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 ethoxy fumarate, 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 Nast vogel'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 2 COOH ch 3 
i ‘ i 
C : N,HPh = 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 2 . CO 
I I I 
C : N.N^p h = C:N.NPh + H 2 0 
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. 
