Dr. Schunck on Rubian and its Products of Decomposition. 421 



has a dark brownish-red colour. By adding to it sulphuric acid 

 and a large quantity of water, the substances contained in it are 

 precipitated in the shape of a yellow powder. This powder yields 

 nothing to boiling water, which proves the absence of rubianine 

 among the products of decomposition. After being separated 

 by filtration, and washed with w^ater to remove the acid and 

 aluminous salts, it is again dissolved in boiling alcohol, and to 

 the boiling solution there is added an excess of sugar of lead, 

 which causes a dark purple precipitate, the liquid becoming dark 

 yellow. The latter is filtered boiling hot and then mixed with 

 a large quantity of water, which produces a dull orange-coloured 

 precipitate, consisting of rubiagine and rubiadipine in combina- 

 tion with oxide of lead. This precipitate is boiled with sulphuric 

 acid, which turns it yellow ; and after the excess of acid has been 

 removed with water, it is treated with boiling alcohol, which 

 leaves undissolved a quantity of sulphate of lead, and acquires 

 a yellow colour. The alcohol on evaporation leaves a residue 

 consisting of rubiagine and rubiadipine. This residue is treated 

 with cold alcohol, in which the rubiadipine dissolves easily, and 

 is obtained on again evaporating as a dark brown, soft, fatty 

 mass. The rubiagine left undissolved is treated with a small 

 quantity of warm alcohol, which removes an additional quantity 

 of rubiadipine, together with a portion of the substance itself^ 

 and on redissolving it in boiling alcohol and evaporating sponta- 

 neously, it appears in the form of a lemon-yellow mass consisting 

 of small crystalline grains. The dark purple precipitate produced 

 by sugar of lead consists of oxide of lead in combination with rubi- 

 retine, alizarine, verantine and rubiafine. It is treated with boiling 

 muriatic acid, which dissolves the oxide of lead. The yellow 

 flocks left by the muriatic acid are, after washing with water, 

 treated with cold alcohol which leaves a part undissolved, and 

 on evaporation gives a residue consisting for the most part of 

 rubiretine. By treating this residue again with cold alcohol, an 

 additional quantity of substance is left undissolved, and the 

 rubiretine is now obtained in a state of greater purity. Its 

 appearance and properties are the same as when obtained by the 

 action of acids or alkalies on rubian. The substance left undis- 

 solved by the cold alcohol is added to the orange-coloured flocks 

 proceeding from the decomposition of the alumina precipitate, 

 and the mixture is dissolved in boiling alcohol. To the alcoholic 

 solution is added acetate of copper, which gives a dirty purple 

 precipitate, consisting of verantine, rubiafine and a portion of 

 the alizarine in combination with oxide of copper, while the 

 liquid, which has a fine purple colour, contains the greatest part 

 of the alizarine. The latter is obtained from this liquid by pre- 

 cipitating with muriatic acid and water, and purified by crystal- 

 lization. The precipitate produced by acetate of copper is de- 



