84 G. J. BURROWS. 



Here the value of v 8 increases regularly with concentra- 

 tion, whilst the specific contraction also increases up to 

 47*1 per cent, and then decreases. In these two cases the 

 variation of v s with A cannot be interpreted as indicating 

 an increase in the specific volume of the system with 

 increasing concentration of the solute. It follows, there- 

 fore, that a comparison of v s with A is likely to lead to 

 incorrect conclusions. Thus in the examples given above, 

 since the specific volume of the solvent is considered con- 

 stant throughout the series ( = •— ) and v s is found to 



do 



increase with A one would naturally conclude that the 

 specific volume of the system as a whole increased with 

 concentration of the solute, whereas we know that up to a 

 certain concentration in each case it decreases. 



There is no reason to doubt that the same is also true 

 for solutions of solids in water. In the case of sucrose 

 solutions at least, similar results have been obtained. Thus 

 in Table XI, the values under v s are constant within the 

 limits of experimental error, and yet by measuring the 

 actual contractions in the formation of aqueous sucrose 

 solutions, Schwers 1 has shown that the specific volume of 

 the system as a whole decreases with increasing concen- 

 tration up to 70 per cent, sucrose. These results show 

 that the application of Equations I or II in considering the 

 effect of the concentration of the solute on its solution 

 volume is apt to lead to erroneous conclusions. 



From an exhaustive study of the molecular solution 

 volumes of homologous series, Traube 2 found that certain 

 values could be assigned to the solution volumes of the 

 different atoms. The "molecular volume " is equal to the 

 sum of the atomic volumes together with the " molecular 



1 J.C.S., 1911, 99, 1478. 



2 Zeit. anorg. Chem. 1895, 8, 338 Ber., 1895, 28, 2728, 2924, Ber., 

 1896, 29, 1023; Ber., 1897, 30, 265 



