E-text prepared by Peter Yearsley, Josephine Paolucci,
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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, Limited,
EXETER STREET, STRAND.

1904.

[All rights reserved.]

PUBLISHER'S NOTE TO THE NINTH EDITION

PREFACE.

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 under Copper is a 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 on Qualitative 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.

Camborne,   Nov. 1889.

CONTENTS.

A TEXT-BOOK OF ASSAYING.

CHAPTER I.

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, crushing every stone in B into about twenty pieces—B will become the counterpart of A. Selecting in the same manner 5 per cent. of B, there is got a third heap, C. This alternate reduction and pulverising must be carried on until a sample of suitable size is obtained. This may be expressed very clearly thus:—

A  =  1000 tons of rocks and lumpy ore.
B  =    50      "   "    rough stones,  1/20th of A.
C  =    2.5    "    "    small stones,  1/20th of B.
D  =    0.125  "    "    coarse powder, 1/20th of C.