[ 845 ] 



portion is to be decanted off (not filtered), when quite cold, 

 into a porcelain bason and Tincture of Iodine added drop by 

 drop. If any blue colour is noticed while stirring, the pre- 

 sence of starch is to be inferred. 



Another portion of the above liquid, about ^rd of a test- 

 tubeful is taken. To it is added one-third of its bulk of 

 the "sugar test" and boiled for 2 minutes. If a yellow or 

 red precipitate forms the presence of sugar is to be inferred. 



1.423. Sugar test. The "sugar test" consists of a solu- 

 tion of copper sulphate with an excess of Sodium and Potas- 

 sium Tartarate (Rochelle salt) made strongly alkaline with 

 Sodium Hydrate solution. The reaction consists in the reduc- 

 tion of CuO to Cu 2 O (i.e., from black oxide to red oxide of 

 copper). 



1.424. Analysis of oil-cake for manure. If an oil- 

 cake is used both as a fodder and manure, besides mois- 

 ture, ash, fibre, oil, and albuminoids, which are found out 

 in analysing oil cake which is used as fodder alone, the 

 amounts of Sand, Lime, Phosphoric anhydride and 

 Potash, present in the ash should be determined. 

 If, as in the case of castor-cake and mahuacake, the 

 substance is not required for fodder but for manure alone, 

 it is unnecessary finding out the proportions of oil, fibre 

 and albuminoids in the sample, but it is very necessary 

 finding out the proportions of CaCOs, P2O 5 , and K 2 O besides 

 N, and such foreign substances as sand and moisture. 



1.425. After determining the percentage of ash in the 

 usual way, the ash is dissolved in half a litre of distilled 

 water; each 100 litres representing 3 grammes of cake in 

 the example given below, 15 grams of cake being ignited 

 for obtaining the ash for analysis. 



1.426. 200 c. c. of the solution (representing 6 grammes 

 of the cake) should then be taken. Fe 2 C1 6 is then added 

 and NH 4 HO to take down the jelly like precipitate. The 

 precipitate is washed with ammonia water. The precipitate 



