THE AMMONIAOAL DECOMPOSITION OF URINE. 371 



The Ammoniacal Decomposition of Urine. 



By 



IVm. Robert Smitb, M.D., D.Sc, F.R.S.Ed., 



Examiner ia Chemistry and Eorensic Medicine, University of Aberdeen. 



With Plate XXX, 6gs. 1 and 2. 



When freshly voided, healthy urine, as is well known, is a 

 clear, transparent, amber-coloured fluid, with a distinct acid 

 reaction, and a peculiar aromatic odour. If left to itself in an 

 open vessel slight clouds of mucus soon appear which gradually 

 sink to the bottom. After a time the acid reaction is noticed 

 to be slightly increased, and crystals of uric acid and oxalate 

 of lime are deposited. After a longer or shorter interval, de- 

 pendent on the temperature of the surrounding media, this 

 marked acidity begins to diminish and finally disappears, the 

 urine becomes lighter in colour, a whitish scum forms on the 

 surface, and the well-known ammoniacal odour indicates that 

 it has become alkaline ; the uric acid crystals disappear, and 

 whitish granules of urate of ammonia and prismatic crystals 

 of urate of soda take their place, beautiful crystals of phosphate 

 of magnesia and ammonia being subsequently thrown down. 



The increase of acidity is called by Scherer the acid fermen- 

 tation, and is considered by him to be owing to the presence 

 of the vesical mucus. The alkaline change is spoken of as the 

 alkaline or ammoniacal fermentation, and is owing to the de- 

 composition of the urea into carbonate of ammonia. 



These so-called fermentative changes are well known, and 

 have long been recognised. So far back as 1682 Van Helmont 

 spoke of the odour of urine as the effect of a putrefactive 



