MR. SCHUNCK ON RUBIAN AND ITS PRODUCTS OF DECOMPOSITION. 107 
separated, and the substance contained in the liquid was precipitated with muriatic 
acid. The precipitate was yellow. Its analysis proved it to be almost pure verantine. 
0‘3685 grm. gave 0’8760 carbonic acid and 0'1400 water. 
In 100 parts it contained therefore — 
Verantine. 
Carbon .... 64*83 65*11 
Hydrogen . . . 4*22 3*87 
Oxygen .... 30*95 31*02 
It appears therefore that the substance called purpurine cannot even be called a 
compound of alizarine and verantine, for it consists sometimes of one alone, some- 
times of the other, sometimes of a variable mixture of both. 
I now treated some purpurine, made in the same manner as the last, with boiling 
dilute nitric acid. Nitrous acid was disengaged, the bulk of the substance diminished 
very much, and its colour became lighter. After the action was completed, I allowed 
the liquid to cool, added water, collected the yellow flocks on a filter, and washed 
them with water to remove all the acid. After drying their colour was brownish- 
yellow, similar to that of pure verantine. 
0*3820 grm. gave 0*9070 carbonic acid and 0*1240 water. 
In 100 parts — 
Carbon 64*72 
Hydrogen 3*60 
Oxygen 31*68 
Its composition therefore, with the exception of a slight deficiency in the amount 
of hydrogen, was that of verantine. 
The acid liquid filtered from the substance was evaporated almost to dryness, when 
it yielded a quantity of yellow crystals. These were washed with cold water, and 
then redissolved in a little boiling water. The boiling solution was decolorized with 
animal charcoal, and after being filtered boiling hot deposited on cooling a quantity 
of colourless crystals, having the appearance, and as their analysis showed, the com- 
position of Laurent’s naphthalic acid. 
0*5230 grm. gave 1*1020 carbonic acid and 0*1770 water. 
In 100 parts — 
Napthalic acid. 
Carbon .... 57‘46 57*83 
Hydrogen . . . 3*76 3*61 
Oxygen .... 38*78 38*56 
Wolff and Strecker mention, that purpurine yields this acid when subjected to 
the action of nitric acid, but the verantine which is found in an undecomposed state, 
after the action of the nitric acid has ceased, seems to have eluded their observation. 
From these experiments I infer that purpurine, madder-purple, and the various 
similar bodies derived from madder, owe their property as colouring matters to an 
admixture of alizarine, and that they simply consist of the latter substance in a state 
of impurity. 
