LABILITY AND ENERGY IN RELATION TO PROTOPLASM. 399 



reaction with ferric chloride, is the more stable modification at 

 higher temperature and occupies a smaller molecular volume 

 (y. Traube, 1 856). In alcoholic solution the aldo-modification is 

 gradually produced while in chloroform the enol-modification is 

 preserved. 



0=C-H HO-C-H 



I II 

 CH . C 6 H 5 C . C 6 H S 



I I 

 COO R . COOR . 



Aldo-modification. Enol-modification. 



J. Traube also has shown the probability of the existence of 

 two isomeric forms of aceto-acetic ether, each of which very easily 

 can pass into the other.' 1 ' Labile compounds, however, often 

 undergo such changes that reversion to the original substance 

 either requires the expenditure of a considerable amount of energy, 

 as in cases of polymerisation, or has become entirely impossible, 

 since the chemical structure has been altered too much, as, e.g., 

 when amides are formed from oximes, or when ortho nitro-benzene 

 compounds change, by atomic migration, into amido-comjjounds, 

 the lateral chain exchanging a portion of its hydrogen against the 

 oxygen of the nitro-group. (2) Also the changes which amido-acetone 

 and amido-ethyl aldehyde undergo spontaneously under ordinary 

 conditions, when liberated from their compounds with acids, 

 belong to this group of phenomena.' 3 ' 



To give in all these cases a satisfactory explanation of the 

 degree of lability is not an easy matter, for want of clear con- 

 ceptions of chemical affinity and chemical energy. OstzvaldS^ 



(1) Her. Cbem. Ges. 29, 1715. The observations of Friedlcender, Gcchrhig, Knort 

 and others had already shown that this ether can react in two distinct ways. 



(2) The rule that oxygen connected with nitrogen in a compound can easily migrate 

 to carbon, but can never do so in the opposite direction, is easily explained on general 

 chemical principles. 



(3) Of further examples may be mentioned : By treatment with alkaline solutions 

 phenylazoxazol changes into the isomeric oxime of benzoyl cyanide {Ritssmiow); the 

 closely related ' furazan carboxylic ' acid into cyan-nitroso-acetic acid [Wolff and Cans; 

 Ber. 24), and a-methylisoxazol into cyan-acetone [Claist n; ibid. 25 ). Isodiazo-naphthalin 

 isolated from its sodium combination changes at once into ordinary diazonaphthalin 

 [Bamberger; ibid. 27). Phenyl hydroxylamine changes in contact with acids into-para- 

 amidophenol, and the^nitrosamine of that compound changes spontaneously after some 

 time [Bamberger; ibid. 27). 



(4) Outlines of General Chemistry, p. 208. 



