38 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



test if the distillation is finished the flask is lowered and the condensed 

 water is allowed to wash out the inside of the condenser tube for about 

 two minutes : after this time the distillate is tested with litmus paper 

 to ascertain if any more ammonia is being evolved. When finished, 

 the outside of the condenser tube is washed with distilled water and 

 the contents of the flask are titrated with -I N alkali. 



The difference between the amount of standard alkali and standard 

 acid gives the amount of ammonia evolved, from which the amount of 

 nitrogen can be calculated : 



5 c.c.- N H 2 SO 4 = 50 c.c. -iN H a SO 4 . 



37-4 c.c. -iN NaOH used. 



12*6 c.c. *iN difference. 



12-6 c.c. -iN H 2 SO 4 = 12-6 c.c. -iN NH 3 



= r.2'6 c.c. *iN Nitrogen 

 = 12*6 x 0-0014 gm. Nitrogen. 

 .'. 5 c.c. solution contain o ! oi764 



.-. 100 c.c. 0-3528 



The amount of protein to which this amount of nitrogen corresponds 

 is ascertained as follows : 



Proteins contain from 1 5 to 1 6 per cent, of nitrogen. Taking 1 5 -5 as 



T OO 



the average value, or 6*45 times the amount of nitrogen gives the 

 amount of protein. The factor 6-25 is, however, generally used 

 ico c.c. solution thus contain 6-25 x 03528 gm. protein = 2-2 gm. 



