Laws of Molecular Force. 213 



of a substance with its chemical composition. Definition of 

 the Dynic Equivalent of a substance and determination of its 

 value for several radicals. 



12. Close parallelism between Dynic Equivalents and 

 Molecular Refractions. 



13. Return to the discontinuity during liquefaction of com- 

 pounds, and proof that it is due to the pairing of molecules. 



14. Brief discussion of the constitution of the alcohols as 

 liquids. 



15. Methods of finding the virial constant for inorganic 

 compounds, including a theory of the capillarity and com- 

 pressibity of solutions. 



16. Tabulation of the product of the square of the molecular 

 mass by the virial constant for inorganic compounds, and 

 determination of the Dynic Equivalents of the metals in the 

 combined state. Again a close parallelism between dynic equi- 

 valents and molecular refractions or refraction-equivalents. 



17. Meaning of this parallelism ; general speculations as to 

 the volumes of the atoms and their relation to ionic speeds. 



18. Attempt to determine the velocity of light through the 

 substance of the water-molecule. 



19. Suggested relation between the change in the volume 

 of an atom on combination and the change in its chemical 

 energy. 



1. Establishment of the characteristic Equation for Com- 

 pounds above the region of the Critical Volume, with proof 

 that there is discontinuity in the liquefaction of compounds. — 

 Amagat established {Ann. de Chim. et de Phys. ser. 5, t. xxii.) 

 that for gases 'dp/'dT is a function of volume only down to 

 volumes near the critical, but that at lower volumes it begins 

 to vary with temperature. Ramsay and Young (Phil. Mag. 

 May 1887), while verifying the independence of "dp/'dT on 

 temperature above the critical volume for such bodies as ethyl 

 oxide and the alcohols, sought to show that this independence 

 continues right into the liquid state ; but, as a matter of fact, 

 their temperature-range in the experiments below the critical 

 volume is not great enough to decide the question one -way or 

 another. We shall see that in the case of compounds Amagat's 

 conclusion is the correct one, while in the case of the elements 

 Ramsay and Young's contention appears to hold. The con- 

 viction that "dpfdT becomes slightly variable with temperature 

 below the critical volume was one reason that determined me 

 to represent the behaviour of fluids by two equations merging 

 into one another ; the one applying down to near the critical 

 volume, the other below that. 



