XXI.] ABNORMAL CONSTITUENTS OF THE URINE. 137 



of urine in a test- tube and boil. Near the boiling-point, if albumin 

 be present in small amount, it will give a haziness ; if in large 

 amount, a distinct coagulum. On standing, the coagulum is 

 deposited. Some prefer to boil the top of a long column of 

 urine in a test-tube. If the urine be acid, then any haziness 

 formed is readily seen against the clear subnatant fluid. 



Precautions. (i.) Always test the reaction of the urine, for albumin is only 

 precipitated by boiling in a neutral or acid medium. Hence if the urine be 

 alkaline, boiling will not precipitate any albumin that may be present, (ii.) 

 Boil the upper sti'atum of the fluid first of all, holding the tube obliquely, 

 taking care that the coagulum does not stick to the glass, else the tube is 

 liable to break, (iii.) Heat, by driving off the C0. 2 , also precipitates earthy 

 phosphates if they are present in large amount, hence a turbidity on boiling 

 is not sufficient proof of the presence of albumin. The points of distinction 

 are, that albumin goes down before the boiling-point is reached (coagulated 

 at 75 C.), while phosphates are precipitated at the boiling-point. Again, 

 the phosphatic deposit is soluble in an acid e.g., acetic or nitric while the 

 albuminous coagulum is insoluble in these fluids. Some, therefore, advise 

 that the test be done in the following manner : 



(ft.) Acidulate the urine with a few drops of dilute acetic or 

 nitric acid, and then boil. If nitric acid be used, add one-tenth to 

 one-twentieth of the volume of urine. 



Precautions. If the urine contain only very minute traces of albumin, the 

 latter may not be precipitated if too much nitric acid be added, as the acid 

 albumin is kept in solution. If too little acid be added, the albumin may not 

 be precipitated, as only a part of the basic phosphates are changed into acid 

 phosphates, and the albumin remains in solution as an albuminate (a com- 

 pound of the albumin with the base). On heating the urine of a person who 

 is taking copaiba, a deposit may be obtained, but its solubility in alcohol at 

 once distinguishes it from coagulated albumin. This test acts with serum- 

 albumin and globulin, and if the deposit occurs only after cooling, also with 

 albumose, but not with peptone. 



(c.) Heller's Cold Nitric Acid Test. Take a conical test-glass, 

 and place in it 15 cc. of the urine. Incline it, and pour slowly 

 down its side strong nitric acid = a white cloud at the line of 

 junction of the fluids. 



Precautions. A crystalline deposit of urea nitrate is sometimes, though 

 very rarely, obtained with a very concentrated urine. If the urine contain a 

 large amount of urates, they may be deposited by the acid, but the deposit in 

 this case occurs above the line of junction, and disappears on heating. It is 

 not obtained if the urine be diluted beforehand. 



('/. ) Acidulate 10 cc. of urine with acetic acid, add one-fifth of its bulk of a 

 saturated solution of magnesium or sodium sulphate, and boil = a precipitate. 



(.) Acetic Acid and Potassium Ferrocyanide. Acidify strongly with 

 acetic acid, and add a solution of potassium ferrocyanide = a white precipi- 

 tate, varying in amount with the albumin present. The reaction may be 

 done as follows : Mix a few cc. of moderately strong acetic acid with some 

 solution of potassium ferrocyanide, and pour this over some urine in a test-tube 



