160 W. M. DOHERTY. 



regarded as the best, securing the highest price, 1 and 

 though they are not necessarily the richest in vanillin, 

 they contain an adequate amount, averaging about 2 per 

 cent. The Java and Bourbon beans have yielded as much 

 as 2*75 per cent, to 2*9 per cent, respectively. Some Tahiti 

 beans, which I have lately examined, have been very 

 deficient, yielding only from 0*6 to 0*7 per cent. This low 

 yield was a source of much trouble to some of the local 

 manufacturers of vanilla essence who used this inferior 

 fruit, and thus produced an article very deficient in the 

 chief essential. 



Ordinary good essence of vanilla should contain at least 

 the soluble content of one pound of the fruit in one gallon 

 of menstruum. If the beans are of normal quality, the 

 essence will contain about 0*2 per cent, of vanillin. 



For the determination of the vanillin in essences of 

 vanilla I have tried several processes, and consider that 

 which makes use of the aldehyde reaction with bisulphite 

 to be most reliable, although it is somewhat lengthy. (In 

 the presence of such bodies as coumarin or benzoic acid it 

 leaves nothing to be desired). My modification of the 

 process with essence of vanilla is as follows: — Fifty cubic 

 centimetres are distilled, the distillate being utilised in the 

 determination of the alcoholic strength, and in the deter- 

 mination of volatilised vanillin which it invariably contains. 

 The residue is acidified and extracted in a continuous 

 extraction apparatus, shown in Plate VII, or exhausted 

 in the ordinary way, four times with ether. The ether 

 which contains the whole of the vanillin, less the small 

 amount which came over in the alcoholic distillate, is 

 removed by evaporation or distillation from the residual 

 vanillin, etc., until only about three cubic centimetres 

 remain. This is treated with twenty cubic centimetres of 



1 Bourbon beans have lately been sold in Sydney for 20s. per pound. 



