438 
Pure arabinose, prepared from arabinose was oxydised at 
35° C for 24 hours with 24 parts of nitric acid (spec. grav. 
1,2). The superfluous HNO, was removed in the waterbath 
and the residue dissolved in 25 parts of water. This liquid 
was saturated at its boiling temperature with caleiumecarbonate 
and filtrated while hot. The calciumsalt separated on cooling. 
The potassiumsalt was formed by adding the calculated quantity 
of potassiumcarbonate, decoloured with animal charcoal and 
purified by reerystallisation. As the calciumsalt is soluble only 
to a small extent, the acid could only be used in diluted 
dilution’). 
c. The alcoholyroup and one carboaxylgroup made inactive. 
GHG 
ees 
Den — 0 
The methylencitric acid COOH. CH, eae “COOH: 
Methyleneitrie acid is formed by treating citric acid with 
formaldehyde and separating from the unchanged citric acid. 
I was presented with this substance in a very pure condition 
(as neutral sodiumsalt) freshly prepared by the Pharmaceutical 
Laboratory of the Elberfelder Farbenfabriken (Bayer)’). 
This compound was compared with some other dibasie acids 
without aleoholgroup : 
succinic acid COOH.CH,.CH,COOH. 
glutarie acid COOH.CH,.CH,.CH,COOH 
pimilinie acid COOH (CH,),-COOH. 
suberic acid COOH.(CH,),.COOH. 
d. two or three carboxylyroups made inactive. 
OH > COOL 
Symmetric citric acid dimethylester tboon cucu doon 
100 gr. of citric acid were dissolved in 500 gr. methyl- 
alcohol and boiled for one hour after addition of 4 er. H,SO,; 
this mixture was diluted with limewater, neutralized with 
CaCO, and filtered. The filtrate was concentrated in vacuo. 
After addition of HCl. the ester crystallized and was reery- 
stallized from water. Melting-point (not very sharp) 125-127° C.’). 
iy KrLrant, Berl. Bers 23, p. 3007. 
2) 1 am sincerely indebted to the Elberfelder Farbenfabriken for this kindness. 
*) SCHROETER Berl. Ber. 35, p. 2056. 
