acid ester. This tetra-ethylester was saponified in alcoholic 
solution according to the method of Biscnorr *); addition of 
BaCl, precipitated the bariumsalt. This starchy looking salt 
could not be sucked dry ; it was purified by repeated decan- 
tation. The free acid was prepared by adding the calculated 
quantity of sulphuric acid; it was extracted with ether and 
recrystallised with anhydrous ether until it had the right 
melting-point (this never was quite exact because of the 
decomposition on melting). 
EL GOOHR 
best OE 
tricarballylic acid COOH .CH,.C.CH, .COOH 
b. one carboxylyroup made imactive. 
OH CONH, 
Symmetrical citric monoamide COOH. Ne 
To pure acetondicabonicacid-diethylester prussic acid was 
added in statu nascendi; the cyanhydrine was saponified with 
strong sulphuric-acid, after dilution of the H,SO, with ice 
the diethylester of monoamide-citrie acid was extracted with 
chloroform. Tbis was purified by pressing between unglazed 
porcelain plates, dissolving in chloroform and precipitating with 
ligroine, until it had the required melting point and was 
colourless. 
To a weighed quantity of this substance a small excess of 
normal sodium hydroxide solution was added; after 24 hours only 
the 2 estergroups were saponified as was proved by titration. 
The amide is very resistant to diluted solutions of sodium 
hydroxide at ordinary temperature*). 
Such a substituted citrate, in which one carboxylgroup has been 
made inactive, was compared with some acids with two carboxyl- 
groups and one or more hydroxylgroups. As such were chosen: 
OH 
| 
the malic acid COOH. CH. CH, . COOH 
OH OH 
Ade 
the tartaric acid COOH .CH.CH.COOH 
OH OH OH 
ad slit = 4 
the trioryglutaric acid COOH .CH.CH.CH. COOH. 
1) Lieb. Ann. 214, p. 61— 67, 
2) Scnroerter, Berl. Ber. 38, p. 3199. 
