'a Mixture of Carbonic Acid and Nitrogen, 447 



M. Amagat makes use of isothermals of another type, of 

 which the product pv is taken for ordinate, and the pressure 

 p for abscissa. For the sake of comparison they are drawn 

 in fig. 2. The product pv has a minimum value for each 



Fig. 2. 



p and pv lines. 



i-i 



0'9 



0-3 





40 



340 



temperature. The parts of the isothermals which are on the 

 left-hand side of that value are appreciably convex towards 

 the origin, while those which are on the right-hand side seem 

 to converge asymptotically, their curvatures tending to be- 

 come zero. These features belong to isothermals of this type 

 for pure carbonic acid at much higher temperatures ; thus an 

 admixture of a more permanent gas like nitrogen seems to 

 have the same effect as a rise of temperature, as a priori 

 would be probable. The locus of these minima can be found 

 from the characteristic equation, but its equation is almost 

 uselessly complex. The following values were found by 

 trials : — 



