154 COMPOSITION OF FEEDING STUFFS 



nutritive value is not identical with that of the other digestible 

 carbohydrates, and they are sometimes estimated separately, 

 advantage being taken of the fact that the pentose sugars when 

 distilled with HCl are converted into furfural, C4H3O.CHO. 



C5Hio05-3H20 = C5H402. 



Five grams of the material are weighed into a 

 distillation flask fitted with a dropping funnel and 

 connected with a condenser. A mixture of 40 ex. 

 strong HCl and 60 c.c. of water are added, and the 

 liquid heated. As distillation commences, HCl of the 

 same strength is run in drop by drop to replace the 

 liquid distilled off. The process is continued until the 

 distillate no longer reddens filter paper moistened with 

 aniline acetate solution. The distillate is now trans- 

 ferred to a large flask, neutralised with solid sodium 

 carbonate, and then re-acidified with acetic acid. A 

 solution is made up containing 12 grams of phenyl 

 hydrazine and 7-5 grams glacial acetic acid per 100 c.c, 

 and 10 c.c. of this solution are added to the liquid, which 

 is then gently warmed on the water-bath, shaken well, 

 and allowed to stand overnight at the ordinary tempera- 

 ture. The furfural hydrazone formed is filtered through 

 a Gooch, washed well with water, and the residue, 

 together with any material remaining on the sides of 

 the flask, dissolved in alcohol and transferred to a small 

 weighed dish. The liquid is then evaporated to dryness 

 and the dish again weighed. Weight of hydrazone 

 X 0-5 16 = weight of furfural. An addition of 0-025 

 gram is made to correct for solubility. Weight of 

 furfural x 2'-o = weight of pentoses. 



