212 SCIENCE PROGRESS 



melting-point of the substance the amplitude of the vibration 

 attains such a magnitude that the rotational vibration " at 

 last becomes a continuous rotation." " As soon as the rota- 

 tional vibration is changed into a continuous rotation the 

 regular spacing of the molecules breaks down, disorder begin- 

 ning to take place, and therefore the rotation becomes inde- 

 pendent of the translation." The molecules have now two or 

 three degrees of freedom in respect of rotation. " Since the 

 molecular distances in the solid and liquid states do not differ 

 much, the rectilinear motion of the liquid molecules is also 

 vibratory, its amplitude remaining the same." The latent 

 heat of fusion is therefore identified with the bringing into 

 existence of the two or three degrees of freedom of rotation, 

 Honda calculates what this energy amounts to on the basis 

 of the quantum theory, and then proceeds to compare the 

 result with the observed latent heats of fusion. For sixteen 

 elements he finds very satisfactory agreement. In six other 

 cases there is no agreement, and this he explains on the basis 

 of the external and internal work done owing to the change in 

 volume on melting. Honda has also applied his ideas to the 

 fusion of compounds, and finds in certain cases that a similar 

 relation holds good. "It is necessary to assume that these 

 compounds have a molecular structure both in the liquid and 

 the solid, and that in the liquid state the molecules have three 

 degrees of freedom for rotation." In other compounds it is 

 necessary to assume a number from 3 to 6 for the degrees of 

 freedom in order to bring the calculated and observed latent 

 heats into agreement. It is evident that Honda's views are 

 not as applicable to compounds as they are to elements. 

 Nevertheless, the importance of the contribution as pointing 

 the way to an explanation of the mechanism underlying the 

 process of fusion is very considerable. 



Oxonium Compounds. — A further addition has been made 

 to our knowledge of addition compounds between organic 

 acids, phenols, and inorganic acids, by Knox and Richards 

 (Journ. Chem. Soc, 115, 508, 191 9), the method employed 

 being that depending upon the solubility of the organic sub- 

 stance in solutions of hydrochloric, nitric, sulphuric, and in 

 some cases formic and acetic acids. Of the mineral acids, 

 nitric acid shows the greatest, and sulphuric acid the least, 

 tendency to form compounds with organic acids and phenols. 



