ON THE HYDROLYSIS OF SUGARS. 285 



a larger freezing-point depression than the sum of their separate depres- 

 sions. The mechanism by which the osmotic pressure of the sugar is 

 iQoq increased by a salt is not stated. Arrhenius also discussed 



Speransky's results on the same basis. 

 That the condition of sugar in solution is in some way altered by the 

 presence of electrolytes can be seen readily from the results obtained by 

 ISQO Borntrager and also Farnsteiner, who both state that the optical 



rotation of sugar is considerably changed by the mere presence of 

 a neutral salt in solution, 

 1 oArj Euler, who has discussed the action of neutral salts with 



reference to his ionic theory of catalysis, explained that the 

 neutral salt functioned by increasing the osmotic pressure of the ions of 

 sugar and also the reactive capacity of the water. The former effect may 

 result from an increase in the ionising power of the water and the latter 

 ^ qQ , from an association of the salt ions with the ions of the water. 



He has latterly added another alternative — namely, that a neutral 

 chloride increases the amount of dissociated saccharose chloride. 

 1 (VQ i Armsti'ong and Caldwell, on the other hand, revert to the old 



explanation that neutral salts, like all other accelerating ' foreign ' 

 materials, remove water from the system and concentrate the solution. It 

 was shown by them that KCl accelerates the action of HCl in hydrolysing 

 1 qQ/. lactose. The theory has been developed by the author in a recent 



paper, with the object of obtaining a numerical value for the degree 

 of hydration of various salts. The method adopted was to measure the 

 amount of additional water which must be put to a weight-normal 

 solution containing a neutral salt in order to reduce the reaction velocity 

 to the value it would have if no salt were present. The values deter- 

 mined in thi.s way were as follows: JSrH4C1.10H2O; KCl.lOH^O; 

 NaCl . I3H2O ; BaCl^ . I9H2O ; Qa.Q\, . 2211,0. 



Should these rational numbers be substantiated by other methods, the 

 theory must be held to be established. 



K. — Influence of High Pressures on the Inversion Velocity. 



Wilhelmy came to the conclusion that the invei'sion velocity is 

 iQ-Q not affected by external pressure on the solution. 



Rontgen, however, working with much higher pressures, up to 

 1 oq.-) 500 atmospheres, found that the rate of inversion by HCl is dis- 

 tinctly less under a high pressure. This seemed all the more re- 

 markable as the rate of diffusion of salts is increased by pressure. Rontgen 

 therefore concluded that the acid must be less ionised under a high 

 pressure. This conclusion is directly opposite to the result already 

 1885. arrived at by Fink ' by conductivity methods, whilst Tamman * 

 1894. ^^^o from his measurements, formed the opinion that, if anything, 

 the degree of ionisation is slightly increased by 500 atmospheres' 

 18J4. pressure. Fanjung ^ arrived simultaneously at the same result — 

 namely, that the ionisation is slightly increased, whilst the actual con- 

 ductivity is considerably augmented, by high pressure. 

 189r Rothmund repeated Rontgen's observations. The decrease in 



inversion velocity is 1 per cent, per 100 atmospheres with various 

 strengths of nitric and hydrochloric acid as catalysers. Seeing that the 



' Wied. Ann., 26, p. 481. » Zeits. Physik. Chem., 14, p. 444. ' Hid., p. 673. 



