"
Thus, Wolff found that when acetylene was burnt in the "0000 Bray" fish-
tail burner at the rate of 1.377 cubic feet per hour, a light of 77
candle-power was obtained. Hence, putting x to represent the illuminating
power of the acetylene in standard candles, we have:
1.377 / 5 = 77 / x hence x = 280.
Therefore acetylene is said to have, according to Wolff, an illuminating
power of about 280 candles, or according to other observers, whose
results have been commonly quoted, of 240 candles. The same method of
calculating the nominal illuminating power of a gas is applied within the
United Kingdom in the case of all gases which cannot be advantageously
burnt at the rate of 5 cubic feet per hour in the standard burner
(usually an Argand). The rate of 5 cubic feet per hour is specified in
most Acts of Parliament relating to gas-supply as that at which coal-gas
is to be burnt in testings of its illuminating power; and the
illuminating power of the gas is defined as the intensity, expressed in
standard candles, of the light afforded when the gas is burnt at that
rate. In order to make the values found for the light evolved at more
advantageous rates of consumption by other descriptions of gas--such as
oil-gas or acetylene--comparable with the "illuminating power" of coal-
gas as defined above, the values found are corrected in the ratio of the
actual rate of consumption to 5 cubic feet per hour.
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