Influence of Atomic Weight. 379 



Eaoult (Compt. Rend, lxxxvii. p. 167) has further shown 

 that the property which anhydrous salts possess of diminish- 

 ing the vapour-tension of their solutions and of lowering their 

 soiidifying-point appears to be inversely as their molecular 

 weights. 



Division of a Body between two Solvents. — From his experi- 

 ments on the division of a body between two solvents, Ber- 

 thelot {Ann. Chim. Plxys. [4] xxvi. p. 408) concludes, with 

 regard to the relations between the coefficient of division and 

 the chemical composition of the substance dissolved, that ether 

 removes from water with greater facility: — (1) the more 

 highly carburetted of two homologous acids ; (2) a monobasic 

 acid more easily than the corresponding dibasic acid, as acetic 

 rather than oxalic ; (3) a monobasic acid rather than a dibasic 

 acid of nearly the same composition, as acetic rather than 

 succinic. (4) Of two acids containing the same proportion of 

 carbon and hydrogen, that with the smallest number of 

 atoms is the more easily removed, as succinic, C 4 H 6 4 , 

 rather than malic, C 4 H 6 5 , or tartaric, C 4 H 6 O c . 



Molecular or Specific Volumes I = rj. §— ). — 



1 J \ specific gravity / 



Schroeder (Pogg. Ann. clx. p. 199) has proposed the hypo- 

 thesis that "All bodies combine in whole volumes." In the 

 case of gaseous bodies this can be proved, as is well known, 

 without exception by reducing to a common temperature and 

 pressure (Gray-Lussac). For liquids, Kopp {Ann. Chem. 

 Pliarm. xcvi. pp. 153, 303) has shown that the volumes of C, 

 H, 0, and other elements in organic liquids are equal in all 

 compounds if their specific gravity be determined at the 

 boiling-point. The following are his more important results : — 

 (1) Differences of molecular volume are proportional to the dif- 

 ferences between the corresponding chemical formula?. Thus the 

 difference of CH 2 in homologous series corresponds to a dif- 

 ference of 22 in the molecular volume, thus : — 



Molecular Specific 



weight. Tolunie. Difference. 



Formic acid, 46 42 — 



Acetic „ 60 64 22 



Propionic acid 74 86 22 



Butyric „ 88 108 22 



(2) Isomeric liquids belonging to the same chemical type have 



equal molecular volumes. Thus 2 3 tt >0 and p-rT 3 >0 



have the same molecular volume, viz. 63 # 4. (3) Compounds 

 containing as many times two atoms of H less, as others contain 



