(522) 
is omitted the leaves of Indigofera leptostachya yield a gelatinous 
body which greatly impedes the purification of the indican. 17 kilos 
of the leaves of Polygonum tinctoria yielded 5 grams of pure indican. 
Indican crystallized from aqueous solutions consists of spear-shaped 
erystals which Prof. SCHROEDER VAN DER KOLK, as the result of a 
preliminary nomination, declares to belong to the rhombic system. 
The crystals contain 3 mols. of water of crystallisation, melt at 51° 
and losing some of the water are transformed into a gummy-like 
mass which is gradually decomposed on heating above 100°. Dried 
in vacuo over sulphuric acid indican loses its water of crystalisation, 
but when the anhydrous mass is exposed to the air, it reabsorbs 
moisture and practically regains its original weight. Dried indican 
melts at 100°—102°, is tolerably soluble in water, methyl- or ethyl- 
aleohol and acetone, but only slightly soluble in benzene, carbon- 
disulphide and ether. 
Heated on a platinum foil or in a test-tube purple-coloured fumes 
are given off which condense on the sides of the tube: this does 
not take place in a current of carbon dioxide. When an aqueous 
solution of indican is decomposed by the galvanic current, indigotin 
is formed at the anode. 
Indican has a bitter taste. It is optically active, a 2 per cent 
solution gives a polarization of — 2° when examined in a 20 c.m. 
tube at 15°. After acting on the solution with hydrochloric acid 
and oxidizing the resulting indoxyl the liquid shows a right-handed 
polarisation !). As soon as we shall have again at our disposal 
larger quantities of indican, we wil make further experiments with 
a view to determine its specific rotary power and we will also try 
to isolate the sugar formed in the hydrolysis of the indican. 
As will be seen from the subjoined analyses and the determination 
of the molecular weight, the molecular formula of the vacuum- dried 
indiean is C,, H,, NO, this confirming MAaRrcHLEwsKt’s hypothesis. 
The erystallized compound contains 3 mols. of water of crystallization ; 
it may be observed here that amygdaline also contains 3 mols. of 
water of crystallization and also polarises to the left *). 
By passing a current of air through a hot solution of indican in 
dilute hydrochloric acid, containing a little ferric chloride as oxygen 
carrier, 91 per cent of indican was converted into indigotin accor- 
ding to the equation: 
1) Compare C. J. van LOOKEREN CAMPAGNE. Landw. Versuch. XLV, 195. 
2) Indican is, therefore isomeric with Fiscuer’s amygdonitril. Ber. D. Chem. Ges. 
XXVIII, 1508. 
