS COURSES, ETC. Correct and complete maps (in plan, section, and eleva- tion) should be made, giving the " course, dip, width of, and character of walls," faults, horses, slides, breaks, cross courses, ore seams, etc., and barren rock, water, all work done, etc. These will constitute a principal part of the examination ; they should be accompanied by sketches or photographs, and will show the " probabilities," as to the direction and force of the vein, which may rationally be indulged in. A plan for working the mine to best advantage (both immediate and future), may close this section. 6. CHARACTER AND QUALITY OF THE ORES (ASSAYS AND ANALYSES) AND GANGUE. A knowledge of the blowpipe will be of great use here for preliminary determinations (qualitative); while the assay furnace will be needed to settle the practical values of the ores in question. If possible (i.e., if facilities exist) an analysis will not be out of the way. We now come to the sampling. Careful samples of ores at any mill or reduc- tion works, and of tailings, or slags, should be made. They should be average samples. These should be assayed, and values per ton estimated as well as the per cent, reached in the working. Extreme caution should be exercised in order that no "salting" can be perpetrated. A careful record should be kept of these results. Having determined the ores, extracted, the mine should be visited and sampled in all its workings and croppings. A map should be taken 202 APPENDIX. along to mark the localities of the samples, and they should be carefully numbered and recorded, as well as the results, which should not be known to outsiders. Each sample should be sacked and sealed under the eye of the expert. Samples should be selected at random, to avoid the least possibility of collusion. 7 QUANTITY OF (PEOBABLE SUPPLY OF) PAY OEE (DE- DUCED FROM WORK DONE AND PROBABILITIES). This is the important part of the report, and for which it is made. The ore in sight will serve as one of the most important guides towards determining this fact. The other is the "probability" of a continuance of the ore, which experience and the result of observations made (see Section 5) will aid in determining. 8. COST OF MINING, HAULING, AND MILLING (WAGES, MATERIALS, FREIGHTS, ETC.) This depends on the price of labor, supplies, fuel and timber, freights on machinery and supplies, taxes, etc. This part of the examination is not a difficult one. In California, the cost of milling is from $2 to $4 per ton (whether by steam or water power), as also in the Black Hills. In Nevada (on silver ores), it runs from $9 to $20 per ton. Comstock, $11.00. Formerly the cost of quick- silver was a very heavy item, but at date it is very mode- rate. 9. METHOD OF REDUCTION (WHETHER BY AMALGAMATION, LIXIVIATION, OR SMELTING). The report should embody, at this point, a clear state- ment of the most efficient method of working the mine, and of reducing the ores. An analysis will determine whether by smelting, amalgamation (raw, or roasting), or by leaching. It may in some instances be found to be more profitable to concentrate, and ship the product. RULES FOE THE EXAMINATION OF A MINE. 203 10. AVOID BEING SALTED. Never lose sight of this injunction from first to last, but see to all the important points personally. 11. REQUISITES FOE A SUPEEINTENDENT. A superintendent should understand assaying, survey- ing, chemistry, machinery, and book-keeping, so that in no branch of the business can he be deceived. It is not possible for one man to do all of these things at once, but he should be able to inspect every department understand- ingly. A knowledge of law is sometimes very essential. ZETTNOWS SCHEME FOR QUALITATIVE AN ARRANGED BY H. CJ For the Students of the Sc Add hydrochloric acid to the solution, wash, and filter. Precipitate. Boil with water and filter. Filtrate. Add excess of dilute H 2 SO 4 and wash on filter. Solu- tion. Add H 2 S0 4 Preci- pitate Pb Residue. Treat with (NH 4 )HO Precipitate. Agitate with considerable cold water and filter. Solu- tion Add HN0 3 Preci- pitate Residue turns gray or black Hg Filtrate. Add excess of (NH 4 ) 2 C 2 4 Precipitate Ca Residue. Add (NH 4 ) HO and (NH 4 ) 2 C 4 H 4 8 digest and filter. Residue. Boil with Na 2 CO 3 , liter, wash, dissolve on filter with HC1, neutralize filtrate with (NH 4 )HO, and divide into two parts. Filtrate. Add HCC.HgO,) and K 2 CrO 4 Precipitate Pb 1st Half. Add excess of solution of SrS0 4 Predpitat Ba Second Half. Add excess of HoSi 3 Fl 6 and alcohol. Shake, filter, dilute with water, expel alcohol by evapora- tion, add solution of CaSO 4 , and after one or two minutes a precipitate Sr In this scheme regard is had to the following substances in aqueous solution : I. PbO, Ag 2 O, HgO H. CaO,BaO,SrO III. (NH 4 ^ 2 0,Na 2 0,K 2 O IV. Ap 2 O 3 ;As 2 O 5 ,Sb 2 O 3 ,Sb 2 O 5 ,SnO,SnO 2 ,Hg 2 O,CuO, V. FeO,Fe 2 O 3 ,Cr 2 O 3 ,Al 2 O 3 VI. MnO,MgO,CoO,NiO VII. ZnO Filtrate. Divide the solution into tw To i add BaH 2 O 2 and boil. Volatilized (NH 4 ) 2 O Test gas with HC1 and litmus. Solution Add excess (NH 4 ) 2 C0 3 and (NH 4 ) a C 2 4 warm, filter, evaporate to dryness, and ignite residue. Test on platinum wire in colorless flame ; in- tense yellow color in- dicates Na. Violet color seen through blue glass indicates K Place li Vola tilizec Collec spots cold porce lain and treal with NaCl Spot dis- solve As Spot do no dis- solve Sb Test also with AgNC N. B. To test for zinc mix filter, add NaHO in excess, a trate^ boil until all odor of (N solution, a cloud or precipitate YSIS WITHOUT THE USE OF H,S OR (NH^HS. [NGTON BOLTON, PH.D., 1 of Mines, Columbia College. equal parts, J and J. the solution in a Marsh's apparatus, add pieces of zinc and a strip of platinum foil, when but dnc remains heat 15 or 20 minutes, and throw contents of flask on a filter ; wash thoroughly. Residue. Treat with strong HNO 3 , and filter. Filtrate )il with a little HNO 3 and divide into two un- equal parts. Residue. i'ash, boil with (ICl and filter. Filtrate. Divide into two parts. Solu- Resi- 1st Half. Second Half. tion. due. Add HC1, boil, then it in a Add to SnCl 2 add excess of NaHo, 1 >lati- solution wash the precipitate,! num dish >itha >ce of num dish, boil Precipi- tate. on uicer witn water, i then with (NH 4 )HO containing NH 4 C1. zinc. with Hg 1 dark HC1, iot on e pla- inum indi- cates Sb filter and add HgCl 2 Preci- pitate. Sn Residue. Dissolve on filter in very little HC1 and add Filtrate. Divide into two parts. large quan- tity of H 2 O to the fil- 1st Half. Acidify with HC1 2d Half] Add excess of trate. A cloudy pre- cipitate in- dicates and add K 4 Fe 2 Cy 8 NaHO, a white gelatin- ous Bi Precipi- Precipi- tate. tate Cu Cd 1st Portion. Add KCyS Red Color Fe* Second Portion. Neutralize with (NH 4 )HO, add ex- cess of Ba CO 3 , agitate ten min- utes, filter and wash thoroughly. Precipitate. Boil in a porcelain dish with dilute H,S0 4 and filter. A.dd excess of NaHO to filtrate, a few drops of KMnO 4 and a little NH 4 C1, boil, filter, and divide the solution. 1st Half. Add some H(C 2 H,0 2 ) and Cr Half. Add excess of NH 4 C1 Filtrate. Add excess of dilute H 2 SO 4 , filter and saturate filtrate with (NH 4 ) 2 CO 3> warm, fil- ter, and wash. pitate * To determine de- of oxidation of , examine the ori- inal solution with : 4 Fe a Cy 6 and KCyS )rtion of the original solution with HC1,H 2 SO,, .oil. Add a little (NH 4 ) 2 CO 3 and NH 4 C1 to fil- 10 is expelled, and filter. Add K 4 Fe 2 Cy, to nates Zn. fate. Mix a por- tion with Na 2 C0 3 and NaNO 3 , fuse on platinum foil. Green color. Mn Dissolve another portion in HC1, neu- tralize with (NH 4 )HO add con- siderable NH 4 C1 and Precipi fate Ca Solution. Add Na 2 HPO 4 Preci- pitate Mg Solu- tion. Evapo- rate to dryness, dissolve in HC1, add KN0 2 and H(C ? H 3 2 ), filter. Preci- pitate Co Solu- tion. Add NaHo Preci- pitate Ni = LIBRXSy 'UNI OF INDEX. A. PAGE ADJUSTING BALANCES 19 Agents, Sulphurizing 44 Alloys and Gold Ores, Special Me- thods 192 Gold 147 Gold, Lead for Cupel lation. . . 155 Gold, Special Assay of 196 Silver 146 Touch-stone Assay of 194 Amalgamation Assay of Gold Ores. 193 Ammonia, Carbonate of 44 Annealing Cup 38 Antimony, Assay for 61 Ores 61, 142 Remarks on 63 Sources of 61, 142 Apparatus, Assay 37 Blowpipe 184 Chemical 188 Gold Bullion 118 Silver Bullion 112 Appendix 172 Argol 42 Assay, Chlorination 119 Chlorination, Remarks on. ... 119 Crucible for Gold and Silver . 65 for Bismuth 85 for Carbon 102 for Cobalt 99 for Copper. . 91 for Iron 94 for Mercury 83 for Nickel 99 for Platinum 80 for Tin 87 for Zinc 82 of Alloys, Touch-stone 194 of Gold and Silver Ores 64 of Gold Ores, Amalgamation . . 193 of Gold Ores, Mechanical 192 Assay of Gold Sweeps 197 of Ores, Examination Scheme for 197 of Ores, Preliminary 66 of Silver Bullion 109, 111 of Silver Bullion, Preliminary. 110 of Special Alloys of Gold 196 of Tellurides 78 Volumetric for Iron 131 Weights 20, 149 Assays, Fire 55 Wet 106 Assayer's Outfit 191 Assaying, References on 169 Atomic Weights 14 Avoirdupois Weights 148 B. Balances and Weights 18 to Adjust 19 Base Metals, Assay Report 157 Beads, Weighing of 52, 74 Bi-Carbonate of Soda 40 Bismuth, Assay for. ... 85 Determination of in Alloy. . . . 124 Ores 85, 143 Remarks on 86, 125 Sources of 85, 143 Black Flux Substitute 41 Blowpipe Analysis, etc 175 Analysis, Characteristic Tests 177 Analysis, General Remarks on 187 Analysis, Reagents 186 Analysis, Scheme for 180 Apparatus - . 184 Test for Tellurides 179 Borax 40 Box Sieve 35 Bullion, Apparatus for Silver 112 Assay of Silver 109 205 206 INDEX. Bullion, Cupellation Ill Gold 115 Gold, Assay Report 161 Gold, Cupellation for Base Metal 115 Gold, Parting 116 Gold, Platinum Apparatus for 118 Gold, Remarks on 117 Preliminary Assay of 110 Remarks on Silver 113 Silver 109 Silver, Assay Proper Ill Silver, Assay Report 162 Weighing 52 Button, Lead 71 C. Calcination and Roasting 50 Calculation and Formula? 174 of Results 75 Calorific Value of Fuel 103 Capsule, Porcelain 75 Carbon, Assay for 102 Remarks on 104 Sources of 102, 145 Carbonate of Ammonia 44 Cements, Lutes, and Washes 31 Characteristic Tests, Blowpipe An- alysis 177 Characteristics of Metals 140 of Ores 142, 147 Charcoal 42 Lined Crucibles 28 Chemical Apparatus and Reagents 188 Chemicals and Reagents 39, 189 Sundry 45 Chlorination Assay 119 Process for Gold Sulphurets . . 194 Cobalt, Assay for 99 Nickel and Copper, Composi- tion of Arsenides 101 Ores 99, 144 Remarks on 101 Sources of 99, 144 Coins, United States 148 Comparison of Units 150 Composition of Arsenides of Nickel, Cobalt and Copper 101 Copper, Assay for 91 Nickel and Cobalt, Composi- tion of Arsenides 101 Ores 90, 143 Remarks on 93, 130 Scheme for 128 Sources of 90, 143 PAQB Corrections for Loss of Silver in Cupellation Ill Crucible Assay for Gold and Sil- ver 65 Assay Report for Base Metals, 157 Assay Report for Iron 158 Assay, Silver and Gold Re- port 159 Tongs 32 Crucibles 26 Charcoal lined 28 to Line 32 Wash for 32 Cubic Measure, English 150 Measure, French 150 Cup, Annealing 38 Cupel Moulds 35 Tongs 33 Cupels 29, 30 Cupellation 52, 71 for Base Metal, Gold Bullion. . 115 Silver Bullion Ill Cyanide of Potassium 41 I). Decantation 173 Desk, Laboratory 36 Distillation and Sublimation . . 51 E. Elements, Table of 14 English Cubic Measure 150 Evaporation 174 Examination of a Mine, Rules for 199 Scheme for the Assay of Ores. 197 Extra Reagents 190 Ferro-Cyanide of Potassium 41 Filtration 173 Fire Assays 55 Flask, Parting 38 Fluxes for Scorification Assay 69 Formula and Calculation 174 French Cubic Measure 150 Liquid Measure 149 Weights 149 Fuel, Calorific Value of 103 Fuels and Furnaces 21 Furnaces and Fuels 21 Calcining 21 Fusion, etc 21 INDEX. 207 PAGE Furnaces, Muffle 22 Scorification 23, 25 Fusion and Reduction 51 Gold and Silver Ores. . . 68 G. Galena, Special Method for 71 Gold Alloys 147 Assay of, Special 196 Lead for Cupellation 155 Gold and Silver, Crucible Assay Report 159 and Silver, Preliminary Assay of Ores 66 and Silver, Remarks on 76 and Silver, Roasting of Ores. . 67 and Silver, Scorification As- say. . 69 and Silver, Scorification As- say Report 160 and Silver, Sources of 64, 142, 145, 146, 147 Assay of Ores 64 Bullion 115 Bullion Assay Report 161 Bullion, Cupellation for Base Metal 115 Bullion, Parting 116 Bullion, Platinum Apparatus for 118 Bullion, Remarks on 117 Crucible Assay for 65 Determination of, by Specific Gravity 195 Multiplication Table for 154 Ores 64, 143, 145, 146 Ores, Amalgamation Assay. . . 193 Ores and Alloys, Special Me- thods 192 Ores, Fusion of 68 Ores, Mechanical Assay 192 Purple Cassius Test for 178 Sulphurets, Chlorination Pro- cess 194 Sweeps, Assay of 197 Value of Pure 54, 141 Weighing 75 Grain Weights, Values for 154 Gravity, Specific 150 Specific, Determination of Gold by 195 Grinding Plate 34 H. Hardness, Scale of. 139 PAGE Ignition 174 Inquartation 53, 74 Introduction 13 Iron, Assay for .' 94 Crucible Assay Report 158 Metallic 42 Ores ..94 144 Remarks on 98, 132 Scheme for Volumetric As- say 131 Sources of 94, 144 Kandelhardt. Proportions of Lead for Cupelling Gold Alloys. . 155 Laboratory Desk 36 Lead, Assay for 57 Button 71 for Cupelling Gold Alloys 155 Ores 57, 142 Pure 43 Remarks on. 60, 120 Scheme for 120 Sources of 57, 142 Lime 44 Powdered 44 Lining for Crucibles 32 Liquid Measure, French 149 Measure, United States 149 Litharge 40 Lutes, Cements and Washes 31 Good Fire 31 Sundry 31 M. Manipulation, etc 173 Manganese Ores 133, 144 Remarks on 133 Scheme for 132 Sources of 133, 144 Measure. Cubic, English 150 Cubic, French 150 Liquid, French 149 Liquid, United States 149 of Weight and Volume 148 Mechanical Assay of Gold Ores. . . 193 Mercury, Assay for 83 Ores 83, 143 Remarks on 85 Sources of 83, 143 208 INDEX. PAGE Metallic Iron 42 Metals, Characteristics 140 Mine Examination, Rules for 199 Moulds, Cupel 35 Scorification 35 Multiplication Table for Gold 154 N. Nickel, Assay for 99 Cobalt and Copper, Composi- tion of Arsenides 101 Determination of, in the Wet Way 134 Ores 99, 144 Remarks on 101, 135 Nickel, Sources of 99, 144 Nitre , .... 43 Normal Salt Solution 109 0. Ores, Antimony 61, 142 Bismuth 85, 143 Characteristics 142 Cobalt 99, 144 Copper 90, 143 Gold 64, 142, 146, 147 Iron 94, 144 Lead 57, 142 Manganese 133, 144 Mercury 83, 143 Nickel 99, 144 Platinum 80, 142 Preliminary Assay of 66 Preliminary Testing of 45 Relation of Weight to Volume. 147 Silver 64,142, 145, 146 Tin 86, 143 Weighing 49 Zinc 82,143 Outfit, Assayer's 191 Outline Examination Scheme for the Assay of Ores . . 197 P. Part 1 11 II 55 III 106 IV 137 Parting 52, 74, 116 Flask 38 Plate for Grinding 34 Platinum Apparatus for Gold Bul- lion 118 Assay for 80 Ores 80,142 Platinum, Remarks on 81, 122 Scheme for 121 Sources of 80, 142 Porcelain Cap&ule 75 Potassium, Cyanide of 41 Ferro- Cyanide of 41 Powdered Lime 44 Precious Stones. Table of 139 Precipitants 44 Precipitates, Washing 174 Precipitation 173 Preliminary Assay of Ores 66 Assay of Silver Bullion 110 Testing of Ores 45 Preparation of the Normal Salt Solution 109 Problems and Questions 163 Proportions of Lead for Cupelling 1 Gold Alloys 155 Pulverizing 46 Pure Lead , 43 Gold, Value of 54, 141 Purple Cassius Test for Gold. .... 178 Q. Qualitative Analysis, Zettnow's Scheme 204 Quantitative Report 156 Questions and Problems 163 Reagents and Chemicals 39 and Ores, Weighing 49 Blowpipe 186 Chemical 189 Extra 190 Reduction and Fusion 51 References and Tables 137 on Assaying 169 Relation of Weight to Volume, Ores 147 Report, Base Metal Assay 157 General Style of 155 Gold Bullion 161 Iron Assay 158 Quantitative 156 Silver and Gold Assay 159 Silver and Gold Scorification Assay 160 Silver Bullion 162 Reporting 53 Results, Calculation of 75 Tabulating 53 Roasting and Calcination 50 Dishes 29 of Gold and Silver Ores 67 INDEX. 209 Rules for the Examination of a Mine . . .199 S. Salt . 44 Preparation of Normal 109 Sampler 36 Sampling 46 Scale of Hardness 139 Scheme for Blowpipe Analysis. . . 180 for Copper 128 for Lead 120 for Manganese 133 for Platinum 121 for Qualitative Analysis 204 for Sulphur 135 Scheme for Volumetric Assay for Iron 131 for Zinc 122 of Examination for the Assay of Ores 197 Scorification 52, 69 Assay, Fluxes for 69 Assay, Silver and Gold Re- port 160 Moulds 35 Tongs 33 Scorifiers 29 Scraper 33 Sieve, Box 35 Silica 41 Silver Alloys 146 and Gold Crucible Assay Re- port 159 and Gold, Roasting of Ores. . . 67 and Gold Scorification Assay Report 160 Assay of Ores 64 Bullion 109 Bullion, Apparatus for 112 Bullion, Assay Proper Ill Bullion, Assay Report 162 Bullion, Corrections for Cupel- lation Ill Bullion, Preliminary Assay of 110 Bullion, Remarks on 113 Crucible, Assay for 65 Ores 64, 142, 145, 146 Ores, Fusion of 68 Remarks on 76 Sources of 64, 142, 145, 146 Soda, Bi-Carbonate of 40 Solvents 44 Sources of Antimony 61, 142 of Bismuth 85, 143 Sources of Carbon 102, 145 of Cobalt 99, 144 of Copper 90, 143 of Gold 64, 142, 146, 147 of Iron 94, 144 of Lead 57 of Manganese 133, 144 of Mercury 83, 143 of Nickel 99, 144 of Platinum 80, 142 of Silver 64, 142, 145, 146 of Sulphur 135, 145 of Tin 86, 143 of Zinc 82, 143 Special Method for Galena 71 Methods for Gold Ores and Al- loys 192 Specific Gravity 150 Determination of Gold by .... 195 Starch 42 Stones, Precious 139 Style of Report. General 155 Sublimation and Distillation 51 Sulphur, Remarks on 136 Scheme for. .. 135 Sources of 135, 145 Sulphurets, Gold, Chlorination Process for 194 Sulphurizing Agents 44 Sweeps, Gold, Assay of 197 T. Tables and References 137 Tabulating Results 53 Tellurides 78 Blowpipe Test for 179 Test, Blowpipe, for Tellurides ... 179 for Gold, Purple Cassius 178 Thermometers 1 53 Tin, Assay for 87 Determination of, in the Wet Way 125 Ores 86, 143 Remarks on 90, 128 Sources of 86, 143 Tongs, Crucible, etc 32 Tools 32 Touch-stone Assay of Alloys 194 Troy Weights 148 U. United States, Coins of 148 Liquid Measure 149 Units, Comparison of 150 210 INDEX. V. PAGE Value of Pure Gold 54, 141 Values for Grain Weights 154 Volume and Weight, Measures of 148 to Weight, Relation of, Ores. . 147 Volumetric Assay for Iron 131 W. Wash for Crucibles 32 for Scorifiers 32 Washes, Lutes, and Cements 31 Washing Precipitates 174 Weighing Beads and Bullion. .. 52, 74 Gold 75 Ores and Reagents 49 Weight and Volume, Measures of . 148 Weight to Volume, Relation of, Ores 147 Weights and Balances 18 Assay 20, 149 Atomic 14 Avoirdupois 148 French 149 Grain, Values for 154 Troy 148 Wet Assays 106 Z. Zettnow's Scheme for Qualitative Analysis 204 Zinc, Assay for 82 Ores 82, 143 Remarks on 83, 124 Scheme for 122 Sources of 82, 143 1NIVERF YC 6839 UNIVERSITY OF CALIFORNIA- LIBRARY HI