494- Dr. Harry C. Jones on the 



In the Raoult formula m= -r , m= molecular weight of the 



substance dissolved, and A = the specific lowering = — , where 



p is the percentage concentration of the solution ; K = a 



constant ; n = ~; n— number of molecules of the dissolved 

 m 



substance to 100 grs. of the solvent. 



m: 



—/- mA=Km?2 ; 

 A 



From (1) and (2), 



A = Kn. 



(2) 



J\i 2T 2 



100 X 



L = heat of fusion of 1 gr., \=LM, this becomes 



100L 



Vau't Hoff has calculated the constant for water to be 

 1*89. In the following table the values for this constant, as 

 found experimentally from urea, and ethyl and propyl 

 alcohols, are given. The mean of the results, after the 

 molecular lowering has become practically constant, is 

 taken. 



Urea. 



Ethyl Alcohol. 



Propyl Alcohol. 



Concentra- 

 tion, 

 normal. 



Gt. mol. 



Low. 



1-8841 

 1-8882 

 1-8961 

 1-8906 

 1-8753 

 1-9025 

 1-8810 



Concentra- 

 tion , 

 normal. 



G-r. mol. 

 Low. 



Concentra- 

 tion, 

 normal. 



Grr. mol. 

 Low. 



0-1165 

 0-1351 

 0-1530 

 01745 

 0-1949 

 0-5824 

 1-0742 



0-1307 

 0-1514 

 0-1710 

 0-1897 



1-9036 

 1-8554 

 1-8760 

 1-8693 



0-1233 

 0-1583 

 0-1914 



1-8840 

 1-8749 

 1-8736 



Average = 1-8882 



Average = T8761 



Average = 1*8775 



The average value from each compound is slightly lower 

 than 1*89, calculated by van't HofF, using 79 as the latent 

 heat of water. The true latent heat is probably nearly 80, 



