Compound 



paper before the experiment, the difference of the weight gives 

 the weight of hydrazone obtained. From this weight, that of 

 the furfural is calculated as under. 



Furfural = [Hydrazone x 0-538]. The factor 0-538 is the 

 mean number obtained from an extended series of experi- 

 mental determinations. The variations of the results obtained 

 from the theoretical are due to the slight and varying solubilities 

 of the hydrazone in salt solutions of varying concentration. 

 For more exact approximation, the factor must be selected 

 according to the exactly ascertained conditions of its precipita- 

 tion, and the corresponding value determined by Flint and 

 Tollens (loc, at.) being used in calculating from the hydrazone 

 tc the aldehyde. 



In the case of the lignocelluloses we are not able to calcu- 

 late the results to their final expression, i.e. the weight of the 

 parent substance from which the furfural is obtained, for the 

 reason that the constitution of the latter has not been 

 definitely ascertained. The fibre-substance certainly contains 

 pentosanes, and the pentose xylose has been isolated in small 

 quantity as a product of alkaline and acid hydrolysis (Tollens, 

 Berl. Ber. 1889, 1046). As, however, the evidence goes to 

 show that other furfural-yielding groups probably oxidised 

 hexose derivatives are present, we are limited to an approxi- 

 mate estimate of the quantity of the entire furfural-yielding 

 complex. This approximation is furnished by multiplying the 

 weight of hydrazone by 1*1 ; or, in other words, the weight of 

 the furfural-yielding constituents may be taken together at 

 about twice the weight of the furfural obtained. 



Apart from all hypothetical considerations, however, the 

 yield of furfural is an important constant of the fibre-substance, 

 which may be determined as described, within the limits of 

 satisfactorily small errors of experiment. 



Keto R. Hexene Constituent. The characteristic 



