A Textbook of Assaying | Page 8

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.
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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 As{2}O{3} = 23.3 c.c.
Uranium. .'. 100 cc. Uranium = 0.5 gram As.
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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
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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.
Key to following example page of Assay book: DR = DATE
REPORTED. Not Det. = Not detected
EXAMPLE OF PAGE OF ASSAY BOOK.
-------------------------------------------+----+-------+---------------+----
DESCRIPTION OF SAMPLE. | | Water | Assay on |
------+--------------------+---------------| |Lost at| the Dry | Date. |
Material. | Weight. |No. |100° C.|Material. | DR
------+--------------------+---+---+---+---+----+-------+---------------+----
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, | | 24| 1| 0| 73| Not | | | 4 casks | | | | | |
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 |Copper, 0.13% | 11 | | | | | | | det. |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 Amount of ore, &c. to to be determined. be
weighed. 100-10 1 gram. 10-5 2 grams. 5-1 5 " 1-0.1 10 " 0.1-0.01 20 "
[Illustration: ASSAY NOTE]
The rougher the method of assay adopted, the larger should be the
quantity of ore taken. If the degree of accuracy attainable with the
methods and instruments at the assayer's service is known, it is easy to
calculate what quantity should be taken for any particular case. If the
results are good within 0.001 gram, then, taking 1 gram of ore we can
report within 0.1 per cent., or if they are good within 0.0002 gram,

taking 20 grams of ore, we can report within 1 part per 100,000, or
very closely within 6-1/2 dwt. to the ton. If it is wished to be yet more
particular in reporting, larger quantities must be taken. The difficulty
of manipulating very small or very large precipitates, &c., must be
borne in mind. So, too, must the fact that the greater the weight of the
final product of an assay, the less, as a rule, is the percentage error.
The distinction between absolute and