AMMONIA COEFFICIENT OF URINES. }57 



In making the calculation of the ammonia coefficient from the volumes 

 of gas obtained, it is evident that this would be exceedingly simple if 

 the reactions were quantitative. Unfortunately, this is not the case. 

 One gram of urea treated with the mercuric nitrate reagent gives 734 

 cubic centimeters of the gases, carbon dioxide and nitrogen, instead of 

 the calculated 744 cubic centimeters, an error of 2.67 per cent. One 

 gram of urea with the alkaline hypobromite solution gives only 354.3 

 cubic centimeters of nitrogen instead of the calculated 372.7 cubic centi- 

 meters. I have obtained from one gram of ammonium chloride 208 cubic 

 centimeters of the gas, instead of the calculated 211 cubic centimeters. 

 All these volumes were measured under standard conditions of tem- 

 perature and pressure, although for the purpose of the determination of 

 the ammonia coefficient of urine it is not necessary to reduce the volume 

 of the gas to standard conditions. It is only required that the gases in 

 the two ureometers should have the same temperature and be under the 

 same pressure, as the actual quantities of urea and ammonia are not 

 required, but only their ratio. To avoid calculation in the future, I have 

 prepared a table giving the ammonia coefficient corresponding to various 

 volumes of gases. The number of cubic centimeters of urine plus wash 

 water is subtracted from the observed volume of gas and the ammonia 

 index is then read off directly from the table. The table is calculated by 

 dividing the number of cubic centimeters of gas obtained from the mer- 

 curic nitrate solution by 2.05. This number is then subtracted from the 

 number of cubic centimeters of gas liberated from the hypobromite solu- 

 tion, and the ratio of this remainder to the total cubic centimeters of 

 gas from the hypobromite, represents the ammonia coefficient, as ex- 

 pressed by a formula : 



(^~2.05/ 



xioo 



Where A is the ammonia coefficient. 



M = number of cubic centimeters of gas from the mercuric 



nitrate solution. 

 H = number of cubic centimeters of gas from the hypobromite 



solution. 



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