\2 Dr. Thomas Thomson [July 



was put under the exhausted receiver of an air pump, and 

 evaporated to dryness over sulphuric acid. A yellow 

 coloured bitter tasted matter remained, partly brittle and 

 partly viscid. It dissolved in water, except 0*1 gr., which 

 had a brown colour, and the half of which dissolved in nitric 

 acid. 



The aqueous solution being concentrated in a low heat to 

 IJ cubic inch, crystals of nitrate of urea were deposited. 

 These were separated and dried as completely as possible 

 between folds of blotting paper. 



It was found by experiment that at the temperature of 

 50° (that of the \\ cubic inch of residual liquid) 100 parts 

 of water dissolve 19*7 partsof nitrate of urea; consequently, 

 51*94 grs. of it must have remained in solution in the IJ 

 cubic inches of the liquid. The weight of the crystals was 

 3r6 grs.; so that the whole nitrate of urea from 25*64 grs. 

 of urine, (the quantity employed) was 83.54 grs. 



To determine how much urea existed in the 83*54 grs. of 

 nitrate, a portion of it was dissolved in water, and the nitric 

 acid exactly saturated by carbonate of potash. The whole 

 was evaporated to dryness, and the nitrate of potash was 

 washed clean by alcohol and weighed. By this method it 

 was ascertained that nitrate of urea is a compound of 



Nitric acid 6*75 



Urea 17*24 



The whole urea then contained in the 83*54 grs. of nitrate 

 was 60*04 grs. ; consequently, 1000 grs. of urine contain 

 23*64 grs. 



The urea thus determined was not freed from colouring 

 matter, and had a pretty deep reddish-brown colour. 



9. It may be worth while to relate another set of experi- 

 ments made to determine the quantity of urea in 2341 grs. 

 urine of the specific gravity 1*0215. 



The urine was evaporated to dryness, over sulphuric acid, 

 in the vacuum of an air pump. The residue was a buff 

 coloured substance, very tough and hard, and weighing 

 103*4 grs. It was digested in 8 cubic inches of alcohol, of 

 the specific gravity 0*817 for several days. The alcohol 

 assumed an orange-red colour. Being decanted off the 

 undissolved residue, its specific gravity was found less than 



