245 



tlu fact merely as a direct consequence of the general doctrine of 

 symmetry. It simply states that no en.mtionmrphism of stereome- 

 triral arrangement can ever occur, when the configuration of atoms 

 as a whole shows any symmetry-element of the second order 1 ). 

 The same is true with trioxyglutaric acid: 



COOH 



*CHOH 



CHOH 



*CHOH 



COOH 



although a little modification of what was said above will be neces- 

 sary here because the middle one of the three carbon-atoms is in a 

 somewhat peculiar position relative to both the others. For although 

 the carbon-atom in the midst of the molecule is not asymmetric, 

 it has however an influence on the number of possible isomerides, as 

 a second inactive and non-resolvable isomeride may occur here, which 

 also is inactive "by internal compensation", but which differs from 

 the first by the interchange in space of the substitutes H and OH: 

 COOH COOH 



CHOH 

 HCOH 

 CHOH 



and 



CHOH 



I 

 HOCH 



HOH 



COOH COOH 



Of course, we shall therefore have, as in the cases of the meso-tar- 

 taric acid and tartar ic acids mentioned above, not only two active 

 and one inactive form besides the racemic compound, but two active 

 and two inactive isomerides. A carbon-atom as found here in the 

 midst of the molecule of trioxyglutaric acid, is called a pseudo-asym- 

 metric carbon-atom. 



1) A case similar to that of meso-tartaric acid, etc., has also been studied by 

 Werner in the case of tetra-ethylenediamine-p.-amino-nitro-dicobalti-bromide: 



(Etn) 



(Eine) t 



Br A 



Indeed, besides the d-, 1-, and roc. compound, an inactive, non-resolvable 

 isomeride could be obtained; cf. : Ber. d. d. Chem. Ges. 46. 3674. (1913). 



