URINARY SEDIMENTS. 831 



Calcium carbonate occurs in considerable quantities as sediment in 

 the urine of herbivora. It occurs in but small quantities as a sediment 

 in human urine, and in fact only in alkaline urines. It either has the 

 same appearance as amorphous calcium oxalate or it occurs as some- 

 what larger spheres with concentric bands. It dissolves in acetic acid 

 with the generation of gas, which differentiates it from calcium oxalate. 

 It is not yellow or brown like ammonium urate, and does not give the 

 murexid test. 



Calcium sulphate occurs very rarely as a sediment in strongly acid urine. It 

 appears as long, thin, colorless needles, or generally as plates grouped together. 



Calcium Phosphate. The CALCIUM TRIPHOSPHATE, CasCPO^, which 

 occurs only in alkaline urines, is always amorphous and occurs partly 

 as a colorless, very fine powder, and partly as a membrane consisting of 

 very fine granules. It differs from the amorphous urates in that it is 

 colorless, dissolves in acetic acid, but remains undissolved on warming 

 the urine. CALCIUM DIPHOSPHATE, CaHP04+2H20, occurs in neutral 

 or only in very faintly acid urine. 1 It is found sometimes as a thin 

 film covering the urine and sometimes as a sediment. In crystallizing, 

 the crystals may be single, or they may cross one another, or they may 

 be arranged in groups of colorless, wedge-shaped crystals whose wide 

 end is sharply defined. These crystals differ from crystalline alkali 

 urates in that they dissolve without a residue in dilute acids and do not 

 give the murexid test. 



Ammonium-magnesium phosphate, TRIPLE PHOSPHATE, may separate 

 from an amphoteric urine in the presence of a sufficient quantity of ammo- 

 nium salts, but it is generally characteristic of a urine which is ammo- 

 niacal through alkaline fermentation. The crystals are so large that they 

 may be seen with the unaided eye as colorless glistening particles in the 

 sediment, on the walls of the vessel, and in the film on the surface of the 

 urine. This salt forms large prismatic crystals of the rhombic system 

 (coffin-shaped) which are easily soluble in acetic acid. Amorphous 

 magnesium triphosphate, Mgs(PO4)2, occurs with calcium triphosphate 

 in urines rendered alkaline by a fixed alkali. Crystalline magnesium 

 phosphate, Mg3(PO4)2+22H 2 O, has been observed in a few cases in 

 human urine (also in horse's urine) as strongly refractive, long rhombic 

 plates. 



As more rare sediments we fine! cystine, tyrosine, hippuric acid, xanthine, hcema- 

 toidine. In alkaline urine blue crystals of indigo may also occur, due to a decom- 

 position of indoxyl-glucuronic acid. 



1 In regard to the conditions for the appearance of these sediments in urines see 

 C. Th. Morner, Zeitschr. f. physiol. Chem., 58. 



