172 



SCIENCE PROGRESS. 





g be the number of grams of substance present in 100 gr. 

 of solvent, the value of AT/g either slowly increases or 

 slowly diminishes as g increases — the nature of the altera- 

 tion being of the same order as that discussed in connection 

 with the rise in the boiling-point. 



Influence of the chemical nature of the dissolved sub- 

 stance. — The most important result announced by Raoult 

 in his first paper was that, for solutions in the same solvent, 

 the molecular lowering of the freezing-point is the same. 

 If M' be the molecular weight of the dissolved substance, 

 M.'AT/g is a constant, say F, which depends only on the 

 nature of the solvent. This significant conclusion, pub- 

 lished it has to be remembered in 1882, must be regarded 

 as the first broad generalisation arrived at in connection 

 with the stoichiometry of solutions. It gave the clue to 

 the mode of treatment which has been applied with signal 

 success in the case of other properties, as it showed that 

 the solutions which could be most profitably investigated 

 were those containing molecular quantities of dissolved 

 material. 



Since AT/g varies slightly with the value of g, the 

 same must, of course, be true for the molecular lowering. 

 Raoult has not particularly concerned himself with tracing 

 this variation. It is illustrated in the following tables, 

 wherein the observations for water are due to Arrhenius, 

 and for acetic acid to Beckmann. 



SOLUTIONS IN WATER. 



