G. Williams 185 



2. Removal of sulphuric acid. Estimation of ammonia 

 and humin nitrogen. 



The remaining 990 c.c. of hydrolytic liquid were transferred into 

 a four litre flask, heated to boihng, and hot saturated baryta solution 

 added with constant shaking until the reaction was only faintly acid, 

 and the barium sulphate filtered off by suction. The barium sulphate 

 was removed from the funnel, rubbed up into a cream mth distilled 

 water, boiled and filtered. Although this washing process was repeated 

 five times, the final washing liquid was still slightly coloured, and 

 possessed the characteristic beef-tea smell of the original filtrate. The 

 filtrate and washings were evaporated down and made up to 1 htre. 

 Nitrogen estimations in two portions of 5 c.c. each were now made by 

 Kjeldahl's method. 



5 c.c. of Hquid gave NHg equal to 18-63 c.c. N/10 acid 

 - 0-02608 grm. N. 

 1000 c.c. of the liquid contained 5-216 grms. N. 

 N originally present was 5-656 grms. 

 N used in analyses was 0-0566 grm. 

 N left before removal of sulphuric acid is 5-656 — 0-0566 



= 5-599 grms. N. 

 N contained in barium sulphate 



- 5-599 - 5-216 grms. 

 = 0-383 grm. 



This nitrogen is usually said to be contained in the melanin which 

 is held up by the barium sulphate. It is known as " Humin Nitrogen I." 



Humin Nitrogen I = 0-383 grm. =- 6-89 per cent of total nitrogen. 



Two determinations were now made of the amount of nitrogen 

 present as ammonia by distilhng portions of 100 c.c. with magnesium 

 oxide. Before adding the magnesia the solution was made neutral 

 by barium carbonate. 



100 c.c. of liquid gave NHg equal to 25-05 c.c. of N/10 acid 



= 0-03507 grm. N. 

 1000 c.c. of liquid would give 0-3507 grm. N 



= 0-4258 grm. NH^. 



Allowing for losses due to portions used for analyses, 0-4258 grm. 

 ammonia is contained in 35-2414 grms. protein 



= 1-21 per cent, of ammonia. 



