368 Mr Fenton, Oxidation in Presence of Iron. 



for a considerable time, but the free acid was hitherto practically 

 unknown. By the hydrolysis of ethyl ethoxyfumarate, Nef 

 (Annalen, 1893. 230) had prepared an acid apparently identical 

 with this, but it was not obtained in a pure state. 



Oxalacetic acid melts at 176 — 180 01 and is fairly easily soluble 

 in water. Its solutions give an intense blood-red colour with 

 ferric chloride, and the aqueous solution on heating evolves carbon 

 dioxide giving pyruvic acid. 



It is a well-marked dibasic acid ; with phenylhydrazine it 

 yields a beautifully crystalline hydrazone, 



COOH*. CH 2 . CN 2 HPh . COOH, 



and with hydroxylamine the oxim 



COOH . CH 2 . C : NOH . COOH 



is produced. Hydrazine hydrate gives the hydrazine salt of the 

 hydrazone together with Rothenburg's pyrazolon carboxylic acid. 



When oxalacetic acid is oxidized with bromine a product is 

 obtained which gives a violet coloration with ferric chloride, and 

 with phenylhydrazine yields Nastvogel's osazone ; very probably 

 this product is identical with that obtained by oxidation of glyceric 

 acid in presence of iron. 



Comparison of the affinity -constants of acids. 



The hydrazone of oxalacetic acid, described above, when 

 heated with pure water, yields the hydrazone of pyruvic acid and 

 carbon dioxide, 



CH„COOH CH 3 



I " I 



C : NoHPh = C : N 2 HPh + C0 2 



I " i 



COOH COOH, 



but in presence of acids of sufficient concentration an entirely 

 different decomposition occurs, water being lost and Wislicenus' 

 pyrazolon carboxylic acid resulting 



CH 2 . COOH CH„ . CO 



I /H ' I I 



C : N . N^Su = C : N . NPh + H 2 



I ' I 



COOH COOH. 



With acids of insufficient concentration both changes occur 

 simultaneously, the amount of carbon dioxide evolved being less 



1 Wohl and Oesterlin (Ber. 1901. 1139) have since prepared oxalacetic acid 

 from diacetyl tartaric anhydride ; they shew that the acid, whether prepared by 

 this method or that of the present authors, is capable of existing in two forms which 

 melt at 176° and 146° respectively. 



