Consequently, a measured quantity of acid should be used in each assay
and a comparative experiment made with a known weight of pure carbonate
of lime which will yield about the same volume of gas. The number of
c.c. of gas got in the assay multiplied by 4.7 will give the number of
milligrams of pure carbonate of lime that must be taken for the
standard. With ordinary work the error rarely exceeds half a c.c.
The following example will illustrate the calculations:--
One gram of a mineral was taken, and yielded 49.0 c.c. of gas. The
"volume corrector" reading was 100.4 c.c.
0.2405 gram of pure carbonate of lime was then taken, and treated in the
same way; 50.5 c.c. of gas were got. The volume corrector still read
100.4 c.c.
0.2405 gram of carbonate of lime is equivalent to 0.1058 gram of carbon
dioxide; then,
50.5 : 49.0 :: 0.1058 : _x_
_x_ = 10.26 per cent.
~Estimation of Carbonic Acid in the Air of Mines.~--According to a
series of analyses by Angus Smith, the proportion of carbonic acid in
the air of underground workings varied from 0.04 to 2.7 per cent. by
volume. In places where men are working the proportion ought not to
reach 0.25 per cent.
A simple method of determining whether a sample of air reaches this
limit (0.25 per cent.) is described by Dr.
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