CONIFERIN 247 



scales. It is sparingly soluble in cold water but is more soluble 

 in hot alcohol, especially amyl alcohol, and may be extracted 

 from aqueous solutions by means of this solvent. Microscopi- 

 cally, salicin is indicated by the fact that it gives a bright red 

 colour with strong sulphuric acid, also with Frohde's reagent * 

 it yields a violet coloration. 



Salicin may be prepared by boiling the willow bark with 

 water which will extract a certain amount of tannin, colouring, 

 and other matters, together with the salicin ; the solution is 

 then treated with lead acetate and after filtering the filtrate is 

 freed from lead by hydrogen sulphide. After removing the 

 lead sulphide the solution on evaporation yields crystals of 

 saHcin which may be further purified by recrystallization 

 from alcohol. 



Salicin is hydrolysed by the enzyme salicase contained in 



willow bark and also by emulsin from bitter almonds to 



glucose and the alcohol saligenin according to the following 



equation : — 



C13H18O7 + H^O = CgHijOo + QH^OH CH^OH 

 Salicin Saligenin 



On steeping a section in a solution of emulsin, saligenin 

 is produced which gives a blue colour with ferric chloride. 



By the action of sulphuric acid and potassium bichromate 

 salicin is oxidized to salicyhc aldehyde, C6H4OHCHO ; this 

 substance is a fragrant colourless hquid, b.p. 196°, which 

 occurs in the essential oil of Spircea Ulmaria ; it is soluble in 

 water, the solution giving an intense violet coloration with ferric 

 chloride. 



Jowett and Potter f claim to have found a seasonal 

 variation in the salicin content of Salix purpurea, and they 

 regard it as a reserve product which is stored in the winter 

 for use in the following spring ; they also claim to have 

 established that the reserve is drawn upon to a different 

 extent by the male and female plants owing to their special 

 functions, but the data they quote are hardly sufficient to 

 warrant these conclusions ; further work on this subject is 



* Sodium molybdate dissolved in concentrated sulphuric acid, 

 t Jowett and Potter : " Pharm. Journ.," 1902, 15, 157. 



