426 Royal Society. 



states, surpasses all others in facility and certainty of execution, is 

 fully detailed. 



Rubian, when prepared according to this method, is a hard, dry, 

 brittle, shining, perfectly unorystalline substance, similar to gum or 

 dried varnish. It is not in the least deliquescent, as xanthine is 

 described to be. In thin layers it is perfectly transparent, and of a 

 beautiful dark yellow colour ; in large masses it appears dark brown. 

 It is very soluble in water and in alcohol, more so in the former 

 than in the latter; but insoluble in aether, which precipitates it in 

 brown drops from its alcoholic solution. Its solutions have an in- 

 tensely bitter taste. When it is pure, its solution in water gives no 

 precipitates with the mineral or organic acids, nor with salts of the 

 alkalies or alkaline earths. Basic acetate of lead, however, gives a 

 copious light red precipitate in a solution of pure rubian, the solu- 

 tion becoming (lolourless ; but this is the only definite compound of 

 rubian with which the author is acquainted. He states that rubian 

 cannot be considered as a colouring matter in the ordinary sense of 

 the word. It is decomposed by acids, alkalies, chlorine, heat and 

 ferments. The formula for rubian appears to be C*'' H^^ 0'°. 



The action of sulphuric and of muriatic acid on rubian is stated 

 to be precisely the same. The products of the decomposition by 

 those acids are, — 1 st, Alizarine ; 2nd, the substance which the author 

 formerly termed Beta-resin, but which he now calls Verantine; 3rd, 

 the substance which the author in former papers has called Alpha- 

 resin, but to wiiich he now prefers giving the name of Rubiretine ; 

 ^th, a body which has not hitherto been observed, and which he 

 denominates Rubianine; and 5th, a sugar obtained from the acid 

 liquid after the complete decomposition of the rubian. 



1. The alizarine obtained from the decomposition of rubian ex- 

 Jiibits 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 the author has never seen equalled in 

 this substance. The analysis gave the formula C* H* O^ Thus by 

 simply losing 14 equivs. of water, I equiv. of rubian is converted 

 into 4 equivs. of alizarine. 



2. Verantine, in most of its properties, coincides with the substance 

 to which the author formerly gave the name of Beta resin of madder. 

 When prepared according to the method described in the paper, it 

 is obtained in the form of a reddish-brown powder. When heated 

 on platinum foil, it melts, and then burns away without leaving any 

 residue. It dissolves in concentrated sulphuric acid, with a brown 

 colour, and is reprecipitated by water in brown flocks. On heating 

 the solution in concentrated sulphuric acid, it becomes black, sul- 

 phurous acid is disengaged, and the substance is decomposed. Con- 

 centrated nitric acid dissolves it on boiling, with a disengagement of 

 nitrous acid, forming a yellow liquid, from which nothing separates 

 on cooling. It is almost insoluble in boiling water, but readily 

 soluble in boiling alcohol, and is again deposited, on the alcohol 

 cooling, as a brown powder, which is its most characteristic property. 



From an experiment described in the paper, the author is inclined 



