122 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



1 to 3 drops of dilute acetic acid. If the urine contains more 

 than a small amount of albumin, this will settle out in flocks 

 after the addition of acid. When mere traces are present the 

 solution may only become turbid and should then be com- 

 pared to the urine before heating, but to which the same 

 amount of acid has been added. This test is only of value as 

 a positive one. When a negative result is obtained other 

 tests should be tried with a view to confirmation. 



In some cases the addition of acetic acid to boiled urine 

 may give rise to a faint precipitate or turbidity which disap- 

 pears upon shaking. This is caused by the formation of acid 

 albumin, which may be salted out by one-third saturation 

 with NaCl after the addition of more acetic acid to keep 

 the phosphates in solution. Faintly alkaline or amphoteric 

 urine may sometimes give on heating a precipitate due to 

 phosphates, which is sometimes difficult to distinguish from 

 a precipitate of albumin. Again, such a urine may remain 

 perfectly clear and still contain albumin. The addition of a 

 small amount of acid will, in the first case, dissolve the 

 phosphates, and, in the second, precipitate any albumin 

 remaining soluble. Phosphoproteins nor proteoses do not 

 react similarly, since both bodies are soluble in hot acid 

 solutions; but a precipitate settling out upon cooling may 

 point to the presence of such substances. Resins resulting 

 from the administration of petroleum, turpentine, oil of 

 sandal-wood, tolu-balsam, etc., may be present in the urine, 

 and if so, will be precipitated by the acid. Such precipitates 

 easily dissolve in alcohol. 



(6) Heller's Test. Place 5 c.c. of cone. HN0 3 in a test-tube 

 and allow a few c.c. of the urine which is being filtered to flow 

 from the funnel down the sides of the tube. The urine will 

 thus stratify itself on top of the acid, and at the surface 

 of contact of the two liquids the albumin will be precipitated 



