280 REPORTS ON THE STATE OF SCIENCE. 



Ostwalcl supposed that the two sets of values ought to be proportional 

 but that some secondary influence was at work in the case of the inver- 

 sion numbers similar to the influence of the sugar itself (vide G 2). With 

 weak acids the agreement is better. 



With the object of strengthening the ionic theory of catalysis 

 1QO- (Arrhenius), Palmaer has made a careful comparison between the 

 invei'tive power and conductivity of very dilute hydrochloric acid. 

 He eliminated, as sources of error : — 



1. Neutralisation of the acid by the ash in the sugar, by recrystal- 

 lising the sugar many times. 



2. Bi-rotation of the invert sugar, by taking his polariraeter readings 

 at 48° C, the temperature of the thermostat. 



3. Dissolution of the glass, by using a platinum vessel. 



Fair proportionality was found to exist between the rate of inversion 

 and the concentration of the hydrogen ions for strengths less than xott^Ii 

 normal HCl. His conclusions are open to criticism on the ground of his 

 use of platinum vessels. He himself thought that no catalytic oxidation 

 would occur as he worked at 48°, whereas Rayman and Sulc's results were 

 obtained at 80° C. (vide Section B 6). Yet it is a fact, as conductivity 

 measurement will show, that some oxidation of glucose by platinum does 

 occur even at 18° C 



IfiQS ^" '^' ^""^'^^ arrived at the same conclusion as Palmaer for the 



temperature 100°, with the reservation that with weakly disso- 

 ciated acids the accelerating influence of the undissociated material must 

 be taken into account. 



G 2. — hifluence of Initial Concentration of Cane Sugar, 



rieury, who worked with weight-normal solutions, showed that 

 1876. on altering the initial quantity of sugar very little alteration occurs 

 in the rate of inversion. 



nog.-, Urech, however, endeavoured to show that a concentrated 



sugar solution is more slowly inverted than a weak one. His 

 evidence is not convincing. 



1 88^ Ostwald, on the other hand, showed that in volume-normal solu- 



tion the relative rate of inversion is enormously higher in a '40 

 per cent.' cane-sugar solution than in a ' 4 per cent. ' solution. 

 |ngg This was confirmed by Spohr. The latter author saw that in 



these cases, as more sugar is present it displaces more water and 

 hence the concentration of the acid is virtually greater. He made three 

 experiments with weight-normal sugar solutions in deci-normal acid 

 and obtained practically the same velocity when the sugar concentration 

 was considerably varied. The great importance of this point does not 

 appear to have been realised by Spohr and has been generally overlooked. 

 1897 Cohen was also on the same track when he suggested that the 



deviations of the inversion velocity in concentrated solutions are 

 due to the same cause as the deviations from Boyle's law for gases, viz., 

 the actual bulk of the sugar molecules. He gave the equation : — 



K K •• 1 • 1 



•'^20% • ■'^405 



100-620 100-6,0 

 Vide Proc. Roy. Soc, 1906, 78, p. 283. 



