256 PROTEIDS. [CH. X 



50 c.c. of distillate should be diluted to 500 c.c. before 

 being Nesslerised. The first 50 c.c., if Nesslerised with- 

 out dilution, will often yield a precipitate or colour too 

 deep to be accurately compared with the standard.] 



It is absolutely necessary that all the apparatus and 

 water employed should be quite free from ammonia. 

 These operations are best performed in a room kept for 

 the purpose where the apparatus and pure distilled water 

 can be stored. 



If 600 c.c. of water nearly free from ammonia are 

 placed in the retort before beginning the determinations 

 and 100 c.c. are distilled off and thrown away, the 500 c.c. 

 of water will be quite free from ammonia and the whole 

 apparatus perfectly clean. 



The rapidity with which a number of estimations 

 can be made by this process renders it very suitable 

 for comparative experiments involving determination of 

 proteids. 



Ammonia x 10 = Proteids. 



Estimation of soluble Proteids. 



The nitrogen in the precipitate caused by copper 

 acetate may be determined by using Kjeldahl's method on 

 the dry precipitate, or, the precipitate may be suspended 

 in water, decomposed by H 2 S and the proteids estimated 

 in solution (after expelling H 2 S) by the albuminoid 

 ammonia process. 



Estimation of Peptones and Albumoses is seldom 

 required, but methods by which it can be made are men- 

 tioned above, and the details can easily be worked out 



