130 THE SECRETIONS: 



to dryness in the water-bath ; the residue is dissolved in spirit, 

 and sulphuric acid added in order to separate the baryta; 

 nitration is then requisite. The solution, in which sulphuric 

 and hydrochloric acids, and the organic substance, are now con- 

 tained, is boiled with oxide of lead, which removes the acids; 

 and any excess of lead in the filtered solution is removed by 

 sulphuretted hydrogen. On evaporating the filtered solution 

 in a water-bath we obtain a white crystalline mass, neutral in 

 its reaction, with a slightly bitter pungent taste, and easily 

 soluble in water and alcohol. The addition of bichloride of pla- 

 tinum to the alcoholic solution causes no precipitate, but chlo- 

 ride of zinc throws down a copious white deposit, which, on 

 being dissolved in water and evaporated, reproduces the crystals 

 of the zinc-compound exactly as they crystallized from the urine. 

 The pure organic substance gave, as the mean of several 

 analyses : calculated. 



Carbon . . 39'3 39-2 



Hydrogen . . 7'0 6-4 



Nitrogen . . 34-0 34-7 



Oxygen . 19- 7 19' 7 



Hence it may be expressed by the formula C 8 H 8 N 3 O 3 . Hu- 

 man urine emitted in the morning contains about *5 of this 

 body.]v 



9. Hydrochloric acid. The presence of this acid is easily 

 shown. A portion of urine is treated with a little nitric acid, 

 and nitrate of silver is then added, which produces a tolerably 

 abundant curd-like precipitate of chloride of silver. 



10. Sulphuric acid is always present in healthy urine. On 

 treating a portion with nitric acid, and then adding chloride of 

 barium, a white precipitate or turbidity may be observed, which 

 is due to the formation of sulphate of baryta. 



11. Phosphoric acid is recognized by the addition of free 

 ammonia to fresh urine ; earthy phosphates are immediately 

 precipitated. In order to demonstrate the presence of alkaline 

 phosphates, lime water is added to urine from which the earthy 

 phosphates have been removed by filtration ; phosphate of lime 



1 Liebig's und Wohler's Annalen, vol. 52, part 1. 



