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Scientific American Supplement, No. 288, July 9, 1881 by Various
page 11 of 160 (06%)
preferred for some manufacturing purposes and in some markets.
Bituminous steam coals, yielding 75 per cent, of coke, are highly prized
in others. Semi-bituminous steam coals, yielding 80 to 83 per cent, of
coke, are most highly valued, and find the readiest sale abroad; and
anthracite steam coal (dry coals), giving from 85 to 88 per cent, of
coke (using the term "coke" as equivalent to the non-volatile portion of
the coal) is also exported in considerable quantity. Now the estimation
of the ash of any of these varieties of coal would afford no evidence
as to the class to which that coal belongs, and there is no simple test
that will give the calorific power of a coal, and at the same time
indicate the degree of bituminous or anthracitic character which it
possesses.

In order to obtain such information it is necessary that the percentage
of coke be determined together with the sulphur, ash, and water, and
these form data which at once show the nature of a fuel and give some
indication of its value. To ascertain the quantity of the sulphur, ash,
and water with accuracy involves more skill and aptitude than can
be bestowed by the non-professional public; the consequence is that
experiments entailing less time and precision, like those devised by
Berthier and Thompson, have been tried more or less extensively.
In France and Italy, Berthier's method--slightly modified in some
instances--has been long used. It is as follows:

70 grammes of oxide of lead (litharge) and 10 grammes of oxychloride of
lead are employed to afford oxygen for the combustion of 1 gramme of
fuel in a crucible. From the weight of the button of lead, and taking
8,080 units as the equivalent of carbon, the total heat-units of the
fuel is calculated. This experiment is very imperfect and erroneous upon
scientific grounds, since the hydrogen of the fuel is scarcely taken
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