842 gram of silver (from the metallics) must be
added to its produce. We thus get 0.1471 gram (0.1050 + 0.0421).
Referring to the 20 gram column, we get--
0.1 = 163.33
0.04 = 65.33
0.007 = 11.43
0.0001 = 0.16
------ ------
0.1471 = 240.25 ounces per ton.
A more legitimate method of calculation is as follows:--Calculate
separately the produce of each fraction as if they were from different
ores. Multiply each produce (best stated in per cents.) by the weight of
the corresponding fraction. Add together the products, and divide by the
weight of the whole sample. Taking the same example for illustration, we
have:--
_Metallics._--Weight 1 gram.
1 gram of it yielded 0.842 grams of silver.
.'. Produce = 84.2 per cent.
Produce multiplied by the weight is still ~84.2~.
_Sifted Portion._--Weight 399 grams.
20 grams of it yielded 0.105 gram of silver.
.'. Produce = 0.525 per cent.
Produce multiplied by weight (0.525 ? 399) is ~209.475~.
Add together; and divide by 400, the weight of the whole sample--
84.2
209.475
-------
400) 293.675 (0.7342
0.7342 is the total produce of the ore in per cents.
Referring to the 100-gram column in the table we find 239.84 ounces to
the ton as the produce.
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