414 PRACTICAL PHYSIOLOGY 



EXPERIMENT VI. Determine by the above method the amount of 

 nitrogen contained in an acid solution of ammonium sulphate. 1 



Measure out 5 c.c. of the solution with a pipette, place it in the 

 distilling flask A, dilute to 200 c.c. with water. Now measure 



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accurately 20 c.c. y^ acid and place in receiving flask B, adjust 

 distilling tube C, add excess of caustic soda, and distil as above. 



The total amount of nitrogen excreted by the urine per diem in the 

 case of a man living on an ordinary diet varies between 15 grammes 

 and 20 grammes, and, if the total amount of nitrogen taken in the food 

 be ascertained, it will be found to nearly correspond to this. By 

 special precautions it can be made to accurately correspond when 

 the person is said to be in nitrogenous equilibrium? The nitrogenous 

 constituents of the urine, which collectively make up this total amount 

 of nitrogen, vary in their relative amounts according to the amount of 

 nitrogen which the diet contains. This fact has been clearly shown by 

 Folin, who, for the purpose of demonstrating it, first of all elaborated 

 rapid and accurate methods for estimating these nitrogenous bodies. 

 By the use of the older methods, the chemical estimations were too 

 laborious and too complicated to permit of a sufficient number of 

 analyses being made in daily urine. These methods will be described 

 in their proper places, but in the meanwhile it may be well to briefly 

 consider the main results which have been obtained. 



The chief nitrogenous bodies which occur in the urine are urea 

 (CO(NH 2 ) 2 ), uric acid (C 5 H 4 N 4 O 3 ), ammonia (NH 3 ) and creatinin 

 (C 4 H 7 N 3 0). There are several other nitrogenous substances which are 

 present only in small amounts and are estimated together as un- 

 determined nitrogen. In the following table, the first column gives 

 the relative amounts of these bodies in the urine when a diet rich 

 in nitrogen was taken, and the second column the corresponding 

 data when the diet contained very little nitrogen. The diet rich in 

 nitrogen was made up of whole milk (500 c.c.), cream (300 c.c.), 

 eggs (450 grm.), Horlick's malted milk (200 grm.), sugar (20 grm.), 

 salt (6 grm.), and water sufficient to make up to 2000 c.c. Besides 

 this, 900 c.c. water were allowed. The diet contained about 19 grm. 

 of nitrogen. The diet poor in nitrogen consisted of 400 grm. arrowroot 

 starch made into a paste with 1500 c.c. water, then partly digested for 



1 A suitable solution for the purpose is made by dissolving 1*32 grammes of 

 ammonium sulphate crystals in 100 c.c. of 1 per cent, sulphuric acid; 5 c.c. 

 of this solution contains 0*014 gramme N. 



2 Allowance must also be made for the nitrogen in the faeces. 



