164 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



urine may be alkaline when passed, due to fermentative changes 

 occurring in the bladder. All urine, however, if exposed to the air 

 (unless the air is perfectly pure, as on the top of a snow mountain), 

 will in time become alkaline owing to the growth of the micrococcus 

 urea. This forms ammonium carbonate from the urea. 



CON 2 H 4 + 2H 2 0= (NH 4 ) 2 C0 3 



[urea] [water] [ammonium 



carbonate] 



The ammonia renders the urine alkaline, and precipitates the 



n 



O.o 



FIG. 49. Envelope crystals 

 of calcium oxalate. 



FIG. 50. Cystin crystals. 



earthy phosphates. The chief forms of phosphates that occur in 

 urinary deposits are 



1. Calcium phosphate, Ca 3 (P0 4 ) 2 ; amorphous. 



2. Triple or ammonio-magnesium phosphate, MgNH 4 P0 4 + 6H 2 ; 

 coffin-Lds and feathery stars (fig. 51). 



FIG. 51. Triple phosphate crystals. 



I'n. .52. Crystals of phosphate of lime 

 (stellar phosphate). 



3. Crystalline phosphate of calcium, CaHPO,, in rosettes of 

 prisms, in spherules, or in dumb-bells (fig. 52). 



4. Magnesium phosphate, Mg 3 (P0 4 ) 2 i 2H 2 O, occurs occasionally, 

 and crystallises in long plates. 



