and their relation to Molecular Composition. 497 



water and full value for all other atoms, the subjoined 

 illustrate the relationship : — 



Compound. 



LxN 

 T 





Total 



Sodium Thiosulphate, 



Na 2 S 2 3 5H 2 0. 



376x128 _ 

 283 



170 



17 



Sodium Sulphate, 



Na 2 S0 4 10H 2 O. 



51-2x170 _ 

 304 



28-6 



27 



Calcium Chloride, 



CaCl 2 GH 2 0. 



40-7x114 _ 



aoi 



15-4 



15 



Calcium Nitrate, 



CaN0 3 4H 2 0. 



335x122 _ 

 315 



130 



13 



The figures evidently show that the energy of the latent 

 heats of fusion of these compounds is involved in over- 

 coming the forces that exist between the negative electrons 

 around the nuclear charge of the atom, and that in the 

 preceding examples number rather than nature is the pre- 

 dominating factor. Among organic compounds formic acid 

 is probably of a fairly simple structure and it conforms very 

 well to the foregoing rule, and so does chloroform. 



„ 1 LxN No. of 



Compound. — ~ , 



1 r £ atoms. 



Formic Acid, H 2 C0 2 574x24 = ^ g 



281 



Chloroform, OHOL H^2xa8 ~ 5-3 5 



212 



Other compounds that are regarded as being derivatives 

 of methane — CH 4 , such as acetic acid, phenyl acetic acid, 

 give the same ratio, viz. 5. 



r* i LxN -> . 



Compound. — — — Eatio. 



45x32 



-29U~ = ° 



25x72 



Acetic Acid, CH 3 COOH 



Phenyl Acetic Acid, CH 2 C 6 H 5 COOH... 

 Butyric Acid, C 3 H 7 COOH 



^46 



28-4 x48 



273 



Perhaps these relationships refer to the numbers of 

 oscillators involved in the maintenance of the crystalline 

 structure as suggested by H. S. Allen (Proc. of Phys. Soc. 

 1916). No such simple connexion seems to occur with the 

 "closed-ring" or aromatic compounds. 



Phil. Maa. S. 6. Vol. 37. No. 221. May 1919. 2 M 



