436 OX EQUIVALENT VOLUMES. [XVI. 



crystalline state correspond to some multiple of the above 

 formulas, a question to be decided by an examination of the 

 crystallization and specific gravity of species whose equivalents 

 are admitted to be higher. 



Favre and Silbermann, from their researches upon the heat 

 evolved in fusion and solution, have been led to conclude : 

 first, that crystallized salts are polymeric of these same salts in 

 solution, that is, they are represented by formulas which are 

 multiples of those deduced from analysis ; secondly, that double 

 salts and acid salts do not exist in solution, being produced 

 only during crystallization ; and, thirdly, that water, in crystal- 

 lizing, changes from HO to nHO, n being some whole num- 

 ber.* These conclusions are seen to be in accordance with 

 those deduced from a consideration of the relations of density 

 and equivalent volume. A polymerism is evident in such 

 salts as sulphate of potash and cyanide of potassium when their 

 specific gravities are compared with those of alum and the 

 ferrocyanide. 



In the liquid state, the relation between specific gravity and 

 equivalent is not so apparent as in solid species. The con- 

 densation often varies greatly, even in allied and homologous 

 species, but still exhibits a relation of volumes. The alcohols 

 C 2 H 4 2 , C 4 H 6 2 , C 10 H 12 2 , and C 16 H 18 2 have very nearly the 

 same specific gravity, so that the condensation is inversely as 

 their vapor-equivalents. The densities of wine-alcohol, acetic 

 acid, and aldehyde in the liquid state, vary as their equivalents, 

 so that the calculated volumes are 57.5, 55.5, and 55. Formic 

 and valeric acids show a similar relation in density to their 

 respective alcohols, their calculated volumes being to these as 

 37.3 : 39, and 108 : 106.7. If to these we add butyric acid, 

 which gives a volume of 90, and the density of whose alcohol 

 has not yet been determined, the liquid volumes for the four 

 acids, C 2 H 2 4 , C 4 H 4 4 , CgHgOfc and C 10 H 10 4 , are 37.3, 55.5, 

 90, and 108. These numbers approximate to multiples of the 

 liquid volume of water HjjOa, which is 18 ; or taking this as 

 unity, are very nearly as 2, 3, 5, and 6. The interval between 



* Comptes Rendus, XXII. 823 - 1140, and XXIII. 199 - 411. 



