PROGRESS IN PHYSICAL CHEMISTRY. 297 



fore, no direct indication of the molecular state of the iodine. 

 They also made observations of the absorption spectra of 

 solutions in 34 solvents, and in order to explain the results 

 assume with Anschutz and Behrend that molecular 

 complexes (I 2 ) n are formed, the individual molecules of 

 which exert an independent effect on the boiling-point and 

 freezing-point, but behave as a complex as regards the colour 

 of the solution. 



In the case of electrolytic solutions, sufficient work has 

 now been done to prove that although in aqueous solutions 

 the electrolytic dissociation as deduced from the boiling- 

 point agrees with that deduced from the conductivity, this is 

 not so in alcoholic solutions. Schlamp's work (103) on 

 solutions in water and propyl alcohol, and the work of 

 Woelfer (104) together with that mentioned on p. 300 make 

 this point clear. Of course it has to be noticed that the 

 conductivity is generally measured at the ordinary tempera- 

 ture, and the dissociation may be less at the boiling-point. 

 Ostwald (105) thinks, however, that some cause is opera- 

 tive which tends to make the result obtained from the 

 boiling-point too small ; whether or not it is molecular 

 aggregation of undissociated molecules is at present 

 unknown. It is noteworthy that Woelfer finds contrary to 

 Raoult's observations that in alcoholic solution the 

 molecular weights of certain salts are not normal, but too 

 small, and become smaller with the dilution as the dissocia- 

 tion hypothesis demands. 



Freezing-point. — The validity of the methods in use for 

 determining the freezing-point has been the subject of a 

 somewhat heated controversy (106). 



H. C. Jones and Loomis each described a method in 

 which the thermometer was read to the i/io,oooth of a 

 degree, but their results in general differed considerably. 

 F. Kohlrausch suggested that the discrepancies might be 

 due to errors in Jones' method, particularly in connection 

 with his thermometer, the bulb of which contained over 200 

 gr. of mercury. To this Jones replied that his results were 

 in harmony with those deduced from observations on 

 conductivity, and suggested that the substances used by 



