SECT. II.] 
PROPERTIES OF STEAM. 
73 
K 
the lower ranges of temperature, and in the same manner as those on the force of 
the steam of water; but in describing them it will be some advantage to begin 
with the experiments of Cagniard de la Tour, on the space alcohol occupies when 
converted wholly into vapour. To ascertain this point, alcohol of the specific 
gravity '837 was introduced into small tubes of glass, and hermetically sealed, 
with a handle of glass attached to each tube. A tube was two-fifths filled with 
alcohol, and then slowly and carefully heated : as the fluid dilated, its mobility 
increased; and when its volume was nearly doubled, it completely disappeared, 
and became a vapour so transparent, that the tube appeared quite empty. On 
leaving it to cool for a moment, a very thick cloud formed in its interior, and the 
liquor returned to its first state. A second tube, nearly half occupied by the 
same fluid, gave a similar result; but a third, containing rather more than half, 
burst. 
A process was next adopted to ascertain the pressure. It consisted in bending 
a tube into a syphon, one leg to hold the liquid to be tried, and the other leg 
containing air kept at a constant temperature of 73° by a cooling apparatus, and 
separated from the fluid by mercury: both legs being sealed, the end containing 
the liquid was heated, and when the liquid became vapour the diminution in the 
bulk of the air was marked. 
Alcohol of the specific gravity ‘837 w T as reduced into vapour at a temperature of 
497° in a space a little less than 3 times its original bulk; and 476 parts of 
air were reduced to 4 ; indicating a pressure, according to M. Cagniard de la 
Tour, of 119 atmospheres, or 3570 inches of mercury. 1 
105. The experiments on alcohol vapour at lower temperatures are collected 
in the following table. 
1 By the same process as was adopted in finding the constants for calculating the force of the 
steam of water (art. 86.) the formula for the vapour of alcohol of sufficient purity to boil at 
173° is 
■ ■ -* ™ 6 
or, in logarithms, 
log. / = 6 (log. (t + 100) — 2 - 19000^); 
where t is the temperature of the vapour, and /its force in inches of mercury. By this rule the 
force for a temperature of 497° is 3280 inches : the experiment of M. Cagniard de la Tour 
gives 3570 inches.