384 Scientific Intelligence. 



the corresponding salts of the less fusible and less soluble acids. 

 In order to test the first law, 1778 cases of isomeric compounds 

 were examined as to fusibility and solubility; and of these 1755 

 were found to agree with the rule. With regard to the second 

 law, 138 out of 143 cases were found to obey it. Of the 28 

 exceptions to both laws, 16 there is reason to believe are only 

 apparent ; leaving only 12 at the most, not at present explicable. 

 On investigating the influence of the nature of the solvent, the 

 authors find : ] st, that for any series of isomeric compounds the 

 order of solubility is the same whatever be the nature of the 

 solvent. And 2d, that the ratio of the solubilities of the two 

 isomerides in any given solvent is very nearly constant and is 

 therefore independent of the nature of the solvent. The former 

 rule was found to hold in every one of 666 cases examined ; and 

 the latter in the case of the two nitranilines with the 13 solvents 

 as above described. The authors are disposed to regard the rela- 

 tion of fusibility to solubility as but a part of a more general 

 law, i. e., that the properties of the corresponding derivatives of 

 two or more isomeric compounds are related to one another in 

 the same way as those of the primitive isomers themselves. This 

 relation however need not be restricted to isomeric bodies; and 

 the paper shows its existence in the allotropic forms of phos- 

 phorus, selenium and sulphur, in paraffin, and in mixtures of 

 potassium and sodium nitrates. — J. Chem. Soc, liii, 782, Sept., 



1888. G. F. B. 



2. Raoulfs method for determining Molecular Weights. — The 

 method of Raottlt for determining molecular weights consists in 

 measuring the amount by which the solidifying point of a solvent 

 is lowered by a known weight of a dissolved substance; the 

 apparatus required being only a vessel to contain the solvent and 

 a thermometer reading to tenths. V. Meyer, having used it suc- 

 cessfully, somewhat modified, to prove the identity in molecular 

 weight of two isomers he was investigating, his associate Auwees 

 was led to a study of the conditions most essential to its success- 

 ful employment in the laboratory. The formula used is M=T-=- 

 A, in which M is the molecular weight, T the molecular depres- 

 sion and A the depression caused by one gram of substance in 

 100 grams of solution. The value of T is first to be determined, 

 which is accomplished by taking members of the series of com- 

 pounds under consideration (for which this value is constant) of 

 known molecular weight. The selection of a solvent is a matter 

 of prime importance, since it is necessary that no chemical action 

 should take place between it and the substance to be tested. 

 Water is objectionable not only because of its tendency to form 

 hydrates, but also because of its limited solvent power for most 

 organic bodies, and because a considerable amount of material is 

 required. Benzene is better, but its use is also limited. The 

 best solvent is glacial acetic acid, which can be used with a great 

 range of substances. The errors are small and it is quite suffi- 

 cient to secure a depression of about 0-3°. It may be used at 



