Chemistry and Physics. 297 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Solubilities of Liquids. — Several years ago Alexeeff 

 called attention to the solubility of liquids in each other and 

 showed that in the case of mixtures of aniline, phenol and water, 

 it is often difficult to distinguish between the solvent and the dis- 

 solved substance. The same condition has now been observed by 

 Aignan and Dugas in the case of mixtures of acetic acid and 

 benzene, which in various proportions become homogeneous at dif- 

 ferent temperatures. Thus for example : 



Acetic acid 30 cc 40 cc 50 cc 60 cc 70 cc 



Benzene 70 cc 60 cc 50 cc 40™ 30 cc 



Temperature of J 102O 5Q o . ^ 

 homogeneity ) 



The authors show that if Y a and Y b represent the respective vol- 

 umes of two liquids A and B, which are introduced into the 

 sealed glass tube, if a and /3 be their reciprocal solubility coeffi- 

 cients, and if V 1 and V 2 be the volumes of the two layers of 

 liquid respectively, A saturated with B and B saturated with A, 

 then 



V 2 " i +a 'V b -(3V a 



They also point out that a similar relation holds if masses be 

 taken in place of volumes. It follows therefore that when the 

 temperature varies, if a tends towards the value V a /V 6 , the 

 numerator of the first member, V x should tend towards zero ; 

 while if /3 tends towards the value V a /V 6 , then V 2 should tend 

 towards zero. Hence it is necessary to notice toward which 

 extremity of the tube the surface of separation of the liquid dis- 

 appears on heating. With the mixtures named above, when the 

 per cent of acetic acid is 30, 40 or 50, the surface of separation 

 tends towards the bottom of the tube ; so that saturated solutions 

 of acetic acid in benzene occur at 75° and 50°; while with 60 

 and 70 per cent of acetic acid, the disappearance of the surface 

 of separation tends towards the top of the tube ; so that at 30° 

 and 2*5°, the solutions are saturated solutions of benzene in acetic 

 acid.— C. E. y cxxv, 498-500, October 1897. g. f. b. 



2. On the Thermodynamics of the Sicelling of Starch and the 

 Determination thereby of its Molecular Mass. — An investigation 

 upon the thermodynamics of the phenomenon of the swelling of 

 starch has been made by Rodewald. He defines the term 

 " swelling" to be the absorption of water or other liquid by a 

 solid substance which does not show either visible or microscopic 

 pores. The expression which he has deduced from thermody- 

 namical considerations, for the heat set free, in terms of the 



