CH. xxxvn.] URINARY DEPOSITS, 563 



(1) Triple phosphate or ammonio-magnesium phosphate 

 (NH 4 MgPO 4 + 6H 2 O). This crystallises in "coffin-lid" crystals 

 (see fig. 435) or feathery stars. 



(2) Stellar phosphate, or calcium phosphate ; this crystallises 

 in star-like clusters of prisms. 



As a rule normal urine gives no precipitate when it is boiled ; 

 but sometimes neutral, alkaline, and occasionally faintly acid 

 urines give a precipitate of calcium phosphate when boiled : this 

 precipitate is amorphous, and is liable to be mistaken for albumin. 

 It may be distinguished readily from albumin, as it is soluble 

 in :i few drops of acetic acid, whereas coagulated proteid does not 

 dissolve. 



The phosphoric acid in the urine chiefly originates front}, the 

 phosphates of the food, but is partly a decomposition product of 

 the phosphorised organic materials in the body, such as lecithin 

 and nuclein. The amount of P 2 5 in the twenty-four hours' urine 

 varies from 2-5 to 3-5 grammes, of wh^h the earthy phosphates 

 contain about half (i to 1-5 gr.). 



Tests for the Inorganic Salts of Urine. 



Chlorides. Acidulate with nitric acid and add silver nitrate : a white 

 precipitate of si Ivet chloride, soluble in ammonia, is produced. The object 

 of acidulating with nitric acid is to prevent phosphates being precipitated 

 by the silver nitrate. 



Siil/ilniti'x. Acidulate with hydrochloric acid, and add barium chloride. 

 A white precipitate of barium sulphate is produced. Hydrochloric acid is 

 again added first, to prevent precipitation of phosphates. 



Phosphite*. i. Add ammonia ; a white crystalline precipitate of earthy 

 (that is, calcium and magnesium) phosphates is produced. This becomes 

 more apparent on standing. The nlkaline (that is, sodium and potassium) 

 phosphates remnin in solution, ii. Mix another portion of urine with half 

 its vol ime of nitric acid ; add ammonium molybdatc, and boil. A yellow 

 'ry-iallinc precipitate falls. This test is given by both clasps of plm-iphatos. 



yiuintitnf'irr fitti unit inn of the salts is accomplished by the use of solutions 

 ot ' Mandard strength, which are run into the urine till the formation of a 

 precipitate ceases. The standards are made of silver nitrate, barium chloride, 

 and uranium nitrate or acetate for chlorides, sulphates and phosphates 

 respectively. 



Urinary Deposits. 



The different substances that may occur in urinary deposits are 

 formed elements and chemical substances. 



The formed or anatomical elements may consist of blood 

 corpuscles, pus, mucus, epithelium cells, spermatozoa, easts of the 

 urinary tubules, fungi, and entozoa. All of these, with the 

 exception of a small quantity of mucus, which forms a flocculent 

 cloud in the urine, are pathological, and the microscope is chiefly 

 employed in their detection. 



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