132 THE SECRETIONS: 



15. Potash. The presence of this substance is detected by 

 dissolving the fixed salts in some hydrochloric acid, extracting 

 them by alcohol, and adding to the alcoholic solution of chloride 

 of potassium some bichloride of platinum : a yellow precipitate 

 of chloride of potassium and platinum is deposited. 



16. Ammonia. The presence of this substance cannot be 

 very easily demonstrated in healthy urine, on account of the urea 

 and the nitrogenous extractive matters which coexist with it, 

 since the ordinary ammoniacal salts (the chloride of ammonium 

 and the lactate of ammonia) are dissolved with the urea by alco- 

 hol ; and since, moreover, urea develops ammonia when treated 

 with either free potash or its carbonate in just the same man- 

 ner as the ammoniacal salts. The following method appears to 

 me to be the most appropriate : Evaporate the alcohol- extract of 

 urine, dissolve a portion of it in water, and add a solution of 

 caustic baryta. If ammoniacal salts are present, a strong odour 

 of ammonia will be developed. Neither pure urea, nor the 

 nitrate, on being similarly treated, gives off this ammoniacal 

 odour. 



[Healthy urine, according to Liebig, 1 contains only very mi- 

 nute or doubtful traces of ready-formed ammonia, and these 

 traces probably pre-existed, in the food partaken of. Fresh 

 urine evolves ammonia when treated with alkalies, but it yields 

 no precipitate with bichloride of platinum. Dr. Schlossberger 

 made certain experiments to this effect in the laboratory at 

 Giessen ; upon treating fresh urine with bichloride of platinum, 

 and allowing the mixture to stand at rest during the night, 

 crystals were formed in the urine, which, upon examination, 

 manifested all the properties of chloride of platinum and potas- 

 sium. The amount of ammonia formed in the healthy organism 

 is likewise very minute, not being sufficient even to neutralize 

 the acid from which proceeds the acid reaction of urine and of 

 saliva. We cannot assume the presence of any ammoniacal 

 salt in the urine of herbivorous animals, which contains fixed or 

 alkaline carbonates. 



Experiments for the determination of the amount of ammonia 



1 Lancet, June 1844. 



