382 APPENDIX. 



On heating to 130-140 C. : 



,NH 2 O-NH 4 



y- 

 / 

 \O- 



0-NH 4 \NH 2 \O-NH 4 



Carbamate of Ammonia. Urea. Ammonium Carbonate. Urea. 



J$j heating with strong mineral acids or alkalies : 



/NH 2 O-NH 4 



C0 + = C0 



\NH 2 M)-NH 4 



Urea. Carbonate of Ammonia. 



(Krukeriberg.) 



CORRECTION FOR TEMPERATURE AND PRESSURE 

 IN THE HYPOBROMITE METHOD (LESSON XIX.). 



Theoretically I gram of urea evolves 372.7 cubic centimetres of N", but in 

 practice it is found from urine that about 343 cc. are obtained. Suppose 25 cc. 

 of N passes over into the gas-collecting tube, and that the temperature of the 

 room (t)= 10 C. and the barometric pressure 755 mm. Hg, what is the volume 

 at standard temperature and pressure ? 



Let V be the required volume at o C. and 760 mm. Hg ; v be the volume 

 read off ; P = pressure of 760 mm. Hg ; p the barometric pressure of the room ; 

 T the absolute temperature = -273 ; = the temperature of the room (in 

 degrees Centigrade + 273) ; then 



y ,25x755x273 

 760x283 



Next to urea, uric acid is the most important substance present in urine 

 which is decomposed by hypobromite of sodium. It yields 47.7 per cent, of 

 its N. But as the quantity of uric acid present in urine is very small, for 

 practical purposes it may be neglected. 



CORRECTION FOR TEMPERATURE AND PRESSURE OF 

 THE VOLUME OF A GAS, e.g., THE GASES OF THE 

 BLOOD. 



The volume of a gas must be reduced to the standard pressure, 760 mm. of 

 mercury, and standard temperature, o C., according to the formula : 



Vixfr 

 760(1+ at} 



