____________________________________________________________
Purple Ore 5 grams
19/10/89 0.0042 grm.
0.0021 "
———
Colorimetric 0.0063 × 20 = 0.13% Copper
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482
Tough Copper 10 grams
Feb. 1/89 10.5 c.c. Uranium.
= 0.52% Arsenic
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2082
Tough Copper 10 grams
12.7 c.c. Uranium.
= 0.63% Arsenic
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491 10 grams
Tough Copper 13.7 c.c. Uranium
Feb. 1/89
= 0.68% Arsenic
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Standard of Uranium acetate.
0.150 gram As2O3 = 23.3 c.c. Uranium.
∴ 100 cc. Uranium = 0.5 gram As.
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10071 5 grams
Tin Ore Cruc. and SnO2 9.6065 grms.
Feb. 3/89 Cruc. and Ash 9.4235 "
———
SnO2 = 0.1830 = 2.88% Tin
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The Assay Book.—This is the Official book, and is a combination of the Sample and Laboratory books. It corresponds with the report-forms. Without being loaded with detail, it should contain sufficient to characterise each sample.
Example of Page of Assay Book.
Description of Sample.
| Date. | Material. | Weight. | No. | Water Lost at 100° C. | Assay on the Dry Material. | Date Reported. | ||||
| 1889 | ton | cwt | qrs | lbs | ||||||
| Feb. 1 | Tough cake copper | ... | ... | ... | ... | 482 | ... | Arsenic, 0.52% | 7 | |
| " | Tough cake copper | ... | ... | ... | ... | 2082 | ... | Arsenic, 0.63% | 7 | |
| " | Tough cake copper | ... | ... | ... | ... | 491 | ... | Arsenic, 0.68% | 7 | |
| Feb. 2 | Nickel disc for C.R. | ... | ... | ... | ... | X | ... | Copper, 73.75 | 7 | |
| Nickel, 24.34 | ||||||||||
| Iron, 2.18 | ||||||||||
| ——— | ||||||||||
| 100.27 | ||||||||||
| ——— | ||||||||||
| " | Silver precipitate, 4 casks | ... | 24 | 1 | 0 | 73 | Not det. | Silver, 4.851 | 10 | |
| Gold, 0.0215 | ... | |||||||||
| Lead, 19.37 | ... | |||||||||
| Zinc, 2.00 | ... | |||||||||
| Silver, 1584.7 ozs. per ton | ... | |||||||||
| Gold, 7.0 ozs. per ton | ... | |||||||||
| " | Purple ore | ... | 200 | ... | ... | ... | 494 | Not det. | Copper, 0.13% | 11 |
| Sulphur 0.15% | ... |
When the number of samples is small, the Sample Book may be omitted, and the entries made in the Assay Book as the samples arrive.
Report-forms. These should entail as little writing as possible in making out the report. For general purposes the form given on p. 12 is useful.
The quantity of substance to be taken for any particular assay depends largely upon the method of assay adopted. There are, however, some general considerations which should be remembered, and some devices for simplifying the calculations which should be discussed.
The smaller the percentage of the substance to be determined, the larger should be the amount of the ore taken. The following table will give a general idea as to this:—
| Percentage of the substance to be determined. | Amount of ore, &c. to be weighed. |
| 100-10 | 1 gram. |
| 10-5 | 2 grams. |
| 5-1 | 5 " |
| 1-0.1 | 10 " |
| 0.1-0.01 | 20 " |