90 



cyanide of pota8sium blue-green ; chloride of mercury white. 

 Concentrated solutions are also j^recipitated by iodide and by 

 ferro-cyanide of potassium.] 



Gentian Bitter=C40 H30 O24 + 2 HO. The bitter ingredient 

 of the I'oot of Gentiana lutea. Digest the fresh root (the diied root 

 gives no crystalline bitter) with alcohol of 70%, evaporate to 

 honey-consistence, dissolve in three times its weight of water, 

 shake the solution twice ^vith animal charcoal, rinse the latter in 

 cold water, dry and boil with alcohol of 80%. This tincture, 

 when freed from the whole of the alcohol by heating, separates on 

 cooling, or better by diluting with water, a resin which has to be 

 removed, and the liquid digested with . oxyd of lead. Filter hot, 

 remove the lead by sul})huret of hydrogen, evaporate to a syrup 

 consistence and shake ^vith ether. After being left in contact for 

 one day the mixture solidifies to a crystalline mass, which has to 

 be pressed and recrystallised in a little hot water with aid of a little 

 animal charcoal. — Colourless, radially united needles, efflorescent 

 at the air, of a strong and pure bitter taste ; neutral ; loses its 

 water at 100°; fuses at 120° to 125°, becomes carljonised in 

 higher temperatures while emitting an odour of burnt sugar; 

 dissolves readily in water and in hydrated alcohol, less readily 

 in absolute alcohol, not in ether; in concentrated sulphuric 

 acid colourless, changing to a beautiful carmine red on heating ; 

 decomposes with diluted sulphuric acid into siagar and another 

 product; is soluble in alkalies with yellow colour. 



Gentiaiiln, or Gentianic Aci(l=C2s Hio Oio. In the root of 



Gentiana lutea, but is not the bitter ingi-edient. Withdraw from 

 the root most of the bitter ingredient by means of cold Avater, dry 

 the root and exhaust with strong alcohol, evaporate to a syrup, 

 pour water on it, and remove thereby the substances soluble in 

 water, leaving a sediment which contains Gentianin, fat, resin, and 

 the bitter substance. Remove the fat with ether, and recrys- 

 tallise in alcohol. — Light, long, pale, yellow, silky needle-like 

 crystals, inodorous and tasteless, neutral, unchangeable at 

 250°; becomes brown at 300°, sublimates with careful heating, 

 dissolves in 5000 parts cold and in 3850 parts hot water, in 500 

 parts of cold and in 90 parts boiling alcohol, in 2000 parts ether; 

 is not changed by diluted acids; dissolves readily in alkalies 

 with yellow colour, forming salts. 



Gentisin= Gentianin. 



Geraniin. After the roots of species of Geranium are ex- 

 tracted with alcohol, part of the alcohol distilled off from the 

 tincture, the tannic acid removed from the remaining liquid by 

 adding hydrate of lime, the liquid filtered and evaporated, the 

 resin that separates removed, and the liquid brought to dryness;. 



