MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOxMPOSITION. 447 
boiling water, boiling the liquid, and treating the dark green precipitate obtained in 
the same way as the orange-coloured flocks, from the decomposition of rubian. The 
dark green colour of the precipitate in this case proceeds from the decomposition of 
chlorogenine by the acid ; the product of decomposition does not however in any way 
interfere, as it is insoluble in alcohol. It may be remarked, however, that very little 
rubianine is obtained in this manner, its place being supplied, from a cause which I 
shall mention hereafter, by rubiacine. 
There still remains in the acid liquid filtered from the orange-coloured flocks, a 
substance which is an essential product of the action of acids on rubian. This liquid 
has, as I mentioned before, a light yellow colour. After neutralizing the aeid with 
carbonate of lead it becomes almost colourless, while the carbonate of lead acquires 
a pink tinge. After filtration it is found to contain neither sulphuric acid nor lead ; 
nor does it give any precipitate with neutral or basic acetate of lead, nor with alkalies, 
either before or after neutralization, unless it be boiled with an excess of the latter. 
This absence of reaction proves that no substance of a basic nature has been formed 
during the process. The liquid however contains a considerable quantity of an organic 
substance, which is obtained by carefully evaporating at the ordinary temperature 
over sulphuric acid. It is not advisable to evaporate with the assistance of heat, as 
the solution then becomes dark brown from the action of the air. After evaporation 
over sulphuric acid there is left at last a brownish-yellow, transparent syrup, having 
a sweetish taste, which I shall prove by its properties and composition to be a species 
of sugar. 
I shall now describe more in detail the properties of the substances just mentioned. 
Alizarine . — ^The alizarine obtained from the decomposition of rubian exhibits all 
the usual properties of this well-known substance. Its colour is dark yellow without 
any tinge of brown or red. The crystals possess a lustre which I have never seen 
equalled in this substance. Its analysis gave the following results : — 
0*3200 grm. of the crystals, on being heated in the water-bath, lost 0*0580 grm. of 
water=18*12 per cent. According to the formula C 14 H 5 O 44 - 3 HO, they should lose 
18*24 per cent. 
0*2575 grm. of the dry substance, burnt with chromate of lead, gave 0*6550 car- 
bonic acid and 0*0945 water. 
These numbers lead to the following composition : — 
Carbon . . 
Eqs. 
... 14 
84 
Calculated. 
69*42 
Found. 
69*37 
Hydrogen . 
... 5 
5 
4*13 
4*07 
Oxygen 
... 4 
32 
26*45 
26*56 
121 
100*00 
100*00 
0*1050 grm. of the lead compound, prepared by precipitating the alcoholic solution 
with sugar of lead, gave 0*0720 sulphate of lead, equivalent to 0*0529 oxide of lead 
3 M 2 
