189 



Resins, A very large and widely-diffused class of bodies, 

 which seem to originate from volatile oils by the oxydising 

 influence of the atmosphere. Combined with volatile oils, they 

 either exude spontaneously, or by the aid of incisions, or are 

 extracted by solvents. They exhibit the following characteristics: 

 They are colourless or coloured, translucid or transparent, not 

 brittle, mostly amorphous, seldom crystalline, assume negative 

 electricity with friction, are of 0'93 to 1'20 density, inodorous or 

 odoriferous from traces of volatile oil, tasteless, or bitter and acrid, 

 fusible by heat, are decomposed by more heat under carbonisation, 

 burn with a smoking flame ; they are insoluble in water, soluble in 

 alcohol (sometimes only in the strongest), mostly in ether aiid in 

 oils, the solutions being mostly of acid reaction ; they dissolve as a 

 rule in alkalies, yielding soap-like compounds. They contain 

 principally carl)on and hydrogen, mostly oxygen, too, but no nitrogen.. 



Rliaiilllill. Yellow, crystalline ingredient of the unmatured 

 berries of Rhamnus cathartica, associated with rhamnocathartin. 

 Press the berries, boil the remnant repeatedly witli water 

 and allow the decoctions to stand cold. Purify the cauliflower- 

 shaped crystals which are formed, by pressing, dissolving in boiling 

 alcohol, washing the crystals that have formed with cold A\^ater and 

 weak alcohol, and by i-ecrystallising in boiling alcohol with aid of 

 animal charcoal. — Forms pale-yellow, cauliflower-shaped, small 

 grains, seldom tuftily united needles, of a slight, peculiar taste, 

 fuses by heat and decomposes afterwards; not or scarcely soluble 

 in cold water, swells u[) considerably in boiling water, dissolves 

 little in cold, readily in boiling alcohol, not in ether; in cold con- 

 centrated sulphuric and also in hydrochloric acid with safii'on- 

 yellow coloiu" and precipitable by water, also in hot diluted 

 sulphuric acid, and crystallising from it on cooling ; in the liydrates 

 and carbonates of alkalies with saffi-on-yellow coloiir, and precipi- 

 table by acids. 



RlinmilOCill'tliartill. The imcrystal Usable bitter substance of 

 the benies of Rhamnus cathartica. Evaporate the juice of the 

 ripe berries to honey -consistence, exhaust with hot alcohol, evapo- 

 rate the tinctures and mix the remnant with water, which throws 

 down yellow-green, pulverulent rhamnotannic acid; the filtrate, 

 when shaken with animal charcoal until devoid of Ijitter taste, 

 yields up the Rh. to the coal. Wash the latter with cold water, 

 dry, treat with hot alcohol and evaporate the tincture. — Trans- 

 parent, amorphous, yellowish, brittle mass, friable to a yellow 

 powder, assumes on fiiction a peculiar smell, tastes most nauseously 

 bitter and acrid, is of neutral reaction, tolei'ably permanent at the 

 air, fuses by heat to a yellow oil and is afterwards decomposed, 

 dissolves in water in every proportion, likewise in alcohol, not in 

 ether; the aqueous solution assumes with alkalies or with subace- 



