To use the table, find the observed
temperature and the observed reading of the barometer in the border of
the table, and in the space where these vertical and horizontal columns
meet will be found a number by which the observed volume of gas is to be
multiplied in order to find the corresponding volume under normal
conditions. For intermediate temperatures, &c., the factors may be
readily inferred from the table by inspection. This table must only be
applied when the gas is saturated with aqueous vapour, as is ordinarily
the case, and therefore a drier must not be applied to the gas before
measurement.
Hammerschmidt has calculated a similar table for the correction of
volumes of gas measured at temperatures ranging from 0 deg. to 30 deg. C.,
and under pressures from 660 to 780 mm., to 15 deg. C. and 760 mm. It is
based on the coefficient of expansion of acetylene given in Chapter VI.,
but, as was there pointed out, this coefficient differs by so little from
that of the permanent gases for which the annexed table was compiled, that
no appreciable error results from the use of the latter for acetylene also.
A table similar to the annexed but of more extended range is given in the
"Notification of the Gas Referees," and in the text-book on "Gas
Manufacture" by one of the authors.
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