Dr. Schunck on Rubian and its Products of Decomposition. 411 



differently. On adding caustic soda to a solution of rubian, the 

 colour of the solution first changes to blood-red. On boiling 

 the liquid, however, its colour soon changes again from blood-red 

 to purple. This alteration in colour indicates the formation of 

 alizarine. If the boiling be continued, there is deposited, as 

 the liquid becomes more concentrated, a dark purple powder, 

 which consists mainly of a compound of alizarine and soda, 

 and separates in consequence of its insolubility in caustic lye. 

 After the liquid has been boiled for some time, then, provided 

 the quantity of soda employed be sufficiently large, the rubian 

 is entirely decomposed. On now adding sulphuric acid in 

 excess, a quantity of orange-coloured flocks, exactly like those 

 produced by the action of acids on rubian, is precipitated, while 

 the liquid becomes almost colourless. These flocks are separated 

 by filtration and washed with cold water, until the sulphate of 

 soda and sulphuric acid are entirely removed. They now consist 

 mainly of four substances, viz. 1st, Alizarine; 2ndly, Rubiretine; 

 3rdly, Verantine ; and 4thly, a substance which has not hitherto 

 been observed, and to which I shall give the name of Rubiadine. 

 In order to separate these substances from one another, I 

 adopt almost the same method as that employed for the separa- 

 tion of the products of decomposition with acids. The mixture 

 is first treated with boiling alcohol, which dissolves the greatest 

 part, leaving undissolved however a considerable quantity of a 

 dark brown flocculent substance. This substance invariably 

 accompanies the other products of the action. It is, however, 

 as its properties and composition show, a secondary product of 

 decomposition, the formation of which I shall explain pre- 

 sently. To the dark yellow alcoholic solution, after filtration 

 from this flocculent substance, there is added acetate of alumina, 

 which produces a dark red precipitate. This precipitate, which 

 is a compound of alizarine and verantine with alumina, is decom- 

 posed with muriatic acid, and the alizarine and verantine are 

 separated from one another by means of acetate of copper, and 

 purified in the manner which I have before described, when 

 treating of the products of decomposition with acids. The liquid 

 filtered from this alumina compound is still yellow. On adding 

 to it sulphuric acid and a large quantity of water, the substances 

 dissolved in it are precipitated in the shape of yellow flocks, 

 which after filtration and edulcoration ai*e redissolved in boiling 

 alcohol. On adding acetate of lead to this solution, there is. 

 produced a dark purplish-brown precipitate, which consists of 

 rubiretine and verantine in combination with oxide of lead. The 

 liquid still remains yellow, and is filtered from the precipitate. 

 The latter, on being decomposed with boiling muriatic acid, gives 

 a brown powder, which, after filtration and edulcoration, is treated 



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