428 
DR. ANDREWS ON THE GASEOUS STATE OE MATTER. 
pure and anhydrous methyl-alcohol through the apparatus *. About two thirds of a 
litre of the alcohol was distilled over in each observation, the temperature being 
observed by one of the thermometers before referred to. The temperature obtained in 
this way, after every precaution has been taken, is far from being so steady as that 
given by the vapour of water ; but with a little care very accurate determinations can 
be made. A deduction of 0°T4 was made from the direct reading as a correction for 
the error of the thermometer due to irregular expansion of the mercury. 
For temperatures about 100°, vapour of water from a boiler in an adjoining apart- 
ment was passed around the carbonic acid tube and conveyed away by an exit-pipe 
through an outer wall of the apartment. Its pressure when in the vessel around the 
carbonic acid tube was usually about 50 millimetres of water above that of the atmo- 
sphere, as ascertained by a U-shaped water-gauge connected with the apparatus. By 
adding the pressure indicated by the water-gauge to the height of the barometer, the 
elastic force of the steam, and consequently its temperature, was known. 
In the following tables I have recorded the results of direct experiments, all made 
by myself, and reduced by the equations already given. In every case two experiments 
at least, and often more than two, were made, the apparatus being thrown out of adjust- 
ment and readjusted between each observation. The mean numbers given in the tables 
scarcely differed by an appreciable amount from the results of the individual experi- 
ments. 
In Tables I., II., and III., p is the pressure in the carbonic acid tube calculated from 
the indications of the air-manometer, t the temperature of the manometer, s the ratio 
of the observed volume of the carbonic acid at the pressure p and temperature fl to its 
volume at the same temperature t’ under a pressure of one atmosphere, t 1 the tempe- 
rature of the carbonic acid, and 6 the volume to which one volume of carbonic acid, 
measured at 0° and under one atmosphere, is reduced at the pressure p and temperature t 1 . 
By one atmosphere of pressure is meant the pressure of a column of mercury 760 milli- 
metres in length measured at 0° and under the latitude of 45°. 
* Both the air-tube and carbonic acid tube were enclosed in rectangular brass vessels, having plate-glass 
sides inserted before and behind, by which means accurate readings, not attainable in ordinary glass cylinders, 
were secured. Through these rectangular vessels the water or vapour circulated, by means of which the tubes 
were maintained at fixed temperatures. A detailed description, with a figure of the apparatus, will he found 
in my former communication, Philosophical Transactions for 1869, p. 578. 
