A Textbook of Assaying | Page 7

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, in which he enters clearly the particulars of his work--the results obtained, as well as how these results were arrived at. The calculations should be done on scrap-paper, and should not be entered, although, of course, detail enough must be shown to enable the results to be recalculated.
EXAMPLE OF PAGE OF LABORATORY BOOK. _____________________________________________________________
Purple Ore 5 grams 19/10/89 0.0042 grm. 0.0021 " ------ Colorimetric 0.0063 �� 20 = 0.13% Copper ____________________________________________________________
482 Tough Copper 10 grams Feb. 1/89 10.5 c.c. Uranium. = 0.52% Arsenic ____________________________________________________________
2082 Tough Copper 10 grams 12.7 c.c. Uranium. = 0.63% Arsenic ____________________________________________________________
491 10 grams Tough Copper 13.7 c.c. Uranium Feb. 1/89 = 0.68% Arsenic ____________________________________________________________
Standard of Uranium acetate. 0.150 gram As{2}O{3} = 23.3 c.c. Uranium. .'. 100 cc. Uranium = 0.5 gram As. ____________________________________________________________
10071 5 grams Tin Ore Cruc. and SnO{2} 9.6065 grms. Feb. 3/89 Cruc. and Ash 9.4235 " ------ SnO{2} = 0.1830 = 2.88% Tin ____________________________________________________________
The Assay Book.--This is the Official book, and is a combination of the Sample and Laboratory books. It corresponds with the