RECENT ADVANCES IN SCIENCE 627 



PHYSICAL CHEMISTRY. By Prof. W. C. McC. Lewis, M.A., D.Sc., 

 University, Liverpool. 



Stoicheiometry . — In this connection Bousfield (Trans. Chem. 

 Soc. 107, 1 781, 191 5) has continued his investigation of the 

 density and viscosity of aqueous solutions with special reference 

 to nitric acid. The apparatus employed is complex, and the 

 measurements aim at a high degree of accuracy. The results 

 obtained are not easy to interpret, but they form an essential 

 part of the experimental basis upon which a satisfactory theory 

 may eventually be reared. The abnormalities observed must 

 be attributed to the complex nature of water itself and to the 

 changes in the constitution of water brought about by change 

 in temperature and by the presence of the solute. 



It is also necessary to draw attention to the very valuable 

 contribution made by Applebey and Hughes (Trans. Chem. Soc. 

 107, 1798, 191 5) to the determination of the vapour pressures 

 of saturated solutions. The vapour pressures of aqueous 

 solutions of sodium nitrate, sodium sulphate, and thallium 

 nitrate were measured by a static method over a range of tem- 

 perature in the neighbourhood of their boiling points. The 

 two last named salts gave results in excellent agreement with 

 those obtained by Lord Berkeley by the dynamic method. 



Chemical Kinetics and Catalysis. — An ingenious method for 

 the indirect determination of the velocity of hydrolysis of 

 formamide by hydrochloric acid has been worked out by J. C. 

 Crocker (Trans. Chem. Soc. 107, 1762, 191 5). The principle 

 of the method consists in having sucrose present in the solution, 

 the sucrose undergoing inversion, its rate of change being 

 followed by means of a polarimeter. The rate of the inversion 

 depends upon the concentration of hydrogen ions present, 

 which in turn affords a measure of the amount of hydrochloric 

 acid present at any moment. The acid is bdng used up all 

 the time by the hydrolysis of the amide and the rate of inversion 

 gives a measure of the extent of the amide hydrolysis. Natur- 

 ally the hydrogen ion diminishes as time goes on and therefore 

 the rate of inversion falls off due to this cause. It is easy, how- 

 ever, to calculate the true velocity constant of the amide 

 hydrolysis and very concordant values are obtained. The 

 principle of the method is applicable to any reaction where the 

 hydrolyst (the acid) changes in concentration during the reaction 

 and can act as a simple catalyst on a third substance present 



