On the Diffusion of Substances in Solution, 



133 



Table II. — Supplementary Freezing-point Determinations. 



Substance. 



Parts to 

 100 of 

 Water. 



F.-p. 



Substance. 



Parts to 

 100 of 

 Water. 



F.-p. 



Tartaric acid 



Alloxan 



2-152 

 1-425 

 1-453 

 4-670 

 1-603 

 0-667 

 0133 

 0640 

 7940 



-•2966 

 -•2000 

 -•3023 

 -•2463 



-•2228 

 -•0697 

 -•0180 

 -•2669 

 -0609 





27-484 



47943 



2-557 



12-310 



15-804 



10-184 



4-983 



2-473 



- -6208 

 -1-1082 



- -0440 



- -1221 



- T110 



- -0844 



- -0542 



- 0342 





Glycerine 



Maltose 



Tannin 



Pyrogallol 





Gallic acid 









Raffinose 





Amylodextrin . . . 





The u molecular" depression, which, on the theory of 

 osmotic pressure, will be proportional to mv 2 , must, when we 

 take the molecular weights calculated from it (W), be an 

 absolute constant, whereas the values for this same quantity 

 (mV 2 ), when deduced from the diffusion-experiments, and 

 when these same molecular weights are used, are far from 

 being constant; moreover, while the "theoretical" mole- 

 cular weights give the values of mv l in the diffusion expe- 

 riments with dextrin, amylodextrin, and tannin as being- 

 similar to those with the other substances investigated, they 

 will, when used for calculating the molecular depression, give 

 values from \ to ^th only of those obtained with the other 

 substances investigated. These values are given in the last 

 column of the table : molec. dep. = (mean dep. x m) -*■ (mean 

 strength x 17*96) . 



The fact that the results with dextrin, amylodextrin, and 

 tannin are of doubtful accuracy must, it is true, weaken the 

 strength of any conclusions based on them. But, on the 

 other hand, the fact that they do not give exceptional values 

 for mv 2 renders it probable that they are not \ery inaccurate ; 

 and, moreover, the exceptional values which they give for 

 mV are not out of harmony with the results with the other 

 substances ; for the sugars, where the molecular weights are 

 large, give values which are considerably larger than those 

 given by the other substances examined. There seems indeed 

 to be a general tendency for m'v 2 to increase with the mole- 

 cular weight of the substance diffusing : thus, with the first 

 seven substances entered in the table we have molecular 



