003, whereas
that of acetylene, according to Ortloff, is 0.0001319. Secondly, the
mains and service-pipes required for acetylene are smaller, _cateria
paribus_, than those needed for coal-gas. Thirdly, the observed
specific gravity of acetylene is 0.91, that of air being unity, whereas
the density of coal-gas is about 0.40; and therefore, in the absence of
direct information, it would be better to base calculations respecting
acetylene on data relating to the flow of air in pipes rather than upon
such as are applicable to coal-gas. Bernat has endeavoured to take these
and similar considerations into account, and has given the following
formula for determining the sizes of pipes required for the distribution
of acetylene:
Q = 0.001253_d^2_(_hd/sl_)^(1/2)
in which the symbols refer to the same quantities as before, but the
constant is calculated on the basis of Q being stated in cubic metres, l
in metres, and d and h in millimetres. It will be seen that the equation
has precisely the same shape as Pole's formula for coal-gas, but that the
constant is different. The difference is not only due to one formula
referring to quantities stated on the metric and the other to the same
quantities stated on the English system of measures, but depends partly
on allowance having been made for the different physical properties of
the two gases.
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