it has 



been 



shown 



that the 



n 

 or N = 



p—p' 

 p' 





(i) 



Speyers — Weights of Carbon Compounds, etc. 213 



Art. XX. — The Molecular Weights of some Carbon Com- 

 pounds in Concentrated Solutions with Carbon Compounds 

 as Solvents ; by Clarence L. Speyers. 



In some preceding papers,* 

 equation 



n _P~p' 



N + n ~ p 



expresses the vapor pressures of mixtures of liquids miscible in 

 all proportions better than does the equation 



N ~ V ( } 



The latter gives absurd values towards the limits of concentra- 

 tion : the former gives reasonable values throughout the range 

 of experiment. The failure of (2) is hardly to be attributed to 

 experimental error, f because in that case the molecular weights 

 should show far more irregularity than they do. 



Moreover with such simple assumptions regarding molecular 

 weights as are continually being made for non-volatile solutes, 

 it was possible to plot boiling point curves for mixtures of two 

 liquids soluble in each other in all proportions and to state in a 

 general way when a mixture might have a maximum boiling 

 point4 



Last year, J. von Zawidski§ applied Margule's equation 



dip _ dip ' 

 dlx ~ dl(l—x) 9 



where x denotes the fraction of a gram-molecuie of one liquid 

 and 1—x denotes the fraction of a gram-molecule of the other 

 liquid, to a mixture of two liquids miscible in all proportions. 

 In this differential form, the equation seemed to be unsatis- 

 factory, and to integrate it constants of uncertain value are 

 introduced complicating the theoretical investigation. More- 

 over, the equation will not agree with experiment unless 

 molecular association is granted. Taken altogether, Margule's 

 equation is more complicated than equation 1, far more so, 

 and in no case does it give results more concordant with fact 

 than equation (1) does. For one mixture, that of acetone and 

 chloroform, equation 1 fails. But so also does Margule's equa- 



*Jo-arn. Phys. Chein., ii, 347, 362, 1898; Journ. Am. Chem. Soc, xxi, 

 282, 1899. 



t Bancroft. Joum. Phys. Chem., iv, 224, 1900. 



{This Journal, ix. 341, 1900. 



gZeitsch. Phys. Chem., xxxv, 129, 1900. 



Am. Jour. Sci. — Fourth Series. Yol. XTII, No. 75. — March, 1902. 

 15 



