314 



small bulk on a watch-glass, and keep cold, in order to facilitate 

 the formation into crystals. (In concentrating the liquid, traces of 

 resin separate eventually from which the liquid is pre\dously freed 

 by decanting or filteiing). In case of any crystals having formed, 

 the whole filti-ate is concentrated and kept cold for a few days (in 

 summer time in the cellar, and, better still, surrounded by ice). 

 Proceed with the crystals obtained, as indicated under II, B. 



B. — Examination of the portion of the alcoholic extract insoluble 



in water. 



Wax, fat and chlorophyll, having passed into the ethereous 

 solution, the examination, in this case, is entirely confined to 

 resins, a considerable number of which are insoluble in ether, but 

 soluble in alcohol. If the vegetable substance under trial has 

 been rich in resins, most of them, as a rule, will be found in this 

 part of the extract. 



After noting down the physical properties of the substance and 

 its behaviour in the heat, try if you can free it from any dyeing 

 matters, by dissolving a little of it in alcohol under addition of 

 animal charcoal, and digesting for some time. If no alteration 

 of the colour is observable, the colour belongs to the resin itself 

 and cannot be destroyed by this means; in the other case the 

 whole substance is treated in the same manner and again brought 

 to dryness. 



Whether the resin, so obtained and eventually decoloux*ised, be a 

 mixture of several i*esins or not, is now determined by treating 

 successively with cold as well as boiling alcohol of 70, 80, 90, 95, 

 and 100 °/q, and by comparing with each other the single portions, 

 obtained after evaporating. 



Every individual resin is afterwards examined in regard to its 

 fusing-point, its solubility (in amylic alcohol, benzol, chloroform, 

 sulphide of carbon, petroleum, oil of turpentine, concentrated sul- 

 phuric acid), elementary composition, atomic weight (calculated 

 from the compounds with oxyd of lead), and by digesting it with 

 dilute sulphuric acid, in order to ascertain if it be a glucosid 

 or not. 



IV. — Treatment avith Cold Water. 



Re-transfer the substance, exhausted by ether and alcohol, to 

 the flask, as before, add distilled water sufiicient to foim a thin 

 pulp, and keep at the ordinary temperature and under assiduous 

 shaking for six days. In hot weather the flask with its contents, 

 in order to prevent fermentation, is kept either in a cool cellar or 

 in water kept cold by artificial means. After this, expose^ the 

 whole to a temperature not exceeding 30° for one day, and 

 filter in a displacement apparatus. 



