144 RESINS, BITTER PRINCIPLES, ETC. 



Ericiuol is charanterized by its odour. (Compare also §§ 55 and 

 167.) 



Vanillin (cf. § 167), the aromatic constituent of vanilla, is 

 very sparingly soluble in cold petroleum spirit, but might be 

 partially carried into solution in the presence of fixed or ethereal 

 oil J as a rule, however, it may be found in the ethereal extract. 

 It is colourless, crystalline, possesses the pleasant odour of vanilla, 

 and is soluble in 183 parts of water (at 18°), in 4-4 parts of 

 alcohol (specific gravity OSOS), and in 6*24 parts of ether. It 

 melts at 82°, and is soluble in dilute soda ; ferric chloride colours 

 the aqueous solution dark bluish-violet. Being an aldehyde of 

 methylprotocatechuic acid, it combines with acid sulphites 

 (§ 33), and it is upon this property of vanillin that the follow- 

 ing (Thiemann and Haarmann's) method of estimation is 

 based ? 



The ethereal extract of about 30 grams of vanilla is evaporated to 

 150 cc, and thoroughly-shaken for 10 to'20 minutes with a. mix- 

 tiure of water and saturated aqueous solution of bisulphite of soda. 

 The ethereal solution is separated and again shaken with 100 cc. 

 of the bisulphite mixture. The aqueous solutions are united and 

 washed with pure ether to remove- impurities. To eveiy 100 cc. 

 there are then gradually added 150 cc. of a mixture of 3 vols, 

 of pure sulphuric acid with 5 vols,- of water. The sulphurous 

 acid evolved is received- into solution of soda, the remainder being 

 expelled by passing a current of steam through the liquid. After 

 cooling, the vanillin, which has been liberated, is extracted by 

 shaking with 3 to 4 successive portions of ether, and can be 

 weighed after evaporating the ethereal solution. 



Ostrutkiin, which resembles vanillin in being sparingly, soluble 

 in petroleum spirit,'' is not precipitated by that liquid from 

 ethereal solution. It crystallizes in delicate, pale yellow needles, 

 melting at 91° ; is insoluble in cold water, sparingly soluble in 

 boiling water and benzene, freely in alcohol and in ether. The 

 alcoholic solution possesses a feeble blue fluorescence, which is 

 increased by the addition of water. With aqueous alkalies it forms 

 strongly fluorescent solutions, froin , which carbonic acid precipi- 

 tates the ostruthiin unaltered.. It gives no characteristic reactions 



• Zeitschr. f. anal. Chemie, xv. 350, 1875 <,Tourn. Cheni. Soc. xxix. 112). 

 " Compare Gorup-Besanez, Annal. d. Chem. UDd Fbarin. clxxxiii. 321, 1876 

 (Pharm, Joum. and Trans. [3], vU. 984). 



