and quarters to the
ton. The corresponding percentage may be obtained by multiplying by
five; or, inversely, if the percentage is given, the produce may be got
by dividing by five. A produce of 13-1/2 equals a percentage of 13.5?5
= 67.5; and a percentage of 70.0 equals a produce of 70/5 = 14. With
tin ores as raised (in which the percentage is small) the reduction must
be carried to pounds per ton. One per cent. equals 22.4 lbs. to the ton;
consequently, if we multiply the percentage by 22.4, the produce will be
given. Thus, if an ore contains 6.7 per cent. of oxide of tin, the
produce is 6.7?22.4 = 150 lbs. (or 1 cwt., 1 quarter, and 10 lbs.) to
the ton. With gold and silver ores, the proportion of precious metal is
small, and it 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.
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