88 MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 
precipitate falls, which is the lead compound of rubiagine. If no deposit is formed, 
then the addition of water causes an orange-coloured flocculent precipitate, which, 
after being separated by filtration and washed with water in order to remove the 
acetate of lead, is found to be very little soluble in boiling alcohol, but is easily 
soluble in a boiling alcoholic solution of acetate of lead with a dark yellow or orange 
colour. Acetate of copper changes the colour of the alcoholic solution fiom light 
yellow to brownish-yellow, and after some time an orange-coloured precipitate is 
formed. When rubiagine is treated with a boiling solution of perchloride of iron, 
the solution acquires a darker colour, but does not assume the deep brownish-puiple 
characteristic of solutions of rubiafine and rubiacine in that menstruum. The liquid 
being filtered boiling hot, deposits on cooling a quantity of yellow shining scales, but 
the addition of muriatic acid produces no further precipitate. These scales dissolve 
easily in boiling alcohol, and the solution on cooling and standing deposits a numbei 
of small yellow grains and nodules consisting of crystalline needles, which are appa- 
rently nothing but rubiagine itself, for they are not capable of sublimation, and their 
alcoholic solution is not precipitated by acetate of lead. The greatest part of the 
rubiagine is left imdissolved by the perchloride of iron in the shape of a yellowish- 
brown powder, which does not dissolve on treating it with an additional quantity of 
the iron salt. Boiling muriatic acid changes the colour of this powder to yellow, and 
it has then all the properties of rubiagine. Rubiagine is therefore not changed into 
rubiacic acid by the action of persalts of iron. Notwithstanding the great lesem- 
blance which rubiagine bears to the other bodies belonging to the same seiies, its 
reactions prove it to be a distinct substance. It is distinguished from rubianine by 
its insolubility in water ; from rubiadine, for which it might most easily be mistaken, 
by its being incapable of sublimation ; and from rubiafine by its not being convertible 
into rubiacic acid. Its behaviour towards acetate of lead, which is different from 
that of all the other three substances, also serves to characterize it. 
The analysis of rubiagine gave the following results : — 
0’3800grm., prepared directly from madder, gave 0*9490 carbonic acid and 0 1/60 
water. 
In 1 00 parts it contained therefore — 
Carbon 68*10 
Hydrogen 6*14 
Oxygen 26*76 
There are two formulse with which this analysis corresponds, and both of which 
explain the formation of the substance equally well, viz. C 32 H 14 Oio and C 44 Hi; O 13 . 
These formulae require respectively in 100 parts — 
C32H,4 0,o. C44H„Oi3. 
67-13 68*.57 
4*89 4*41 
27*98 27-02 
Carbon . . 
Hyd rogen . 
Oxygen 
