PROGRESS IN PHYSICAL CHEMISTRY. 231 



A lengthy discussion on the law of corresponding boiling- 

 points has been initiated by Duhring (25), who maintains that 

 his law has been ascribed to Colot by Young. The only point 

 of importance which has arisen is due to Kahlbaum and Wirk- 

 ner, who show, as Duhring himself has admitted, that the specific 

 factor in his formula is not independent of the temperature. 



A new formula, connecting the boiling-points of homo- 

 logues, has been put forward by Walker (26). It is based on 

 the view (due to Burton) that the percentage difference in 

 the boiling-point of two members of a series is proportional 

 to the percentage difference in their molecular weights. It 

 is of the shape T = a M 6 , where T is the absolute boiling- 

 point, M the molecular weight, and a and b are constants 

 varying with the series. The formula applies to a large 

 number of series, but not to the alcohols, and the alkyl 

 bromides and iodides. Without exception, the initial 

 members of series do not agree with the formula. That the 

 boiling-points of initial members is anomalous has long been 

 known, and many other physical properties give evidence of 

 the same kind of irregularity, particularly magnetic rotation, 

 viscosity, and melting-point. It is even noticeable, accord- 

 ing to Eykman's recent work (27), in the case of refraction 

 and dispersion. 



Cohn (28) has attempted to trace stoichiometric relation- 

 ships in the case of certain boiling-points. He finds that 

 corresponding normal propyl and allyl compounds have the 

 same boiling-point, and that if two acids form a ketone, con- 

 taining normal alkyl radicles, CO, being eliminated, the 

 boiling-point of the ketone is 178° lower than the sum of the 

 boiling-points of the acids. Of the other relations he. obtains 

 the most noteworthy are, that an aldehyde boils at the same 

 temperature as the amine with the same number of carbon 

 atoms in the molecule, and that the displacement of phenyl 

 by carboxyl does not alter the boiling-point. 



Viscosity. — For the past four years Thorpe and Rodger 

 {15) have been engaged on the study of the viscosity of 

 liquids, and an account of their work was the subject of the 

 Bakerian lecture- for 1894. Observations were made on 

 over seventy liquids at temperatures between 0° and the 



