456 
by acetylation; of the carboxylgroups one, two, or three can be 
removed by preparing the mono-, di- and tri-amides, or mono-, di- 
and tri-esters *). 
a. The alcoholgroup made inactive. 
C,H,O, COOH 
The acetyleitric acid COOH. raden „COOH 
Anbydrous citric acid was boiled with acetylchloride ac- 
cording to Easterrenp and Ser *); the acetylcitrie anhydride 
formed is purified by washing with acetylchloride and dried 
in the exsiccator above sodium Liydroxide. Immediately before 
use, this substance was reerystallised with chloroform until 
it had the exact melting-point. A weighed quantity of this 
substance was dissolved in water of 50° C., when the anhy- 
dride changes into acetyleitrie acid, and then was neutralized 
with titrated sodium hydroxide solution. Three equivalents of 
sodium hydroxide were used pro molecule acetyl-citric an- 
hydride, as should be the case when no acetic acid is split 
off. Such a solution is relatively very stable at ordinary 
temperature and only becomes acid after several weeks (by 
breaking up into acetic acid and citric acid). 
When the alcohol-group of citric acid is made inactive, the substance 
has become comparable with other miulti-basic aliphatical acids 
without alcohol group. It therefore is interesting to compare some 
of these acids with acetyleitrie acid as to their action on milk- 
eurdling *). 
For comparison were chosen : 
COOH 
Eth 
aconitic acid COOH . CH, C = CH . COOH 
Purity controlled by melting point. 
COOH COOH 
isoallylentetracarbonic acid COOH . CH, .C .CH,COOH. 
The tetra-ethylester of this acid was prepared by conden- 
sation of malonic ester with 2 molecules of monochlor-acetic- 
1) | am indebted to Dr. J. Branxsma for his amiable advice in synthetical 
difficulties. 
2) Journ. of the Chem. Soc. 61, p. 1003—1012. 
8) In order to prevent secondary complications I have for comparison chosen 
acids which differ as little as possible in structure from the original ones Acids 
in which the carboxylgroups are nearer to one another than in the citric acid- 
molecule were excluded, because in such cases other properties so often appear. 
