166 Proceedings of the Royal Society of Edinburgh. [Sess.. 
heat of adsorption at constant volume plus the heat introduced by the 
gas entering the adsorption chamber at a temperature higher than that of 
the chamber. 
Sulphur dioxide does not accurately obey the law pX = RT. In cor- 
recting, the author made use of the data obtained by various observers. 
(1) In correcting for temperature he used the data given by Leduc * 
in the deduced form 
Tfj = V 0 (l + -00396f), 
when t is near 20° C. and the pressure is constant and not more than two 
atmospheres. 
(2) The pressure correction was calculated from the data of Jacquerod 
and Pintza,*(* and of Baume.f From their measurements of density at 
0° C. a table was drawn up giving the values p' to be read for p the 
observed pressure, so as to make the gas conform to the equation 
p'X = constant = RT/ T023. Specimen values thus found are given below. 
p 76-00 60-00 40-00 20 00 10-00 TOO 
p 76-00 59-70 39-55 19-65 T79 TOO 
The application of the above corrections refers all volumes of gas to 
actual c.cms. at N.T.P., where the density of the gas is 1*023 times that 
calculated from the simple gas law pX = RT. 
The observations are now given in the tables below, where 
p = final pressure in cm. mercury; 
a = c.cm. adsorbed measured at N.T.P. ; 
A a— „ „ „ „ during an experiment ; 
/3 = c.cm. evolved from the calorimeter and measured at N.T.P. ; 
At = excess temperature of gas in reservoir over gas in ad- 
sorption bulb ; 
P — vapour pressure in cm. mercury. 
As after a certain amount was adsorbed the rate of adsorption fell 
considerably, the stopcock was closed after forty minutes or so, and such 
non-equilibrium readings are given in brackets. In the course of work, 
however, opportunity was allowed for the adsorption to proceed for twenty- 
four hours or longer, and such readings are not enclosed in brackets. 
After the stopcock was closed a very small additional amount of gas 
would be adsorbed, but too small to affect appreciably the calculations. 
* Comptes Rendus , cxlviii, p. 1173 (1907). 
t Ibid., cxxxix, p. 129 (1904). 
I Journal de Ghim. pliys., vi, jd. 1 (1908). 
