630 SCIENCE PROGRESS 



per litre of solution, and secondly as gram molecules per 1,000 

 grams of water. Solutions made by dissolving a gram molecule 

 of solute, or some fraction of the same, in 1,000 grams of water 

 are called weight-normal, to distinguish them from volume-normal 

 solutions, prepared by dissolving the given weight of solute in 

 water and then diluting to i litre. The third column gives the 

 osmotic pressures recorded by Messrs. Morse and Frazer for 

 the various solutions, while the fourth and fifth columns contain 

 the calculated values (i. and n.) of the osmotic pressure. The 

 values under i. are those calculated on the basis of the simple 

 van't HofT proposition, the values under n. are calculated on 

 the basis of the modified proposition enunciated by Morse 

 and Frazer. 



There is no doubt which set of calculated values is the 

 more in harmony with the observed osmotic pressures, and the 

 agreement between the figures in the third and last columns 

 leaves little to be desired. At the same time it must be said 

 that the standard osmotic volume should almost certainly be, 

 not the volume occupied by 1,000 grams of water in the pure state, 

 but the volume occupied by 1,000 grams of water in the solution. 



It would be interesting to know whether the osmotic 

 pressures of still more concentrated solutions, such as those 

 examined by Lord Berkeley and Mr. Hartley, could be calculated 

 on the same principle, but the data necessary for the calculation 

 are not available at present. 



The general result, then, of Messrs. Morse and Frazer's work 

 is to show that when weight-normal solutions are considered, 

 the osmotic pressure is proportional (1) to the concentration, 

 and (2) to the absolute temperature — in other words, the gas 

 laws are applicable to solutions of cane sugar. This result is 

 all the more interesting in view of the recent criticism of 

 Prof. Kahlenberg, who, on the strength of some experiments 



