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



cooling, either in yellow needles or as a brownish-yellow crystal- 

 line mass. If its colour is not a pure yellow, or if it is imperfectly 

 crystallized, it contains verantine and must be purified. For 

 this purpose the whole of the mass which has been deposited on 

 the alcohol cooling, after being collected on a filter, is again 

 dissolved in boiling alcohol, and sugar of lead is added to the 

 solution, by which means the verantine is precipitated in com- 

 bination with oxide of lead, while the rubianine remains in 

 solution and is again deposited, when the solution, after being 

 filtered boiling hot, is allowed to cool, in long, lemon-yellow 

 silky needles, which may be rendered perfectly pure by re- 

 crystallization. The compound of verantine and oxide of lead 

 may be decomposed with sulphuric acid, and the verantine 

 separated from the sulphate of lead by boiling alcohol. The 

 alcoholic liquid from which the rubianine has been deposited 

 contains the three other substances besides a portion of the 

 rubianine. By adding acetate of alumina to it, the whole of 

 the alizarine as well as a part of the verantine are precipitated, 

 in combination with alumina, in the shape of a dark red powder, 

 while the liquid retains a dark brownish-red colour. This 

 precipitate, after being collected on a filter and washed with 

 alcohol until the latter runs through colourless, is decomposed 

 with muriatic acid, which dissolves the alumina, leaving behind 

 red flocks consisting* of alizarine and verantine. These flocks, 

 after being filtered off and washed with water, are again dis- 

 solved in alcohol, to which is then added a solution of neutral 

 acetate of copper. This instantly changes the colour of the liquid 

 to a beautiful dark purple. The copper compound of alizarine 

 remains dissolved, while the verantine is entirely precipitated, in 

 combination with oxide of copper, as a dark reddish-brown 

 powder. The dark purple liquid, after filtration and evaporation, 

 leaves a purple mass of alizarine-oxide-of-copper, which is de- 

 composed with muriatic acid. Yellow flocks, consisting of 

 alizarine, remain behind, which after being washed with water 

 are dissolved in alcohol. The alcoholic solution on evaporation 

 gives crystals of alizarine, which may be purified by recrystal- 

 lization. The compound of verantine with oxide of copper is 

 decomposed with muriatic acid. The liquid filtered from the 

 alumina compound of alizarine and verantine is evaporated to 

 dryness, muriatic acid is added to the residue, which is placed 

 on a filter and washed with cold water until all the acid and salts 

 of alumina are removed. On being now treated with boiling water, 

 a quantity of dark brown resinous drops sink to the bottom of 

 the vessel and cohere into a semi-fused mass, while brownish- 

 yellow flocks float in the water. The water is decanted from 

 the mass at the bottom, carrying with it the flocks. This pro- 





