236 Mr. William Sutherland on the 



Now we can calculate K t . from the experimental values of 

 K by the relation 



*~ p BTBT* 



Let us then make a comparison in the case of ethyl oxide, 

 using E. Wiedemann's value '3725 for K for the vapour at 

 0°, and Regnaulfs value "529 for the liquid at 0° ; then, con- 

 verting to ergs per degree C, we get 



Vapour at D . Liquid at 0°. 



A(E-Y) = 1-68 xlO 8 15-3 xlO 6 , 



K„ or ^(E-P) = 14-4 x 10 6 17«9xl0 6 . 



Thus we see that while in the liquid d(E — Y)/BT is nearly 

 equal to ^(E — P)/c)T, there is a great difference in the 

 vapour : 



3(V— P)/BT= 12-7 for the vapour and only 2*6 for the liquid. 

 Or, while K v is nearly the same in the two states, B (E — Y)/3T 

 has in the liquid state increased to nine times its value in the 

 vaporous. We have here, therefore,^an interesting opening 

 into the regions of chemic force ; but meanwhile we must 

 restrict ourselves to the question of molecular force at present 

 in hand, calling attention, however, to the fact that our energy 

 term in its two forms for elements and its two forms for com- 

 pounds is well worthy of the closest study. It summarizes a 

 lot of information about the internal dynamics of molecules — 

 perhaps about the relations of matter and aether ; but these 

 would need to be extracted by a special research on the term 

 and its relation to our experimental knowledge of specific heat. 

 It is worth mentioning here that Clausius's equation of the 

 virial, as usually applied to molecular physics, takes no account 

 of the mutual action of matter and aether — an action which we 

 know must exist, from the radiation of heat by gases as well as 

 by liquids and solids. According to ordinary views of the 

 aether this may be neglected, on account of the smallness of 

 the mass and of the specific heat of the aether ; but it is well 

 to remember that we are neglecting it. 



6. Consideration of Van der Waals's generalization. — We 

 are now in a position to consider how far Yan der Waals's 

 generalization holds, namely : — If the volume, pressure, and 

 temperature are measured for each substance in terms of the 

 critical values as units, then one and the same aw holds for 

 all substances. 





