195 



green lustre; dissolves slightly in boiling water with reddisli-yellow 

 •colour, little in cold, more in boiling alcohol, readily in ether, little 

 in diluted sulphuric acid, in concentrated sulphuric acid with 

 yellow colour and undecomposed even on boiling, in ammonia 

 with bi'ownish, in potash-ley with rose-red, in soda-ley with orange 

 ■colour, turning blood-red on boiling. 



Rllbiau - C56 H34 O30. Bitter glucosid of the root of Rubia 

 tinctorum. Boil with water and preci})itate the decoction with 

 diluted sulphui-ic or hydrochloric acids, to produce a dark-brown 

 deposit which, freed by cold water from the acid, contains diflerent 

 substances, viz., Rubian, alizarin, rubiacin, rubiretin, verantin, 

 ])ectic acid, and a dark-brown decomposition-product. (In the 

 filtrate remains chlorogenin and sugar). Boil the deposit moist 

 with several changes of alcohol as long as the latter assumes a 

 yellow colour, pectic acid and the decomposition-product remaining 

 undissolved, while the dark-bi-own decoction on cooling frequently 

 throws down the verantin as a dark-brown resinous powdei-, 

 removable by filtering. Heat the alcoholic solution to boiling, 

 adding newly precipitated hydrate of alumina and allow to digest 

 until the solution is nearly decolouiised, precipitating thereby 

 alizarin, Rubian, rubiacin, and portions of rubiretin and verantin. 

 Collect the alumina-deposit and add to it, after washing with 

 alcohol, a concentrated boiling solution of carbonate of ])otash, 

 filter the deep-red solvition, containing all the other substances, 

 from the undissolved alizarin-alumina (convertible into pure ali- 

 zarin as described above); precipitate the alkaline filtrate witli 

 hydrochloric acid, to throw down Rubian* rubiacin, I'ubiretin, and 

 verantin, collect the deposit and wash thoroughly with water. As 

 soon as the water passes ofi" without acid reaction, the Rubian, 

 being insoluble in acid water but soluble in pure water, begins to 

 dissolve, imparting to the latter a yellow colour and a bitter taste. 

 By dissolving it in this manner and evaporating the filtered liquid, 

 it is obtained as a yellow extract. The latter is freed from pectic 

 acid by dissolving in alcohol, but retains 5% to 8% inorganic 

 substances, from which it cannot be se])arated. — Hard, dry, brittle, 

 amorphoxis mass, similar to dried varnish or to gum-arabic, j^erma- 

 nent at the air, dark yellow, intensely bitter, is decomj^osed at 

 130° under loss of water; gives out orange-coloured vapours, 

 consisting mostly of alizarin, when heated to a higher temperature, 

 and leaves much coal; fuses on platinum-foil, dissolves most readily 

 in water, a little less so in alcohol, not in ether, in concentrated 

 sulphuric acid with blood-red colour, and becomes carbonised by 

 heat; is decomposed by boiling with diluted sulphuric or hydro- 

 chloric acid, into sugar and into opalescent, afterwards orange- 

 coloured flocks, consisting of alizarin, rubiretin, ivibiacin and 

 verantin; dissolves in hot caustic potash-ley with blood-red, then 



