Mr Fenton, Oxidation in Presence of Iron. 367 



ketonic groups are generally unacted upon by hydrogen dioxide, 

 either in presence or absence of iron, at the ordinary temperature, 

 or at any rate the amount of change, if any, is altogether in- 

 significant in comparison with the 'active' acids above mentioned. 

 [But that such acids may to some extent be oxidized in this 

 manner is shewn by the recent investigations of Hopkins and 

 Cole (Proc. Roy. Soc. 1901. 21), who find that a notable quantity 

 of glyoxylic acid may result from acetic acid by oxidation 

 and that the change is accelerated by the presence of iron.] 



All the hydroxy-acids examined are oxidized almost instan- 

 taneously in this manner, generally with evolution of heat, and 

 the operations have, as a rule, to be conducted with special 

 cooling arrangements to avoid rise of temperature. 



In this manner glyoxylic acid is obtained from glycollic acid, 

 pyruvic from lactic, and mesoxalic from tartronic acid. Glyceric 

 acid yields a product which gives a violet coloration with ferric 

 salts and with phenyl-hydrazine gives Nastvogel's osazone, 



CHN 2 HPh . CN 2 HPh . COOH ; 



for these and other reasons it is shewn that the product must be 

 either hydroxy pyruvic acid, CH 2 (OH) . CO . COOH, or dihydroxy- 

 acrylic acid, CH(OH) : C(OH) . COOH. 



Malic acid yields oxalacetic acid : owing to the importance of 

 the latter acid the reaction has been fully investigated and the 

 results will be described below. 



Mucic and saccharic acids yield products which give a violet 

 coloration with ferric chloride ; these products are still under 

 examination. 



Oxalacetic Acid. 



CH 2 .COOH 



I 



CO. COOH. 



[Fenton and Jones, Trans. Ghem. Soc. 1900. 77, 1901. 91, and 

 Proc. Ghem. Soc. 1901. 24.] 



When malic acid is treated with rather less than the calculated 

 quantity of hydrogen dioxide in presence of ferrous iron, the 

 liquid turns dark red, and if the temperature be allowed to rise a 

 violent decomposition takes place with evolution of carbon 

 dioxide. But if the mixture be very carefully cooled and the 

 reagent slowly added no gas is evolved, and if strong sulphuric 

 acid is cautiously added and the mixture extracted by ether a 

 white crystalline substance is obtained which proves to be pure 

 oxalacetic acid. The esters of this acid have of course been known 



