I70 ROOTS, GREEN FODDERS, ETC. 



water, and the mixture expressed. The filtrate reacts 

 acid to the usual indicators. The liquid extract is now 

 distilled until the distillate is no longer acid. 



{a) Residue. — The residual material is filtered and 

 shown to be acid to litmus paper. Excess of zinc 

 carbonate is then added, the liquid filtered, and the 

 solution allowed to evaporate. Crusts of zinc lactate 

 separate out. These are recrystallised from water and 

 identified, if desired, by estimating the zinc present. 

 Crystallised zinc lactate contains i8-2 per cent, water of 

 crystallisation and 27-3 per cent, zinc as ZnO. 



(b) Distillate. — The distillate is made alkaline with 

 caustic soda and again distilled. The new distillate now 

 contains any alcohol originally present, together with 

 volatile aldehydes and other products formed in the 

 silo. The first 5 c.c. of distillate are made alkaline with 

 NaOH. and iodine solution added until the reddish tint 

 just remains. The solution is then warmed gently. 

 The presence of alcohol is detected by the formation of 

 iodoform, which may, however, be insufficient to separate 

 out and only be detected by its characteristic smell. 



The alkaline liquid in the distilling flask is now 

 acidified with dilute HgSO^ and again distilled. The 

 distillate will contain any acetic and butyric acids. The 

 latter may be detected by its smell, the acetic acid by 

 the following tests : — 



(i.) A few drops of alcohol are added to 2 or 3 c.c. of 

 distillate, and then an equal volume of strong 

 sulphuric acid. On warming gently the charac- 

 teristic smell of ethyl acetate may be noticed. 



(ii.) A small quantity of the distillate is neutralised 

 by adding excess of ammonia and boiling till 

 neutral. The solution is cooled, and mixed 

 with a few drops of ferric chloride. A red 



