196 



purple-red colour under decomposition. The Rubian in aqueous, 

 solutions also becomes blood-red with caustic baryta or ammonia. 

 Tlie aqueous solution of Rubian is not px-ecipitated by acids; is 

 not altered on boiling with phosphoric, oxalic, acetic, or tartaric 

 acids, is not precipitated by alum or the acetates of alumina, lead, 

 copper, or zinc, the chloride of tin, mercury, gold, the sub-nitrate- 

 of mercury, or the nitrate of silver. 



RubiclllOl'ic Aci<l=:Ci4 Hg On- In the root and herb of Rubia 

 tinctorum, in the herb of Asperula odorata, Galium Aparine, G. 

 Molugo and G. verum, and probably therefore largely present in 

 that group of the Rubiacese to which these herbs belong. Occiu-s- 

 iu traces in the deposit pi^oduced by acetate of lead from the 

 aqueous decoctions of the above vegetable parts; in a little larger 

 quantity in the deposit produced by sub-acetate of lead, in the 

 filtrate, and in the largest quantity in the deposit, efiected by 

 ammonia, from the liquid remaining after the filtration of the 

 two former preci^ntations. In operating with Asperula adorata, 

 for instance, the third mentioned deposit has to be washed with 

 alcohol, and is then, suspended in alcohol, decomposed with 

 sidphuret of hydrogen. Free the liquid from the sulphide of 

 lead and from the sulphuret of hydrogen, precipitate again with 

 alcoholic solution of acetate of lead and a little ammonia, decompose 

 the deposit in alcohol with sulphuret of hydrogen; filter and 

 evaporate in a vacuxim. — Colourless or slightly yellowish, amorphous 

 mass, inodorous, of an insipid nauseous taste, dissolves readily in 

 water and in alcohol, not in ether, becomes yellow with alkalies 

 and is decolourised by acids; becomes on heating with hydro- 

 chloric acid blue, aftei-wards green, forming dark-green flocks 

 (chlorrubin), under formation of formic acid. 



Klll>ir(*tiu = Ci4 He O4 (isomeric with hydrated benzoic acid). 

 In the root of Rxibia tinctorum. It takes its origin, according to 

 Higt>in, like verantin by the boiling with water or as decomposition- 

 product of purpurin, according to Strecker and Woltf, under the 

 influence of alkalies. As to preparation see Rubian and Rubiacin. — 

 Dark reddish-brown brittle resin, soft at 65°, fuses at 100°, yields 

 usually with more heat a slight siiblimate of alizarin, dissolves 

 little in boiling water, readily in alcohol, in alkalies with purple- 

 red colour. 



Kubitaiillic Acid = Cu H s O 9. In the leaves of Rubia tinc- 

 torum. Precipitate the aqueous extract by means of acetate of 

 lead, treat the deposit with diluted acetic acid, filter, precipitate the 

 liquid with ammonia, wash the deposit with alcohol and decompose 

 under alcohol with sulphuret of hydrogen ; mix the liquid, after it has 

 been filtered and the alcohol is driven ofi', with water, precipitate 

 with subacetate of lead, decompose the deposit under water with 

 sulphuret of hydrogen and evaporate the filtered liquid. — Yery 



