OF GASES AT CONSTANT VOLUME. 
981 
did the more recent one of Clausius* afford an agreement with the results of experi¬ 
ment. M. Sanan (‘Comptes Rendus,’ vol. 94, 1882)t has shown that Clausius’ 
form of the characteristic equation possesses hut a limited applicability to carbon 
dioxide when tested with Amagat’s results. It is easy to test this point by calcu¬ 
lating for the pressure at the density 0‘1800 at some chosen temperature, and com¬ 
paring with Amagat’s results. A deficiency in the value of the pressure given by 
the formula to the extent of some 12 per cent, is obtained. The close agreement 
between this line, p = OT800, and the neighbouring one, p = 0T973, is, I think, 
strongly confirmatory of tlie accuracy of both. Indeed, the quantities of precipitated 
steam then dealf. with are so large that I do not see how serious error could have 
arisen. I therefore venture to think that they truly represent the variation of the 
specific heat with temperature at these densities. 
* ‘ Phil. Mag.,’ June, 1880. 
t See ‘The Theory of Heat,’ T. Preston, p. 422. 
