158 CONCENTRATED FOOD-STUFFS 



N 

 determined by titration with — iodine solution (i c.c. 



= 0-00027 gram HCN). 



HCN + l2 = CNl + HI. 



This method is much more satisfactory for these 

 distillates than the silver nitrate titration method, since 

 reducing substances, which interfere with the end-point, 

 are apt to be present in the distillates. 



151. Crude Fibre in Cotton-seed Cake. 



Several kinds of cotton-seed cake are placed on the market, 

 differing according as the seeds have been husked or not. The 

 principal varieties are : — 



Decorticated Cake (American) . . Husk removed. 

 Decorticated Cake (Egyptian) . . Most of the husk removed. 

 Undecorticated Cake (Egyptian) . Husk present, but no cotton 



fibre. 

 Undecorticated Cake (Bombay) . Husk present together with 



much cotton fibre. 



Samples of different cotton-seed cakes .should be 

 examined qualitatively with regard to their content of 

 husk and fibre. The crude fibre is to be estimated 

 (see p. 151) in decorticated, Egyptian and Bombay cakes 

 and the differences noted. 



152. Examination of Rape Cake. 



Rape cake frequently contains considerable quantities of wild 

 mustard seed, which renders it undesirable as a feeding stuff ; it is, 

 consequently, frequently extracted with solvents to remove the oil, 

 and the residue used as a fertiliser (see p. 142). 



A few grams of the cake are reduced to a powder in 

 the mill, soaked with water, and allowed to stand in a 

 corked flask in a thermostat or other warm place. It 

 should retain its original mild taste. If, at the end of 

 a few hours, it tastes hot or pungent or makes the eyes 



