236 SCIENCE PROGRESS 



and indications are not wanting 1 that the increase in the velocity 

 of change which is produced by adding water to the alcoholic 

 solvent is accompanied by, and is probably due to, an increase 

 in the proportion of this hydrate. 



The action of alkaline catalysts requires separate considera- 

 tion. The hydroxylic isomeride of nitrocamphor is a fairly 

 strong acid, and if the alkali were efficient only in the free 

 state its catalytic action would be immediately destroyed by 

 neutralisation. In discussing the way in which an alkaline 

 catalyst acts it is therefore desirable to work out a scheme in 

 which the active material is the sodium or ammonium salt of 

 ^S£7/«fo-nitrocamphor rather than sodium ethoxide or free caustic 

 soda. 



In the case of compounds such as benzamide and cyanuric 

 acid which form two series of salts, the acceleration of isomeric 

 change by alkalis might be attributed to the increase of " ionisa- 

 tion " which results from the neutralisation of a weak acid, the 

 idea being that the separation of the kathion in an ionic form 

 would leave the anion free to undergo an almost instantaneous 

 rearrangement of linkages, e.g. 



//O /O— 



C 6 H S . C(/ % C 6 H 5 . C/ 



\NH— vnh 



This explanation is difficult to apply to the case of nitro- 

 camphor in view of the fact that there is no evidence whatever 

 that normal nitrocamphor is capable either of being " ionised " 

 or of giving rise to a series of "ionised" salts. There is, 

 however, no difficulty in devising a satisfactory scheme based 

 upon the formation of an additive compound of one molecule 

 of nitrocamphor with one molecule of its sodium salt ; such 

 a compound could dissociate in two ways so as to liberate 

 the nitrocamphor either in the normal or in the pseudo modifi- 

 cation, and the conditions of its formation and dissociation 

 would appear to be entirely favourable to a very rapid inter- 

 action. It is hardly necessary to discuss at this point the 

 exact structure of the intermediate additive compound, but one 

 method of formulation is given below for purposes of illus- 



1 See Trans. Chem. Soc. 1904, 85, p. 1569. 



