400 
air a colouring matter, showing properties very much akin to those 
of urobilin !). Whether these two colouring matters are really identi- 
cal or not, we are at present unable to say; the optical properties of 
urobilin are not sufficiently characteristic for the purpose of identifi- 
cation. We must therefore also defer any assumption concerning the 
nature of the first reduction product of methyl-n-propyl-maleic imide. 
Presuming that Küster will follow up his former researches, 
we will not of course tresspass upon his field of researches, but we 
shall endeavour to find out new means of identifying the reduction 
product of methyl-n-propyl-maleie acid and study the behaviour 
towards redueing agents of other homologues of maleie imide. 
The chief reaction on which all the above experiments are 
based, the production of homologs of maleie acid by the elegant 
synthesis, discovered by Michael and Tissot, is eleared up in 
all its details. The first stage leads to the formation of hydroxyeya- 
nides which on being saponified lead to homologs of hydroxysuc- 
einie acid. The latter containing one or two, as the case may be, 
of asymmetrical carbon atoms must be liable to splitting up into 
optical isomers. These views are completely in agreement with 
facts, as we were able to ascertain. The combination produet of 
acetoacetie ether with hydrocyanie acid yields after being saponi- 
fied a methyl-malie acid: 
CH,.CO.CH,.C0O0G,H, — CH,.C(OH)(COOH).CH,.COOH 
which, containing only one asymmetrical carbon atom, must exist 
in two optical isomerie modifications. We sueceeded in isolating one 
of them, the dextro-rotatory antimer, in the pure erystalline state, 
whereas the other, laevo rotatory, we could not up to the present 
obtain in erystals. The splitting up of the racemic acid takes place 
easily by fractional erystallisation of its strychnine salt. The com- 
bination of the dextro-antimer being less soluble crystallises first in 
the form of fine white needles, which are laevorotatory. By the 
action of sodium hydrate this salt is decomposed in the usual way, 
and the recovered acid erystallised from acetie ether. Its melting 
point is 108°—109° and [a] — + 22.830 (e= 1.5). 
1) The fumes of the distilled artificial colour produce upon a piece of resi- 
nous pine-wood a red colouring. 
