5 66 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



(6) Ammonium Magnesium Phosphate. 



Ammonium magnesium phosphate crystals separate in the form of knife- 

 rests from faintly acid urine (Fig. 82). They are soluble in acetic acid. The 



FIG. 82. Deposit of triple phosphate 

 (am. mag. phosphate) and ammonium 

 urate. (After Funke.) 



FIG. 83. Deposit of uric acid, sodium 

 urate and calcium oxalate. (After 

 Funke.) 



smaller crystals may resemble calcium oxalate in appearance, but are distin 

 guished by their solubility in acetic acid. 



(7) Calcium Hydrogen Phosphate. CaHPO 4 . 2H 2 O. 



Large prismatic crystals, often arranged in rosettes, consist of calcium 

 hydrogen phosphate. On adding a solution of ammonium carbonate, the 

 crystals are eaten into and break down into an amorphous deposit. They 

 are easily soluble in dilute acetic acid. 



(8) Bilirubin or Haematoidin. 



These occur as small yellow rhombic plates which give Gmelin's reaction 

 <Fig. 84). 



Fio. 84. Hsematoidin. 



