A Text-book of Assaying: For the Use of Those Connected with Mines.

J. J. (John Jacob) Beringer, Cornelius Beringer

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The Project Gutenberg eBook, A Textbook of Assaying: For the Use of Those Connected with Mines., by Cornelius Beringer and John Jacob Beringer

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Title: A Textbook of Assaying: For the Use of Those Connected with Mines.

Author: Cornelius Beringer and John Jacob Beringer

Release Date: July 3, 2006 [eBook #18751]

Language: English

Character set encoding: ISO-8859-1

***START OF THE PROJECT GUTENBERG EBOOK A TEXTBOOK OF ASSAYING: FOR THE USE OF THOSE CONNECTED WITH MINES.***

E-text prepared by Peter Yearsley, Josephine Paolucci, and the Project Gutenberg Online Distributed Proofreading Team (http://www.pgdp.net/)

Transcriber's Note:

Parentheses have been added to clarify fractions. Letters in brackets with a = sign before it means that the letters have a macron over them, e.g. H[=A=c] signifies that the Ac has a macron over it.

Minor typographical errors have been corrected. Footnotes have been moved to the end of the chapter, and all advertisements have been moved to the end of the book.

A TEXT-BOOK OF ASSAYING:

FOR THE USE OF THOSE CONNECTED WITH MINES.

BY

C. AND J. J. BERINGER.

REVISED BY

J. J. BERINGER,

ASSOC. OF THE ROYAL SCHOOL OF MINES; FELLOW OF THE CHEMICAL SOCIETY AND OF THE INST. OF CHEMISTRY; PRINCIPAL OF THE CAMBORNE MINING SCHOOL; AND LATE PUBLIC ANALYST FOR THE COUNTY OF CORNWALL.

With numerous Diagrams and Tables.

NINTH EDITION.

LONDON: CHARLES GRIFFIN AND COMPANY, L IMITED , EXETER STREET, STRAND.

1904.

[All rights reserved.]

PUBLISHER'S NOTE TO THE NINTH EDITION

The continued popularity of the present work, the last edition of which was published only a little over a year ago, continues to be a source of gratification to the publishers, who have much pleasure in issuing the present edition.

January 1904.

PREFACE TO THE SIXTH EDITION

The principal changes in this edition are additions to the articles on Gold, Cyanides, and Nickel, and a much enlarged Index. The additional matter covers more than forty pages.

J. J. BERINGER.

C AMBORNE , January 1900.

PREFACE.

The Text-book now offered to the public has been prepared to meet the existing want of a practical "handy book" for the Assayer.

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To mining men the word "assaying" conveys a sufficiently clear meaning, but it is difficult to define. Some writers limit it to the determination of silver and gold, and others imagine that it has only to do with "furnace-work." These limitations are not recognised in practice. In fact, assaying is becoming wider in its scope, and the distinction between "assayers" and "analysts" will in time be difficult to detect. We have endeavoured rather to give what will be of use to the assayer than to cover the ground within the limits of a faulty definition.

At first our intention was to supply a description of those substances only which have a commercial value, but on consideration we have added short accounts of the rarer elements, since they are frequently met with, and occasionally affect the accuracy of an assay.

Under the more important methods we have given the results of a series of experiments showing the effect of varying conditions on the accuracy of the process. Such experiments are often made by assayers, but seldom recorded. Statements like those generally made—that "this or that substance interferes" —are insufficient. It is necessary to know under what conditions and to what extent.

Students learning any particular process cannot do better than repeat such a series of experiments. By this means they will, at the same time, acquire the skill necessary for performing an assay and a confidence in their results based upon work under different conditions.

The electrolytic method of copper assaying given underCoppera is modification of Luckow's; it was introduced by us into the offices of the Rio Tinto Copper Company, and has been in use for many years with success. This modification is now employed in copper-works in Spain, Germany, and England, and is used in place of the dry assay for the commercial valuation of copper ores.

We have adhered to the gram and the "c.c." as the units of weight and volume. Those who prefer working with grains and grain-measures can use the figures given, multiplied by ten. For example:—When 1 gram is mentioned, 10 grains should be used, and 10 grain-measures take the place of 1 "c.c." It is not advisable to mix the two systems, as by using gram weights and grain- measures.

We have intentionally to a large extent omitted to mention the names of those who have originated or modified the various processes. The practice of naming a process after its discoverer has developed of late years, and is becoming objectionable. It is a graceful thing to name a gas-burner after Bunsen, or a condenser after Liebig; but when the practice has developed so far that one is directed to "Finkenerise" a residue, or to use the "Reichert-Meissl-Wollny" process, it is time to stop.

We are indebted to the standard works of Allen, Crookes, Fresenius, Lunge, Michell, Percy, and Sutton, and wish to express our sense of special indebtedness to Mr. Richard Smith, of the Royal School of Mines. One or two of the illustrations are taken from Mr. Sexton's excellent little book onQualitative Analysis. Our obligation to some others is mentioned in the text.

Finally, we have to thank for assistance in the experimental work Messrs. Bailey, Beswick, Clarke, Grant, Higgins, and Smith.

THE AUTHORS.

C AMBORNE ,Nov. 1889.

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Gravimetric methods Mechanical separations Dry assays  (a) Fluxes  (b) Reducing agents

 (b) Standardising

PART I.

CONTENTS.

 (c) Oxidising agents  (d) Apparatus

Wet gravimetric methods

 (a) Solution

 (b) Precipitation

[Pg ix]

Quantity to be taken for an assay Exercises CHAPTER II. METHODS OF ASSAYING.—DRY GRAVIMETRIC METHODS. Methods of assaying

Page 1 1 5 7 9 11 14

Object of assaying Sampling Drying: determination of moisture Calculation and statement of results Laboratory books and report forms

CHAPTER I. INTRODUCTORY.

Titrometric assays

 (a) Standard solutions

 (c) Methods of working  (d) Indirect titration Colorimetric assays

 (c) Filtration  (d) Drying and igniting CHAPTER IV. VOLUMETRIC ASSAYS.

CHAPTER III.

WET GRAVIMETRIC METHODS.

15 15 16 16 16 21 22 24

27 29 30 31 32

35 36 37 42 43 44

Gasometric assays CHAPTER V. WEIGHING AND MEASURING. Weighing Measuring liquids  (a) Graduated flasks  (b) Pipettes

 (c) Burettes Measuring gases

Acids, &c. Bases, salts, &c.

Formulæ, equations, &c.

Introductory

CHAPTER VI. REAGENTS.

CHAPTER VII.

CHAPTER VIII.

SPECIFIC GRAVITY.

Determination of specific gravity—

 (a) Hydrometers  (b) Specific gravity bottles Calculations depending on specific gravity PART II.

CHAPTER IX. SILVER, GOLD, PLATINUM, CYANIDES, MERCURY. Silver—Detection  Dry assay  (1) Scorification

 (2) Pot assays, average ores  " ores with metallic oxides  " ores with metallic sulphides  Explanatory notes on the fusion  The effect of charcoal, flour, &c.

 The effect of nitre

 The effect of mineral sulphides

44

47 49 49 50 51 52

54 59

68

75

76 78 84

87 87 88 90 91 91 93 94 95 95

 (3) Cupellation  The loss of silver  Condition affecting the loss

 Methods of correction

 Lead required for cupellation  (4) Calculation of the results in ounces to the ton of 2240 lbs. Table  Ores with metallic particles  (5) Explanatory notes  (6) Examples of dry silver assays

 Wet assays

 Gravimetric method

 Gay-Lussac's method

 Volhard's method

 A modified Gay-Lussac

 Volhard's method applied to arsenic

Gold—Detection

 Amalgamation assay

 Dry assay

 (1) Size of charges

 (2) Sampling

 (3) Assay tons

 (4) Small buttons, weighing  " " measuring  (5) Concentration in lead  Quartz ores  Ores with oxide of iron

 Ores with metallic sulphides

 (6) Cyanide charges, residues, &c.

 (7) Cupellation

 Cupels

 Cupellation temperature

 Cupellation loss

 (8) Inquartation  (9) Flatting  (10) Parting, in flasks  " in test tubes  " in glazed crucibles  " Loss, &c.  (11) Check assays, surcharge  (12) Bullion assays in special apparatus  Silver, &c., in gold bullion  (13) Sampling of base bullion, &c.

98 101 102 103 105

107

108 110 113 116 117 119 121 123 124 126 126 127 127 127 131 131 133 136 136 138 139 140 142 142 143 145 146 149 151 152 153 154 154 156 157 157

Cyanides—Commercial cyanides

 Double cyanides  Prussic acid  Gold-dissolving power of cyanide liquor

 Assay for cyanide strength

 Assay of commercial cyanide

 Alkalinity of cyanides

 Acidity of ores

 Metals in cyanide liquors  Cyanicides Platinum Iridium Mercury  Dry assay  Wet method CHAPTER X. COPPER, LEAD, THALLIUM, BISMUTH, ANTIMONY. Copper—Introductory

 Dry assay

 Valuation of copper ores

 Wet methods

 (1) Electrolytic assay

 Volumetric methods

 (1) Cyanide method

 (2) Iodide method

 (3) Colorimetric method  Examination of commercial copper Lead  Dry assay  Wet assay

 (1) Gravimetric method

 (2) Volumetric method  (3) Colorimetric method Thallium Bismuth  Dry assay

 Wet method

 (1) Gravimetric determination  (2) Colorimetric assay Antimony

160 161 162 162 163, 165 167 167 168 169 169 170 171 171 172 173

175 176 181 183 184 194 194 199 203 205 211 211 213 213 214 218 219 220 221 221 222 223 225

 Dry assay

 Wet method

 (1) Gravimetric assay

 (2) Volumetric method CHAPTER XI. IRON, NICKEL, COBALT, ZINC, CADMIUM. Iron  Gravimetric determination

 Permanganate and bichromate methods

 Stannous chloride method  Colorimetric determination Nickel  Dry assay  Electrolytic assay  Titration by cyanide Cobalt Zinc  Gravimetric method

 Volumetric method  Gasometric method Cadmium

Tin  Vanning  Dry assay  Detection, &c.

CHAPTER XII.

TIN, TUNGSTEN, TITANIUM.

 Gravimetric determination

 Volumetric determination

 Examples Titanium Tungsten Niobic and Tantalic Oxides CHAPTER XIII.

MANGANESE, CHROMIUM, ETC. Manganese  Gravimetric determination  Volumetric determination

 Ferrous sulphate assay

225 227 228 229

231 233 234 244 247 251 251 254 255 259 261 262 263 266 269

271 273 276 279 281 282 284 292 295 297

298 300 300 301

 Iodine assay  Colorimetric determination Chromium Vanadium Molybdenum Uranium CHAPTER XIV.

EARTHS, ALKALINE EARTHS, ALKALIES.

Alumina Thoria Zirconia Cerium Lanthanum and Didymium Yttria Beryllia Lime Strontia Baryta Magnesia The Alkalies  Sodium  Potassium  Lithium  Cæsium  Rubidium  Ammonium

PART III.

CHAPTER XV. OXYGEN AND OXIDES—THE HALOGENS. Oxygen Oxides Water The Halogens

 Chlorine  Bromine  Iodine  Fluorine

302 306 307 310 311 312

314 317 317 318 319 319 319 320 324 326 328 330 334 336 338 339 340 340

344 345 350 358 359 361 362 363

CHAPTER XVI.

SULPHUR AND SULPHATES.

Sulphur  Gravimetric determination  Volumetric determination Sulphates Selenium Tellurium

CHAPTER XVII.

ARSENIC, PHOSPHORUS, NITROGEN. Arsenic  Gravimetric determination  Volumetric method, "iodine"  " " "uranic acetate" Phosphorus Gravimetric determination Volumetric determination Nitrogen and Nitrates CHAPTER XVIII. SILICON, CARBON, BORON. Silicon and Silicates Carbon and Carbonates Coals Shales Carbonates Boron and Borates APPENDIX A. Table of atomic weights and other constants Table for converting degrees of the centigrade thermometer  into degrees of Fahrenheit's scale Tables showing strengths of aqueous solutions of nitric and hydrochloric acids,  of ammonia and of sulphuric acid APPENDIX B. Estimation of small quantities of gold Practical notes on the iodide process of copper assaying Method of separating cobalt and nickel APPENDIX C.

367 369 370 377 379 379

381 383 384 389 394 396 397 400

405 414 418 420 424 429

433

435

436

440 441 442

A lecture on the theory of sampling

Index

A TEXT-BOOK OF ASSAYING.

CHAPTER I.

INTRODUCTORY.

444

450

Assaying has for its object the determination of the quantities of those constituents of a material which add to or detract from its value in the arts and manufactures. The methods of assaying are mainly those of analytical chemistry, and are limited by various practical considerations to the determination of the constituents of a small parcel, which is frequently only a few grains, and rarely more than a few ounces, in weight. From these determinations calculations are made, which have reference to a mass of material of, perhaps, hundreds of tons. But in all cases, whether the mass under consideration be large or small, whether the material be obtained by mining, grown, or manufactured, the assayer is supposed to receive a small quantity, called "the sample," which is, or ought to be, the exact counterpart of the mass of material that is being dealt with. The taking and making of this sample is termed "sampling"; and the men whose special work it is to select such samples are "the samplers."

But although "sampling" is thus distinct from "assaying," the assayer should be familiar with the principles of sampling, and rigorous in the application of these principles in the selecting, from the sample sent him, that smaller portion upon which he performs his operations.

Sampling.—In the case of gases, there is absolutely no trouble in mixing. The only difficulty is in drawing off a fair sample where, as in flues, the body of the gas is in motion, and varies a little in composition from time to time. In this case, care must be taken to draw off uniformly a sufficient volume of the gas during a prolonged period; any portion of this larger volume may then be taken for the analytical operation.

In the case of liquids, which mix more or less easily—and this class includes metals, &c., in the state of fusion—more or less severe agitation, followed by the immediate withdrawal of a portion, will yield a fairly representative sample.

In the case of solids, the whole mass must be crushed, and, if not already of fairly uniform quality, mixed, before sampling can take place. Most of the material which a sampler is called upon to deal with, is, however, in a more or less divided state and fairly uniform. In practice it is assumed that 5 per cent. of the whole (= 1/20th), if taken in portions of equal weight and at frequent and regular intervals, will represent the mass from which it was taken. Taking a heap of ore, A, and selecting one out of every twenty spade-, bag-, barrow-, or wagon-fuls, according to the quantity of stuff in the heap, there is obtained a second heap, B, containing one-twentieth of the stuff of the heap A. If we crush the stuff in B until this heap contains approximately the same number of stones as A did—which means, crushingeverystone in B into about twentypieces—B

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