SHORT AND SIMPLE METHOD FOR DETERMINATION OF VANILLIN. 161 



a ten per cent, aqueous solution of sodium bisulphite and 

 after shaking and contact for at least an hour, at ordinary 

 temperature, is well washed with ether. This ether is 

 treated with a further Ave cubic centimetres of the 

 bisulphite solution, and after separation may be washed 

 and evaporated and the residue examined for the presence 

 of foreign substances such as coumarin, the active principle 

 of the Tonkin Bean, benzoic acid, acetanilide, etc. The 

 bisulphite solution is added to the main portion, which is 

 then acidified with dilute sulphuric acid, and this must be 

 added in sufficient quantity to decompose the bisulphite 

 and so set free the aldehyde. The bisulphite compound 

 may be thus shown: — 



OHQ HS0 3 Na 



OCH3 



OH 



It will be seen that one molecule of vanillin (molecular 

 weight 152) requires one molecule of sodium bisulphite 

 (molecular weight 104), and as 2*5 grammes of the salt are 

 used it follows from the known reaction between sulphuric 

 acid and bisulphite that at least an equal weight of sul- 

 phuric acid should be added, but this should not be greatly 

 in excess. The sulphurous acid produced in the reaction 

 may be eliminated from the solution by passing carbon 

 dioxide through it. The vanillin is then extracted with 

 chloroform using twenty cubic centimetres, fifteen cubic 

 centimetres, and ten cubic centimetres successively. The 

 chloroform solutions are combined and washed twice with 

 distilled water to free them from acid, and allowed to 

 spontaneously evaporate. The wash waters are added to 

 the chloroform- extracted acid liquor, and this is separately 

 extracted with ether, which is evaporated, and whatever 



K— October 1, 1913. 



