12 THE ULTIMATE CONSTITUENTS OF PLANTS 



constant shaking until the mixture is decidedly alkaline, 

 as shown by the indicator added. The ammonia liber- 

 ated is then distilled over into 20 c.c. normal sulphuric 

 acid coloured with a few drops of methyl orange, and 

 contained in a conical flask. After boiling for about 

 half an hour, all the ammonia should have passed 



Fig. 2. — Kjeldahl distillation apparatus without condenser. 



over, and the end of the delivery tube is then with- 

 drawn from the acid, the adhering liquid washed into 

 the conical flask with distilled water, and the contents 

 of the flask titrated with normal NagCOg or NaOH 

 solution. The amount of normal acid neutralised by 

 the ammonia is thus determined, and from a knowledge 



N 

 that I c.c. — acid is equivalent to -014 gram nitrogen 



in the form of NH3, the percentage of nitrogen in the 

 original substance can be calculated. 



