436 REPORTS ON THE STATE OF SCIENCE. 



Aa will be seen, (his equation contains no term relating to the 

 solvent, and the author concludes that the curve of solubility of a given 

 substance is independent of the nature of the solvent. This prediction 

 was supported by determinations of the solubility of salts one in 

 another, salts being chosen which form neither isomorphous mixtures 

 nor combine to form double compounds. 



In support of Walker's conclusion that a substance in the liquid 



state when at a temperature below its m.p. would be more soluble than 



the solid at the same temperature, Bruner's 233 results may bo 



quoted. He found the solubility of supercooled sodium thiosul- 



phate in aqueous alcohol was much greater than the solid at the same 



temperature, 



IV. B. — Nature of the Solute — Chemical. 



The earliest observation on the relation between the nature of the 

 solute and its solubility appears to be due to Bunsen 19 , who 

 stated as a conclusion from his work on the absorption of gases 

 that the absorption coefficient is dependent upon the nature of the gas. 

 This was followed some time afterwards by Berthelot and 

 1 • Jungfleisch's 49 statement of a relationship they found between 

 the coefficient of distribution (vide Section VI.) and the chemical compo- 

 sition of the dissolved substance. These authors remark how ether 

 more readily removes from aqueous solution (1) the more highly car- 

 buretted of two homologous acids ; (2) monobasic rather than dibasic 

 acids of nearly the same percentage composition; (3) the compound 

 containing least oxygen of acids which contain the same number of 

 carbon and hydrogen atoms. 



An interesting comparison of the solubility at 0° C. of benzoic acid, 

 salicylic acid, oxybenzoic acid, and p-oxybenzoic acid was made 

 by Ost, 72 but no definite conclusions could be arrived at. 

 In the same year Bourgoin 7S traced the solubility-temperature 

 curves of benzoic and salicylic acids; below 40° C. salicylic acid was 

 found to be less soluble and above 40° C. more soluble than benzoic acid. 

 A large number of isomeric carbon compounds were examined 

 1S82. by Carnelley, 88 who endeavoured to ascertain whether any rela- 

 tionship existed between the solubility and the constitution of organic 

 compounds (vide Section IV. A). Those possessed of greatest atomic 

 symmetry were found to be most soluble. 



A conclusion similar to this was arrived at by Tilden " from 

 a study of the melting-point and solubility of various inorganic 

 salts. Further work by Tilden 101 extended this rule to isomorphous 

 hydrated salts having the same amount of water of crystallisation, in 

 which case it was found that the order of solubility and fusibility of such 

 salts was the same at all temperatures below the point of fusion or 

 dissociation of the hydrate. 



The observation of Nicol 102 on the relation between molecular 

 volume of a salt and its solubility (vide Section VII., 1883) was found 

 by him to hold whether the composition of the salt remained unchanged 

 or not, 



