602 SCIENTIFIC RECORD FOR 1883. 



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the salt in lOO"-*'* of water, the monad metal be replaced by an equivalent 

 quantity of a dyad or polyad metal, the depression of the freezing point 

 is diminished by a quantity sensibly constant and equal to 10-5; and, 

 2d, with regard to acids, that if in the solution of a salt of a strong 

 monobasic acid, containing one equivalent of the acid in lOO"**'' of 

 water, the monobasic acid be replaced by an equivalent quantity of a 

 strong dibasic acid a diminution of the depression of the freezing point 

 is observed which is nearly constant and approaches 14. From the 

 partial depression values given in the paper, the molecular depression 

 produced by any salt may be calculated from its molecular weight. 

 {Ann. Chim. Phijs., VI, IV, 401; Am. J. ScL, May, 1885, III, xxix,399.) 



Bouty has suggested the hypothesis that the molecular latent heats 

 of all bodies measured at their normal temperatures of ebullition are 

 proportional to the squares of these temperatures. This assumes (1) 

 that the normal density of saturated vapors corresponds to half their 

 molecular weights ; and (2) that Dalton's law is rigorously true. To 

 test the question he gives a table of values obtained from seventeen or- 

 ganic bodies, chiefly alcohols and ethers, in which the quotient of the 

 molecular latent heat by the square of the absolute ebullition tempera- 

 ture is nearly constant. For water the value is 0-0694 ; for the alcohols, 

 0-0730; for aldehyde, 0-0695 ; for the haloid ethyl ethers, 0-0691 ; and 

 for compound ethers, 0-0735. {J. Phys., January, 1885, II, iv, 26.) 



On theoretical grounds J. Thomson had reached the conclusion that 

 the maximum elastic force of a vapor in contact with its liquid is greater 

 than the maximum elastic force of a vapor in contact with the corre- 

 sponding solid, contrary to the opinion of Eegnault, who held them to 

 be the same. Kamsay and Young have now verified experimentally 

 this conclusion of Thomson's. Their experiments were made partly in 

 barometer tubes, partly in an apparatus specially constructed for the 

 purpose. They plotted the curves representing the variation of the 

 elastic force with the temperature for camphor, benzene, glacial acetic 

 acid, and water, and noticed that the curves where these bodies were 

 in the solid state did not coincide with those where they were liquids, 

 the deviation being in the direction predicted by Thomson. The au- 

 thors regard the result as general, and applicable in all cases. {Proc. 

 Boy. Soc, XXXVI, 499 ; J. Phys., February, 1885, II, IV, 91.) 



Miiller-Erzbach has suggested a new method for determining the elastic 

 force of the vapor of water in hydrated salts, which consists in determin- 

 ing simultaneously the loss of weight which two identical tubes suffer, 

 one of which contains water the other the hydrated salt, in an atmos- 

 phere dried by means of sulphuric acid. The ratio of loss of weight 

 the author regards as rigorously equal to the ratio of the elastic forces 

 of the vapor of water in the two tubes. In this way he finds that the 

 evaporation from hydrated salts in completely dry air gives constant 

 dissociation tensions. From the variations of these tensions, the exist- 

 ence of three hydrates of sodium phosphate is inferred, corresponding, 



