152 COMPOSITION OF FEEDING STUFFS 



take place. After the NaOH digestion the residue is 

 filtered through calico again, washed well with hot water, 

 and then transferred, by washing, into a weighed 

 platinum dish. The water is evaporated off on the 

 water-bath, the residue dried in the oven, and weighed. 

 It is then ignited and weighed again. The difference 

 in weight is the " crude fibre." 



{h) Carbohydrates — Non-nitrogenous Extractive 

 Matter. 



These substances, consisting chiefly of sugars and 

 starch, are generally estimated by difference from lOO 

 after all the other determinations are made. If it is 

 desired to estimate them separately, the following 

 methods are adopted. 



145. Soluble Carbohydrates or Sugars. 



(i) Reducing Sugars estimated as Dextrose. — About 

 5 grams of substance (less if it contains much sugar) are 

 stirred with water and allowed to stand for some time — 

 say overnight — in about 50 c.c. of cold water. The 

 solution is filtered and the residue washed. The filtrate 

 and washings are made up to 250 c.c. 



The dextrose is then estimated polarimetrically (see 

 17 and 18, pp. 31-34), or by reduction of Fehling's solution 

 as follows : — 25 to 30 c.c. of Fehling's solution are put in 

 a 250 c.c. beaker and diluted with 50 c.c. of boiling 

 water. The liquid is kept in a water-bath containing 

 boiling water, and after six or seven minutes (the liquid 

 being quite clear) 50 c.c. of the sugar-containing 

 solution are added and the mixture maintained in the 

 boiling water for twelve to fourteen minutes. If the 

 blue colour of the liquid be destroyed within a few 

 minutes, the assay must be recommenced with a smaller 

 quantity of saccharine liquid. The precipitated cuprous 



