A Textbook of Assaying | Page 7

is necessary to carry the reduction to ozs. and dwts. to the ton;
and since gold and silver are sold by troy weight, whilst the ton is
avoirdupois, it is of importance to remember that the ounces in the two
systems are not the same. A ton contains 15,680,000 grains, which
equal 653,333.3 dwts. or 32,666.6 ozs. (troy). The following rules are
useful:--
To get ozs. (troy) per ton, multiply parts per 100,000 by 0.327; To get
dwts. per ton, multiply parts per 100,000 by 6.53; To get grains per ton,
multiply parts per 100,000 by 156.8.
Where liquids are being assayed, cubic centimetres are held to be
equivalent to grams, and the usual method of statement is, "so many
parts by weight in so many by measure." Where the statement is made
as grams per litre or grains per gallon, there can be no doubt as to what
is meant; and even if it be expressed in parts per 100,000, parts by
weight in a measured volume must be understood unless the contrary is
expressly stated.
In some cases, where the density of the solution differs greatly from

that of water, the percentage by weight may be given; and in others,
mixtures of two or more liquids, the percentages may be given by
volume or by weight; as so many c.c. in 100 c.c., or as so many grams
in 100 grams, or even as so many grams in 100 c.c. In such cases it
must be distinctly shown which method of statement is adopted.
One grain per gallon means 1 grain in 70,000 grain-measures, or one
part in 70,000. Dividing by 7 and multiplying by 10 will convert grains
per gallon into parts per 100,000. Inversely, dividing by 10 and
multiplying by 7, will convert parts per 100,000 into grains per gallon.
Grams per litre are parts per 1000; multiplying by 100 will give parts
per 100,000, and multiplying by 70 will give grains per gallon.
Among foreign systems of weights, the French is by far the best.
Kilograms (2.205 lbs.) per quintal (220.5 lbs.) are parts per cent.; and
grams (15.43 grs.) per quintal are parts per 100,000. From the rule
already given, grams per quintal may be converted into ounces to the
ton by multiplying by 0.327.
The German loths per centner (1/2 oz. (avoirdupois) to 100 lbs.) equal
parts per 3200; they are converted into parts per cent. by dividing by 32,
or into ounces (troy) per ton by multiplying by 10.208.
In the United States, as a sort of compromise between the avoirdupois
and metric systems, a ton is taken as 2000 lbs. There, too, the custom is
adopted of reporting the gold and silver contents of an ore as so many
dollars and cents to the ton. In the case of gold, an ounce is considered
to be worth 20.6718 dollars. With silver, the nominal value is 1.2929
dollars per ounce, but frequently in assay reports it is taken as one
dollar. The practice is objectionable. The prices of metals vary with the
fluctuations of the market, and if the assayer fixed the price, the date of
his report would be all important; if, on the other hand, he takes a fixed
price which does not at all times agree with the market one, it leaves a
path open for the deception of those unacquainted with the custom.
American "dollars on the ton of 2000 lbs." may be converted into
"ounces in the ton of 2240 lbs." by dividing by 1.1544 in the case of
silver, and by 18.457 in the case of gold.

~Laboratory Books and Report Forms.~--The record which the assayer
makes of his work must be clear and neat, so that reference, even after
an interval of years, should be certain and easy. One method should be
adopted and adhered to. Where there are a large number of samples,
three books are required.
Sample Book.--This contains particulars of the samples (marks, &c.),
which are entered by the office-clerk as they arrive. He at the same
time puts on each sample the distinguishing number.
EXAMPLE OF PAGE OF SAMPLE BOOK.
+----------+----------+--------------------------+----------------+ | Date. |
Number. | Sample. | Remarks. |
+----------+----------+--------------------------+----------------+ | Feb. 1 |
482 | Tough Copper | For Arsenic. | | " 2 | X | Piece of Metal | For Ni
and Cu. | | " | 483 | Tough Copper. | | | " | 73 | Silver Precipitate, | With
Letter. | | | | 4 casks, 24 cwt. 1 qr. | | | " | 494 | Purple Ore, 200 tons. | | | "
| 1 J.T. | Lead Ore, 1 J.T. | From Corsica. | | " | 2 J.T. | " 2 J.T. | |
+----------+----------+--------------------------+----------------+
Laboratory Book. This is the Assayer's note-book,