286 REPORTS ON THE STATE OF SCIENCE. 



' ionisation ' and ' ionic mobility ' are both increased by high pressure and 

 in fact the catalysis of methyl acetate is also accelerated, Rothmund con- 

 cluded that the effiect of high pressure is to decrease the amount of 

 ' active part ' of the cane sugar. 

 1 cq« Stern has also confirmed Rontgen's observations, showing that 



the effect is independent of the temperature and concentra- 

 tions. In the case of weak acids, such as phosphoric and acetic, a high 

 pressure increases the reaction velocity. 

 -loqn Bogojawlensky and Tamman expressed the effect of pressure 



on inversion velocity by a differential equation and showed that 

 in the case of methyl acetate catalysis, as noted by Rothmund, a high 

 pressure is favourable. The effect of pressure on weak agents is much 

 more pronounced than on strong ones. These authors estimate that 

 under some 50,000 atmospheres' pressure all acids and bases would be of 

 equal strength. 

 1 oqo The unfavourable effect of pressure has also been noticed by 



Rayman and Sulc in the so-called catalytic inversion by platinum 



black. 

 , QQc. Recently the author has suggested that the rate of attack of the 



acid on the cane sugar is diminished by the hydration of the 

 sugar molecules. A high pressure should increase the degree of protective 

 hydration and hence diminish the inversion velocity. 



L. — Measurement of Hydrolytic Dissociation, 



The salt of a weak acid with a strong base or of a strong acid with a 

 weak base is partially decomposed in solution, giving free acid and base. 

 In order to estimate the amount of this hydrolytic decomposition it is 

 desirable to use a method which does not involve disturbing the equilibrium 

 during the measurement. For the former case the catalysis of an ester 

 has been applied by Schields,' whilst for the latter the inversion of cane 

 sugar is a convenient method. 

 ^ QOQ The first experiments of this kind were made by Walker,'^ who 



measured the rate of catalysis of methyl acetate by the hydrochlo- 

 rides of very weak bases, such as thiazol and urea. The first measurements 

 ,000 by means of cane sugar were made by Bruner, who estimated the 



amount of hydrolytic decomposition of a large number of salts at 

 40° and in varying concentrations. In the case of ferric chloride the hydro- 

 lysis is especially large, amounting to 14'7 per cent, in a ^ molecular solu- 

 tion. Bruner's work was overlooked until it was republished in 1900. 

 ,r.QK The same method was applied by Walker and Aston to the 



hydrochlorides of a number of organic bases varying from pyridine 

 (2 per cent, hydrolysis) to thio-urea (97 per cent, hydrolysis) and to 

 several inorganic nitrates, such as aluminium nitrate, which is hydrolysed 

 to the extent of 0'7 per cent, in half-normal solution. The method, as 

 these authors observe, is subject to an unknown error, due to the influence 

 of the undissociated salt on the rate of inversion {vide Section J). 

 1 RQfi Cohnheim made use of Walker and Aston's method to measure 



the basicity of various albumins. His results have been criticised 

 1898 ^7 Burgarsky and Liebermann, on the ground that the increase in 



viscosity caused by the presence of an albumin would explain the 



' Zeits. Phys. Chem., 1893, 12, p. 167. » lUd., 1889, 4, p. 319. 



