11 
 
WESTERN 
 
 MILL AND SMELTER METHODS 
 OF ANALYSIS 
 
 (THIRD EDITION.) 
 
 A Practical Laboratory Handbook for the Assayer and 
 
 Chemist, Describing the Methods of Analysis in 
 
 Every-day Use in Western Mills, Smelters 
 
 and Custom Assay Offices. 
 
 BY 
 
 PHILIP H. ARGALL, B.S., M.A. 
 
 \ i 
 
 Sometime Assistant Chemist 'Grant Plant, A. S. & R. Co. 
 Assistant Chemist Washoe Plant, Anaconda Copper Mining Co. 
 Chemist (student) Metallic Extraction Co.'s Works. 
 Chemist Cyanide and Electrum Mining and Milling Co.'s Works, 
 
 St. Elmo, Colo. 
 Assistant Chemist Selby Smelting and Lead Co. 
 
 1908. 
 MINING SCIENCE PUBLISHING COMPANY. 
 
 (Publishers of Mining Science.) 
 DENVER, COLORADO, U. S. A. 
 
A7 
 
 COPYRIGHT 1905 
 
 BY 
 
 THE INDUSTRIAL PRINTING AND PUBLISHING CO. 
 COPYRIGHT NOW OWNED 
 
 BY 
 THE MINING SCIENCE PUBLISHING CO. 
 
 >*'. I * '" ' 
 
 ' ' - 
 
CONTENTS 
 
 CHAPTER I. 
 STANDARD SOLUTIONS. 
 
 Standardizing Solutions Potassium Bichromate, Potas- 
 sium Permanganate, Potassium Ferro-cyanide, Po- 
 tassium Cyanide, Sodium Thiosulphate, Ammonium 
 Molybdate 7-15 
 
 CHAPTER II. 
 
 SLAG ANALYSIS. 
 
 Determinations Lead Slags: Iron, Silica and Lime, 
 Manganese, Zinc, Magnesium, Alumina; Copper 
 Slags: Silica and Iron, Lime, Copper; Reverbera- 
 tory Furnace Slags: Silica and Iron, Copper, Lead; 
 Mattes; Conversion Table 16-26 
 
 CHAPTER III. 
 
 ORES. 
 
 Silica, Iron and Lime; Zinc; Manganese; Sulphur; 
 Copper and Lead; Baryta; Antimony and Arsenic; 
 Standard Iodine Solution: Modification; Mixture 
 Beds; Alumina, etc.; Briquettes: Silica and Iron, 
 Lime . 27-39 
 
 CHAPTER IV. 
 
 COAL AND COKE. 
 
 Proximate Analysis : Coke 40-41 
 
 CHAPTER V. 
 
 OTHER METHODS OF ANALYSIS. 
 
 Antimony and Arsenic; Pattenson's Method (modified) 
 Slags, Iron, Lime, Lead, Copper; Colorimetric, to 
 make up the standard, Copper in Slags and Tail- 
 ings, Specimen Lead Slag Analysis; Specimen Bed 
 Analysis for Lead Smelter; Specimen Briquette 
 Analysis 42-53 
 
 36483? 
 
CHAPTER VI 
 
 CYANIDE PROCESS DAILY WORK. 
 Titrations of Cyanide Solutions; Titration of Alkalinity; 
 Estimation of Alkalies; Manganese in Cyanide So- 
 lutions; Estimation of Free Cyanide; Estimation of 
 Total Cyanide; Estimation of HCN; Estimation of 
 Ferrocyanide by means of Potassium Permanganate; 
 Estimation of Thio-cyantes by means of Iodine; Es- 
 timation of Total Cyanogen; Estimation of Zinc by 
 Decomposition with HNO 3 and HC1; Estimation of 
 Copper; Estimation of Gold; Estimation of Silver; 
 Purple of Cassius Test for Gold; Qualitative Detec- 
 tion of Gold; Estimation of the Reducing Power of 
 Solution; Estimation of Alkaline Sulphides; Esti- 
 mation of Sulphides by Colorimetric Test with 
 Sodium Nitro-Prusside; Estimation of Bromo Cya- 
 nogen and Potassium Bromate . 54-83 
 
 CHAPTER VII. 
 
 ESTIMATION OF OXYGEN IN WORKING CYANIDE 
 
 SOLUTIONS. 
 
 Apparatus Necessary; Solutions; Calculations; Precau- 
 tions; Specimen Analysis of Mill Solutions 84-92 
 
 CHAPTER VIII. 
 
 ORE TESTING BY THE CYANIDE PROCESS. 
 Preliminary Tests; Consumption Test; Preliminary Ex- 
 traction Tests; Roasting; Modification of Bottle 
 Test; Percolation Tests 93-105 
 
 CHAPTER IX. 
 
 THE ANALYSIS OF BRONZING AND BEARING METALS. 
 Bronzes; Determination of Phosphorous; Bearing 
 
 Metals 106-110 
 
 CHAPTER X. 
 REFINERY METHODS. 
 
 Mill Slags; Slags; Silver Determination on Anode 
 Copper by Fire Assay; Bismuth in Metallic Copper; 
 Electrolytic Copper Determination 111-130 
 
 CHAPTER XI. 
 THE LABORATORY. 
 
 The Hot Plate; Filter Racks; Burette Stand; Distilled 
 Water; Balances; Miscellaneous; The Assay Ton 
 System; Impurities in C. P. Acids; Hydrochloric 
 Acid; Nitric Acid; Sulphuric Acid; Ammonia; In- 
 ternational Atomic Weights 131-144 
 
PREFACE. 
 
 In May, 1904, I presented, in part fulfillment of the 
 requirements for the degree Master of Arts in the 
 University of Colorado, a thesis entitled "Smelter and 
 Mill Methods of Analysis in Use in the West." This 
 thesis was later published in Volume II., No. i,of the 
 University Studies, and though primarily intended for 
 the use of students in the University, it has been found 
 to be of considerable help to practical chemists in all 
 parts of the West. 
 
 This treatise, revised and enlarged from the thesis, 
 is intended for the use of practical chemists and assayy 
 ers, and presupposes a thorough knowledge of chem- 
 istry. Hence no attempt is made to explain the nature 
 of the chemical reactions that take place, a simple and 
 clear outline alone is given. The methods of analysis 
 given are those in every-day use in lead and copper 
 smelters and in cyanide mills. 
 
 Acknowledgment is due Mr. J. E. Clennell for the 
 description of a number of determinations in connection 
 with the cyanide process from his paper "Analytical 
 Work in Connection With the Cyanide Process/' which 
 was read before the Institute of Mining and Metallurgy 
 in London on May 21, 1903 ; and to Mr. Philip Argall 
 for much of the material in the chapter on "Ore Test- 
 ing by the Cyanide Process." 
 
 Other authors have been freely consulted and due 
 credit is given when any method so obtained has been 
 used in this treatise. 
 
 To-day the metallurgical chemist almost entirely 
 relies on volumetric methods for the analytical deter- 
 minations required in metallurgical work. The opera- 
 tions of mill and smelter are being more and more 
 directed according to the results obtained in the lab- 
 oratory and the metallurgical chemist is now required to 
 
6 MILL AND SMELTER METHODS. 
 
 make daily a number of determinations that would 
 appall his predecessor of even a few years ago. -The 
 time allowed for making individual determinations is 
 also being steadily reduced. Hence, 'the chemist is 
 debarred from making the slower, but possibly more 
 accurate, gravimetric determinations. He is driven, 
 therefore, to using volumetric methods as far as possi- 
 ble. The speed and the comparatively small amount of 
 attention required by individual assays in volumetric 
 work also makes for the adoption of these methods. A 
 few years ago furnace and gravimetric methods of 
 analysis were standard; today, except for gold and sil- 
 ver, volumetric methods are used almost exclusively. 
 
 The standard solutions used are made up in large 
 quantities at a time, and are kept, as far as possible, in a 
 cool, dark place. Most of the solutions used maintain 
 their standard for a considerable length of time. 
 
 Selby Works, March ist, 1905. 
 
 The second edition of this book has made possible 
 the correction of errors in the former edition and has 
 enabled me to add some new methods and to include 
 others overlooked in the first instance. Very little that 
 is actually new has turned up in the ordinary smelter 
 routine in the past three years, but a gradual uniform- 
 ity in methods, which did not exist then, has come 
 about, and in changing from one laboratory to another 
 now one has no new methods to learn. 
 
 The first edition of this work was very favorably 
 received, and I hope that this will be no less so, for, 
 while many shortcomings will be found, I believe that 
 the ground covered has been thoroughly gone over. 
 
 Selby Works, September, 1908. 
 
CHAPTER 1. 
 
 Standard Solutions. 
 
 The following standard solutions are in general 
 use in the lead and copper smelters of the West: 
 
 Amount of Salt in 
 
 Name of Solution. One Litre. 
 
 Approximate 
 
 Used for 
 
 Theoretical. 
 
 Practical 
 
 . Standard. 
 
 Determining. 
 
 Potassium Bichromate 4.381 
 
 4.4 
 
 lcc=r.005 Fe. 
 
 Fe. 
 
 Sodium Thiosulphate 19. 59 
 
 20.0 
 
 lcc=.005 Cu. 
 
 As, Cu, I, Sb. 
 
 
 
 
 Mn, CaO. 
 
 Potassium Permanganate. 5.643 
 
 5.8 
 
 lcc=.005 CaO. 
 
 Fe, Sb. 
 
 Potassium Ferrocyanide. . 
 
 22.5 
 
 lcc=.005 Zn. 
 
 Zn. 
 
 Ammonium Molybdate 
 
 4.28 
 
 lcc=.005 Pb. 
 
 Pb. 
 
 Potassium Cyanide 
 
 44.5 
 
 lcc=.010 Cu. 
 
 Cu. 
 
 Oxalic Acid 11.25 
 
 11.46 
 
 lcc=lcc K Mn0 4 . 
 
 Mn. 
 
 
 
 =lcc .01 Fe. 
 
 
 Potassium Sulphocyanate. 8.981 
 
 10.0 
 
 lcc=.01 Ag. 
 
 Ag, As, 
 
 Barium Chloride 76. 25 
 
 76.25 
 
 lcc=.01 S. 
 
 S. 
 
 Ammonium Oxalate 40 grams per litre 
 
 Barium Chloride 20 
 
 Mercuric Chloride 50 " 
 
 Sodium Phosphate 100 " " " 
 
 Stannous chloride, made by saturating hydrochloric 
 acid with tin, diluting with an equal volume of water, 
 and adding a slight excess of water from time to time. 
 A strip of metallic tin is kept in the bottle. 
 
 From the potassium permanganate solution above 
 
8 MILL AND SMELTER METHODS. 
 
 I cc. equals .005 Lime, the following comparison is 
 deduced : 
 
 100 CaO=253-3 ammonium oxalate. 
 
 100 CaO=2O3.3 oxalic acid. 
 
 100 Fe. =700.0 ferrous ammonium sulphate. 
 
 All of these solutions, except potassium cyanide, 
 keep well if kept in dark bottles ; Messrs. Walter M. 
 Gardner and B. North* found that a solution of 
 potassium permanganate kept its strength for twelve 
 months and that a solution of ammonium oxalate 
 deteriorates at the rate of I % in two weeks. 
 
 In actual practice these solutions are made to read 
 i cc.=.oo5, so that the reading will be direct on \ 
 gram of ore or slag. 
 
 Impurities in the chemicals, even in the so-called 
 C~ P., as well as dust and organic matter (sometimes 
 in the water obtained in the condensation of boiler 
 steam, and due to the use of organic boiler com- 
 pounds) generally affect the solutions more or less, 
 hence it is well to let them stand a few days before 
 using. If the laboratory possesses a suction pump, 
 the flask containing the newly made solution may be 
 fitted with a cork containing two pieces of glass 
 tubing, one piece reaching to the bottom of the flask 
 
 * Journal of the Society of Chemical Industry, June 15, 
 1904, page 599. 
 
MILL AND SMELTER METHODS. 9 
 
 and the other ending just above the surface of the 
 liquid, the latter piece being connected to the pump by 
 a rubber tube, air may be drawn through the solution 
 over night, thoroughly mixing it. These solutions 
 should be made up in quantities of not less than four 
 litres, and in large laboratories, especially where it 
 is necessary to let them stand a few days before using, 
 one flask should be standing while its duplicate is 
 in use. 
 
 The difference between the theoretical and prac- 
 tical columns in the table is due to impurities in the 
 chemicals and in the water used. 
 
 Standardizing Solutions. 
 
 Potassium Bichromate. 
 
 Weigh out a piece of C. P. iron wire approxi- 
 mately .200 gram. Cut the wire into small pieces, 
 place in a beaker and pour 15 cc. cone, hydrochloric 
 acid and 15 cc. boiling distilled water over it and heat 
 until dissolved. Dilute with 100 cc. of water and 
 boil. Remove from the heat and while still hot reduce 
 with a few drops of stannous chloride solution, stir- 
 ring vigorously. When quite cold add 20 cc. of a 
 strong solution of mercuric chloride and stir well. 
 
io MILL AND SMELTER METHODS. 
 
 The solution should now look white and silky from 
 the presence of mercurous chloride, and is ready for 
 titration. 
 
 Titrate with the standard solution using a solu- 
 tion of potassium ferricyanide as an indicator. Divide 
 the weight of iron taken by the number of cc/s used, 
 then the quotient will represent the amount of iron 
 in the ferrous condition which I cc. of the solution 
 is capable of oxidizing. . 
 
 The mercuric chloride solution is simply a con- 
 centrated solution of the salt in distilled water. 
 
 The ferricyanide indicator is prepared by adding 
 two or three grams of the salt to 200 cc. of distilled 
 water, and should be made fresh daily. 
 
 Potassium Permanganate. 
 Three methods are in general use: 
 
 (a) By iron wire. 
 
 (b) By oxalic acid. 
 
 (c) By ferrous ammonium sulphate. 
 
 Comparing the following equations: 
 io FeS0 4 + 2 KMn0 4 + 8 H 2 SO 4 = 5 Fe 2 (SO 4 ) 8 + 
 
 K 2 SO 4 +2 MnSO 4 +8 H 2 O and, 
 5(H 2 C 2 O 4 , 2 H 2 O)+2 KMnO 4 +3 H 2 SO 4 =io CO 2 + 
 
 2 MnSO 4 +K 2 SO 4 +i8 H 2 O. 
 
 it will be seen that two equivalents of iron .require 
 the same amount of permanganate solution for oxida- 
 
MILL AND SMELTER METHODS. n 
 
 tion as one equivalent of oxalic acid, or, 2/56 iron is 
 equal to 126 oxalic acid, i. e., as 8:9. Taking oxalic 
 acid, therefore, we simply multiply the weight taken 
 by 8/9 to find the 'equivalent in iron. 
 
 The composition of ferrous ammonium sulphate is 
 Fe(NH 4 ) 2 (SO 4 ),6H 2 O, the molecular weight is 392, 
 of which 56, or 1/7, is iron. 
 
 (a) To Standardize with Iron Wire. Weigh out 
 approximately .200 gram of iron wire, cut it into small 
 pieces and place in a flask. Pour upon it 20 cc. cold 
 water and 5 cc. cone, sulphuric acid and heat until all 
 the iron is dissolved. When completely dissolved add 
 20 to 30 cc. of hot water and a spoonful of granulated 
 zinc (aluminum foil is just as good) and boil for a few 
 minutes. Remove and cool the beaker and test the 
 solution with potassium sulphocyanide. If no pink 
 colpration is shown add 100 cc. cold water, stir, allow 
 the zinc to settle, decant the solution and wash with 
 water, being careful that none of the zinc passes over. 
 The solution is now ready for titration with the per- 
 manganate solution. Run in rapidly, with constant 
 stirring, until a faint pink appears. 
 
 (b) To Standardize with Oxalic Acid. Weigh 
 out about | gram of the pure acid, which has been 
 kept in a well stoppered bottle. Dissolve in a No. 3 
 beaker in about 350 cc. of boiling water. In another 
 beaker place 50 cc. cold water and add to it 20 cc. 
 
12 MILL AND SMELTER METHODS. 
 
 strong sulphuric acid ; mix by shaking around gently, 
 then pour this hot acid into the oxalic acid and titrate 
 at once with the volumetric solution. 
 
 (c) To Standardize with Ferrous Ammonium 
 Sulphate. Coarsely powder about 3 grams of the salt 
 in a porcelain mortar, weigh out about 2.1 grams and 
 dissolve it in 250 cc. cold water. Add 20 cc. sulphuric 
 acid ( i part acid, 5 parts cold water) and when the 
 salt has completely dissolved titrate with the volu- 
 rnetric solution. 
 
 Potassium Ferrocyanide. 
 
 Ignite in a porcelain crucible about 3 grams of 
 C. P. zinc oxide. Cool in a dessicator. When cold 
 weigh out as rapidly as possible .250 gram, place in a 
 No. 2 beaker and add 25 cc. boiling distilled water and 
 5 cc. hydrochloric acid. Warm until completely dis- 
 solved. Add 7 grams ammonium chloride and 15 to 
 25 grams test lead,* dilute to 200 to 225 cc. and boil. 
 
 Take off the hot plate when boiling, add I to 2 cc. 
 of a concentrated solution of sodium sulphite (the 
 solution should smell of sulphur di-oxide) and titrate, 
 using a solution of uranium acetate as an indicator. 
 
 * The addition of the lead is not necessary here, but 
 since lead is invariably used to precipitate copper when 
 testing for zinc ores (Low's method) it is desirable to have 
 the same conditions here. 
 
MILL AND SMELTER METHODS. 13 
 
 The writer has found it a good plan to divide the 
 solution before adding the sodium sulphite, leaving 20 
 to 30 cc. on the lead in the beaker, and to this part 
 adding the sodium sulphite. Titrate the other portion 
 rapidly until a good end reaction is reached, then pour 
 in the other part, lead and all, rinse carefully and com- 
 plete the titration slowly. This precaution prevents 
 running past the end point. 
 
 The uranium acetate indicator is prepared by dis- 
 solving sufficient uranium acetate in water to give a 
 pretty strong solution and clarified by adding a few 
 drops of acetic acid. 
 
 Or, weigh carefully about 0.2 gram of pure zinc 
 and dissolve in 10 cc. of strong HC1, using a 400 cc. 
 covered beaker. Dilute and put in a piece of litmus 
 paper and make faintly alkaline with ammonia. 
 Acidify with HC1 and then add 3 cc.'s in excess of 
 the strong acid. Dilute to 300 cc. and heat nearly 
 to boiling and titrate the hot solution with the ferro- 
 cyanide solution, proceeding as above. 
 
 [Note.- The end point is always passed by a test 
 or two and the burette reading must be corrected ac- 
 cordingly.] 
 
 Potassium Cyanide. 
 
 Weigh out a piece of copper foil, approximately 
 .250 gram, place in a beaker and dissolve in 5 cc. 
 strong nitric acid. Boil off the red fumes and cool by 
 
14 MILL AND SMELTER METHODS. 
 
 dipping in cold water. Add 20 cc. cold water, then 
 10 cc. strong ammonia, stir and cool. Titrate with 
 the volumetric solution of potassium cyanide. 
 
 Sodium Thiosulphate. 
 
 Weigh out .200 gram copper foil, and dissolve it in 
 a beaker in 5 cc. strong nitric acid. Boil off the red 
 fumes carefully to avoid trouble later on when any 
 nitrous acid present would liberate iodine. Remove 
 from the heat and add 15 cc. of water and from 6 to 7 
 grams of zinc acetate and boil for a few minutes. 
 Remove from the heat and allow to become quite 
 cold, then add 50 cc. cold water and from 3 to 4 grams 
 of potassium iodide, stirring until dissolved. Cuprous 
 iodide will be precipitated and iodine liberated. 
 
 2 Cu(C 2 H,O 2 ) 2 +4 KI=Cu 2 I 2 +4 KC 2 H,O 2 +I 2 . 
 
 The free iodine is soluble in potassium iodide and 
 colors the solution brown. Titrate at once with the 
 thiosulphate solution until the brown tinge has become 
 weak, then add about 5 cc. of starch solution and 
 continue the titration until the blue color disappears, 
 leaving the solution milky and somewhat yellow. 
 
 The starch solution is prepared by adding ^ gram 
 of starch to 200 cc. boiling distilled water and stir- 
 ring. A new solution should be made every few days. 
 
MILL AND SMELTER METHODS. 15 
 
 Ammonium Molybdate. 
 
 Weigh .200 gram of C. P. anhydrous lead sul- 
 phate and place in a No. 2 beaker. Add 10 grams of 
 ammonium acetate and 100 cc. of boiling water. Heat 
 until the lead sulphate is dissolved. Titrate boiling 
 hot with the molybdate solution, using a solution of 
 tannio acid as an indicator. 
 
 The tannic acid solution is prepared by adding 200 
 cc. of water to 1/20 gram of tannic acid. 
 
16 MILL AND SMELTER METHODS. 
 
 CHAPTER II. 
 
 Slag Analysis. 
 
 The composition of a slag in any given smelting 
 operation has probably a greater influence on the 
 success of the process than any other single factor, 
 regarded either from a technical or financial stand- 
 point. 
 
 Smelting may be regarded as the fusion or reduc- 
 tion of an ore or ores, so that the resulting metal or 
 matte, by reason of its greater specific gravity, may 
 sink through the fused gangue and be collected for 
 further purification freed from the earthy metals 
 which form the slag. In order that this separation 
 may be complete and perfect, the slag must fuse at 
 a temperature as near the fusing point of the metal 
 as possible, and in most cases, the more fluid the slag, 
 and the lower its specific gravity, the better it is. In 
 the lead, copper and iron industry, the slags are 
 invariably complex silicates ; that is, a silicate of 
 numerous bases. The ratio of acid to base has an 
 exceedingly important influence on the perfect separa- 
 tion of the metals from the slag, affecting, as it does, 
 the specific gravity, the fusibility, the influence on the 
 furnace walls and the influence on the oxide of the 
 metal to be separated. 
 
MILL AND SMELTER METHODS. 17 
 
 In general it has been found that "singulo- 
 silicates" are the most fluid, fuse at the lowest temper- 
 ature and are most commonly used where econom- 
 ically possible. (A slag in which the ratio of the 
 oxygen combined in the silica is to the oxygen com- 
 bined in the bases as i : i is called a singulo-silicate. ) 
 
 It has been found that if a slag be suddenly chilled 
 either by pouring into water, or upon a cold piece of 
 steel, or even by dipping a cold steel bar into the 
 fluid slag and quickly removing it with its adhering 
 slag, the slag so treated has a vitreous lustre and 
 decomposes rapidly and completely with acids. If, 
 however, it is allowed to cool slowly, as it would 
 under ordinary circumstances, it is no longer decom- 
 posed by acids, but requires fusion with alkaline 
 carbonates. With singulo-silicates the decomposition 
 is perfect when the slag is chilled, but as the slags 
 become more acid they become more difficult to 
 decompose, and when slags approach 40% silica the 
 decomposition is no longer satisfactory. 
 
 In all lead smelters at least one sample of slag is 
 analyzed daily, and from the analysis the fluxes are 
 adjusted. This slag analysis is the first thing taken 
 up by the chemist when he arrives at the plant in the 
 morning, and since the results are expected by 10 a. m. 
 very rapid methods are required. 
 
 The figures generally required on lead slags are 
 silica, iron, lime, zinc, manganese, magnesium and 
 alumina; lead and silver are determined by the fire 
 
i8 MILL AND SMELTER METHODS. 
 
 assay.* A separate portion of J gram is weighed out 
 for iron, manganese, zinc and aluminum ; silica and 
 lime are determined on one weighing. 
 
 On copper slags silica, iron and lime are the only 
 elements usually called for, so silica and iron are 
 made on one weighing and lime on a separate one. 
 
 The slag is usually delivered to the chemist ground 
 and screened, so that he may weigh up at once. 
 
 Determinations Lead Slags. 
 
 Iron. 
 
 To -J gram of slag add 20 cc. boiling water and 15 
 cc. strong hydrochloric acid. Boil until all action 
 ceases. Now add 3 drops of stannous chloride solu- 
 tion and allow to cool. When cold add 15 cc. mercuric 
 chloride to neutralize the excess tin. Titrate with 
 bi-chromate solution, using the potassium ferricyanide 
 indicator. 
 
 This method of the complete solution of the slag 
 in water and hydrochloric acid is of value in another 
 way, as it gives an indication of incomplete reduction 
 in the furnace i. e., if the solution has a yellow color 
 it shows that some of the iron is present in the ferric 
 state, and when this is the case it may be necessary 
 to give an increased amount of fuel ; such a fact 
 should be noted on your report. 
 
 * It has recently become the practice in Colorado to 
 make wet leads also on slags. 
 
MILL AND SMELTER METHODS. 19 
 
 Silica and Lime. 
 
 Weigh into a No. 3 R. B. casserole -J gram of 
 slag and moisten it with water. Then add 4 to 5 cc. 
 hydrochloric acid and stir with a glass rod (keep stir- 
 ring while adding the acid in order to prevent the 
 silica gelatinizing and forming lumps.) Evaporate 
 to dryness on the hot plate, being careful to avoid 
 "spitting." Take up with 5 cc. hydrochloric acid and 
 5 cc. water, and boil. Dilute, filter into a beaker 
 containing 3 cc. of nitric acid. Burn the filter paper 
 in a porcelain crucible in the muffle, cool and weigh 
 as silica. 
 
 To the filtrate acid with nitric acid, add ammonia 
 until all the iron is precipitated : re-dissolve the iron 
 in oxalic acid and boil. Filter off the calcium oxalate 
 and wash carefully with hot water. Put the filter 
 paper containing the calcium oxalate in a beaker ; 
 half fill it with hot water and add 10 cc. dilute sul- 
 phuric acid warm and titrate with permanganate. It 
 will be observed that no nitric acid is used during the 
 first evaporation ; this to avoid the exidation of the 
 sulphur which is combined in the slag as a sulphide, 
 and which by treatment with hydrochloric acid alone 
 is eliminated as hydrogen sulphide. If the sulphur 
 were oxidized to sulphuric acid, some barium sulphate 
 would be formed, and remaining with silica, make 
 the result too high. 
 
 The nitric acid is used in the second stage to 
 oxidize the iron. 
 
20 MILL AND SMELTER METHODS. 
 
 There is invariably a small amount of carbon .in 
 the slag which will make the silica look dark before 
 ignition, but it burns off in the muffle. 
 
 Care must be taken in the evaporation to dryness 
 not to heat too strongly; sometimes the iron when 
 heated too strongly becomes oxidized to Fe 2 O 3 and 
 obstinately refuses to dissolve, in which case a new 
 determination is necessary. It will be noticed that 
 the technical term "silica" embraces all that is insolu- 
 ble in acids. 
 
 Lime in Slags. 
 
 A better method is the following: To 4 gram 
 of slag in a casserole add a pinch of potassium chlorate, 
 moisten with a little water and add 4 cc. of strong 
 hydrochloric acid. Evaporate to dryness. Take up 
 in ammonia water, first adding about 5 grams of 
 ammonium chloride. Boil well. Filter through a 
 fluted filter paper. Redissolve the ppt. and again 
 precipitate with ammonia filter and add the filtrate to 
 that obtained in the first filtration. Wash well, heat 
 to boiling and ppt. with hot ammonium oxalate, 
 and proceed as before. 
 
 Manganese. 
 
 Weigh out in a No. 2 beaker one-half gram of slag 
 and treat with 20 cc. water and 5 cc. nitric acid. Boil. 
 Dilute with hot water, add enough zinc oxide emulsion 
 to neutralize, and titrate with potassium permangan- 
 ate solution. Since this solution is standardized with 
 
MILL AND SMELTER METHODS. 21 
 
 iron we have simply to multiply by 165 divided by 560 
 equals .2946 to obtain the value in manganese. 
 
 Another method is to add 5 cc. nitric acid and 
 4 to 5 cc., hydrochloric acid and boil in a casserole 
 until decomposed. Now add 4 to 5 cc. sulphuric 
 acid and evaporate carefully to dryness. Take up with 
 water and boil for ten minutes, then transfer to a 
 beaker, neutralize with ammonia, then make slightly 
 acid with sulphuric. Now add the zinc emulsion and 
 proceed as before. 
 
 Zinc. 
 
 To -J gram of ore in a No. 3 R. B. casserole add 
 10 cc. of chlorate mixture (a saturated solution of po- 
 tassium chlorate in nitric acid) and evaporate slowly 
 to dryness. Now -add 10 grams of ammonium chlo- 
 ride crystals and 20 cc. of ammonia, boil, filter and 
 wash with ammonia and then with water. To the ni- 
 trate add a small piece of litmus paper and make the 
 solution acid with hydrochloric acid and then add 5 
 cc. in excess. Now add 2 to 3 grams of test lead and 
 boil. Titrate hot with the potassium ferrocyanide so- 
 lution, using the uranium acetate indicator. Add 
 about 3 cc. of the sodium sulphite solution before ti- 
 trating. (See standardizing the solution.) 
 
 Some chemists evaporate, to dryness first with ni- 
 tric acid and then take up and boil with nitric acid, 
 adding a pinch of potassium chlorate, this method giv- 
 ing steady results. 
 
22 MILL AND SMELTER METHODS. 
 
 Sources of error in the ferrocyanide titration 
 method for zinc losses may result from : * 
 
 1. Volatilization of zinc as the chloride. 
 
 2. Recombination of zinc with silica. 
 
 3. Imperfect decomposition by acids. 
 
 4. Occlusion by ferric hydroxide, .etc. 
 
 5/ The use of hydrogen sulphide for separating 
 Cu. Cd., etc. 
 
 6. Failure to make the final titration under the 
 same conditions as in standardizing. 
 
 7. Insufficient dilution of the solution. 
 
 8. Too great haste in titrating, especially with 
 cold solutions. On the other hand, results may be too 
 high owing to: 
 
 9. The presence, in the solution, of Cd. Cu. Sb. 
 Mn. Al. or some organic acid, as tartaric, oxalic, etc. 
 
 10. The decomposition of the ferrocyanide solu- 
 tion by Cl. Br., nitrous oxides, hydrogen peroxide, 
 etc. 
 
 11. The addition of an inordinate excess of acid 
 to the solution. 
 
 12. The use of an incorrectly standardized solu- 
 tion of ferrocyanide. 
 
 Magnesium. 
 
 To | gram of slag add 15 cc. water, then 10 cc. 
 hydrochloric acid and 5 cc. nitric acid, boil, precipi- 
 tate the iron with ammonia and add 5 cc. bromine 
 
 * George Waring, Jour. Am. Chem. Soc., Vol. XXVI., 
 Jan., 1904. 
 
MILL AND SMELTER METHODS. 23 
 
 water (or hydrogen peroxide) and filter. The iron 
 is then dissolved with 5 cc. of hydrochloric acid, di- 
 luted, and again precipitated with ammonia and bro- 
 mine as before. The filtrates from the two precipi- 
 tates are then combined and boiled. Ammonium oxa- 
 late is now added to precipitate the lime, which is 
 then filtered off. The filtrate is boiled to a small bulk 
 and 5 cc. sodium phosphate solution added and placed 
 in a flask under running water to cool. When quite 
 cold add 20 cc. ammonia and shake for 15 minutes 
 when all the magnesium phosphate is precipitated. 
 Filter, wash with cold ' dilute ammonia, burn and 
 weigh. 
 
 Alumina. 
 
 Weigh out in. a No. 3 R. B. casserole -J gram of 
 slag and treat as if for silica, but, on filtering, do 
 not add nitiric acid to the filtrate. This will give yo.. 
 a check on your silica. 
 
 Wash the filter paper carefully with dilute hydro- 
 chloric acid and then with water before removing. 
 Then to the filtrate add ammonia until the solution 
 becomes dark red in color, but contains no precipi- 
 tate. Now add 3 cc. hydrochloric acid and 20 cc. 
 sodium phosphate solution, constantly stirring; then 
 add 50 cc. sodium thiosulphate solution and 10 cc. 
 of 99.5% acetic acid. Heat to boiling and boil for 
 30 minutes ; filter rapidly, wash with hot water, burn 
 in a porcelain crucible and weigh as aluminum phos- 
 
24 MILL AND SMELTER METHODS. 
 
 phate, which, multiplied by .41847, gives the weight 
 of AL 2 O 3 . 
 
 It is necessary in burning off the precipitate to 
 burn at a low temperature, otherwise the aluminum 
 phosphate will fuse. 
 
 Copper Slags. 
 
 On copper blast furnace slags, as a general rule, 
 only silica, iron and lime are required. Hence only 
 two weighings are required; one for silica and iron, 
 one for lime. 
 
 Silica and Iron. 
 
 Weigh into a No. 3 R. B. casserole -J gram of the 
 slag and treat it essentially as in the case of a lead 
 slag. Do not oxidize the filtrate from the silica, how- 
 ever, but heat it to boiling, reduce with stannous chlo- 
 ride, cool and titrate with the bichromate solution. 
 Lim ( e. 
 
 To -J gram of the slag in a No. 2 beaker add 20 cc. 
 hot water, 10 cc. hydrochloric acid and a pinch of po- 
 tassium chlorate. Stir carefully, and see that no slag 
 is allowed to stick to the bottom of the beaker. Boil 
 for a few minutes, then remove from the heat and pre- 
 cipitate the iron, etc., with ammonia. Boil, filter off 
 the precipitate, and place the filtrate on the hot plate 
 to boil. When boiling precipitate the lime with am- 
 monium oxalate, allow to settle, filter and wash care- 
 fully with hot water. Place the filter paper and its 
 contents in a beaker, half fill with warm water and 
 
MILL AND SMELTER METHODS. 25 
 
 add 10 cc. of dilute sulphuric acid, boil and titrate 
 hot with the permanganate solution. 
 
 Copper. 
 
 To i gram of the slag in a small beaker add 20 cc. 
 water and 10 cc. of nitric acid : place on the hot plate 
 and boil gently until the fumes cease; remove, cool, 
 precipitate the iron with ammonia and titrate with 
 the potassium cyanide solution. 
 
 Reverberator/ Furnace Slags. 
 
 On these slags silica, iron, copper and lead are 
 usually required. Ordinarily the copper and lead 
 values are so low that they will not injure the crucible 
 if fused direct. 
 
 Silica and Iron. 
 
 Fuse -J gram of the slag in a silver crucible with 
 about 3 grams of potassium hydroxide. When cold, 
 remove the fused mass with hot water arid evaporate 
 to dryness in a casserole after adding 15 cc. of hydro- 
 chloric acid. Take up in water and hydrochloric acid 
 and proceed as before. 
 
 Copper. 
 
 As given under copper slags. 
 Lead. 
 
 To i gram of slag in a small beaker, add 15 cc. of 
 nitric acid and 10 ec. of sulphuric acid and heat un- 
 til dense white fumes of SO 3 are given off. Remove 
 from the heat and allow to become quite cold. Add 
 100 cc. of cold water and filter. Wash the lead sul- 
 phate from the filter paper into the original beaker, 
 
26 MILL AND SMELTER METHODS. 
 
 add 10 grams of ammonium acetate, boil and titrate 
 hot with the molybdate solution. 
 
 Mattes. 
 
 Matte, roasted matte, fused ore, etc., are treated in 
 the same way as slags. The insoluble residue will in 
 most cases have to be fused in the silver crucible with 
 potassium hydroxide, or in a platinum crucible with 
 alkaline carbonates. All these substances will contain 
 copper and lead, and care must be taken to see that 
 they are removed before fusion. 
 
 The chemist is now ready to make his report to 
 the metallurgist, and since the elements found must 
 be reported as oxides, the following conversion table 
 will prove useful. Any Pb ore which has been sin- 
 tered during a roasting process requires an HF lead 
 except in case SiO 2 is not present. 
 
 CONVERSION TABLE. 
 Fex 1.29= FeO 
 
 Mnx i.29=MnO 
 Zn x 1.25 = ZnO 
 Cu x 1.25 = CuO 
 Pbxi.oS = PbO 
 
 S x 2.50 = SO 3 
 As x 1.32 = As 2 O 3 
 Sbx i.27=Sb 2 O 4 
 
 S x 747 = PbS 
 
MILL AND SMELTER METHODS. 27 
 
 CHAPTER III. 
 
 Ores. 
 
 The figures called for on ores will, of course, vary 
 with the nature of the ores, but the following are the 
 elements that the metallurgist requires to know about : 
 Silica, iron, lime, zinc, copper, sulphur, lead, baryta, 
 antimony and arsenic. 
 
 True Silica. 
 
 True silica is the expression used to distinguish 
 the silica of ordinary smelter parlance (meaning, 
 really, that which is insoluble in acids) from the actual 
 silica. 
 
 On ores, briquettes, etc., fuse in a silver crucible 
 about two-thirds of a stick of silica-free potassium 
 hydroxide, adding, if there be much sulphur present, 
 a little potassium nitrate (in the case of heavy sul- 
 phides add quite a little' nitre) and allow to cool. 
 When cold weigh out -J gram of the material to 
 be analyzed and brush it into the crucible. Place the 
 cover in place and fuse, beginning with a very low 
 heat. Be very careful, if you are working on a sul- 
 phide, to raise the heat very gently at first, as the union 
 of the sulphur and nitre takes place very violently. 
 After the mass in the crucible has become quiet raise 
 the heat and heat for about 15 minutes. Have a 
 
28 MILL AND SMELTER METHODS. 
 
 large casserole heated nearly to the temperature of 
 the stove. When the fusion is ready remove the 
 casserole to the table and pour the contents of the 
 crucible into it. Set the crucible in also, upright. 
 When quite cold rinse out with hot water ; finally, fill 
 the crucible with strong hydrochloric acid, upset it 
 and roll around in the solution a few times, rinse off 
 and remove. Evaporate to dryness. Take up in 
 hydrochloric acid and water, boil and filter Wash 
 once or twice with hot I to i hydrochloric acid and 
 water, then several times with hot water. Burn and 
 weigh. 
 
 If the silica is black after burning, some silver 
 chloride has been left in the silica and has been reduced 
 to metallic silver in the muffle ; but,, if the washing 
 with hot dilute hydrochloric is thorough this will not 
 occur. 
 
 Silica, Iron and Lime 
 
 In ores these three elements are generally deter- 
 mined on the one weighing. To gram of the ore 
 add 15 cc. of hydrochloric acid and 10 ce. of nitric 
 acid and evaporate to dryness in a beaker. Take up 
 in 10 cc. of hydrochloric acid and 20 cc. of water, boil 
 and filter. Burn and weigh the insoluble residue, 
 which, in smelter parlance, is called the silica. To the 
 filtrate add ammonia to precipitate the iron, boil a 
 few minutes and filter. To the filtrate add ammonium 
 oxalate, boil and filter off the calcium oxalate. 
 
 The iron on the filter paper is dissolved with hy- 
 
MILL AND SMELTER METHODS. 29 
 
 drochloric acid, warmed, reduced with stannous chlo- 
 ride, cooled, titrated with potassium bichromate. 
 
 The calcium oxalate is proceeded with as in lime 
 in slags. 
 
 In the case of copper ores, where there is no lime 
 present, the hydrochloric acid solution of the iron may 
 be reduced with test lead ; the copper will not then in- 
 terfere with the bichromate titration. 
 
 If the ore is a sulphide, the first evaporation to 
 dryness should be made with 15 cc. of the "chlorate 
 mixture." 
 
 Zinc. 
 
 Zinc in an ore is treated essentially as in slags, by 
 a modification of Low's method. Cadmium may be 
 removed when necessary by passing hydrogen sul- 
 phide through the acid solution before adding the test 
 lead. CdS and CuS are then precipitated together 
 and must be filtered out. The addition of test lead 
 is then unnecessary. The hydrogen sulphide will not 
 interfere. 
 
 Manganese. 
 
 Essentially as in slags. Often, however, it is only 
 necessary to boil the ore with hydrochloric acid. 
 Sulphur. 
 
 To I gram of ore add 10 cc. of chlorate mixture 
 and evaporate to dryness. Take up in 10 cc. hydro- 
 chloric acid and 10 cc. water and boil. Now add 20 cc. 
 of ammonia and 5 cc. of hydrogen peroxide and fil- 
 ter (the lead, iron, etc., will be on the filter paper). 
 
30 MILL AND SMELTER METHODS. 
 
 Boil the filtrate after making it acid with hydro- 
 chloric acid, then add -J gram of a solution of barium 
 chloride. Allow to settle, filter, wash well with water, 
 burn in the muffle and weigh as barium sulphate. The 
 weight times .13734 gives the per cent of sulphur. 
 Copper and Lead. 
 
 To i gram of ore add 15 cc. of hydrochloric acid 
 and boil for a few minutes. Now add 15 cc. of nitric 
 acid and 10 cc. of sulphuric acid and evaporate to 
 dense white fumes of SO 3 . Cool, add 30 cc. of cold 
 water and filter. 
 
 Place in the filtrate a small piece of aluminum 
 foil (ij inches square and with the diagonal corners 
 bent in opposite directions) and boil until all the cop- 
 per is precipitated on the aluminum. Filter and test 
 the filtrate for copper with hydrogen sulphide. Dis- 
 solve the copper in as little nitric acid as possible, 
 add a few drops of water and evaporate to about 5 cc. 
 Cool, add 20 cc. of water and 5 cc. of ammonia, boil 
 three to four minutes, add 5 cc. of acetic acid, cool 
 and titrate with the sodium thiosulphate solution. Be- 
 fore proceeding to titrate, add 3 grams of potassium 
 iodide crystals and shake well. Add a few drops of 
 the starch solution after the yellow color has begun 
 to fade. (See standardizing the solution.) 
 
 Now take the filter paper containing the lead sul- 
 phate, place it in a beaker with 10 grams of ammonium 
 acetate and 50 cc. of hot water. Heat until all the 
 sulphate is dissolved. Remove from the heat. 
 
MILL AND SMELTER METHODS. 31 
 
 add a few drops of acetic acid and titrate with the 
 ammonium molybdate solution, using the tannic acid 
 indicator. 
 
 Baryta. 
 
 The insoluble residue from the acid treatment is 
 fused with alkaline carbonates, dissolved in hot water, 
 the precipitate of barium carbonate filtered out, dis- 
 solved in dilute hydrochloric acid, boiled, the barium 
 precipitated as barium sulphate by means of sulphuric 
 acid. Or, the weight of the residue in the platinum 
 crucible being known, add a few drops of sulphuric 
 acid and a few drops of hydrofluoric acid, place on 
 the hot plate and evaporate to dryness. Weigh ; the 
 difference between the two weights will be the true 
 silica. 
 
 Antimony and Arsenic. 
 
 In ores, mattes or speiss, flue dust, dross, etc. To 
 i gram of ore in a 3-inch casserole add 10 cc. nitric 
 acid and warm. After the evolution of red fumes 
 has nearly ceased, add about 10 cc. of sulphuric acid 
 and run down to copious fumes of sulphuric acid. Do 
 not boil too long after the dense white fumes of sul- 
 phuric acid have started, or some small amounts of 
 arsenic may be volatilized. 
 
 Allow the casserole to cool and add 40 cc. of cold 
 water and 10 cc. of hydrochloric acid. Some tartaric 
 acid should be added also if antimony is to be deter- 
 mined. Boil to dissolve all soluble matter. If much 
 gangue is present, filter; if not, wash into a No. 3 
 
32 MILL AND SMELTER METHODS. 
 
 Griffin lipped beaker, using warm water, and reduce 
 to a colorless solution \vith a mixture of one part of 
 ammonium bi-sulphite and two parts of strong am- 
 monia. The reduction is best made by adding the am- 
 moniacal solution drop by drop with constant stirring, 
 waiting for the precipitate formed to dissolve after 
 each addition. Do not add any more sulphite than 
 that necessary to reduce to the colorless stage. Add 
 a little more hydrochloric acid in case all the hydrates 
 formed do not dissolve. If there is much gold, sele- 
 nium or tellurium in the ore, these metals will be pre- 
 cipitated by the excess of sulphurous acid and darken 
 the solution; so, if, after the solution is nearly color- 
 less, this darkening occurs, no more sulphite need be 
 added. 
 
 Boil the solution a few minutes until there is no 
 apparent odor of sulphurous acid, and then while still 
 warm, pass in a lively current of hydrogen sulphide 
 gas for about fifteen minutes, or until the precipitate 
 gathers together and the super-natant liquid does not 
 appear murky. It is safer to pass the gas through for 
 a longer time, but in case of hurry, after some expe- 
 rience, the point may be told almost with certainty by 
 inspection. 
 
 Filter the precipitated sulphides through an n 
 cm. filter paper and wash the sulphides all onto the 
 paper with water. Wash out the iron salts. Test the 
 filtrate with hydrogen sulphide gas. 
 
 Put the paper containing the sulphides into a 
 
MILL AND SMELTER METHODS. 33 
 
 4-ounee distillation flask, the arm from the neck of 
 which is bent down at the end so as to connect with 
 a 12-inch Liebig condenser set vertically. If the, sul- 
 phides are too bulky to wrap in the paper and put 
 into the flask, pierce the filter and wash most of the 
 precipitates through the funnel into the flask, using a 
 minimum wash of a volume of hydrochloric acid and 
 i volume of water, used in a wash bottle with a Bun- 
 sen valve. 
 
 Remove the paper and put it into the flask, then 
 pour through the funnel to wash it 50 cc. of the cupric 
 chloride solution. Always pour the chloride solution 
 in through a funnel reaching below the opening at the 
 side of the neck, so as to avoid getting copper into the 
 distillate. 
 
 A thermometer through a rubber stopper is in- 
 serted in the neck of the flask, reaching to within 
 about jr inch from the bottom. The flask is set on a 
 sand bath 4 inches in diameter, so that .the naked 
 flame shall not play on the sides of the flask, thus 
 avoiding the raising of the temperature at any spot, 
 above that desired. Allow the outlet of the condenser 
 to dip about J an inch into a beaker of cold water. 
 
 Heat the flask gradually until the thermometer 
 reads 115 degrees centigrade, then remove the stopper 
 and add 10 to 25 cc. of strong hydrochloric acid, col- 
 lecting the second distillate in water as before. 
 
 The distillate is poured into a No. 3 beaker, made 
 alkaline with ammonia, just acidified with hydro- 
 
34 MILL AND SMELTER METHODS. 
 
 chloric acid, cooled, about 8 grams of bicarbonate of 
 soda and some starch solution added, and titrated 
 with the standard iodine solution. 
 
 Antimony may now be determined after removing 
 the stopper containing the thermometer and inserting 
 another through which is a glass tube reaching nearly 
 to the bottom of the flask and connected to a hydro- 
 chloric acid generator. This generator contains hy- 
 drochloric acid into which sulphuric acid is allowed to 
 drop from a separatory funnel at the rate of about 
 two drops per second. The condenser is sealed with 
 cold water as for the arsenic distillation and heat is 
 applied to the flask until the contents become about 
 dry. Do not heat to a much higher point, since cop- 
 per chloride is liable to come over. Remove the 
 beaker containing the distillate, add a little tartaric 
 acid, almost neutralize with ammonia and pass in hy- 
 drogen sulphide gas. If the orange antimony sul- 
 phide shows up, put under the condenser other beak- 
 ers of water as seals, keeping up the heating and pass- 
 ing in of the hydrochloric acid gas until no precipi- 
 tate is formed with hydrogen sulphide. 
 
 Filter the sulphide of antimony into a tarred 
 Gooch crucible, heat in an air bath at 255 degrees C. 
 for one hour, and weigh. The weight multiplied by 
 71.40 will give the amount of antimony. 
 
 It takes about fifteen minutes each for the arsenic 
 and antimony distillations. In the distillation some 
 uncombined sulphur comes over, but does not affect 
 
MILL AND SMELTER METHODS. 35 
 
 the results. No sulphurous acid or hydrogen sulphide 
 will be found with the arsenous chloride distillate. 
 Antimoriious chloride can not be titrated, owing to 
 other decompositions from the high temperatures re- 
 quired to distill it. 
 
 The solutions required are : Cupric chloride ; dis- 
 solve 300 grams of pure cupric chloride crystals in I 
 litre of hydrochloric acid. This solution is mixed with 
 i litre of a solution of zinc chloride, which boils at 
 180 degrees C. The zinc chloride may be made by 
 adding successively to i pound of pure stick zinc 500 
 cc. of water and 1,250 cc. of hydrochloric acid. After 
 the zinc is in solution, bring to a boil and evaporate 
 a little to bring the boiling point up to 180 degrees C., 
 this making about 1,100 cc. of solution. 
 
 Standard Iodine Solution. 
 
 This is best made so that i cc. equals .00$ grams 
 of arsenic. Dissolve about 40 grams of potassium 
 iodide in a minimum of water, and to this add 17 
 grams of iodine. After the iodine is all dissolved, 
 make up to i litre with distilled water. 
 
 To standardize, dissolve .300 mgs. of C. P. arse- 
 nious acid in a little caustic soda or potash, dilute to 
 about .200 cc., acidify slightly with hydrochloric acid, 
 add about 2 grams of sodium bicarbonate, some starch 
 solution and titrate to a permanent blue. The arse- 
 nious acid contains 75.76% of arsenic. 
 
3 6 MILL AND SMELTER METHODS. 
 
 This method is due to Messrs. Lewis B. Skinner 
 and R. H. Hawley of Colorado Springs, Colorado. 
 
 Modification. 
 
 Treat the ore with nitric acid, and when violent 
 action ceases, add 5 to 10 cc. of hydrochloric acid and 
 evaporate to dryness. If the sample contains organic 
 matter, as in the case of flue dust, treat with nitric 
 acid and potassium chlorate. Take up in water and 
 hydrochloric acid, filter off the residue, neutralize 
 with ammonia, make acid with hydrochloric acid to 
 re-dissolve the precipitate, then add some sodium sul- 
 phide solution and heat to drive off the excess of sul- 
 phur dioxide. Precipiate with hydrogen sulphide 
 solution and proceed as before. 
 
 Mixture Beds. 
 
 Smelter ore beds vary in size from 1,000 tons to 
 several thousand tons, and are built up of the daily 
 ore supplies that reach the works. This ore is spread 
 out in layers, so as to have as even a mixture as pos- 
 sible. When a given bed is about completed, it be- 
 comes necessary to determine its exact chemical com- 
 position, so that the last layer can be added of ores 
 of such nature as to bring the whole up to the definite 
 composition required for the smelter charges, or the 
 metallurgist can, if he so desires, add the necessary in- 
 gredients to each charge. When this is done the fur- 
 naces are run continuously on the given bed, receiving, 
 
MILL AND SMELTER METHODS. 37 
 
 of course, ore of uniform composition and obtaining 
 uniform metallurgical results. 
 
 In order to analyze an ore bed, the chemist makes 
 up a miniature ore bed from the samples of the ores 
 that formed that particular bed. He is given such a 
 list as the following : 
 
 Weight of Ore Sample 
 
 Mine in Pounds. Number. 
 
 Portland 243,342 820 
 
 Summit 23,800 560 
 
 Hercules 44,160 900 
 
 The chemist has already analyzed these ores and 
 still has the samples. From these he now makes up 
 a miniature bed, substituting grams for thousand 
 pounds. Hence, on Summit No. 560, above, he would 
 weight out 23.8 grams, and so on. Since the beds aver- 
 age over 1,000 tons, he will have a very large sample, 
 which he will mix thoroughly and quarter down to a 
 sample of about J pound. From this he will make 
 his analysis, saving the remainder of the sample in 
 case it should be necessary to repeat the determina- 
 tion. 
 
 On all beds the following are determined: Total 
 insoluble,, true silica, iron, lime, manganese, baryta 
 and sulphur; sometimes zinc, alumina, lead (when not 
 determined by fire assay), copper and other elements 
 may be called for. 
 
 Silica, iron, lime, manganese, copper and lead are 
 
38 MILL AND SMELTER METHODS. 
 
 determined by any of the mtehods already given un- 
 der "Ores." 
 
 Alumina, Etc. 
 
 A hydrochloric acid solution of the soluble portion 
 of the ore is obtained, the insoluble residue ignited and 
 weighed in a platinum crucible, fused with alkaline 
 carbonates, extracted with water and HC1, evapo- 
 rated to dryness to separate the silica. Then proceed 
 as in slags, after adding the portion soluble in acid 
 .above, and from which the copper has been removed. 
 
 Briquettes. 
 
 When flue dust, fine ore and sweepings are to be 
 used in the blast furnace, the customary method is to 
 briquette the material first. Such briquettes will con- 
 tain all sorts of material, but the customary analyses 
 call for silica, iron, lime, lead, copper, sulphur and 
 zinc. 
 
 Silica and Iron. 
 
 Place about 2 grams of the sample in an agate 
 mortar and crush as finely as possible (this is made 
 necessary by the fact that fine coke is often disposed 
 of in the briquettes). From this pulverized portion 
 weigh -J gram into a small evaporating dish, add 10 
 cc. of chlorate mixture and evaporate to dryness. 
 Remove and cool the dish and then run to dryness 
 once more with 10 cc. of HC1. Take up in HC1 and 
 water, filter out the insoluble residue and burn it in 
 
MILL AND SMELTER METHODS. 39 
 
 the muffle. Now place the insoluble residue in a sil- 
 ver crucible and fuse it with the smallest possible 
 amount of KOH. Dissolve in hot water, add 5 cc. of 
 HC1 and evaporate to dryness in a casserole ; take up 
 in water and HC1 as before, filter off the silica, burn 
 and weigh. 
 
 The filtrate from the insoluble residue and that 
 from the silica are now combined, boiled, reduced 
 with stannous chloride and titrated with potassium 
 bichromate. 
 
 Lime. 
 
 Since the lime is usually added to the "bricks" 
 in the form of slaked lime, it is easily soluble in dilute 
 HC1. To one gram of the sample, add from 10 to 15 
 cc. of dilute HC1 and bring to a boil. Precipitate the 
 iron with ammonia and add 3 cc. of hydrogen perox- 
 ide to hold up the lead. Boil and filter. Heat the 
 filtrate to boiling and precipitate the lime with am- 
 monium oxalate. Filter and wash thoroughly with 
 hot water. Proceed as in lime in "Slags." 
 
 Zinc, copper, lead and sulphur are determined as 
 in any of the methods already given. 
 
 Note. Fine grinding is only necessary for the 
 portion on which the silica is to be determined; the 
 ordinary sample room fineness of 100 mesh is suffi- 
 'ient for all the other determinations. 
 
40 MILL AND SMELTER METHODS. 
 
 CHAPTER IV. 
 
 Coal and Coke. 
 
 Proximate Analyses (Heinrichs). 
 
 Weigh out in duplicate I gram of powdered coal ; 
 place in a small beaker, cover with a watch glass and 
 place on the steam dryer for twenty-four hours. Take 
 off and weigh ; the loss found multiplied by 100 equals 
 the percentage of moisture in the coal. 
 
 Weigh i gram of the powdered coal into a medium 
 sized porcelain crucible, put the cover on and place 
 the crucible in a medium hot muffle and allow it to 
 remain until fumes cease to come out around the 
 edge of the cover. Remove, cool and weigh ; the loss 
 less the moisture previously found, multiplied by 100, 
 equals the percentage of volatile combustible matter. 
 This should also be done in duplicate and the results 
 should check. 
 
 After weighing the volatile matter, put the mate- 
 rial back in the crucible, replace the cover and return 
 to the muffle until the ash turns white, showing the 
 carbon to be completely burned off. Remove, cool 
 and weigh. The difference between this weight and 
 the last, multiplied by 100, equals the percentage of 
 fixed carbon ; the remainder is ash, which, multiplied 
 by 100, equals the percentage of ash. 
 
MILL AND SMELTER METHODS. 41 
 
 Coke. 
 
 Essentially the same method as for coal. Coke 
 ash is, however, analyzed for silica, iron, alumina and 
 lime, as follows : Burn about 5 grams of coke in the 
 muffle in order to have sufficient ash. Pulverize 
 about 2 grams finely in an agate mortar and from this 
 weigh out and fuse in a platinum crucible gram 
 with from 5 to 7 grams of mixed alkaline carbonates. 
 Dissolve in water and hydrochloric acid and run to 
 dryness, take up with hydrochloric and nitric acids 
 and filter off the silica, burn and weigh. The filtrate 
 is neutralized and boiled with caustic potash. The 
 iron is filtered off, dissolved in hydrochloric acid, re- 
 duced with stannous chloride and titrated with po- 
 tassium bichromate. 
 
 To the filtrate from the iron add hydrochloric acid 
 in very slight excess, neutralize with ammonia, boil, 
 filter and burn the precipitate and weigh as A1 2 O 3 . 
 
 On the filtrate from the alumina, made alkaline 
 with ammonia, lime is determined by means of ammo- 
 nium oxalate. 
 
 Magnesium, when called for, may be determined 
 essentially as in the method given under magnesium 
 in slags. 
 
42 MILL AND SMELTER METHODS. 
 
 CHAPTER V. 
 
 Other Methods of Analysis, 
 
 The methods mentioned previously are those in 
 general use. There remain, however, other methods 
 designed to meet exceptional cases, etc., and methods 
 that may be used as checks on those already given. 
 Antimony and Arsenic. 
 
 To I gram of material add dilute nitric acid (50%) 
 and evaporate almost to dry ness ; take up in 5 to 10 
 cc. HC1 and boil. Add an excess of sodium sulphide 
 and boil well. (In the presence of copper avoid am- 
 monium sulphide.) Filter and retreat the black sul- 
 phides. Now combine the filtrates, acidify with HC1, 
 boil and filter (avoid an excess of HC1). Wash the 
 sulphides off the filter with water, add potassium chlo- 
 rate and boil until free chlorine ceases to come off. 
 Cool, make strongly alkaline with ammonia, add mag- 
 nesium chloride (in case very little arsenic is pres- 
 ent, let stand five to six hours, agitating), filter and 
 wash with strong ammonia. Dissolve the magnesium 
 arsenate in 50% HC1, add potassium iodide and let 
 stand because the action is slow. Titrate with the 
 thio-sulphate solution as in copper. 
 
 Acidify the filtrate from the magnesium arsenate 
 
MILL AND SMELTER METHODS. 43 
 
 with HC1, then lead in hydrogen sulphide gas, warm 
 and filter. Dissolve the precipitated antimony sul- 
 phide in KOH, wash into a flask, washing the filter 
 paper with HC1 containing a little potassium chlo- 
 rate. Now add in the flask a little more chlorate and 
 boil until no chlorine is apparent on iodide starch 
 paper (be careful at this stage not to volatilize the 
 antimony), cool, add potassium iodide and 2 cc. of 
 carbon di-sulphide and titrate with the thio-sulphate 
 solution. 
 
 When tin is present, run down with 50% HC1, but 
 avoid dryness. Add yellow potassium sulphide, or 
 sodium sulphide, and boil well for an hour. Filter, 
 (Sb and Sn are in the filtrate. Volumetrically tin 
 does not interfere with As and Sb.) Acidify with 
 H'Cl, warm and filter. Wash the precipitate into a 
 beaker, rinse the filter paper with a hot concentrated 
 solution of oxalic acid (in which stannic sulphides are 
 soluble), boil and filter. Add nitric acid, boil until 
 red fumes cease (oxalic acid goes to carbonic acid), 
 evaporate to dryness, take up in yellow ammoniiim 
 sulphide, re-precipitate with HC1, filter into a Gooch 
 crucible and ignite in the muffle. Weigh as SnCX. 
 
 Note. There are three ways of getting rid of 
 oxalic acid in the above by permanganate of potas- 
 sium, by sulphuric acid, by nitric acid. The latter is 
 to be preferred, because nitric acid is a volatile acid 
 and can be evaporated. 
 
44 MILL AND SMELTER METHODS. 
 
 Pattinsons Method (Modified). 
 
 Weigh into a No. 4 casserole ^ gram of ore, treat 
 with HNO 3 and HC1, according to requirements, i. e., 
 if an oxidized ore, little or no nitric acid will be re- 
 quired ; if a sulphide, from 5 to 8 cc, will be required. 
 Evaporate to dryness, dissolve in 15 cc. strong HC1, 
 dilute with 100 cc. boiling water, add an emulsion of 
 oxide of zinc until the solution turns red, then a slight 
 excess; now add from 20 to 50 cc. strong bromine 
 water, according to the amount of manganese present, 
 50 cc. being sufficient to ppt. about 40% Mn, boil until 
 all the excess Br has been expelled, and filter through 
 a large filter, washing by decantation, until free from 
 chlorides and bromides. Remove the filter and its 
 contents carefully from the funnel, open it against 
 the side of a No. 3 beaker, wash the ppt. into the 
 beaker with boiling water, cleaning the filter paper 
 as thoroughly as possible. 
 
 Fill a burette with a volumetric solution of oxalic 
 acid (see table on page i) ; from this burette run into 
 the casserole 10 cc. of the solution, add 20 cc. dilute 
 sulphuric acid ( i to i ) and a little boiling water. Dis- 
 solve all the MnO 2 , etc., adhering to the casserole with 
 this mixture, and then pour it over the filter in the 
 beaker, to remove what still sticks to it ; wash the 
 filter with boiling water and remove it from the 
 beaker. Now add to the mixture in the beaker about 
 30 cc. more of the oxalic acid solution (an excess is 
 required), and 200 cc. boiling water. If everything 
 
MILL AND SMELTER METHODS. 45 
 
 does not dissolve, heat until it does and the solution 
 becomes clear. Titrate with the volumetric solution 
 of potassium permanganate until just pink. 
 
 Now determine the value of the oxalic acid solution 
 in terms of the permanganate solution, as follows : 
 Into a No. 3 beaker run 40 cc. oxalic acid solution, add 
 200 cc. boiling water, then 20 cc. dilute sulphuric 
 acid (i to i), and titrate with the permanaganate (it is 
 best to make the solutions exactly equal in value so 
 that i cc. equals I cc). Divide the amount of perman- 
 ganate solution into the amount of oxalic acid solution, 
 to find its value in terms of oxalic acid, multiply 
 the number of cc.'s of permanaganate solution used in 
 the titration by this factor, and subtract from the 
 amount of oxalic acid solution used in the above 
 case 40 cc.'s this will give the amount of oxalic acid 
 oxidized by the MnO 2 , obtained from the ore. 
 
 We have previously found (standardizing a solu- 
 tion of potassium permanaganate) that the ratio of iron 
 to oxalic acid is as 8 to 9. Hence, 
 
 1. Standardize the oxalic acid solution with the 
 permanganate solution and find its equivalent in Fe. 
 Thus, if i cc. equals i cc. exactly, then i cc. oxalic 
 acid equals .01 Fe, or, if I cc. oxalic acid equals .9 cc. 
 permanganate solution, then i cc. oxalic acid solution 
 equals -.009 grams Fe, etc. 
 
 2. Multiply the equivalent in iron by 1.125 to 
 find the value per cc. in oxalic acid, i. e., to find ex- 
 actly how much H 2 C 2 O 4 , 2H 2 O, i cc. of the oxalic 
 
46 MILL AND SMELTER METHODS. 
 
 acid solution contains. This amount is then marked 
 on the bottle. 
 
 3. Multiply the amount of oxalic acid oxidized 
 by the MnO 2 of the ore by .4365 to find the equivalent 
 in Mn, then calculate the per cent. ; or the last two 
 may be combined and the value in iron multiplied by 
 (1.125x4365) equals .49106. 
 Slags. 
 
 Slags which will not decompose by treatment with 
 acids may be either sintered or fused. 
 
 The sintering is performed (see Furman's Man- 
 ual) in a small platinum dish by mixing -J gram of 
 the slag with about ij (one and one-half) grams 
 sodium carbonate in a small agate mortar; transfer 
 this to the platinum dish, brushing the mixture to a 
 small heap in the center ; now place in the muffle and 
 heat until the mass sinters together. Fusion must 
 not take place, since the lead would be reduced and 
 spoil the platinum dish. Remove from the muffle, 
 cool by dipping the bottom of the dish in cold water, 
 then add 2 cc. water and 5 cc. HC1, and proceed as 
 previously directed under silica. 
 
 Fusion, when necessary, is conducted as follows : 
 One-half gram of slag is mixed with about three 
 times as much fusion mixture, and -J gram of potas- 
 sium nitrate (this is added to keep the lead from re- 
 ducing and spoiling the crucible) and fuse in a plat- 
 inum crucible in the muffle. Cool the crucible and 
 place in a No. 4 casserole with about 50 cc. boiling 
 
MILL AND SMELTER METHODS. 47 
 
 water; boil until clean, take out crucible, rinse with 
 hot water, using finger cot if necessary, boil until dis- 
 solved. Cover with a watch glass and add through a 
 pipette 10 cc. strong HC1 ; wash off the cover, remove 
 it, and evaporate to dryness. Treat the dry mass 
 with 50 cc. dilute HC1, boil, dilute with 50 cc. water, 
 filter, wash, ignite and weigh silica. 
 
 Iron. 
 
 To the filtrate add ammonia in slight excess to 
 ppt. the iron, filter and wash, dissolve the ppt. in 
 dilute HC1 and proceed in the usual way. 
 
 Lime. 
 
 To the filtrate from the iron add 10 cc. of a 10% 
 solution of oxalic acid, then make slightly alkaine 
 with ammonia, boil, allow to settle, filter, wash, pro- 
 ceed in the usual manner. 
 
 Lead. 
 
 The purchase and sale of lead ores is at present 
 based on the fire assay. This method, though inaccu- 
 rate, appears to meet the commercial requirements.* 
 The titration by ammonium molybdate already given 
 is the method irf general use where lead is determined 
 in the wet way, but another way, by titration with 
 potassium permanganate, is also in use. 
 
 In this method the lead is separated first as metal, 
 
 * The Colorado Scientific Society is at present gather- 
 ing information as to the best method of determining lead 
 in ores of varying composition. 
 
48 MILL AND SMELTER METHODS. 
 
 then dissolved and pptd. as oxalate, the acid oxalate 
 being titrated with permanganate of potassium. 
 
 Treat -J gram of ore with 15 cc. strong nitric and 
 10 cc. strong sulphuric acids, and evaporate to white 
 fumes over a strong heat, cool, add 50 cc. cold water 
 and 2 grams of Rochelle salts, boil, filter, wash with 
 dilute sulphuric acid ( I to i ) , and then with water. 
 
 Wash the lead sulphate back into the casserole, 
 add 10 grams ammonium chloride, 25 cc. water, ana 
 boil until dissolved; filter and wash with a little more 
 solution of ammonium chloride, wash with boiling 
 water. The filtrate should be received in a No. 2 
 beaker, containing the Al foil, such as was used in 
 the Cu determination. Boil five minutes, when the 
 lead will be completely pptd., and, if in considerable 
 quantity, will usually separate from the foil and unite 
 into a spongy mass. Decant the solution from the 
 lead and aluminum into the casserole and fill the 
 beaker with boiling water; discard the solution in the 
 casserole, being careful that no lead has escaped. Now 
 remove the Al foil and, with the finger cot, remove 
 any adhering lead, wash the foil with boiling water, 
 decanting as closely as possible the last time. Pour 
 over the piece of Al foil 6 cc. dilute nitric acid, to 
 dissolve any particles of lead adhering to it. remove 
 the foil with a glass rod, washing it slightly with a 
 stream of water from the wash bottle, heat the acid in 
 the casserole to boiling so as to dissolve the particles 
 of lead, then pour it upon the greater portion of lead 
 
MILL AND SMELTER METHODS. 49 
 
 in the beaker, heat until dissolved, add a few drops 
 of an acid solution of phenolphthalein, then add a so- 
 lution of sodium hydroxide until slightly alkaline, 
 then 10 cc. of a solution of oxalic acid (i in 10), cool, 
 filter, wash with cold water several times until excess 
 of oxalic acid is removed. Remove the filter paper 
 from the funnel, open against the side of a No. 2 
 beaker, wash the ppt. from the paper into the beaker 
 with hot water, add" 5 cc. dilute sulphuric acid and 
 titrate with a solution of potassium permanganate 
 made by diluting i volume of the i% solution with 4 
 volumes of water, making a solution of which I cc. 
 equals .002 Fe. Multiply the value of the solution in 
 Fe by 1.85 to obtain its value in Pb. 
 Comparing the equations : 
 
 10 FeSO 4 + 2 KMnO 4 + 8 H 2 SO 4 = 5 Fe 2 (SO 4 ) 3 
 + K 2 SO 4 + 2 MnSO 4 + 8 H 2 O 
 and 
 
 10 FeSO 4 + 2 KMnO 4 + 8 H 2 SO 4 = 5 Fe 2 (SO 4 ) 3 
 +2 MnSO 4 +K 2 SO 4 +5 PbSO 4 +8 H 2 O 
 We see that the same amount of potassium perman- 
 ganate will oxidize five equivalents of Pb oxalate, or 
 ten equivalents of ferrous sulphate; 5x207, the 
 atomic weight of lead, therefore, are equivalent to 
 10x56, the atomic weight of Fe. From this we obtain 
 the above factor, 
 5 
 
 560 
 
50 MILL AND SMELTER METHODS. 
 
 Copper. 
 
 Cyanide Method. Weigh i gram into an 8-ounce 
 flask, add from 8 to 15 cc. strong nitric acid (accord- 
 ing to the amount of sulphides in the ore), then add 
 5 cc. strong H 2 SO 4 and evaporate to white fumes 
 over a strong heat, eliminating all nitric acid; remove 
 and place on a piece of asbestos to cool ; when cold, 
 add 30 cc. cold water and 6 grams of sheet zinc in 
 strips ; allow to stand until the evolution of hydrogen 
 has nearly ceased, then add 10 cc. strong commercial 
 H,SO 4 and 50 cc. water, mix by shaking the flask, 
 and allow it to stand until the zinc has completely 
 dissolved, all action has ceased, and the black or red 
 ppt. of copper has completely settled to the bottom 
 of the flask. Fill up the flask with hot water, shake, 
 and allow to settle completely. Carefully decant off 
 as much of the liquid as possible, leaving all the ppt, 
 in the flask ; repeat this washing three times. Dis- 
 solve the pptd. Cu in 5 cc. strong nitric acid and boil 
 off the red fumes, cool, add 20 cc. cold water, then 
 10 cc. strong ammonia, then 50 cc. cold water, mix, 
 titrate with the volumetric solution of KCN until 
 the blue color has become faint,, but still indicates Cu. 
 Filter rapidly through a 20 cm. Prat Dumas plaited 
 filter paper, using a funnel with a 2-inch stem, wash 
 with a little water, then finish the titration exactly 
 as in standardizing the solution. 
 
 Multiply the number of cc. used by the standard 
 
MILL AND SMELTER METHODS. 51 
 
 previously found, and the result by 100, gives the 
 percentage Cu.* 
 
 Or, if the assay of the ore is known (since 2 Ag 
 equals I Cu, or i% Ag equals 0.3% Cu), deduct .1% 
 Cu for each 100 ounces Ag present. Zinc and nickel, 
 which interfere with the titration by cyanide, not 
 being pptd. by the zinc, have been removed. Lead has 
 been converted into insoluble sulphate, or subse- 
 quently that derived from the sheet Zn used, has been 
 pptd. as hydrate by ammonia. 
 
 In both the iodide method (given previously) and 
 in this method, when the Cu is over 20%, a standard 
 of C. P. Cu. should be run at the same time as the 
 ore, and the ore should be run in duplicate, and the 
 results should check. 
 
 Colorimetric To Make Up the Standard. 
 
 One gram.C. P. copper foil is dissolved in just as 
 little HNO 3 as possible, then 10 cc. more of HNO 3 is 
 added. Thoroughly boil off the red fumes, and add 
 distilled water up to 1000 cc. From this solution 
 i cc. is used for every 1/10%. Make alkaline with 20 
 cc. NH 4 OH, and add enough distilled water to bring 
 the bulk up to 350 cc. The standards are placed in 
 
 * Only Ag interfers with this method; it can be re- 
 moved by adding- a few drops of HC1 to the nitric acid 
 solution of the copper before adding the ammonia; shake 
 well to make the silver clot, then filter into another flask 
 and wash well with cold water; add 10 cc. of ammonia and 
 proceed as before. 
 
52 MILL AND SMELTER METHODS. 
 
 large salt-mouth bottles of colorless glass, with 
 glass stoppers. These are kept in a suitable rack, 
 which is lined with white paper and placed in a well 
 lighted part of the room. 
 
 Copper in Slags and Tailings. 
 
 Weigh 2 grams of the pulp into a No. 2 beaker, 
 add 5 cc. HC1, and run to dryness on the steam 
 bath. Take up with 5 cc. HNO 3 and boil until copi- 
 ous fumes are driven off. Now add distilled water 
 and remove from the plate. Add 20 cc. NH 4 OH, and 
 filter into glass bottles. Wash twice with boiling wa- 
 ter, to wash any salt of copper out of the precipitate. 
 Fill the bottle with water to the 350 cc. mark. The 
 bottle is then compared with the standards and the 
 reading divided by 2. 
 
 The mill tailings run higher in copper, hence use 
 only i gram. Add 5 cc of a mixture of HNO 3 +KC1O 3 
 and heat for 1-5 minutes. Now add 30 cc. water and 
 remove. Proceed as before. 
 
 Specimen Lead Slag Analysis. 
 
 % 
 
 Si0 2 30.0 
 
 FeO 28.7 
 
 MnO 54 
 
 CaO 14-2 
 
 MgO 2.3 
 
 ZnO 57 
 
 A1 2 3 5-6 
 
 91.9 
 
MILL AND SMELTER METHODS. 53 
 
 Specimen Bed Analysis for Lead Smelter. 
 
 Total Insoluble, 42.4%. 
 
 % 
 
 SiO 2 33.2 
 
 Fe 12.4 
 
 Mn 4.0 
 
 CaO 4-5 
 
 BaSO 4 9.2 
 
 MgO 0.7 
 
 Zn 2.2 
 
 A1 2 O 8 6.0 
 
 Pb 14.7 
 
 Cu 0.3 
 
 S 47 
 
 Specimen Briquette Analysis. 
 
 % 
 
 SiO 2 . . . . 15.0 
 
 Fe 35.0 
 
 Zn 2.2 
 
 CaO 4.1 
 
 Cu 3.1 
 
 Pb 14.5 
 
 S 4-3 
 
54 MILL AND SMELTER METHODS. 
 
 CHAPTER VI. 
 
 Cyanide Process Daily Work. 
 
 The daily work of a chemist in a cyanide plant 
 varies very much; there is no standard western prac- 
 tice that i know of. In some plants simple titra- 
 tions for strength of cyanide with an occasional de- 
 termination of the gold in solution and heading and 
 tailing assays is all that is called for. On the other 
 hand, at the large works of the Metallic Extraction 
 Company (capacity 10,000 tons per month of sulpho- 
 telluride ore), the routine determinations were as fol- 
 lows: 
 
 Sulphur in ores led to the roasting furnaces. 
 
 Sulphur, soluble and insoluble, in the roasted 
 product. 
 
 Gold in the solutions entering and leaving the 
 precipitators. 
 
 Gold in the final drains from all leaching tanks. 
 
 Titrations of various mill solutions for KCN, alka- 
 linity, protective alkali and the reducing power of 
 mill solutions, etc. 
 
 Bottle tests on all ores received and on all roasted 
 ores, determining acidity, extraction and cyanide con- 
 sumption. 
 
 A weekly analysis of the mill solutions, made up 
 
MILL AND SMELTER METHODS. 55 
 
 in the laboratory from proportional parts of the daily 
 samples received for analysis. This full analysis was 
 afterwards changed to monthly determinations. 
 
 Complete screen analysis of the monthly composite 
 sample (representing all the ores charged to the leach- 
 ing tanks, and all the tailings discharged from the 
 plant), showing the gold value contained at each 
 mesh from 50 to 200 mesh, and the percentage of ex- 
 traction. In addition to the foregoing, special re- 
 search on some line of work always in hand. The 
 general work of a cyanide chemist will, therefore, lie 
 somewhere between the extremes given above, to 
 cover the ground, however, I give in the following 
 notes all the satisfactory analytical methods I am ac- 
 quainted with, many of them will be needed daily, 
 others at much longer intervals, but in time they may 
 all prove useful to the cyanide chemist. 
 
 i. Titration of Cyanide Solutions. *This is in- 
 variably made by Liebig's well known method, de- 
 pending on the fact that when a solution of nitrate of 
 silver is added, drop by drop, to the solution to be 
 tested, each drop of the silver solution forms a white 
 cloud of silver cyanide, which disappears on agitation 
 
 * Mr. J. McDowell recommends for the rapid deter- 
 mination of cyanides, e. g., in the valuation of potassium 
 cyanide for gold extraction, titration with a standardized 
 solution of copper sulphate to which excess of ammonia 
 has been added. The presence of chlorides has no influence 
 on the results. 
 
56 MILL AND SMELTER METHODS. 
 
 so long as the free cyanide is in excess, the reactions 
 being as follows : 
 
 (a) AgNO 3 +KCN=AgCN+KNO 3 . 
 
 (b) AgCn+KCN=KAg(CN) 2 . 
 
 The completion of the reaction is shown by the 
 permanence of a white turbidity or opalescence. As 
 soon as the whole of the free cyanide has been con- 
 verted into the double silver salt, a further drop of 
 silver nitrate in excess gives a ppt. of silver cyanide 
 which does not redissolve on agitation. 
 
 (c) AgNO 3 +KAg(CN) 2 =2 AgCN+KNO 3 . 
 
 From these reactions it is evident that 169.55 parts 
 of AgNO 3 are equivalent to 130.04 parts of KCN. 
 Standard Silver Nitrate Solutions. 
 
 Dissolve 6.519 grams of AgNQ 3 in I litre of water. 
 Every cc. of this solution is equivalent to .005 gram 
 KCN. Hence, if we take 50 cc. of the liquid to be 
 tested, every cc. of the standard AgNO 3 added will 
 represent .01% KCN. 
 
 From the solution to be tested take, by means of 
 a pipette, 50 cc., place in a beaker ; dilute with 50 cc. 
 H 2 O; add 5 cc. of a i% neutral solution of Ki,* and 
 titrate with the standard solution. Or for strong cya- 
 nide solutions, take 13.038 grams of pure crystallized 
 nitrate of silver, dissolve in distilled water and dilute 
 
 * The addition of KI corrects the slight errors due to 
 the presence of caustic alkalis, ammonia, alkaline car- 
 bonates, chlorides, ferrocyanides, thio-cyanates, thio- sul- 
 phates and perhaps some other salts. 
 
MILL AND SMELTER METHODS. 57 
 
 to 1,000 cc. Each cc. of this solution is of course 
 equivalent to o.oi gram KCN and by taking 10 cc. of 
 the solution to be tested each cc. of the silver nitrate 
 solution used in titration will represent 0.10% of free 
 cyanide. 
 
 It is advisable to place about 9 inches of rubber 
 tubing over the end of the pipette, as a safeguard 
 against drawing cyanide solution into the mouth. 
 When the pipette is blown out, fill it with an equal 
 volume of water and add to the cyanide solution in 
 the beaker or flask. The pipette is thus washed out 
 and ready for the next measure of cyanide solution. 
 The method of titration for KCN herein given is for 
 solutions, say, over 0.10%. Below this strength it is 
 not advisable to dilute with water. 
 
 The practice varies considerably in different mills, 
 both regarding the strength of the silver nitrate so- 
 lution, and also the amount of the working cyanide 
 solution taken for analysis. In some works but 10 cc. 
 of solution is taken, and the silver nitrate standard- 
 ized, so that each cc. equals o.io Ibs. of cyanide per 
 ton of solution, or .005%. 
 
 Liebig's method works admirably with pure cy- 
 anide solutions, but gives uncertain and inaccurate 
 results in ordinary working solutions, particularly in 
 the presence of zinc. As, however, it is generally 
 only necessary to obtain relative commercial results, 
 and a knowledge of the real strength of the working 
 
58 MILL AND SMELTER METHODS. 
 
 solution in actual free KCN or its equivalent is not 
 essential, this method is in general use. 
 
 Titration of Alkalinity. 
 
 2. KCN and other simple cyanides of the same 
 class are alkaline to ordinary indicators. The whole of 
 the alkali may be determined by titrating with stand- 
 ard acid, using methyl orange as an indicator. With 
 phenolphthalein the end point is indefinite, owing to 
 the faint action of HCN on this indicator. 
 
 The double cyanide of zinc and potassium is like- 
 wise alkaline to methyl orange. 
 
 For practical purposes it is most important to 
 know the alkalinity exclusive of cyanide, as it is this 
 alkali which is chiefly of use in preventing the un- 
 necessary waste of cyanide by reactions due to base 
 metal compounds, and to the carbonic acid of the air. 
 This may be done (accurately in the absence of zinc) 
 by adding silver nitrate till a slight turbidity is pro- 
 duced, adding phenolphthalein to this turbid solution, 
 and titrating, without filtering, with N/io acid. The 
 result indicates generally 
 
 Equivalent to hydrates in terms of N/io acid plus 
 equivalent of half the alkali metal in normal (mono) 
 carbonates, in terms of N/io acid. 
 
 The reactions in a typical case are : 
 
 KOH+HNO 3 = KNO 3 +H 2 O. 
 K 2 C0 3 +HN0 3 =KHC0 3 +KN0 3 . 
 
 Bi-carbonates are . neutral to phenolphthalein, 
 
MILL AND SMELTER METHODS. 59 
 
 hence are not determined. They have no protective 
 influence in this case. 
 
 When zinc is present the total cyanide is first 
 determined by titration with silver nitrate, using the 
 alkaline iodide indicator. Another portion, say 50 cc. 
 of the original solution, is now taken, an excess of 
 ferrocyanide solution added, and then a little more 
 silver solution than was used in the previous test, to 
 insure the complete conversion of all cyanides into 
 silver salts. Phenol-phthalein is then added and the 
 liquid titrated with standard acid as in the previous 
 method.* 
 
 j. Estimation of Alkalies. 
 Generally only two determinations are attempted: 
 
 (1) What is known as the "total alkali," which may 
 be denned as the equivalent, in terms of KOH, of all 
 the ingredients which are alkaline to methyl orange. 
 
 (2) What is known as "protective alkali." This 
 means, in practice, the alkalinity which the solution 
 shows to phenol-phthalein, after sufficient AgNO 3 
 has been added to convert all the cyanogen of the 
 free cyanides into the double silver salt. 
 
 (i) Titration of Total Alkalies. A measured 
 quantity of the liquid is titrated with N/io acid (any 
 mineral acid may be used, but HNO 3 is preferable), 
 a few drops of a .1% solution of methyl orange being 
 used as indicator. If the addition of acid should 
 
 * Proc. Inst. Min. & Met., Vol. X., pp. 29-37, Green. 
 
6o MILL AND SMELTER METHODS. 
 
 cause a ppt. (as when Zn, Cu or Ag salts are present) 
 it is better to add a moderate excess of acid, make up 
 to a definite volume, and titrate an aliquot portion- 
 with N/io caustic alkali. The substances determined 
 are: cyanides, hydrates, carbonates, bi-carbonates, 
 sulphides, zincates, etc., of the alkali and alkaline 
 earth metals and of ammonium. 
 
 The double cyanides of Zn, Ag, Cu, and perhaps 
 some other metals, give ppts. which represent a con- 
 sumption of acid proportional to the amount of such 
 bodies as may be present, e. g. : 
 
 K 2 Zn(CN) 4 +2 HNO 3 = Zn(CN) 2 + 2 KNO 3 + 
 2 HCN. 
 
 HCN and carbonic acid do not affect methyl or- 
 ange. Ferro-cyanides, ferri-cyanides," and thio-cyan- 
 ates of potassium, sodium, etc., are neutral to all in- 
 dicators. 
 
 (2) Titration of Protective Alkalies. This has 
 already been described. (See above.) All results 
 should be calculated as the equivalent of KOH. 
 4. Manganese in Cyanide Solutions* 
 
 The following process is based on the method 
 given by C. and J. Beringer 1 for the colorimetric es- 
 timation of manganese in ores and compounds free 
 from chlorides : 
 
 * J. C. Clennell, Engineering- and Mining Journal, No- 
 vember 24, 1904. 
 
 1 "Text Book of Assaying," 9th Edition, p. 306. 
 
MILL AND SMELTER METHODS. 61- 
 
 Detection. 
 
 To 100 cc. of the cyanide solution to be examined 
 add 10 cc. concentrated nitric acid. Heat to boiling, 
 then add gradually ^ gram of lead peroxide ; continue 
 boiling for a few minutes, allow to settle, and cool. 
 The presence of manganese is shown by the pink 
 color, due to permanaganic acid. The reaction is very 
 delicate, quantities less than one part in a million of 
 solution being easily recognized. The test is very simple 
 and rapid. If lead peroxide is not at hand, it may 
 easily be prepared by digesting red lead with nitric 
 acid and filtering. 
 
 Estimation. 
 
 An approximate quantitative estimation may be 
 made as follows: The contents of the flask contain- 
 ing the extract from 100 cc., which will be somewhat 
 concentrated by boiling, are again made up to 100 cc. 
 or to some other definite volume, with distilled water 
 recently boiled and cooled. Stir well, and filter 
 through a small paper, rejecting the first portions of 
 the filtrate, say 10 cc. By means of a pipette, draw 
 off an aliquot part of the filtrate, say 50 cc. ; compare 
 the tint immediately with that of an equal volume of 
 distilled water in a similar vessel, to which the stand- 
 ard permanganate is added drop by drop, with con- 
 stant stirring, until the tints of the liquids appear 
 identical. A one-foot test tube of about 60 cc. ca- 
 pacity may be conveniently used for holding the 
 
62 MILL AND SMELTER METHODS. 
 
 liquids; the color should be observed against a white 
 background. 
 
 Standard Permanganate. 
 
 This is made by dissolving 0.1435 gm. of potassium 
 permanganate in 100 cc. pure water, adding 10 cc. 
 pure concentrated nitric acid and diluting to a litre. 
 One cc. of this solution will contain 0.00005 g m - f 
 manganese. Hence, if 50 cc. be taken for a test on 
 an extract from 100 cc. of the original cyanide solu- 
 tion, representing half the original quantity, every cc. 
 of the standard solution used will correspond to 
 0.0001% or i part manganese in 1,000,000. 
 Cautions. 
 
 If the test is merely to be made occasionally, it i< 
 advisable to prepare only a small quantity of this 
 standard solution as required, as it soon loses its 
 strength. 
 
 The success of the process depends entirely on 
 the purity of the reagents used. The distilled water 
 must be quite free from organic matter, iron salts or 
 other reducing agents. In all cases a blank test should 
 be made, using the same quantities of nitric acid, water, 
 lead peroxide, etc., as in the actual assay. The filtrate 
 from this should be colorless, but should give a tint, 
 permanent for at least five minutes, on adding i cc. of 
 the standard permanganate. If this is not the case, 
 a correction must be made -for the reducing power of 
 the reagents. 
 
 Ordinary filter papers have a slight action on the 
 
MILL AND SMELTER METHODS. 63 
 
 permanganate, but this does not materially affect the 
 result, if the test be carried out as described, reject- 
 ing the first part of the filtrate. Attempts to filter 
 through glass wool were not successful, as some finely 
 divided particles of lead peroxide invariably passed 
 through and obscured the tint of the filtrate. 
 
 Influence of Manganese in Cyanide Liquors. 
 
 The presence of manganese may, in some cases, 
 exert an important influence on extraction and pre- 
 cipitation, although the addition of permanaganate 
 has been advocated as an aid to extraction. It appears 
 to exist, at any rate, in the cyanide liquors obtained 
 here, in a very unstable form. It is deposited as a 
 brownish precipitate- on boiling the solution, or even 
 in some cases merely on standing. It is thrown down 
 in a similar form in the zinc boxes at ordinary tem- 
 peratures. When present in considerable quantity it 
 also interferes with the filtration of the cyanide by 
 silver nitrate, sometimes to such an extent as to ren- 
 der the estimation of cyanide impossible. The man- 
 ganese always can be removed, however, by treatment 
 of the solution with sodium sulphide, the excess of sul- 
 phide being afterwards removed by agitation with 
 carbonate of lead in the ordinary way. 
 
 5. Estimation of Free Cyanide. 
 
 Differential Method. Where zinc is the only 
 metal present which is capable of forming easily 
 decomposable double cyanides of the character of 
 K 2 Zn(CN) 4 , a determination of the so-called "total 
 
64 MILL AND SMELTER METHODS. 
 
 cyanide" by the method given below, together with 
 a determination of the zinc, enables us to calculate 
 the free cyanide, assuming one part of zinc equiva- 
 lent to four parts of KCN converted into K 2 Zn(CN) 4 . 
 In this case: 
 
 Free cyanide equals total cyanide minus 4xZn. 
 
 The presence of cyanogen, in the form of ferro- 
 cyanides or thiocyanates, does not affect this re- 
 sult. 
 
 6. Estimation of Total Cyanide. 
 
 Strictly speaking, the term "total cyanide" 
 should indicate the equivalent of all the cyanogen 
 contained in the solution. Practically, it is generally 
 taken to mean "the equivalent, in terms of KCn, of 
 all the cyanogen existing in the form of simple cy- 
 anides, HCN, and certain readily decomposable dou- 
 ble cyanides, such as that of zinc." Some other dou- 
 ble cyanides, such as those of silver and copper, are 
 generally excluded, together with ferro and ferri-cy- 
 anides, thio-cyanates and similar bodies. 
 
 Method Based on Use of Alkaline Iodide Indicator. 
 An indicator is prepared by dissolving 40 grams 
 of caustic soda and 10 grams of KI in water, and 
 making up to a litre. Fifty cc. of the cyanide solu- 
 tion are taken, and 5 cc. of the above indicator added. 
 The liquid is titrated with standard AgNO 3 (6.519 
 grams per litre) until a distinct yellow coloration is 
 obtained, disregarding any white turbidity. This lat- 
 ter may sometimes be removed by adding NH 4 OH, 
 
MILL AND SMELTER METHODS. 65 
 
 which in moderate amounts does not affect the ac- 
 curacy of the test : 
 
 i cc. of AgNO 3 used equals .01% KCN (equiva- 
 lent to total cyanide). 
 
 7. Estimation of HCN* 
 
 Estimation of free HCN in presence of alkaline 
 cyanides and of zinc double cyanides : 
 
 (a) The free cyanide is first estimated in the or- 
 dinary way without addition of alkali. It is assumed 
 that the presence of free HCN does not affect this te- 
 sult. 
 
 (b) Another portion of the liquid is mixed with 
 a solution of potassium or sodium bi-carbonate con- 
 taining no normal carbonate or free CO 2 . The mix- 
 ture is titrated with AgNO 3 as before, the reaction as 
 regards HCN being: 
 
 2HKC0 3 +AgN0 3 +2 HCN KAg(CN) 2 +KN 
 O 3 +2 CO 2 +2 H 2 O. 
 
 The difference of the two titrations gives the 
 equivalent in terms of KCN of the amount of HCN 
 present. 
 
 Bi-carbonates do not decompose K 2 Zn(CN) 4 , but, 
 both titrations being subject to some indefiniteness 
 as to the finishing point, the method is not very satis- 
 factory. 
 
 * Bettel. Proc. Chem. and Met. Soc. S. A., Vol. I., 
 p. 165. 
 
66 MILL AND SMELTER METHODS. 
 
 8. Estimation of F err o cyanide by Means of Potas- 
 sium Permanganate. 
 
 The ferro-cyanide is pptd. as Prussian blue by 
 means of an acidulated solution of ferric chloride. 
 The ppt. is collected and washed thoroughly. It is 
 then decomposed by hot caustic potash, yielding ferric 
 hydrate and potassium ferro-cyanide, filtered, the fil- 
 trate acidulated with H 2 SO 4 , and titrated with stand- 
 ard permanganate. The finishing point is shown by 
 the change from yellow to reddish yel-low. When much 
 ferro-cyanide is present the solution must be diluted, 
 otherwise the end-point is not sharp. About 100 cc. 
 of H 2 O should be added for every o.i grams ferro- 
 cyanide present. The permanganate must be stand- 
 ardized against a solution of pure potassium ferro- 
 cyanide; 3.16 grams KMnO 4 are equivalent to 42.2 
 grams of K 4 Fe(CN) 6 , 3 H 2 O, the reaction being: 
 
 KMn0 4 +5 K 4 Fe(CN) 6 + 4 H 2 SO 4 =5 K 3 Fe(CN) 6 
 +3 K 2 S0 4 +MnS0 4 + 4 H 2 O. 
 
 A centi-normal solution (0.316 grams KMnO 4 per 
 litre) may be conveniently used. 
 
 The chief objection to this method is the difficulty 
 of thoroughly washing the ppt. of Prussian blue. This 
 is absolutely necesasry, as other bodies, e. g., thio-cy- 
 anates, are almost invariably present, which would 
 likewise reduce permanganate in acid solution, 
 p. Estimation of Thio-Cyanates by Means of Iodine* 
 
 * Hupp and Schied. J. S. C. I., 1902. 
 
MILL AND SMELTER METHODS. 67 
 
 This depends on the fact that the thio-cyanates re- 
 act with iodine in the presence of alkaline carbonate, 
 thus: 
 
 KCNS+KHC0 3 +8 I+ 3 H a O=KHSO 4 +6 .HI+ 
 C0 2 +KI+ICN. 
 
 A known quantity of the solution is first boiled for 
 about 15 minutes with | gram of tartaric acid in an 
 open flask to get rid of all HCN, cooled and made up 
 to 100 cc. Of this liquid, 10 cc. are then taken for 
 determination of thio-cyanate. A measured amount 
 of N/io I., more than sufficient for the reaction, is 
 then added, and about one gram of NaHCO 3 . After 
 standing in a stoppered bottle for -J hour in the 
 dark, the excess of I is titrated with N/io thio-sul- 
 phate. 
 
 Shaking the bottle should be avoided in order to 
 prevent the evolution of CO 2 . It is stated that the 
 presence of cyanogen iodide prevents the use of starch 
 as an indicator. It is advisable to work with such 
 quantities that not more than 20 cc. of iodine solu- 
 tion are required. The end of the reaction is shown 
 by the disappearance of the yellow color. 
 
 When zinc compounds of ferro-cyanides are pres- 
 ent, a white or bluish ppt. occurs on boiling with tar- 
 taric acid, which must be filtered off before adding 
 NaHCO 3 and I. 
 
 10. Estimation of "Total Cyanogen." 
 
 The term "total cyanogen" is here taken to imply 
 cyanogen existing in every form, whether as free cy- 
 
68 MILL AND SMELTER METHODS. 
 
 anides, double cyanides, cyanates, thio-cyanates, ferro- 
 and ferri-cyanides, etc. 
 
 (a) Estimation by precipitation with AgNO 3 , 
 using chromate indicator. (Based on Vielhaber's 
 method.) 
 
 This method involves the separate determination 
 of the various cyanogen compounds, and can only be 
 regarded as a check on the combined results. It is 
 not applicable in presence of chlorides, unless they 
 also be separately determined and allowed for. Pro- 
 tective alkali must first be neutralized. 
 
 Standard silver solution is then run in until the 
 reddish color of silver chromate becomes permanent 
 on shaking. The indicator consists of a few drops of 
 a strong solution of neutral (yellow) potassium 
 chromate ; it is advisable to insure the absence of 
 chlorides in the indicator by adding silver nitrate to 
 the chromate solution till a red color is produced, and 
 allowing the ppt. to settle. In this process, cyanides 
 (chlorides), thio-cyanates, iso-cyanates and ferro-cy- 
 anides are pptd. as silver salts. 
 
 (b) Total cyanogen by boiling with oxide of mer- 
 cury and removing mercury by alkaline sulphide. 
 (H. Rose, modified.) 
 
 In case where ferro-cyanides and similar com- 
 pounds are present, the solution is boiled with excess 
 of oxide of mercury until complete decomposition is 
 effected, the liquid nearly neutralized with HNO 3 and 
 filtered. The filtrate is then mixed with Zn(NO 3 ) 2 , 
 
MILL AND SMELTER METHODS. 69 
 
 dissolved in NH 4 OH and H 2 S added gradually until 
 a perfectly white ppt. begins to appear. The ppt. is 
 then allowed to settle, filtered, washed with very di- 
 lute NH 4 OH, and the nitrate titrated with AgNO 3 , 
 with addition of KI as indicator. 
 
 ii. Estimation of Zinc by Decomposition with HNO 3 
 and HCl, and Proceeding by Low's 
 
 Method, Volumetric. 
 12. Estimatio'/i of Copper. 
 
 Volumetrically by iodide titration. Method of A. 
 H. Low. (See Chapter on Smelting.) 
 
 Qualitatively, the presence of copper may readily 
 be detected, even in very small quantities, by acidu- 
 lating the liquid with any mineral acid, and adding 
 a few drops of dilute ferro-cyanide solution, which 
 gives the characteristic reddish-brown color, 
 ij. Estimation of Gold. 
 
 Where the gold or silver are present in quantities 
 sufficient to be easily weighed up from one assay ton 
 of solution, 30 cc. are placed in a lead foil tray 
 3"X2"Xi"> evaporated to dryness, the lead tray 
 rolled up and placed on the hot cupel and the result- 
 ing bead parted and weighed in the usual manner. 
 Due care must be exercised to prevent loss from spit- 
 ting during the last few moments on the sand bath 
 or hot asbestos plate. The following method, while not 
 so rapid, is accurate, and is preferable in all cases 
 where large quantities of solution must be taken for 
 assay : 
 
70 MILL AND SMELTER METHODS. 
 
 Argall's Method. Take 500 cc. of the solution, or, 
 for greater convenience, prepare a pipette to hold 20 
 A. T. of the solution. Take a tall beaker, add 7 grams 
 of zinc dust and pour in the 20 A. T. of solution; 
 next add 10 cc. of commercial H 2 SO 4 , stir well with a 
 glass rod and cover with a watch glass. When the ac- 
 tion begins to fall off add another 10 cc, of acid. The 
 precious metals will be completely pptd. in from 10 to 
 20 minutes, but the solution had best be left in the 
 beaker till the Zn is practically dissolved, usually oc- 
 cupying 30 minutes. A smaller quantity of Zn should 
 not be used, and if the gold and silver is over 0.05 ozs. 
 per ton, 10 grams should be taken. 
 
 When action is completed, filter, add 3 grams of 
 SiO 2 to the residue on the filter paper, fold, place in a 
 10 gram crucible, incinerate in the muffle, remove 
 crucible, and when cool add 10 grams each of flux 
 and litharge; thoroughly mix in the crucible, fuse, 
 cupel, weigh, and part in the usual manner. The flux 
 used consists of 42 parts potash, 84 NaHCO 3 , 2 borax- 
 glass and 9 of flour. Should copper be present in the 
 solution, a larger proportion of flux will be required, 
 and scorification may be necessary. 
 Chiddey Method. 
 
 Five assay tons of the solution is placed in a 
 beaker and brought nearly to boiling. Add 12 cc. of 
 a saturated solution of lead acetate (must be acid, 
 with acetic acid to prevent the precipitation of lead 
 as a hydrate), then add -J gram of zinc dust, allow 
 
MILL AND SMELTER METHODS. 71 
 
 to stand for a few minutes and then add 12 cc. HC1. 
 
 When the sponge is well formed add a small piece 
 of aluminum foil to precipitate any remaining lead, 
 and which keeps the sponge already formed from 
 breaking up. When the excess of zinc appears to 
 have dissolved pour about 10 cc. of HC1 upon the 
 sponge. Remove and decant the liquor, squeeze the 
 sponge together with a rubber policeman and place 
 it upon a piece of lead foil about two inches square. 
 Squeeze as much moisture as possible from the sponge, 
 fold the lead over it and roll it into a ball, making a 
 small hole for steam to escape. Place in a hot cupel. 
 14. Estimation of Silver. 
 
 In the Argall method for gold we determine the 
 combined weight of gold and silver, from which the 
 silver may be calculated after parting the bead with 
 HNO 3 and weighing the gold. I have not tested this 
 method where large amounts of silver were present in 
 solution, but up to 16 oz. per ton I know it gives cor- 
 rect results and without the formation of silver sul- 
 phates. If on richer solutions this was feared, hy- 
 drochloric acid could be substituted for the sul- 
 phuric. 
 
 The following method, recommended by Alfred 
 Chiddey,* has not been tested, though it is claimed to 
 give higher results than the evaporation process in 
 ordinary use. The proportion of silver to gold in the 
 
 * Engineering and Mining Journal, March 2S, 1903, 
 p. 473. 
 
72 MILL AND SMELTER METHODS. 
 
 solutions on which Mr. Chiddey used it is 10 to I, 
 and in case of nearly pure gold solutions the addi- 
 tion of a known quantity of silver nitrate dissolved in 
 cyanide is suggested. Introduce into a porcelain dish 
 four assay tons, or more, of the solution to be as- 
 sayed ; add 10 cc. of a 10% solution of acetate of lead, 
 then 4 grams of zinc shavings ; boil a minute, add 20 
 cc. of hydrochloric acid. When the action has ceased 
 boil again ; wash the spongy lead with distilled water ; 
 transfer it with a stirring rod to a piece of filter pa- 
 per; squeeze into a compact lump and place in a hot 
 cupel. The mouth of the muffle should contain a 
 piece of dry pine wood, so that the muffle is filled with 
 flame at the moment of introducing the spongy 
 lead. 
 
 15. Purple of Cassius Test for Gold* 
 
 Precipitate the gold with zinc dust; dissolve the 
 excess of zinc with dilute sulphuric acid ; dissolve the 
 gold in aqua regia and add a few drops of tin chloride 
 Compare the color obtained with a standard. 
 
 The cyanide solution to be tested must be strength- 
 ened by the addition of a few drops of a strong cy- 
 anide solution, say of 15% KCN, so that the solution to 
 be assayed may contain i% free KCN. To 200 cubic 
 centimeters of the solution add about I gram of zinc 
 dust. Heat the solution to boiling point. Filter off 
 the cyanide solution. Add to the remaining zinc dust 
 
 * A. Prister. Journal of the Chemical and Metallurg- 
 ical Society of South Africa. 
 
MILL AND SMELTER METHODS. 73 
 
 about 20 cubic centimeters of dilute (10%) sulphuric 
 acid and dissolve all the zinc by gently warming. Fil- 
 ter off through the same filter the solution of zinc 
 sulphate formed. Dissolve the residual metals in 10 
 cc. of aqua regia and pass while boiling repeatedly 
 through the same filter, and collect the gold solution 
 in a test tube. 
 
 To the gold solution a few drops of stannous chlo- 
 ride are added after the solution has been cooled by 
 holding the test tube in water. 
 
 If the solution is rich in gold, the purple of Cas- 
 sius coloration will appear directly ; if it is poor, the 
 color will require a few minutes to become evident. 
 The aqua regia used can be made by mixing six parts 
 of strong hydrochloric acid, two parts of strong nitric 
 acid and six parts of distilled water. 
 
 16. Qualitative Detection of Gold. 
 
 The presence of gold in quantities less than o.i 
 mgr. may be detected in cyanide solution by acidulat- 
 ing, boiling till most of the HCN is expelled, then 
 adding KC1O 3 and again boiling till most of the 
 chlorous gases are driven off, and finally adding stan- 
 nous chloride, which gives the well known purple of 
 Cassius. The final solution should not be too strongly 
 acid, or the color may not appear. It frequently be- 
 comes more marked on allowing to stand for some 
 time. 
 17. Estimation of the Reducing Power of Solution. 
 
 Definition: The reducing power of a solution is 
 
74 MILL AND SMELTER METHODS. 
 
 the number of cubic centimeters of N/io perman- 
 ganate which must be added to give a permanent col- 
 oration with i cc. of the solution to be tested, a suffi- 
 cient amount of free sulphuric acid to be present in 
 every case. 
 
 Indirect Estimation by Adding Excess of Perman- 
 ganate.* 
 
 Acidify the solution to be tested and add a mod- 
 erate excess of permanganate, allow to stand for some 
 time, then add an excess of potassium iodide to the 
 pink liquid until the color changes to brownish yel- 
 low; in this reaction iodine is liberated in proportion 
 to the excess of permanagante present. Titrate the 
 iodine with standard thiosulphate, using a starch in- 
 dicator prepared with the addition of caustic soda. 
 Deduct the equivalent of the iodine thus found, in 
 terms of standard permanganate, from the total 
 amount of permanganate added, and the remaining 
 permanganate corresponds to the reducing agents 
 present in the solution tested. 
 
 To standardize the permanganate, add an excess 
 of potassium iodide to a measured volume and deter- 
 mine the amount ot thiosulphate required to destroy 
 the color. 
 
 Standard permanganate, 3.16 grams per litre. So- 
 dium thiosulphate, 24.8 grams per litre. Potassium 
 iodide, 16.6 grams per litre. 
 
 *J. E. Clennell, "The Chemistry of Cyanide Solutions." 
 
MILL AND SMELTER METHODS. 75 
 
 18. Estimation of Alkaline Sulphides* 
 
 On adding an excess of a solution of the double cy- 
 anide of silver to a liquid containing alkaline sul- 
 phides, free cyanide is produced in proportion to the 
 amount of sulphide present. 
 
 2 KAg(CN) 2 +K 2 S=Ag 2 S+4 KCN. 
 
 Filter off the precipitated sulphide of silver and 
 estimate the cyanide by adding potassium iodide and 
 titrating in the usual way with silver nitrate. 
 
 If there be any cyanide present in the original 
 liquid it may be separately determined after treat- 
 ment with lead carbonate and deducted from that 
 previously found. 
 
 Prepare the silver double cyanide by adding sil- 
 ver nitrate to a solution of 0.5% KCN until a slight 
 permanent turbidity is formed. Allow to stand for 
 a time, then filter. 
 Estimation of Sulphides by Colorimetric Test with 
 
 Sodium Nitro-prusside. 
 
 The following method by Dr. J. Loevey of Johan- 
 nesburg is quite simple and can be rapidly carried 
 out: The required solutions are : (a) Standard so- 
 dium sulphide, Na 2 S 40 grams and NaOH, 0.2 gram, 
 dissolve to one liter, i cc. of this solution=o.oo53 
 gram, (b) Standard zinc sulphate: ZnSO 4 7 H 2 O, 
 44.15 grams per litre. I cc.=o.oi gram Zn. (c) 
 Sodium nitroprusside : 5 grams of the salt dissolved 
 
 * J. E. Clennell, "The Chemistry of Cyanide Solutions." 
 
76 MILL AND SMELTER METHODS. 
 
 in 100 cc. of water, to which 5 drops of 5% cyanide 
 are added. Sodium nitroprusside is prepared in the 
 following manner: Dilute concentrated nitric acid 
 with an equal volume of water and mix with pow- 
 dered potassium ferrocyanide in the proportion of 2 
 parts K 4 FeCN 6 3H 2 O to 5 parts diluted HNO 3 . Warm 
 on the water bath until the liquid gives a dark green 
 or slate colored precipitate instead of blue, with fer- 
 rous sulphate. It is then cooled, neutralized with 
 sodium carbonate and filtered. Two similar cyaniders 
 are taken. In one is placed a measured volume of the 
 liquid to be tested, and in the other an equal volume 
 of pure cyanide solution free from sulphide, and con- 
 taining approximately the same amount of free cya- 
 nide as the first. One cc. of 5% solution of sodium 
 nitro-prusside is now added to each. If the liquid 
 in the first cylinder contains sulphides, a coloration 
 is produced, while that in the second cylinder remains 
 colorless. Sodium sulphide solution (about 4%) is now 
 run in from a burette, drop by drop, to the second 
 cylinder till the color in the two vessels is the same. 
 The amount used gives the amount of sulphide, calcu- 
 lated as Na 2 S, present in the first cylinder. The so- 
 dium sulphide solution should be carefully standard- 
 ized ; this may be done by any of the ordinary meth- 
 ods, as, for example, by means of a zinc sulphate solu- 
 tion of known strength, using ferric hydrate as exter- 
 nal indicator. 
 
MILL AND SMELTER METHODS. 77 
 
 Qualitative Tests for Alkaline Sulphides. 
 
 (a) Place a few' drops of the clear solution on a 
 piece of clean, bright silver, or agitate the solution 
 gently with a piece of clean silver foil; if sulphides 
 are present the silver will be blackened. 
 
 (b) The most delicate test, however, is nitro- 
 prussides. 
 
 Add a little of the nitro-prusside solution to the 
 cyanide solution to be tested; if an alkaline sulphide 
 is present the solution will assume a purple color. 
 
 The following method for estimating cyanogen in 
 commercial cyanide is said to be more accurate than 
 Liebig's and is recommended by Adair.* 
 
 The method to be described was originally devised 
 for the estimation of ferro-cyanide in pot-metal (a 
 very impure product). It can be readily adapted for 
 the estimation of cyanogen in commercial cyanide, 
 and is preferable to the silver methods for this pm- 
 pose because, although not quite so quick, only the 
 useful cyanide is estimated. Cyanates, sulpho-cy- 
 anides, sulphides and chlorides, even in large percent- 
 ages, do not sensibly affect the result. 
 
 The outline of the method is to convert the cy- 
 anide as such into ferro-cyanide ; next to oxidize with 
 KMnO 4 , in the presence of H 2 SO 4 . The ferro-cy- 
 anide is oxidized to ferri-cyanide only, whereas cy- 
 anates, sulpho-cyanides and other impurities are either 
 distinctively oxidized or converted into substances 
 
 * Jour, of the Chem. Soc. of So. Africa, Jan., 1903. 
 
78 MILL AND SMELTER METHODS. 
 
 which do not interfere with the final steps of reducing 
 the ferri-cyanide to ferro-cyanide, and the titration of 
 the latter with KMnO 4 in acid solution. 
 
 Estimations can be made in 15 minutes, and con- 
 cordant results are obtained in different operators' 
 hands. 
 
 The solutions required are: 
 
 25% caustic alkali. 
 
 20% H 2 SO 4 pure. 
 Saturated solution of KMnO 4 , approximate strength 
 
 only. 
 Saturated solution of FeSO 4 , approximate strength 
 
 only. 
 
 N/io KMnO 4 . i cc. equals .156 grams total Cn, or 
 more convenient strength, I cc. equals .100 total CN. 
 
 The solution is standardized with K 4 Fe(CN) 6 + 
 3 Aq. 3 grams are dissolved in 300 cc. H 2 O and 15 cc. 
 of the 20% acid are added. 
 
 88oX3 
 
 =Value CN in grams per cc. 
 
 i57-9Xcc. consumed 
 
 ip. Method. 
 
 Ten grams of the cyanide are weighed into a litre 
 flask and about 200 cc. water used to dissolve it; add 
 2 cc. of the alkali solution and a quantity of Ire 
 FeSO 4 solution equal to 12 grams FeSO 4 +7 Aq. Add 
 the latter 5cc at a time and shake well. 
 6 KCN&FeS0 4 +alkali=K 4 Fe ( CN ) 6 +K 2 SO 4 +alkali. 
 
 The reaction is immediate. Add H 2 SO 4 and Prus- 
 
MILL AND SMELTER METHODS. 79 
 
 sian blue is formed. Then 15 cc. H 2 SO 4 and saturated 
 solution of permanganate until the color remains per- 
 sistent ; the color can be seen through the edges. 
 
 One or two cc. or more in excess does not matter. 
 The above quantity of acid is enough for each gram of 
 KMnO 4 added, but if more than I gram KMnO 4 is 
 used, acid must be added in the same proportion, viz : 
 15 cc. to each gram of KMnO 4 used. If much sulpho- 
 cyanide is present allow to stand 15 minutes, and, if 
 necessary, a further addition of KMnO 4 may be re- 
 quired. The reaction is: 
 
 5 K 4 Fe(CN) 6 +4H 2 S0 4 +KMn0 4 =5 K 3 Fe(CN) 6 
 +3 K 2 SO 4 +MnSO 4 +4 H 2 O. 
 
 Next add FeSO 4 solution in quantity equal to 15 
 grams and immediately 15 cc. alkali solution. The so- 
 lution must be strongly alkaline. Shake thoroughly 
 and make up to the mark, again mixing thoroughly. 
 
 Filter through a large folded filter. The titration 
 is completed by taking 500 cc. or an aliquot portion, 
 adding 20 cc. H 2 SO 4 and adding the standard KMnO 4 . 
 
 The influence of the precipitate on the results is 
 small. It may be ascertained by testing a weighed 
 portion of pure K 4 Fe(CN) 6 , 3 H 2 O, adding the quanti- 
 ties of solutions as for an impure sample.* 
 
 Impurities in commercial cyanide may be detected 
 in the following manner.* Potassium cyanate will dis- 
 solve in alcohol of specific gravity 0.849, an d this so- 
 
 t Allen, Engineering and Mining Journal, Aug. 15, 1903, 
 p. 239. 
 
8o MILL AND SMELTER METHODS. 
 
 lution, on addition of hydrochloric acid, will evolve 
 carbon dioxide. Or, on adding water to the alcoholic 
 solution, and boiling off the alcohol, the liquid will 
 give a precipitate of calcium carbonate with calcium 
 chloride. Cyanate may also be detected by the follow- 
 ing application of Blomstrand's color reaction: A 
 strong solution of the sample is decomposed by passing 
 carbon dioxide through it until no more hydrocyanic 
 acid is evolved. By these means E. A. Schneider 
 (Journal, Society Chemical Industry, 1895, p. 887) 
 found that 3 grams of potassium cyanide were decom- 
 posed in 45 minutes. To the resulting liquid Schnei- 
 der adds sufficient 95% alcohol to precipitate the pot- 
 assium carbonate formed. The filtrate is then slightly 
 acidified with acetic acid, and some cobalt acetate so- 
 lution added. An intense blue color, due to the forma- 
 tion of the double cyanide of cobalt and potassium, is 
 produced, which renders easy the detection of as little 
 as 0.35% of cyanate. If present in smaller quantities, 
 more of the cyanide must be taken, dissolved in the 
 smallest possible quantity of water, and the greater 
 part of the cyanide precipitated by the addition of 
 absolute alcohol. The filtrate is then treated with car- 
 bon dioxide, and tested as before. 
 
 Chlorides may be detected by silver nitrate, added 
 in excess, which throws down silver cyanide as a white 
 curdy precipitate. They may be determined by Sie- 
 bold's volumetric method. 
 
 L. Siebold has shown that chlorides, when present, 
 
MILL AND SMELTER METHODS. 81 
 
 may be conveniently determined in the same liquid in 
 which the cyanide has been estimated by neutralizing 
 the excess of free alkali (which should not be am- 
 monia) by the cautious addition of dilute nitric acid, 
 adding a few drops of a solution of neutral potassium 
 chromate and continuing the addition of the silver so- 
 lution until the red tint due to the formation of silver 
 chromate remains permanent. If cyanide only be 
 present, the volume of silver solution now required 
 will be exactly equal to that previously employed to 
 obtain a permanent turbidity, whereas any excess over 
 this amount represents the silver solution correspond- 
 ing to the chlorides present. 
 
 Formates, if present, will cause the salt to blacken 
 on ignition. They may be detected more certainly by 
 precipitating the cold dilute solution of the samplo 
 with excess of silver nitrate solution, filtering cold and 
 heating the clear liquid. In presence of a formate, 
 metallic silver will be precipitated. The nitrate from 
 the precipitate produced by silver nitrate will also give 
 a red color with ferric nitrate or sulphate if a formate 
 be present. 
 
 Carbonates will remain insoluble on treating the 
 sample with hot alcohol of 0.849 specific gravity. 
 
 Silicates can be detected and estimated in the ordi- 
 nary way by evaporation to dryness with hydrochloric 
 acid, the residue insoluble in acidulated water being- 
 silica. 
 
 Sulphates are detected by the formation of a white 
 
82 MILL AND SMELTER METHODS. 
 
 precipitate on adding barium chloride to a solution of 
 the sample previously acidulated by hydrochloric 
 acid. 
 
 Sulphides will give a black precipitate with mer- 
 curic chloride and a yellow precipitate with a solution 
 of cadmium. They can be separated by agitating the 
 solution with lead carbonate. 
 
 Free ammonia can be recognized by the smell and 
 determined by treating the solution with an alkaline 
 solution of sodium hypo-bromite and measuring the 
 nitrogen gas evolved. 
 
 20. Estimation of Bromo Cyanogen and Potassium 
 Bromate. 
 
 An N-io solution of sodium-thio-sulphate is used 
 in the determination of bromo cyanogen and potas- 
 sium bromate. This solution will contain 12.4 grams 
 of Na 2 S 2 O 3 5 H 2 O, therefore I cc. will be equivalent 
 to 0.00265 gram of bromo cyanogen or to 0.00141.' 
 grams of potassium bromate. 
 
 Potassium Bromate. Take 200 milligrams of the 
 dry salt, dissolve in 100 cc. of distilled water, then 
 add about 15 to 20 cc. of dilute hydrochloric acid, 
 and 3 to 5 grams of potassium iodide. Iodine will be 
 liberated and the solution is then titrated to colorless- 
 ness by N-io sodium-thio-sulphate solution. For 
 more accurate work starch solution should be used as 
 an indicator. 
 
 Bromo Cyanogen. Take 5 to 10 cc. of the solu- 
 tion to be estimated, dilute with 25 to 50 cc. of dis- 
 
MILL AND SMELTER METHODS. 83 
 
 tilled water, add 5 cc. of dilute hydrochloric acid and 4 
 to 5 grams of potassium iodide, iodine is liberated and 
 the solution is then titrated to colorlessness by N-io 
 sodium-thio-sulphate solution, or starch solution can 
 be used as an indicator. 
 
 The presence of potassium cyanide in the solution 
 will not interfere with the titration for bromo cyano- 
 gen, consequently the method can be used on mill so- 
 lutions and it is also noteworthy that in the estima- 
 tion of potassium cyanide in the same solutions with 
 silver nitrate, in the usual way, bromo cyanogen does 
 not interfere with the test, except in the presence of 
 cyanogen, due to the reactions between bromo cyano- 
 gen and potassium cyanide, and in this case the 
 method gives somewhat lower results. 
 
84 MILL AND SMELTER METHODS. 
 
 CHAPTER VII. 
 
 Estimation of Oxygen in Working Cyanide Solutions. 
 
 It is a well known fact that in the cyanide process, 
 as ordinarily used, the solution must contain oxygen 
 in order to dissolve the gold. Realizing the import- 
 ance of this, about ten years ago the Chemical and 
 Metallurgical Society of South Africa offered a gold 
 medal to anyone who should find a method of actually 
 determining the oxygen in a working cyanide solution. 
 This medal was awarded to Mr. Andrew F. Crosse, in 
 January, 1899. 
 
 The following description of his method is adapted 
 and condensed from Mr. Crosse's articles published in 
 Volume II. of the Transactions of the Chemical and 
 Metallurgical Society of South Africa, pages 396, 419 
 and 476. 
 
 Estimation of Oxygen in Working Cyanide Solutions. 
 By A. F. Crosse. 
 
 The ordinary working cyanide solution contains 
 substances which prevent the direct application of 
 Thresh's well known method for the determination of 
 oxygen dissolved in water, as described in Sutton's 
 Volumetric Analysis, pages 277-283. By preliminary 
 treatment, however, these substances can either be re- 
 moved or neutralized, without affecting the oxygen 
 
MILL AND SMELTER METHODS. 85 
 
 present in the solution, leaving it amenable to Thresh's 
 method. This method is based on the fact that iodir.e 
 is liberated when potassium nitrate and sulphuric acid 
 are brought together in water containing free O, 16 
 parts of O liberating 254 parts of I. 
 
 Apparatus Necessary. 
 
 i "Winchester quart" white glass bottle, with ac- 
 curate fitting glass stopper and of known capacity. 
 about 2,\ litres. 
 
 i Smaller glass bottle 16 oz. 
 
 i 50 QC. burette, for ZnSO 4 solution. 
 
 1 Rubber stopper, with two holes, to fit large bottle. 
 
 2 293 cc. Thresh's separatory tubes, ground glass stop- 
 
 pers. 
 
 i Large, wide-mouthed bottle, white glass, 
 i Rubber stopper, with 4 holes, to fit same, 
 i 50 cc. burette for hyposulphite solution. 
 i Small pipette with stopcock for NaNO 2 , KI solution, 
 i Small pipette with stopcock for H 2 SO 4 solution, 
 i 350 cc. flask. 
 
 Beakers, glass tubing, rubber tubing, etc. 
 
 Solutions. 
 
 ZnSO 4 , 7 H 2 O. 200 grams made up to i litre ; i cc. 
 solution=2 grams ZnSO 4 , 7 H 2 O. 
 Phenolphthalein . 
 
 Na 2 S 2 O 3 7.75 grams per litre water. 
 Bromine water. 
 
86 MILL AND SMELTER METHODS. 
 
 ( NaNO 2 .5 grams. 
 KI and sodic nitrite solution : KI 20 grams. 
 
 ( H,O ioo cc. 
 KI and starch. 
 
 The Method Consists in : 
 
 First Adding KOH. 
 
 Second Adding ZnSO 4 , 7 H 2 O. 
 
 Third Determining hyposulphite required by 
 Thresh's method with clear solution decanted from 
 precipitates formed in the closed bottle. 
 
 Fourth Qualitative tests for nitrites. 
 
 Fifth Correction for nitrites and reagents used. 
 
 The Winchester quart and the 16 oz. bottle are 
 filled with the solution to be tested; the contents of 
 the latter to be used for preliminary work, and the 
 former for the actual analysis. 
 
 Take ioo cc. from the small bottle, add a few drops 
 of phenolphthalein and run in the 20% solution of 
 ZnSO 4 until the alkaline action has disappeared, which 
 is seen at once by the characteristic magenta color hav- 
 ing vanished. It is advisable to filter the solution after 
 the first disappearance of the pink coloration, as the 
 ppt, carries down the coloring matter. The amount 
 required for the Winchester quart, the contents 01 
 which are known, can then be calculated. 
 
 Add 5 or 6 grams of solid KOH to the Winchester 
 quart, and, when dissolved, add the required amount of 
 solid ZnSO 6 , 7 H,O, taking care not to allow any air to 
 enter the solution. Replace the stopper, shake the bot- 
 
MILL AND SMELTER METHODS. 87 
 
 tie well and let it stand for some time, so that the floc- 
 culent ppt. of cyanide of zinc may settle, and obtain 
 a clear supernatant liquid. If possible, let stand over 
 night. When the ppt. has settled sufficiently, the 
 liquid is siphoned off. Use a two-holed rubber stopper, 
 with a siphon passing through one hole, and a short, 
 bent tube through the other, and start the action by 
 blowing through this bent tube, as one would use a 
 wash bottle. The end of the siphon in the liquid should 
 have a small bag of lint tied over it, to prevent the 
 carrying away of any small particles of ppt. In this 
 way, fill the two 293 cc. separatory tubes and put them 
 aside for the present. Draw off the same quantity, 
 293 cc. into a beaker, add I cc. H 2 SO 4 (half acid and 
 half water) and i cc. of iodide of potassium and starch. 
 From a burette, add carefully, drop by drop, dilute 
 bromine water (i bromine water to 2 of water) till a 
 blue color is obtained, and note the number of drops. 
 
 Take this tube with the solution to be tested, add i 
 cc. NaNO 2 and KI solution and i.o cc. H 2 SO 4 (half 
 acid, half water) and the number of drops of bromine 
 water required, put in the stopper and turn over the 
 tube several times. Iodine is at once set free in pro- 
 portion to the oxygen in the solution, and is ready to 
 be determined by titration with hyposulphite, accord- 
 ing to Thresh's method. 
 
 The wide-mouthed glass bottle, having a rubber 
 stopper pierced with four holes, is here used, and coal 
 gas, or CO 2 , must be passed through it during the ex- 
 
88 MILL AND SMELTER METHODS. 
 
 periment. The CO 2 must be purified by passing- 
 through a potassium iodide and freed from oxygen. 
 The tube containing the solution is inserted through 
 the third hole and the hyposulphite burette through 
 the fourth. Coal gas (or CO 2 ) is passed through the 
 bottle for 15 minutes, and then the KCN solution is 
 allowed to flow into the bottle and also a few drops 
 of starch solution, which becomes blue at once. The 
 stopcock is turned off and the free iodine is deter- 
 mined by dropping in hyposulphite solution, slowly, 
 until the blue color disappears ; 7.75 grams of hypo- 
 sJphite in I litre of water gives a solution, I cc. of 
 which corresponds to .25 milligrams of O. A correc- 
 tion must be made for the O in the reagents used. 
 
 Nitrate of potash (or soda) is oxidized by the ad- 
 dition of bromine water, and liberates iodine. To de- 
 termine the correction necessary for this iodine, take a 
 350 cc. extra strong flask, and pour into it the same 
 amount of solution as taken for the analysis. Add a 
 few drops of KOH and close the flask with a one-hole 
 rubber stopper containing a glass tube with stopcock. 
 Boil the solution for several minutes and close the 
 cock. Cool the flask, pour the contents into the tube, 
 add i cc. of iodide of potassium and nitrate solution, 
 and i cc. dilute H 2 SO 4 (half and half) . Place the burette 
 in the stopper of the wide-mouthed glass bottle, turn 
 on the gas, and after 10 minutes run the solution into 
 the bottle ; add a few drops of starch, and titrate, as 
 before. The quantity required will give the correc- 
 
MILL AND SMELTER METHODS. 89 
 
 tion for the nitrates in the solution, and also for the 
 reagents used, as the same amount of H 2 SO 4 , and also 
 the same amount of KI, containing- potassium nitrite, 
 is used in each case. 
 
 Calculations. 
 Let 
 
 L = capacity of Thresh's tube, minus reagents 
 used = 293 3 = 290 cc. 
 
 X = milligrams of oxygen per litre in the solution 
 under examination. 
 
 M = correction for nitrites and oxygen in the 
 reagents used. 
 
 N = hyposulphite of soda used in the final deter- 
 mination. 
 Then, 
 
 (N M)X .25X1000 
 
 - =X. 
 L 
 
 . In actual analysis the following results were ob- 
 tained : 
 
 N = 10.2 cc. M = 2.8cc. 
 (10.2 2.8) X .25X1000 =6.3 mg. O per litre. 
 
 290 =.0063 grams O per litre. 
 
 Precautions. 
 
 In all stages of the analysis care should be taken 
 to prevent the addition of air to the solution. 
 
 The bromine water in the lower part of the bur- 
 ette under the stopcock quickly detoriates by loss of 
 
90 MILL AND SMELTER METHODS. 
 
 Br, and should, therefore, be run off before beginning 
 the titration. 
 
 The following shorter method is recommended bN 
 Prister:* 
 
 The oxygen in cyanide solutions is determined by 
 measuring the volume of the gases expelled from the 
 solution on boiling, absorbing the oxygen by alkaline 
 pyrogallate solution, and measuring the residual ni- 
 trogen ; the weight of the oxygen is obtained by meas- 
 uring in a Japp gravi-volumeter a quantity of air cor- 
 responding to the volume of oxygen found. To re- 
 ceive the gases expelled from the boiling solution a 
 Lunge nitrometer may be used, to the side tube of 
 which a flask completely rilled with the cyanide solu- 
 tion is connected by a piece of capillary tubing, also 
 rilled with the solution, the pyrogallate being intro- 
 duced through the funnel after disconnecting the flask. 
 Or else a Rammelsburg burette filled with water free 
 from air may be used to receive the gases, the side 
 tube of the burette being connected to a vessel con- 
 taining water, whilst the upper end is joined, after 
 the gases have been expelled from the cyanide solu- 
 tion, to a U-shaped tube containing the pyrogallate 
 solution ; the mixed gases are forced to enter this 
 tube repeatedly by raising and lowering the water res- 
 ervoir. The boiling of the cyanide solution must in 
 this case be continued until the water in the burette 
 
 * A. Prister. Journal of the Chemical and Metallurg- 
 ical Society of South Africa. 
 
MILL AND SMELTER METHODS. 91 
 
 becomes warm, when it may be assumed that any 
 gases dissolved by it have been again expelled. Not 
 less than 300 cc. of the solution should be taken for 
 each test. Either modification of the method is said 
 to give good results. 
 
 Specimen Analysis of Mill Solutions. 
 
 The exact composition of mill solutions is, of 
 course, constantly changing with the nature of the 
 ores treated, or through other causes, but on the whole, 
 after it has taken up 'its zinc and formed the decom- 
 position products, the solution, when properly looked 
 after, does not change materially. This is to be ex- 
 pected, as while apparently the same solution is used 
 over and over, this is not strictly so. Part of the solu- 
 tion is lost in every charge worked, zinc is pptd. in 
 every charge of ore and other reactions take place, so 
 that, broadly speaking, the solution is continually 
 changing through chemical reactions, is being wasted 
 and lost in one end of the process and added to and 
 made up in the other. The following specimen analy- 
 sis of the solutions in use at the works of the Metallic 
 Extraction Company show great uniformity even 
 after years of use. 
 
 Starting in with a pure solution of potassium cya- 
 nide, (a) shows its composition after one-half year's 
 use, (b) after two and one-half year's use, and (c) 
 after six vears' use. The same amount of variation 
 
92 MILL AND SMELTER METHODS. 
 
 could easily have been found in an examination of the 
 analysis for the first six months. 
 
 (a) % '(b) % (c) % 
 
 KCN 0.455 o-53 0-3 80 
 
 HCN 0.058 0.0269 0.060 
 
 K 4 Fe(CN) c 0.095 0.0580 0.036 
 
 KCNS 0.023 0.0388 0.050 
 
 ZN 0.338 0.3340 0.374 
 
 Ca 0.085 0.1560 0.176 
 
 Alkalinity 0.560 0.5400 0.720 
 
 Total solids in solution i .970 1 .9020 1 .962 
 
MILL AND SMELTER METHODS. 93 
 
 CHAPTER VIII. 
 
 Ore Testing by the Cyanide Process. 
 
 A very important part of the duties of the chem- 
 ist in a cyanide works is to make extraction and con- 
 sumption tests on the ores received. It is not unusual, 
 in large custom works, to make such tests on each' lot 
 of ore received. But of greater importance, perhaps, 
 is the testing and examination of ores for the pur- 
 pose of determining their adaptibility to cyanide 
 treatment. 
 
 Preliminary Tests. 
 
 A physical examination of the ore will give a good 
 idea of the screen aperture through which it must be 
 passed in order to obtain a good extraction. For ex- 
 ample, if the ore is a porous or cellular oxidized -pro- 
 duct, perhaps, crushing through a 0.44" screen aper- 
 ture will suffice; if of dense and solid structure it 
 'should be crushed to pass screen apertures varying 
 from 0.024 to 0.018 inch. Flinty material, pyritic and 
 telluric, silver ores, etc., may have to be reduced to 
 impalpable powder to obtain the desired extraction. 
 
 Roasting, apart from oxidizing or driving off the 
 volatile metals, also resembles fine crushing in that it 
 makes the ore porous, allowing the solutions to pene- 
 trate between the individual ore particles, much as if 
 
94 MILL AND SMELTER METHODS. 
 
 they had been reduced to a very fine state of division. 
 Consumption Test. 
 
 These are best made with direct cyanide solutions, 
 and, as lime is invariably used to correct acidity, add 
 it at once and note results. Weight up 4 separate A. 
 T.'s of the crushed ore and place in 250 cc. glass 
 stoppered bottles ; add fresh slacked, pure lime, at the 
 rate of 5, 10, 15 and 20 Ibs. to the ton of ore and then 
 30 cc. of cyanide solution to each bottle; place on the 
 agitator for 30 minutes; filter and determine cyanide 
 consumption. 
 
 The lowest consumption may be found with 10 Ibs. 
 of lime (excess of lime will itself consume cyanide)* 
 -indicating that about 10 Ibs. of lime should be used per 
 ton of ore. 
 
 If a high consumption of cyanide is shown when 
 15 to 20 Ibs. of lime are added, see if soluble cyanides 
 can be removed by preliminary water washes (use 
 three washes, each double the volume of the ore). 
 
 Should the cyanide consumption remain high after 
 water washing, look out for oxidized copper com- 
 pounds, and, if their presence is proven, treat the ore 
 first to three washes of 5% sulphuric acid, followed by 
 an alkaline wash (sodium hydrate preferably). 
 
 * The consumption of cyanide in laboratory tests when 
 pure solutions are used is usually 25% higher than mill 
 results with zinciferous solutions. (P. Argall, Min. Indus- 
 try, Vol. VI., page 373.) 
 
 > 
 
MILL AND SMELTER METHODS. 95 
 
 Organic compounds are often rendered harmless 
 by a preliminary treatment with sulphuric acid. 
 
 If the acid wash fails, try concentrating out the 
 heavy minerals previous to cyaniding. Copper, anti- 
 money, lead and other sulphides are thus removed, and 
 the tailings are invariably rendered amenable to cya- 
 nide treatment. 
 
 _ A 
 
 Preliminary Extraction Tests. 
 
 These are preferably made in the glass stoppered 
 bottles used for the cyanide consumption tests. Should 
 the ore under investigation be a gold ore, containing 
 no appreciable amount of silver, weigh up loj A. T.'s 
 of the puverized ore, add the amount of lime found 
 necessary to neutralize acidity, and place in the glass 
 stoppered bottles. Make up the following solutions 
 of cyanide from the stock bottle : 
 
 0.300% Put 30 cc. in each of two bottles. Dupli- 
 cate tests. 
 
 0.200% Put 30 cc. in each of two bottles. Dupli- 
 cate tests. 
 
 0.100% Put 30 cc. in each of two bottles. Dupli- 
 cate tests. 
 
 0.050% Put 30 cc. in each of two bottles. Dupli- 
 cate tests. 
 
 0.025% Put 30 cc. in each of two bottles. Dupli- 
 cate tests. 
 
 Place on agitator for eight hours. Allow to stand 
 for four hours, so far as one set of bottles are con- 
 cerned, allowing the duplicates to remain on the agi- 
 
96 MILL AND SMELTER METHODS. 
 
 tator sixteen hours. Remove, decant on to dry filter 
 paper, take up 10 cc. of the filtrate and titrate for 
 cyanide consumption. Now wash out the bottles and 
 give two water washes on the filter, dry and assay the 
 residue for gold in the usual manner. 
 
 From these tests the following are deduced : 
 
 (1) The proper strength of the solution to attain 
 the best results on the ore. 
 
 (2) The time required for agitation, eight, six- 
 teen or more hours. 
 
 (3) The cyanide consumption. 
 
 These tests are quickly and cheaply made, and can 
 be repeated or modified and concordant results ob- 
 tained, results which are satisfactory to competent 
 cyanide experts. 
 
 It has been found that, for silver ores, solutions 
 from 0.25% to 0.75% are necessary to attack the sul- 
 phides, hence the following solution strengths are rec- 
 ommended for silver or for gold-silver ores: 0.25%, 
 0.30%, 0.40%, 0.50%, 0.75%. 
 
 The lime found necessary in bottle tests to neutral- 
 ize the acidity is about 35% more than is required on 
 a full working scale. Mass action in the latter case 
 probably accounts for this. 
 
 Should the extraction on all the series of bottles 
 be low, put on another series, using the percentage 
 of cyanide that promised the better results in the 
 previous case, but have the ore reduced to different 
 degrees of fineness, say to pass a screen aperture of 
 
MILL AND SMELTER METHODS. 97 
 
 o.on" About 40 apertures to the inch. 
 0.0087" About 50 apertures to the inch. 
 0.0055" About 100 apertures to the inch. 
 0.0030" About 150 apertures to the inch. 
 0.0025" About 200 apertures to the inch. 
 
 These would show the increased extraction due to 
 fine grinding,* and, should the extraction remain un- 
 satisfactory, add, after two hours' agitation, in a new 
 series of bottles, 0.15% to 0.25% of the weight of the 
 cyanide present in 'solution, of cyanogen-bromide. 
 This salt will often give good gold extraction- on 
 heavy sulphides or medium-grade gold telluride ores, 
 particularly when the ore is ground fine. Moreover, 
 by the use of cyanogen-bromide, the cost of roasting 
 may be avoided, and it then becomes necessary to 
 compare the cost of fine grinding plus -bromo cyanide 
 with that of roasting. 
 
 The bromo cyanogen is best added at intervals of 
 two or more hours, as its action is rapid and is not 
 maintained for any considerable time. If, for exam- 
 ple, the agitation test is to be for a period of eight 
 hours, the bromo is best added at two hours, four 
 hours and six hours from the starting of the test ; the 
 bromo cyanogen acts as a cyanogen liberator, displac- 
 
 * The finer the ore is ground, the easier and quicker 
 the silver sulphides are attacked by weak solutions. Com- 
 mercial results will thus lie between fine grinding anfl high 
 cyanide consumption, for, the weaker the solution the 
 lower the cyanide consumption. 
 
98 MILL AND SMELTER METHODS. 
 
 ing one molecule of cyanogen from the KCN present 
 and at the same time giving- off its own cyanogen 
 thus : 
 
 KCN+Au+KCN ( 
 
 Br CN+Au+KCN j = 
 
 Potassium cyanide has practically no action on 
 gold tellurides, but the cyanogen liberated in the 
 nascent state in the cyanide solutions, by the addition 
 of bromo cyanogen, acts as a powerful solvent, both 
 of the gold and the tellurium, provided the ore is in 
 the finest possible state of division. It will be noted 
 that oxygen is not required in the above reaction, and. 
 unlike agitation tests with plain cyanide, the bottles 
 can be filled with ore and solution, or very nearly so, 
 whereas with cyanide only, ample air space should be 
 left in the bottles and the stoppers removed once or 
 twice during the agitation and the air renewed. 
 
 Bromo- cyanogen is a very difficult substance to 
 obtain in the West, but, in reference to its use in West 
 Australia, Mr. Alfred James states:* ''It is now usu- 
 ally made on the spot, from imported bromo-salts, in 
 view of the difficulty of getting the steamship com- 
 panies to carry the actual bromo-cyanide crystals. 
 The method of preparation is as follows : Bromo salts 
 include potassium bromide and bromate, roughly in 
 quantities required for the reaction. Assuming this 
 to be 2KBr+KBrO 3 + 3KCN + 3H 2 SO 4 =3BrCN + 
 
 Engineering and Mining Journal, Jan. 7, 1904. 
 
MILL AND SMELTER METHODS. 99 
 
 3 K 2 S0 4 + 3H 2 0. 238 + 167 + 195 + 294 318 + 
 522 + 54- 
 
 "Bromo salts imported from Germany are very 
 impure, but contain the correct mixture to satisfy the 
 above reaction. The charge used at Kalgoorlie to gen- 
 erate 100 pounds of BrCN is : 
 
 Mixed bromo salts 125 Ibs. 
 
 Cyanide ( 100% ) 65 Ibs. 
 
 Sulphuric acid (70%) 147 Ibs. 
 
 "The salts are agitated in a wood or lead lined vat 
 of about 200 gallons' capacity, securely covered by a 
 lid, through which a revolving stirrer or paddle works. 
 Above this is a small vat, in which is stored the neces- 
 sary charge of cyanide dissolved in forty gallons of 
 water. The vat is first three-fourths filled with water, 
 the agitator started, and the sulphuric acid added 
 slowly and carefully. The whole charge is now left 
 to stand until cool, say one hour, as the great heat 
 generated by the addition of the acid would destroy 
 the bromo-cyanide. When cool, the mixed bromo- 
 salts are added gradually and the solution of cyanide 
 run in simultaneously with constant stirring. The re- 
 action commences almost immediately, but is not thor- 
 oughly completed until after six hours' continuous 
 agitation." 
 
 This method can be modified for laboratory use 
 where the bromo-salts are not available, as, for exam- 
 ple, following the equation given above, we may pro- 
 ceed as follows: 
 
ioo MILL AND SMELTER METHODS. 
 
 Weigh up 25 grams of potassium bromate and 
 35-5 grams of potassium bromide and dissolve them 
 in about 400 ce. of cold water. (Solution A.) 
 
 Weigh up 29.25 grams of potassium cyanide and 
 dissolve in 200 cc. of water. (Solution B.) 
 
 Dilute 44 grams of sulphuric acid to 400 cc. and 
 cool thoroughly. (Solution C.) The strength of the 
 sulphuric acid should be determined with an N-io so- 
 lution of sodium hydrate, I cc. of which is equivalent 
 to .0049 grams sulphuric acid. 
 
 Place solution (C) in a large flask when quite 
 cool, place a funnel in neck and pour in solutions 
 (A and B) simultaneously and in very small streams, 
 allowing them to mix in the funnel and drop into the 
 acid solution in the large bottle. Finally agitate the 
 mixture for six hours, When the reaction should be 
 complete and the solution ready for use. This solu- 
 tion should titrate about 4.5% bromo cyanogen (4.7% 
 theoretically). If the reactions are completed the solu- 
 tion should be neutral to methly orange and phe- 
 nolpthalein ; should it be acid, however, it must be 
 carefully neutralized by an N-io potassium or sodium 
 hydrate solution, as alkali decomposes bromo cyano- 
 gen care must be used to avoid any excess. Bromo 
 cyanogen made in this way will, according to Fulton,* 
 keep several months in a tight stoppered bottle. 
 
 For accurate tests or delicate research work, pure 
 
 * Bulletin No. 1 of the South Dakota School of Mines, 
 which see for fuller details, if required. 
 
MILL AND SMELTER METHODS. 101 
 
 crystals of bromo cyanogen can be made from bromine 
 and mercuric cyanide, as follows: When one part of 
 liquid bromine is allowed to flow gradually on 2 parts 
 of mercuric cyanide (dry salt) in a retort t surrounded 
 by ice, bromo cyanogen and mercuride bromine are 
 formed with great evolution of heat. 
 
 Bromo cyanogen sublimes in needles, contaminated 
 with free bromine, which, however, flows back into the 
 retort and enters into complete combination. Gentle 
 heat, by means of an alcohol lamp, is then applied and 
 the Br CX sublimed into a receiver surrounded by ice 
 water. Bromo cyanogen crystals obtained in this way 
 can be kept in a tightly-corked bottle in a cold place 
 for use indefinitely. 
 
 Roasting. 
 
 Should none of the foreging tests give satisfactory 
 results the ore may be roasted in the muffle, first to 
 a dead roast ; second, in case of silver ores, by a chlo- 
 ridizing roast, as plain roasting invariably interferes 
 very seriously with silver extraction, and almost as 
 persistingly greatly increases the extraction of the 
 gold. 
 
 In a chloridizing roast the loss of gold by volatili- 
 zation is often very heavy, and should, in all cases, 
 be determined in the following manner : 
 
 f The apparatus for this work is best a small retort 
 and receiver, the retort having an opening for a small 
 thistle tube with stop cork for the introduction of bro- 
 mine. 
 
102 .MILL AND SMELTER METHODS. 
 
 Mix the necessary amount of dry salt with the ore, 
 and reduce to pass the desired screen aperture. As- 
 say for gold and silver, then weigh up 50 to 100 grams 
 of the mixed ore and salt, place in a roasting dish 
 and set in a cool muffle.* Gradually raise the temper- 
 ature to cherry-red. When the fumes cease coming 
 off, remove, cool and weigh. Note the loss of weight, 
 then assay for gold and silver and calculate the loss 
 of precious metals. 
 
 In practice the salt is often added toward the end 
 of the roasting furnaces to prevent gold losses in the 
 earlier stages of roasting. Chloridizing roasting is 
 only necessary for silver ores, and where the amount 
 of the silver is considerable, it may be preferable to 
 leach the roasted ore first with sodium thiosulphate to 
 remove the silver chloride ; wash well, and extract the 
 residue of the gold and some of the silver compounds 
 by cyanide solutions. Except for the fact that gold is 
 soluble in thiosulphate solutions, a combination of the 
 former, with the cyanide process, could be used on 
 chlorodized ores ; the former to remove the silver, the 
 latter the gold. I have found that thiosulphate would 
 extract in some cases 50% of the gold present in chlori- 
 
 * Chloridizing roasts must be started at a very low 
 temperature and gradually raised to cherry-red at the end, 
 moreover, when the sulphur exceeds 4%, a preliminary 
 roast is desirable, then cool, add the salt and complete the 
 roast. Gold is easily volatilized as chloride, but is, to a 
 large extent, recoverable from the dust collected in a 
 proper system of condensing flues. 
 
MILL AND SMELTER METHODS. 103 
 
 dized ores, while subsequent cyanide treatment ex- 
 tracted not only a large proportion of the remaining 
 gold, but also, in cases, as much as 10% of the remain- 
 ing silver values. The Patera process is cheaper than 
 cyanide in the treatment of these ores, but it never 
 gives a satisfactory gold extraction. Therefore, when 
 the cyanicides can be removed by preliminary water 
 washes, followed by an alkaline wash, the cyanide 
 process will extract both the gold and silver in one 
 operation, greatly shortening and simplifying the 
 treatment of the ore. In testing ores, as above out- 
 lined, the chemist should clearly keep in mind that 
 the solution of his problem is, that process or combi- 
 nation of processes that will give the highest results 
 at the least expense of operation, and, if possible, the 
 the smallest investment of capital in a plant. 
 
 Modification of Bottle Test. 
 
 In the foregoing tests it is assumed the ore treated 
 in the bottles is fine enough for assaying. Should 
 this not be the case, the extraction can be determined 
 by assaying the solutions by the evaporation, or the 
 Argall method (see page 67). The solutions from one 
 bottle would be used for determining cyanide con- 
 sumption, the duplicate being used for this assay. 
 Apart from this it is always advisable to test an occa- 
 sional solution assay against the corresponding tailing 
 assay, the one giving the precious metal extraction, 
 the other the amount remaining in the tailings, and 
 
104 MILL AND SMELTER METHODS. 
 
 they should check within the limits of experimental 
 error. 
 
 If the ore experimented with is to be treated by 
 agitation, the bottle tests give all the information re- 
 quired, if, by percolation, it is necessary to establish 
 the ratio of time between agitation and percolation. 
 It is, of course, variable, but approximates i for agita- 
 tion to 4 for percolation. 
 
 Percolation l^ests. 
 
 These can be made in glass percolators holding 
 about four pounds of ore. The ore, in which is thor- 
 oughly incorporated the required amount of lime, 
 should be placed evenly and carefully in the percola- 
 tor, gently pressed around the sides to prevent chan- 
 neling, and the solution added on top. The strength 
 of the solution to be used has been previously deter- 
 mined from the results of the bottle tests. 
 
 Allow the solution to stand on the ore four hours, 
 then allow to percolate through. Allow the ore to 
 drain dry every day ; after the second day's treatment, 
 turn the ore out from the percolator when drained 
 dry, and cut out a sample for assay, to show the ex- 
 traction, and return the remainder to the percolator. 
 Keep up this sampling, daily, until the final extrac- 
 tion is reached, so far as one percolator is concerned. 
 Allow the duplicate to run on without being disturbed, 
 but it must be drained dry daily. 
 
 The percolator tests should follow the usual cya- 
 nide practice : 
 
MILL AND SMELTER METHODS. 105 
 
 1. Water, or alkaline wash, if required. 
 
 2. Weak solution. 
 
 3. Strong solution. 
 4 Weak solution. 
 
 5. Water wash. Finish. 
 
 If the preliminary wash is unnecessary, add at 
 once the strong solution, followed by No. 4 and No. 5. 
 
 When copper or organic compounds are present, 
 or to obtain details of change in the solutions, sev- 
 eral small-sized working tests may be made in wooden 
 or steel vats, holding 1,000 or 2.000 pounds of ore. 
 Proceed as with the percolators, but allow the solution 
 to pass through filiform zinc in two or more glass or 
 porcelain cells. Note the precipitation and analyze 
 the solutions on completion of the tests. Be careful 
 that the solutions are aerated before returning them to 
 the leaching vats, for, as the solutions in percolating 
 through a charge of ore are gradually deprived of their 
 oxygen, it is found that the lowest layers of ore, those 
 nearest the filter, do not extract as well as those layers 
 above. This can be remedied by running on an occa- 
 sional aerated solution from below. This must be per- 
 formed slowly, to avoid forming holes or channels in 
 the charge. In this way solutions rich in oxygen are 
 brought in contact with the bottom portions of the 
 charge, and a more even extraction thus obtained. 
 
io6 MILL AND SMELTER METHODS 
 
 CHAPTER IX. 
 
 The Analysis of Bronzes and Bearing Metals. 
 
 By I-I. E. Walters and O. I. Affelder.* 
 
 Bronzes. 
 
 Weigh I gram of the sample (-J gram if the lead 
 is over 15%) into a No. 2 beaker, cover with a watch- 
 glass, add 10 cc. nitric acid (Sp. Gr. 1.42) and warm 
 until all is dissolved. When in solution, add 40 cc. 
 hot water and boil five minutes, filter, wash with a 2% 
 nitric acid solution, burn and weigh as SnCX. To the 
 filtrate add 25 cc. strong ammonia and heat to boiling, 
 then add about 5 grams ammonium per-sulphate and 
 boil from five to ten minutes. Make acid with sul- 
 phuric acid, filter and wash with hot water. The lead 
 will remain on the filter as lead peroxide. Transfer 
 the precipitate and lead to a beaker in which the pre- 
 cipitation was made, add water and stir well to disin- 
 tegrate the filter paper. Dilute to 600 to 700 cc. with 
 cold water, add about 3 grams potassium iodide and 
 some starch solution. When all the iodide is dissolved, 
 add 10 cc. hydrochloric acid, stir well and titrate with 
 1/20 normal solution sodium thio-sulphafe until the 
 solution changes from the dirty and dark yellow solit- 
 
 * Journal American Chemical Society, June, 1903. 
 
MILL AND SMELTER METHODS. 107 
 
 tion to a bright lemon yellow ; or an excess of sodium 
 thio-sulphate may be added and the excess titrated 
 with 1/20 normal iodide solution until the color 
 changes from the bright yellow of the lead iodide 
 present to the dirty and dark yellow. The number 
 of cc. of sodium thio-sulphate used, multiplied by 
 0.5175, will give the percentage of lead. Where speed 
 is not desirable the lead may be determined by adding 
 sulphuric acid to the filtrate from the oxide of tin, or 
 the lead and copper may be deposited with the elec- 
 tric current. 
 
 Dilute the filtrate from the lead peroxide to 500 
 cc., heat to boiling and add 50 cc. of a 20% sodium 
 thio-sulphate solution, boil five minutes, filter, wash 
 with hot water, burn and weigh as CuO. 
 
 Copper may also be determined as in the following 
 method, which is a modification of Low's method : 
 Dissolve gram of the sample in 10 cc. nitric acid. 
 When in solution, dilute with cold water and add so- 
 dium carbonate until the solution is alkaline, make 
 acid with acetic acid and add about 3 grams potassium 
 iodide and some starch solution. Titrate with a so- 
 dium thio-sulphate solution which has been standard- 
 ized with pure copper. 
 
 Oxidize the filtrate from the copper sulphide 
 thrown down by the thio-sulphate as described above, 
 with nitric acid and potassium chlorate and evaporate 
 until the volume is about 300 cc. Make a basic acetate 
 separation and determine iron or aluminum by the 
 
io8 MILL AND SMELTER METHODS. 
 
 well-known methods. Make the filtrate from the iron 
 or alumina strongly alkaline with ammonia, heat to 
 boiling and add ammonium per-sulphate, boil five 
 minutes, filter, and wash with hot water, burn, and 
 weigh as Mn..O 4 . 
 
 To the filtrate from the manganese add ammonium 
 phosphate in excess, .heat to boiling, and add hydro- 
 chloric acid until there is but a slight excess of am- 
 monia, boil five minutes, filter, and wash with hot 
 water. The ppt. may be dried and weighed as 
 ZnNH 4 PO 4 , or it may be filtered on a Gooch 'crucible 
 and ignited to Zn 2 P 2 O 7 . It may also be titrated with a 
 standard acid and alkali. 
 
 Any nickel which may be present will be found 
 in the filtrate from the zinc, and may be pptd. as 
 sulphide and ignited to NiO. 
 
 If manganese is present in small quantities, it may 
 be determined in a separate portion by the following 
 method: Weigh 0.2 gram of the sample into a suit- 
 able test tube, add 10 cc. nitric acid (Sp. Gr. 1.20), and 
 warm until the sample is dissolved and all nitrous 
 fumes are driven off. Add 15 cc. silver nitrate solu- 
 tion (1.33 grams of the salt to I litre of water) and 
 about -J gram of ammonium per-sulphate, warm until 
 the manganese is oxidized to permanganic acid, cool, 
 transfer to a beaker, dilute to 100 cc. and titrate with 
 standard sodium arsenite or hydrogen peroxide until 
 disappearance of the pink color. 
 
MILL AND SMELTER METHODS. 109 
 
 Determination of Phosphorus. 
 
 To determine phosphorus, dissolve I gram of the 
 sample in 5 cc. fuming nitric acid, evaporate to expel 
 most of the free acid, add 10 cc. cone. HC1 and water, 
 heat to boiling and ppt. the lead, tin and copper with 
 metallic zinc, filter and wash with hot water. To the 
 filtrate add some iron solution free from phosphorus 
 and 10 cc. HNO 3 , boil a few minutes, and then ppt. 
 with ammonia and filter to separate most of the zinc, 
 dissolve the ppt. in hot HNO 3 and ppt. the phosphorus 
 with molybdate solution. The yellow ppt. may be 
 weighed or titrated. 
 
 Bearing Metals. 
 
 If the sample is high in tin and low in lead, pro- 
 ceed as outlined for bronzes ; but if the sample is high 
 in lead and contains antimony, proceed as suggested 
 by Mr. George Hopkins, chemist to the Carrie fur- 
 naces of the Homestead Steel Works, he having found 
 that the addition of an excess of pure tin will insure 
 the complete separation of the antimony with the 
 oxide of tin. Weigh 0.5 gram of the sample and J 
 gram of pure tin into a tall No. 2 beaker, cover with 
 a watch-glass, add 20 cc. HNO 3 (Sp. Gr. 1.33) and boil 
 down to a pastiness, add 40 cc. hot H..O and boil a few 
 minutes, filter and wash with a 2% HNO 3 , burn an.1 
 weigh as SnO,+Sb 2 O 4 . The filtrate is made strongly 
 alkaline with caustic potash and the lead oxidized by 
 adding about 10 grams ammonium per-sulphate. Tl.c 
 
no MILL AND SMELTER METHODS. 
 
 rest of the analysis is carried out as outlined for 
 bronzes. 
 
 To determine the antimony, weigh i gram of the 
 sample and i gram KI into a No. 2 beaker, add 80 cc. 
 HC1, (Sp. Gr. i.io) and boil gently for one hour, filter 
 on a weighed paper of Gooch crucible and wash with 
 dilute HC1, and then with hot H,O until free from 
 chlorides. Wash once with alcohol, dry for one hour 
 at iooC. and weigh. The increase in weight is me- 
 tallic antimony. Calculate this to Sb L ,O 4 and subtract 
 from the weight of the stannic mixed oxides ; calcu- 
 late the tin from the weight of the stannic oxide found 
 and subtract the tin which was added. 
 
 Arsenic is determined in a separate portion by any 
 of the well-known distillation methods. 
 
 Bismuth, if present, would be found with the cop- 
 per sulphide, and can be determined by dissolving the 
 copper sulphides in HNO n and ppting. the bismuth 
 with ammonia. 
 
MILL AND SMELTER METHODS, in 
 
 CHAPTER X. 
 
 Refinery Methods. 
 
 Determination of Lead in Base Bullion. The 
 most accurate method that the author has been able 
 to find is due to Dr. Paul Jannasch (Praktischer Leit- 
 faden der Gewichtsanalyse, Heidelberg, 1897).. The 
 sample is taken by means of a punch, from one to four 
 samples being taken from each bar in the lot. These 
 samples, representing the whole lot, are melted in a 
 graphite crucible and poured into a wide, shallow 
 mould. Such a bar will represent a lot of from one 
 to thirty or more tons ; one-half of the bar, cut length- 
 wise, goes to the shipper, while from the other half 
 samples are cut with a cold chisel for assay. The 
 chemist is thus supplied with about 1X3 inches of the 
 sample, from which he removes sufficient for his de- 
 termination with a file. Set the piece lengthwise in a 
 vise and first remove the oxidized outer surface with 
 the coarse file, then take the part for assay. 
 
 To i gram of the filings in a 3-inch casserole add 
 5 cc. nitric acid and 3 cc. water and evaporate to dry- 
 ness. Be careful not to oxidize the Sb present to SbO 2 . 
 Add 15 cc. of water and again evaporate to dryness, 
 when the lead will be seen to be crystallized. Take 
 up in dilute nitric acid, boil and filter. Heat the fil- 
 
ii2 MILL AND SMELTER METHODS. 
 
 trate to boiling, and in a test-tube heat 15 to 20 cc. of 
 a 10% solution of potassium bichromate. Add the boil- 
 ing bichromate solution to the boiling nitrate, grad- 
 ually, and with constant stirring. Now add while 
 still warm,, 25 cc. of a I to 3 mixture of water and 
 ammonia, carefully, and with stirring. Remove from 
 the heat and allow to cool. When quite cold, filter 
 and wash with a cold dilute solution of i part ammo- 
 nia to 25 parts water. Dry the precipitate at 100 C. 
 Brush the precipitate out on a piece of glazed paper, 
 removing as much as possible from the filter paper. 
 In a weighed porcelain crucible burn the filter paper 
 at a low heat, then add the precipitate from the glazed 
 paper, cover, and gradually raise the heat, by a blast 
 lamp, to a cherry red. After keeping at this heat for 
 from fifteen to twenty minutes, remove the crucible, 
 cool in a desiccator and weigh as PbCrO 4 . Multiply 
 by 64.05 to obtain the percentage of lead. 
 
 Knoor Method for Determining Arsenic and Anti- 
 mony in Lead Bullion, by Distillation in 
 the Knoor Distilling Flask. 
 
 Take \ or I gram of the material, depending upon 
 the amount of As or Sb present the greater the 
 amount, the less the material taken but never more 
 than i gram on account of the difficulty of washing 
 thoroughly a bulky precipitate of sulphides. Treat 
 directly in the Knoor flask with 10 cc. cone, sulphuric 
 acid and take down to dense fumes. Allow the flask 
 
MILL AND SMELTER METHODS, nj 
 
 to cool. Add 10 to 15 cc. water and allow to cool 
 again. Now connect with the condenser and receiver 
 and add 20 cc. cone, hydrochloric acid. Commence 
 distilling, adding through the funnel drop by drop 
 continually hydrochloric acid stock solution made by 
 adding 200 cc. of water to an acid bottle full of C. P. 
 hydrochloric acid. The rate of this addition should 
 not be so great as to greatly increase the bulk in the 
 flask, yet an excess of HC1 must be present to form the 
 "OUS" chloride. The arsenic comes over in the first 
 five minutes, the beaker is changed for another and a 
 proof run for one minute to be sure that the As is com- 
 pletely distilled. Another beaker is then substituted 
 and the distillation for antimony commenced. The 
 heat is raised gradually until fumes show in the con- 
 denser. The density of these fumes is the guide ; they 
 should not be too dense, otherwise the heat is too great, 
 and should you be working on copper material the 
 cuprous chloride would come over. Hydrochloric acid 
 is now dropped in much more slowly, the rate being 
 diminished as soon as the arsenic is distilled. The only 
 reason for adding HC1' during the antimony determina- 
 tion is that the top of the flask would become too hot 
 and the solution "buck" or draw back. The antimony 
 distills in from 40 minutes to one hour, during which 
 time the flask must be protected from absolutely any 
 drafts even walking by quickly will cause a draft 
 which will cause the flask to cool off slightly and 
 "buck." 
 
114 MILL AND SMELTER METHODS. 
 
 The arsenious chloride and the antimonius chloride 
 are precipitated with hydrogen sulphide, allowed to set- 
 tle over night, filtered onto a Gooch crucible, washed 
 with water, alcohol, carbon sulphide, alcohol and 
 ether, in the order named. This treatment is neces- 
 sary, especially with antimony, in order to avoid high 
 results. In the antimony determinations, to the dis- 
 tillate is first added some tartaric acid to prevent pre- 
 cipitation of the antimony as oxychloride, the distillate 
 is then neutralized with ammonia, made just acid with 
 HC1 and precipitated with hydrogen sulphide. 
 
 The arsenic may also be determined by titration 
 with iodine, using starch as an indicator. 
 
 The apparatus as shown (see cut) is supported 
 on an upright iron rod. Attached to the lower part of 
 thjs is a ring and clamp supporting the water cooler hi 
 which is immersed the beakers for receiving the dis- 
 tillate. Above this is a piece of glass tubing which 
 will slide up or down on the rod and can be supported 
 at any height by a screw clamp. The ring supporting 
 the flask and the clamps holding the condenser are 
 attached to this tube, thus permitting the flask and 
 condenser to be raised at once, and- quickly, in the 
 event of the distillate drawing back into the condenser 
 tube. The flask is set in a disk of asbestos mounted on 
 
 Note. The apparatus as designed by Mr. Knoor is 
 manufactured by E. Matchlett & Co., 143 E. 23rd St., 
 New York City. One set of one condenser and three 
 flasks for $5.00. 
 
MILL AND SMELTER METHODS. 115 
 
 an iron ring so that about an inch of the flask is below 
 the asbestos. This arrangement keeps the top of the 
 flask cool enough to permit of the dropping in of HC1 
 from the funnel. The burner used must give a hot 
 concentrated flame. Bumping of the flask may occur 
 while taking down to fumes, and may be prevented by 
 rotating the flask. 
 
 box 
 
 
 Khoor bifefiHing Fl* 
 
 ^sl^ exnd CondenAtr. 
 
 Materials decomposed by sulphuric acid can be 
 weighed into the flask direct and treated as lead bul- 
 lion, save that the reducing agent must be used. Cop- 
 per bullion is dissolved in nitric acid in a beaker, taken 
 down to dryness and then evaporated with hydro- 
 chloric acid to expel all nitric acid, transferred to a 
 
n6 MILL AND SMELTER METHODS. 
 
 flask, sulphuric acid added and evaporated to approx- 
 imately 40 cc. Connect up condenser and funnel. Re- 
 duce the solution with 'a 10% solution of hypo-phos- 
 phorous acid and distill. Samples containing much 
 silica must be filtered in order to prevent bumping in 
 the flask. The amount of reducing agent .must be de- 
 termined by the change of color in the solution to a 
 light green, which becomes almost colorless when 
 down to fumes. An excess of reducing agent will 
 cause the flask to boil over when taking down to 
 fumes. 
 
 The flow of water through the cooler must be just 
 sufficient to prevent the water becoming warm. 
 
 The distinction between the arsenic and the anti- 
 mony distillation is that the arsenic is distilled without 
 fumes showing in the condenser, while the antimony 
 distillation should just show fumes in the condenser 
 and no more. 
 
 Antimony in Hard Lead. 
 
 After the arsenic has been distilled off, the remain- 
 ing solution in the flask is rinsed out with hot water, 
 add a solution of sodium hydroxide to slightly alkaline 
 reaction, then from 15 to 20 cc. of sodium sulphide 
 (made by dissolving I Ib. sodium sulphide in i litre of 
 water), which precipitates the lead and copper as sul- 
 phides. Allow to settle for a few minutes, then filter 
 off the precipitates and wash them thoroughly with 
 hot water, 
 
MILL AND SMELTER METHODS. 117 
 
 To the filtrate, which contains nothing but the anti- 
 mony, add hydrochloric acid (i to i) to slight acid 
 reaction, stir thoroughly and let stand over night to 
 settle. Filter off the antimony sulphide and wash 
 thoroughly and dry on the hot plate. When the pre- 
 cipitate is dry, brush off the filter and oxidize the 
 paper in a weighed porcelain crucible with fuming 
 nitric acid, ignite and to the crucible add the ppt. of 
 Sb 2 S 3 . Add a little nitric acid and evaporate several 
 times until all the Sb 2 S 3 is converted into Sb 2 O 4 , ignite 
 and weigh. The precipitate of Pb and Cu from the 
 sodium sulphide can be used in the determination of 
 lead, by dissolving in i to i nitric acid, hot, and pro- 
 ceeding in the usual way. 
 
 The Knoor method will check the above closely. 
 
 Determination of Bismuth in Refined Lead. 
 
 The quantity taken for analysis depends somewhat 
 on the purity of the lead. In ordinary cases, where the 
 bismuth is about 0.040% or over, 50 grams are enough ; 
 in cases of greater purity the quantity should be in- 
 creased to 100 or 200 grams. 
 
 The clean metal is rolled out as thin as possible and 
 cut in pieces of 5 to 10 grams each and dissolved in a 
 flask or beaker in dilute nitric acid, using for each 
 gram of lead 1.2 cc. of strong nitric acid (1.42 Sp. G.) 
 diluted with 3.5 times its volume of water. Solution is 
 aided by heat and evaported water being replaced from 
 time to time to preserve the initial volume, the idea 
 
n8 MILL AND SMELTER METHODS. 
 
 being always to keep the solution sufficiently dilute to 
 prevent the separation of lead nitrate. On this account, 
 too, no more nitric acid than is necessary should be 
 used, as lead nitrate is much less soluble in nitric acid 
 than in water. When solution is complete, precipitate 
 with sulphuric acid, adding enough to combine with all 
 the lead and leaving about 10 cc. excess. Bring the so- 
 lution and precipitated lead sulphate to a known 
 volume, mix thoroughly, allow to settle and siphon or 
 filter off a measured amount of the clear or nearly 
 clear supernatant liquid. This portion is used for the 
 determination, the remaining liquid with the lead sul- 
 phate being rejected. This procedure is to be pre- 
 ferred to any attempt to filter off and wash this, large 
 mass of lead sulphate. 
 
 Allowing for the space occupied by the ppt., a 
 simple calculation will give the amount of material 
 that the solution to be used actually represents (the 
 lead sulphate from 100 grams of lead occupies 22.5 cc) . 
 
 For regular use in this work, where determinations 
 are being made constantly, a set of flasks, one holding 
 810 cc., the other 529 cc. Flasks can easily be grad- 
 uated with a burette, the meniscus being marked on the 
 neck with a sharp file. 
 
 To start the analysis, 75 grams of lead are dis- 
 solved in a beaker in 90 cc. of strong nitric acid, 
 diluted to 400 cc. As soon as everything is dissolved, 
 the solution is transferred to the larger flask, in which 
 30 cc. of strong sulphuric acid, somewhat diluted, ha.s 
 
MILL AND SMELTER METHODS. 119 
 
 already been placed; the flask is filled to the mark, 
 corked and well shaken. After allowing the ppt. a few 
 moments to subside, the liquid is filtered through a 
 dry, rapid-running paper into the small flask, which is 
 filled exactly to the mark. This whole operation is 
 performed so very quickly that the slight change of 
 volume due to cooling can be neglected. 
 
 The following calculation shows how much ma- 
 terial the 529 cc. of solution represents : 
 
 Volume of liquid and ppt 829 cc. 
 
 Volume of lead sulphate from 75 grams of 
 lead 16.875 cc - 
 
 Actual volume of liquid 793.125 cc. 
 
 Then : 
 
 793.125 : 529 :: 75 : 
 
 x = 50.02 
 
 or, in round numbers, 50 grams are in actual use for 
 determination. 
 
 The solution from which the bulk of the lead has 
 thus been removed is at once evaporated in a large 
 beaker or other suitable vessel. When 'jufficiently con- 
 centrated it is transferred to a porcelain dish or casser- 
 ole of about 4 inches diameter, and the evaporatioi. 
 continued until sulphuric acid fumes come off freely. 
 It is now removed from the heat and as soon as cool 
 enough diluted with cold water to about 125 cc., then 
 boiled briskly for several minutes to insure the re- 
 solution of all the bismuth sulphate. 
 
120 MILL AND SMELTER METHODS. 
 
 After allowing the solution to cool and settle for 
 two or three minutes, filter, washing the ppt. of lead 
 sulphate with dilute sulphuric acid (10 cc. of acid to 
 I litre of water). Heat the filtrate nearly to the boil- 
 ing point and pass hydrogen sulphide gas through it 
 for 10 to 15 minutes, allow to stand warm until the 
 ppted. sulphides have collected and settled, then filter, 
 washing well with hot water. When washed, without 
 removing the filter paper, return the ppt. to the beaker 
 in which the precipitation took place, using as little 
 water as possible, and then add 15 to 20 cc. of yellow 
 alkaline sulphide. (The alkaline sulphide, prefereably 
 that of potassium, is best prepared from pure mater- 
 ials by the operator ; the article of commerce is seldom 
 or never pure.) Heat to boiling, dilute somewhat, 
 allow to settle and decant through the paper already 
 used for filtering off the sulphides. Repeat the treat- 
 ment with a fresh portion of the alkaline sulphides, 
 finally transferring the ppt. to the filter and washing 
 with water containing some of the alkaline sulphide. 
 
 When washed, place the filter and ppt. in the same 
 beaker, add 5 cc. of strong nitric acid diluted to 25 cc., 
 warm until the sulphides are dissolved, and filter into a 
 porcelain dish. Burn the papers at a low heat, adding 
 the ash to the solution, then add about 3 cc. of sul- 
 phuric acid and evaporate, as before, to sulphuric 
 acid fumes. When cool, dilute, boil, allow to cool and 
 settle, filter and wash with dilute sulphuric acid. The 
 amount of lead removed here is generally very slight ; 
 
MILL AND SMELTER METHODS. 121 
 
 still, it is not safe to omit this evaporation. To the 
 filtrate add a solution of sodium carbonate until the 
 solution is slightly alkaline (a drop of methyl-orange 
 is a good indicator to use here) and a few drops of a 
 strong solution of potassium cyanide. Boil for a few 
 minutes and allow to stand warm until the ppt. has 
 collected and the supernatant liquid is perfectly clear; 
 this operation usually requires about half an hour. 
 Filter through a moderately close filter paper and wash 
 with warm water. Dissolve the ppt. from the filter in 
 warm dilute nitric acid, add ammonia to alkalinity and 
 about 3 to 5 cc. of ammonium carbonate solution. Heat 
 to the boiling point and let it stand warm until the 
 bismuth carbonate has settled well ; then, filter and 
 wash. Dry the paper and ppt. and remove the latter 
 as completely as possible, burning the paper sepa- 
 rately. Ignite in a small porcelain crucible at a low 
 red heat and weigh as Bi 2 O 3 . 
 
 Bi 2 O 8 x.8g65 = Bi. 
 
 Bismuth in Lead Bullion. 
 
 The determination of bismuth in lead bullion is 
 started in the same way as in the method for refined 
 lead as regards the quantity of material, solution, ppt. 
 of the bulk of the lead and the taking of a measured 
 portion of the liquid. In this last point the fact that 
 the lead bullion is only about 95% lead can be taken 
 into account, if desired, though it is rather a needless 
 refinement. The only difference in these preliminary 
 
122 MILL AND SMELTER METHODS. 
 
 steps is, that in the case of bullion, just about enough 
 sulphuric acid to combine with all the lead is added, 
 instead of having 10 cc. in excess. Thus in the case 
 cited under refined lead, where 75 grams were taken, 
 only 20-22 cc. of sulphuric acid are added instead of 
 30 cc. 
 
 Lead bullion does not make a perfectly clean solu- 
 tion like the refined lead, a considerable residue usu- 
 ally being left after the action of the nitric acid has 
 ceased. This residue is chiefly gold and antimonial 
 compounds and in a bismuth determination can be 
 neglected, it being removed with ppted. lead sulphate. 
 
 The measured portion of the solution, from which 
 the bulk of the lead has been removed, instead of being 
 at once evaporated, as in the case of refined lead, is 
 made ammoniacal, 50 cc. excess of ammonia water 
 added and hydrogen sulphide passed into the hot liquid 
 with the formation of yellow ammonium sulphide. The 
 gas is passed nearly to saturation, then about 20 cc. 
 more of ammonia water added and the whole allowed 
 to stand, warm, until the ppt. has completely subsided. 
 The supernatant liquid should be clear yellow and the 
 ppt. dark brown. By this means a large part of the 
 arsenic and antimony are kept in solution and gotten 
 rid of at once, although some always remains with the 
 ppt. and must be gotten rid of subsequently. Filter 
 and wash slightly. Place the paper and ppt. in a 
 beaker, add 15 cc. of strong nitric acid and dilute to 
 60 cc, Warm until the sulphides are decomposed and 
 
MILL AND SMELTER METHODS. 123 
 
 filter into a four-inch porcelain dish. Burn the paper 
 and add the ash, then 10 cc. of strong sulphuric acid 
 and evaporate to dense fumes. This point corresponds 
 with the first evaporation when working on refined 
 lead, and with slight modifications the determination is 
 now carried on exactly as in the preceding method. At 
 the stage where the sulphides are treated with alkaline 
 sulphide, more of the latter is usually required than in 
 the case of refined lead, owing to the larger amount of 
 arsenic and antimony to be removed the quantity of 
 these remaining here being generally larger than the 
 total amount in refined lead. 
 
 At the second evaporation it is advisable, on ac- 
 count of the quantity of silver and copper present, to 
 increase the sulphuric acid to 5 or 6 cc. instead of 3 
 cc. When precipitating with sodium carbonate and 
 potassium cyanide, enough of the latter must be added 
 to bring all the silver, copper and cadmium into so- 
 lution. 
 
 Notes on the Bismuth Determination. 
 
 By the method detailed above, the complete sepa- 
 ration of bismuth from arsenic, antimony, gold, silver, 
 copper, cadmium, lead, iron and zinc is readily and 
 perfectly effected. The only point to be especially 
 watched is the removal of the arsenic and antimony 
 when working on lead bullion, and no trouble will be 
 experienced here if the alkaline sulphide is used in 
 sufficient quantity. Preventing the loss of bismuth, and 
 consequently low results, is, however, a more difficult 
 
124 MILL AND SMELTER METHODS. 
 
 matter. The following are some of the numerous 
 ways in which such loss can readily occur : 
 
 Throughout the work hydrochloric acid and chlor- 
 ides must be rigidly excluded. The tendency of bis- 
 muth to form insoluble oxychloride is so strong that 
 the only safe plan to pursue is to avoid its possibility. 
 
 While trying different methods of analysis on lead 
 bullion, which often contains over i% of silver, the 
 attempt was made to remove most of the silver at the 
 start by adding a few drops of hydrochloric acid to the 
 sulphuric acid used to ppt. the lead. While this gen- 
 erally succeeded, in many cases bismuth oxychloride 
 was also precipitated, and, of course, lost with the lead 
 sulphate and silver chloride; hence this modification 
 was abandoned as too unreliable. 
 
 Along the same line was the attempt to remove 
 the silver and copper by the use of ammonia (and 
 ammonium carbonate) as precipitants in the first 
 solution. In spite of the utmost care, results obtained 
 in this way were invariably low. To the mass action 
 of the bulky solution and large amount of salts, the 
 loss of bismuth here, owing to incomplete precipitation, 
 is probably due. 
 
 When solutions have been evaporated to sulphuric 
 acid fumes, they should, as soon as cool enough, be 
 diluted, boiled and filtered. If such evaporated solutions 
 are allowed to stand cold for a few hours, or over night, 
 the bismuth is very apt to separate in an extremely 
 soluble form, doubtless as basic sulphate, and on sub- 
 
MILL AND SMELTER METHODS. 125 
 
 sequent dilution and boiling, fail to redissolve. In 
 such a case, of course, it would be filtered off with the 
 lead sulphate and lost. Should this happen at the first 
 evaporation, where considerable lead sulphate is sep- 
 arated, it would be completely masked, and could be 
 detected only by analysis of the lead sulphate. At the 
 second evaporation, where the lead sulphate separated 
 is generally so slight as to be scarcely visible, if a 
 white, or yellowish white, rather granular ppt. is no- 
 ticed which seems insoluble on dilution and boiling, 
 it is almost certain to be a bismuth compound. Pro- 
 longed boiling, with occasional decantations and addi-. 
 tions of fresh portions of dilute sulphuric acid will 
 generally affect its solution ; but both here and at the 
 first evaporation there is no danger of loss if unneces- 
 sary delay is avoided. 
 
 When precipitating with sodium carbonate and po- 
 tassium cyanide but a very slight excess of the car- 
 bonate solution should be added, otherwise precipita- 
 tion will be incomplete. Where this trouble is sus- 
 pected it can be corrected by the cautious addition of 
 ammonium chloride until the carbonate is mostly con- 
 verted to chloride. With proper care, however, the 
 necessity should not arise. In both this precipitation 
 and the succeeding one with ammonia and ammonium 
 carbonate the solution should be heated to boiling, or 
 nearly so, until all the free carbonic acid is expelled 
 and then allowed to stand in a warm place until the 
 ppt. has thoroughly collected. As both of these ppts. 
 
126 MILL AND SMELTER METHODS. 
 
 have a tendency to run through the filter, fairly fine- 
 textured papers should be used. 
 
 Where bismuth carbonate is precipitated to ^e 
 ignited and weighed, it must always be done by am- 
 monia and ammonium carbonate from a nitrate solu- 
 tion, and care must be exercised to remove the dried 
 ppt. from the paper as completely as possible, for re- 
 duction and volatilization very readily take place. A 
 low red heat is best for igniting the carbonate, the 
 change to oxide easily taking place. At bright red- 
 ness there is no more loss in weight, but the oxide 
 fuses and is then difficult to remove from the crucible. 
 Bismuth in Ores. 
 
 In ores carrying lead to the extent of 10% or 
 over, nearly, if not all, the bismuth will be found in 
 the lead buttons obtained in fire assay. And as this 
 method of determining the lead is the one in common 
 use at lead smelters, and as these buttons are being 
 constantly made, they can be taken and the above 
 methods applied. In iron-lead ores, by the addition 
 of some bismuth-free lead salt carbonate or sulphate 
 the same procedure may be followed. A number of 
 buttons from different lots of the same ore can be 
 mixed to represent an average of a very considerable 
 amount of the ore. Or, owing to the presence of anti- 
 mony or arsenic, these buttons can be scorified to- 
 gether with the addition of some silica and borax glass, 
 the loss of bismuth in a short scorification being very 
 small. 
 
MILL AND SMELTER METHODS. 127 
 
 Of course this method is not very accurate, but it 
 serves the purpose of informing the metallurgist what 
 ores the bismuth is coming from so that he may avoid 
 them as far as possible in his operations. In the re- 
 finery, bullion carrying much bismuth is run sepa- 
 rately, such bullion being all right for shot or pipe 
 but not fit for corroding purposes. 
 Determination of Copper in Silver Mud and Silver 
 
 Mill Slags. 
 
 Treat -J gram with 5 cc. HNO 3 , and, when action 
 has become quiet, add 3 cc. H 2 SO 4 , and evaporate to 
 white fumes ; cool, add 50 cc. H 2 O, and heat to dis- 
 solve the soluble sulphates ; add NaCl solution in 
 slight excess, heat to boiling, remove and filter off the 
 AgCl. To the filtrate add sodium sulphite and a 
 small excess of NH 4 CNS, stir and warm; Cu 2 (CNS) 2 
 will precipitate ; filter, wash thoroughly, ignite gently 
 in a porcelain crucible. Dissolve the residue in 5 cc. 
 HNO 3 , and determine Cu electrolytically. 
 
 Slags. 
 
 Treat i gram in a Pt dish with 6 cc. HNO 3 and 6 
 cc. HF. Add 4 cc. H 2 SO 4 , and proceed as before. 
 Silver Determination on Anode Copper by Fire Assay. 
 
 The silver is pptd. as AgCl, scorified and cupelled. 
 
 Weigh i A. T. of the sample in duplicate, place in 
 a large beaker, add 200 cc. cold water +130 cc. HNO n 
 and let stand until completely dissolved. Then add 
 175 cc. of cold water and 8 cc, NaCl sol, (i cc. equals 
 
128 MILL AND SMELTER METHODS. 
 
 184 mgs.). Stir the solution well for a few minutes 
 and allow to stand for twelve hours, to allow AgCl 
 to settle. Filter and wash, add a couple of grams of 
 litharge and set the filter paper on a 2^-inch scorifier, 
 place in a muffle and burn off the filter paper at a very 
 low temperature. Take the scorifier from the muffle 
 and add about 35 grams of lead with 4 grams of borax 
 for a cover. Place the scorifier in the muffle at a 
 cherry red heat and scoriiy^at a low temperature. This 
 gives about an 1 8-gram button. Cupel and weigh. 
 
 Bismuth in Metallic Copper. 
 
 Dissolve 10 to 50 grams of the. copper in HNO 3 and 
 H 2 O. If much insoluble matter is present, filter off 
 and fuse it with Na 2 CO 3 . Dissolve the fusion in HNO 3 
 and add to main solution. To the solution in HNO 3 
 add Na 2 CO 3 until a slight permanent precipitate is 
 formed. All the Bi will be included in this ppt. Fil- 
 ter it from the main solution, dissolve the ppt. from 
 the filter with warm dilute HC1. Evaporate the HC1 
 solution on a water bath till free acid is driven off, 
 then add five or six drops acid and 2 or 3 cc. of water. 
 The solution should be clear if not, add a few drops 
 HCI to clarify, then pour into the solution a large 
 volume of water (400 to 500 cc.), and let the ppt. of 
 BiOCl separate over night. Weigh as BiOCl on 
 Gooch crucible. 
 
 Electrolytic Copper Determination. 
 Copper All samples containing more than 2 or 
 
MILL AND SMELTER METHODS. 129 
 
 3% copper, such as mattes, ores, copper cakes, etc., are 
 run for copper by the electrolytic method, as follows : 
 
 Weigh out from -J to I gram of ore in a No. 3 
 beaker; just moisten with a drop or two of water, 
 then add from 10 to 15 cc. of strong nitric acid, and 5 
 to 8 cc. of sulphuric acid, and heat until white fumes 
 of sulphuric acid are given off. Be sure that all of 
 the ore (which is soluble in acids) has been dissolved, 
 then dilute to about 80 cc. r heat again just to boiling, 
 to distintegrate the mass ; filter off the residue in which 
 the lead and silica may be determined if necessary. 
 Filter the solution into a No. 2 beaker, add i or 2 
 strips of heavy aluninum foil, boil for ten or fifteen 
 minutes, which is generally sufficient to insure com- 
 plete precipitation of the copper. Pour off the solu- 
 tion and wash three times by decantation with hot 
 water. Then add 3 or 4 cc. of strong nitric acid to 
 the contents of the beaker, allowing the acid to flow 
 over the aluminum. Boil to expel the nitrous fumes, 
 decant into another beaker (a long, narrow one) and 
 rinse the aluminum with a few drops of water ; just 
 neutralize the solution with ammonia, and add about 
 15 cc.'s of i to 10 sulphuric acid. Place platinum 
 cylinder into the solution, connecting it with the neg- 
 ative or zinc element of the battery ; inside the cylinder 
 place a platinum wire spiral, reaching almost to the 
 bottom of the beaker, being careful not to allow the 
 spiral to touch the cylinder. 
 
 A very good battery for this purpose is a Bunsen 
 
130 MILL AND SMELTER METHODS. 
 
 cell ; about eight hours is usually required for a total 
 precipitation of the copper. To determine whether or 
 not all the copper has been pptd., remove a few drops 
 of the solution in a pipette and test it with H 2 S water. 
 If the test shows that all copper has been removed, 
 then, without turning off the current, remove the cyl- 
 inder and place immediately into a beaker of warm 
 water, so as to wash off as quickly as possible all acid 
 from the cylinder. After the cylinder has been thor- 
 oughly washed, place it in a beaker of alcohol, which 
 removes the water, then dry as quickly and carefully 
 as possible, avoiding the oxidation of the copper on 
 the cylinder. The pptd. copper should be a bright, 
 rose-red color. 
 
 In case the ore contains only a trace of arsenic, 
 antimony or bismuth, the precipitation of the copper 
 on the aluminum foil may be dispensed with. In that 
 case, after the ore has been dissolved and the mass 
 disintegrated, add enough ammonia to just neutralize 
 this solution, add ^ gram NH 4 NO 3 and 15 cc. of i to 
 10 H 2 SO 4 , and place on the battery as before. From 
 Chemists' Handbook, Western Chemical Company. 
 
MILL AND SMELTER METHODS. 131 
 
 CHAPTER XI. 
 
 The Laboratory. 
 
 In technical laboratories, where quick and accu- 
 rate work is required, the general arrangement and 
 convenience of the laboratory itself is of the greatest 
 importance ; so a word or two about the general equip- 
 ment will not be out of place in this book. The aver- 
 age chemist will be called on for from forty to eighty 
 determinations a day, varying from silica, iron and 
 lime to antimony, arsenic and even an occasional rare 
 element, yet the greater part of the work can be so 
 arranged that all ores and mattes, etc., requiring the 
 same elements determined can be run together, thus 
 making little more work for ten samples than is re- 
 quired for two. To facilitate this arrangement ample 
 heating space, filter racks, and hot, distilled water 
 must be provided, and space so economized that no 
 unnecessary steps are required in moving from one 
 piece of apparatus to another. The best plan for such 
 a laboratory is as follows : 
 
 The laboratory should consist of two rooms con- 
 nected by a swinging door, one room being considerably 
 larger than the other. The larger room will contain 
 the hot plate, the filtering stands, the burette stands, 
 water condenser, etc., while the smaller room will con- 
 
132 MILL AND SMELTER METHODS. 
 
 tain the balances, reserve chemicals and apparatus and 
 will be used as a sort of office. Both of these rooms 
 should be well lighted and the larger room should be 
 provided with ample ventilation, preferably by means 
 of a skylight. 
 
 The Hot Plate. This consists of a stand of sheet 
 iron raised about four inches above the flame and on 
 top of which is laid a sheet of J-inch asbestos. The 
 best size for the top is. 4 feet in length by 2\ feet 
 in width, and such a top will require four gasoline 
 burners to heat it. In many plants, gasolene is not 
 used and a very good substitute is found in the ordi- 
 nary four-hole coal oil stove. In other plants a coal 
 fire under a heavy cast iron plate protected by fire 
 brick has been tried, but the results are not satis- 
 factory. 
 
 The hot plate should be surmounted by a hood, 
 preferably of brick built up in the manner of the old- 
 fashioned fire-place and terminating in a chimney of 
 sufficient height to furnish ample draught. The top 
 of the plate should be 3^ feet above the level of the 
 floor. 
 
 At the Selby Plant electric stoves are used. These 
 have a No. 10 steel plate i8"xi4"xi" for a top; con- 
 tain two circuits of No. 16 climax wire in parallel, 52 
 feet of wire in each circuit, wound on a 5/16" rod. 
 Each circuit no volts, *j\ amperes. Temperature ap- 
 proximately 150 degrees C. 
 
 Filter Racks. These should be of wood and be 
 
MILL AND SMELTER METHODS. 133 
 
 fastened to a table running lengthwise of the room 
 and parallel to the hot plate. Space should be ar- 
 ranged for twenty funnels in all and these should be 
 selected with care so as to have all alike, then the filter 
 paper will always fit and filtering will be rapid. Above 
 the table at a height of two feet above the top of the 
 funnels will be placed a reservoir containing five gal- 
 lons of distilled water which is kept boiling by a 
 flame underneath. A rubber tube of sufficient length 
 to reach to each end of the filter rack is connected 
 to the reservoir, ample wash water being thus supplied. 
 But one step should be necessary in taking a beaker 
 from the plate to the filter rack. 
 
 Burette Stand. On the opposite side of the room 
 and preferably in front of a window, should be placed 
 the burette stand. The best arrangement of this kind 
 was designed by Mr. E. M. Johnson, and was in use 
 in the Grant smelter in Denver. The burettes were 
 held in position against an upright frame work by 
 means of wire bird cage springs while the solutions 
 were placed on a shelf underneath the table. Connec- 
 tion was made between the burette and the solution by 
 means of three-way cock and a glass tube running 
 from this, through the table and down to the bottom 
 of the solution bottle. Through another tube air was 
 forced into the bottle, thus causing the solution to rise 
 in the burette. A turn of the cock shuts off the supply 
 when the burette was full, another turn would release 
 the solution when titrating, and still another turn. 
 
134 MILL AND SMELTER METHODS. 
 
 when the titration was completed, would allow the ex- 
 cess of solution to return to the bottle below. The top 
 of the table underneath the spout of the burette was 
 
 covered with a plate of glass underneath which was 
 placed a sheet of white glazed paper. 
 
MILL AND SMELTER METHODS. 135 
 
 With such an apparatus, with separate burettes 
 for each of the standard solutions in daily use, the 
 time required in titrating is cut down to almost noth- 
 ing. For ease in removing an empty solution bottle 
 and replacing with a full one, the connection between 
 the glass tube and the burette is made with a small 
 piece of rubber tubing. By slipping this off, drawing 
 the tube up through the table, etc., the exchange is 
 easily made. 
 
 The advantages of this arrangement are : No rub- 
 ber tubes to burst and release the solution, as is the 
 case when the burette is filled by gravity ; no solution 
 allowed to remain in the burette exposed to the light 
 when not in use; and the fact that the burettes are 
 always ready for business. 
 
 Distilled Water. The best apparatus for distilling 
 water for laboratory use, provided steam can be ob- 
 tained, is the following: A cylindrical tank four feet 
 in height, made of three sections fitting together, each 
 section being made of ^-inch copper sheet. In the 
 top section steam at ninety pounds' pressure circulates 
 in a copper spiral, which is generally protected with 
 tin. Cold water surrounds this spiral, and the steam 
 produced is led off at the top in a tin-lined pipe and 
 passed through a spiral pipe surrounded by running 
 cold water in the second section. The condensed water 
 then drops into the third or bottom section. Taps are 
 placed just above the bottom of each section to provide 
 a means of washing out the sediment at certain inter- 
 
136 MILL AND SMELTER METHODS. 
 
 vals. Such a still, with each section 18 inches high 
 and 12 inches in diameter, will furnish one-half gal- 
 lon per hour of distilled water. 
 
 Balances. There should be two balances, one for 
 weighing pulp and one for analytical work. These 
 should be placed on a firm table, with ample room 
 allowed on each side for samples and for the beakers 
 or casseroles into which the material is to be weighed. 
 
 Having such a laboratory, the day's work would 
 proceed as follows: First of all, the fires are started 
 and the receptacle for distilled water is filled ; then 
 the still is started and regulated, if it so happens that 
 the supply of water is low. Next the chemist goes to 
 the balance room and arranges the samples that are 
 to be analyzed in proper order on the lefthand side of 
 the pulp balance. Then he returns to the other room 
 and selects the necessary beakers and casseroles and 
 arranges them on a flat wooden tray. Placing this 
 tray on the right side of the balance, he proceeds to 
 weigh up, throwing the samples to one side as he fin- 
 ishes them. Taking his tray, he now proceeds to a 
 small table at the left of the hot plate, where the acid 
 bottles, etc., are kept. The acids are added and the 
 samples placed on the hot plate. While waiting for 
 the samples to boil the chemist puts the samples of 
 ore away in regular order, for they will be needed 
 again later on for mixture beds, prepares the filter pa- 
 pers, etc., and in general gets everything ready for in- 
 stant service, From this time on the work follows a 
 
MILL AND SMELTER METHODS. 137 
 
 definite system and the only pauses in this regular 
 rush of work come when it is necessary to go out to 
 
 STILL 
 
 Top for C/eap/yo Out 
 Water QuMet 
 
 Wafer 
 
 the fire room to use a muffle. By noon the worst of 
 the work is over, so the afternoons are usually spent 
 
138 MILL AND SMELTER METHODS. 
 
 on some unusual work, or in standardizing solutions, 
 etc., and in preparing for the work of the following 
 day. 
 
 Among the minor pieces of apparatus which are 
 found to be of use in the laboratory, the following in 
 particular may be mentioned. It consists of a -J-litre 
 
 /7L 7E/?//v(j- 
 
 Perforated 
 P/*t,n<jm DISH 
 fuaeof Into Class 
 
 flask fitted with a rubber cork through which pass two 
 pieces of glass tube, reaching just through the cork. 
 One piece, bent in the shape of the letter U, reaches 
 down on the outside to within \ an inch of the table, 
 having the end spread and a piece of perforated plat- 
 
MILL AND SMELTER METHODS. 139 
 
 inum inserted and the glass melted around it to hold 
 it in place. The other piece of tubing merely serves to 
 attach the tube from a suction pump. In another 
 flask is placed some shreds of asbestos covered with 
 water. For such operations as filtering off the solu- 
 tion when the copper has been precipitated on alumi- 
 num foil, this apparatus is a great time saver. The 
 flask is connected to the suction pump and then dipped 
 into the asbestos. The asbestos will cover the plati- 
 num with a fine coat which will prevent the passage of 
 fine particles of solid matter, but will allow the solu- 
 tion to pass freely. When coated, the tube is trans- 
 ferred to the solution to be filtered. 
 
140 MILL AND SMELTER METHODS. 
 
 Miscellaneous. 
 
 The Assay Ton System. 
 
 i Ib. avoirdupois equals 7,000 grains. 
 
 2,000 Ibs. avoirdupois equals I ton. 
 
 2,000x7,000 equals 14,000,000 troy grains in I ton 
 avoirdupois. 
 
 480 troy grains equals I ounce troy. 
 
 14,000,000/480 equals 29,166 troy ounces in 2,000 
 Ibs. avoirdupois. 
 
 There are 29,166 milligrammes in i assay ton (A. 
 T.), hence 
 
 2,000 Ibs. : i A. T. : : i ounce troy : i milligramme. 
 
 Impurities in C. P. Acids. 
 Hydrochloric Acid 
 
 For iron, dilute, and add KSCN ; if it shows a red 
 color, there is iron present. 
 
 For arsenic, dilute, pass in hydrogen sulphide 
 gas; if a distinct yellow precipitate is obtained, it 
 would indicate traces of arsenic ; also try by the Marsh 
 test. 
 
 For sulphuric acid, dilute, add barium chloride ; 
 a white precipitate would be obtained if sulphuric 
 acid were present. 
 Nitric Acid 
 
 For chlorine, add silver nitrate; if a slight opal- 
 esence occurs, it shows the presence of chlorine. 
 
MILL AND SMELTER METHODS. 141 
 
 Sulphuric Acid 
 
 For arsenic, dilute and pass in hydrogen sulphide 
 gas ; if a distinct yellow precipitate is the result, it 
 shows the presence of arsenic ; also try by the Marsh 
 test. 
 
 For iron, dilute, add KSCN ; if red color appears, 
 it shows presence of iron. 
 Ammonia 
 
 For organic matter, dilute, acidify with nitric 
 acid ; if a red color appears, it shows the presence of 
 organic matter. After acidifying with nitric acid, 
 add barium chloride ; if a white precipitate is obtained, 
 it shows the presence of sulphuric acid. 
 
 In making these tests be sure that all the apparatus 
 is clean and be sure that the distilled water contains 
 no impurities. 
 
 International Atomic Weights. 
 
 Aluminum Al 27.1 26.9 
 
 Antimony Sb 120.2 119.3 
 
 Argon A 39.9 39.6 
 
 Arsenic As 75.0 744 
 
 Barium Ba 137.4 136.4 
 
 Bismuth Bi 208.5 206.9 
 
 Boron B 1 1 10.9 
 
 Bromine Br 79.96 79.36 
 
 Cadmium Cd 112.4 m.6 
 
 Caesium Cs 133 132 
 
142 MILL AND SMELTER METHODS. 
 
 Calcium Ca 40.1 39.8 
 
 Carbon C 12.00 11.91 
 
 Cerium Ce 140 139 
 
 Chlorine Cl 35,45 35.18 
 
 Chromium Cr 52.1 51.7 
 
 Cobalt Co 59.0 58.56 
 
 Columbium (Niobium) Cb 94 93.3 
 
 Copper Cu 63.6 63.1 
 
 Erbium E 166 164.8 
 
 Fluorine F 19 18.9 
 
 Gadolinium Gd 156 155 
 
 Gallium Ga 70 69.5 
 
 Germanium Ge 72.5 71.9 
 
 Glucinium (Beryllium) Gl 9.1 9.03 
 
 Gold Au 197.2 195.7 
 
 Helium He 4 4 
 
 Hydrogen H i .008 1 .000 
 
 Indium In 114 1 13.1 
 
 Iodine I 126.85 I2 5-9 
 
 Iridium Ir 193.0 !9!-5 
 
 Iron Fe 55.9 55.5 
 
 Krypton K 81.8 81.2 
 
 Lanthanum La 138.9 l 37-9 
 
 Lead Pb 206.9 2O 5-35 
 
 Lithium . Li 7.03 6.98 
 
 Magnesium Mg 24.36 24.18 
 
 Manganese Mn 55.0 54.6 
 
 Mercury Hg 200.0 198.5 
 
 Molybdenum .............. Mo 96.0 95.3 
 
MILL AND SMELTER METHODS. 143 
 
 Neodymium Ne 143.6 142.5 
 
 Neon 20 19.9 
 
 Nickel Ni 58.7 58.3 
 
 Nitrogen N 14.04 13.93 
 
 Osmium Os 191 189.6 
 
 Oxygen '. O 16.00 15.88 
 
 Palladium Pd 106.5 IO 5-7 
 
 Phosphorus P 31.0 30.77 
 
 Platinum Pt 194.8 193-3 
 
 Potassium K 39-15 38.86 
 
 Praseodymium Pr 140.5 J39-4 
 
 Radium Ra 252 223.3 
 
 Rhodium Rh 103.0 102.2 ' 
 
 Rubidium Rb 85.4 84.8 
 
 Ruthenium Ru 101.7 100.9 
 
 Samarium Sm 150 148.9 
 
 Scandium Sc 44.1 43.8 
 
 Selenium Se 79.2 78.6 
 
 Silicon Si 28.4 28.2 
 
 Silver Ag 107.93 107.12 
 
 Sodium Na 23.05 22.88 
 
 Strontium Sr 87.6 86.94 
 
 Sulphur S 32.06 31.83 
 
 Tantalum Ta 183 181.6 
 
 Tellurium Te 127.6 126.6 
 
 Terbium Tb 160 158.8 
 
 Thallium Tl 204.1 202.6 
 
 Thorium Th 232.5 230.8 
 
 Thulium Tm 171 169.7 
 
144 MILL AND SMELTER METHODS. 
 
 Tin Su 119.0 118.1 
 
 Titanium Ti 48.1 47.7 
 
 Tungsten W 184.0 182.6 
 
 Uranium U 238.5 236.7 
 
 Vanadium V 51.2 50.8 
 
 Xenon ....:.... X 128 127 
 
 Ytterbium Yb 173.0 171.7 
 
 Yttrium Yt 89.0 88.3 
 
 Zinc Zn 65.4 64.9 
 
 Zirconium . Zr 90.6 89.9 
 

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