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, 1896). In alcoholic solution the aldo-modification is 
gradually produced while in chloroform the enol-modification is 
preserved. 
ho-c-h 
II 
c. c 6 h 5 
I 
COOR . 
. — -— 
Enol-modification. 
y. 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-compounds, 
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. Ostzvald (4) 
O = C — H 
I 
CH . C 6 H 5 
I 
COOR . 
Aldo-modification. 
(1) Ber. Chem. Ges. 29 , 1715. The observations of Friedlœnder, Gœ living, Knorr 
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 {Russanow); the 
closely related ‘ furazan carboxylic’ acid into cyan-nitroso-acetic acid {Wo/ff and Gans; 
Ber. 24), and a-methylisoxazol into cyan-acetone (C/aisen; 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'jnti'osamine of that compound changes spontaneously after some 
time ( Bamberger; ibid. 27 ). 
(4) Outlines of General Chemistry, p. 208. 
