384 PHYSIOLOGICAL CHEMISTRY. 



Detection of albumin. There are chiefly three methods by 

 which the presence of albumin in urine may be demonstrated; 

 they are based upon the coagulation of albumin by heat, by 

 nitric acid, or by picric acid. 



The urine used for any of these tests must be perfectly clear; 

 if it be not clear, it must be rendered so by processes which 

 vary according to the nature of the substance causing the tur- 

 bidity. In most cases filtration through good filter-paper may 

 be sufficient; but if this does not accomplish the desired result, 

 it may become necessary to use other means. Thus, if earthy, 

 amorphous phosphates be present (which, especially in alkaline 

 urine, are apt to pass through the best filter-paper), they may 

 be removed by adding to the urine about a fourth part of potas- 

 sium hydrate solution, warming the mixture, and filtering. If 

 the turbidity be caused by urates, the urine will generally be- 

 come clear by passing the test-tube once or twice through a 

 flame. 



The clear urine is then tested by either (or all) of the follow- 

 ing methods : 



a. Coagulation by heat. A test-tube is filled about one-half 

 with the urine, to which, if not distinctly acid to test-paper, a 

 few drops of acetic acid are added. (In case potassium hydrate 

 has been added in order to precipitate the phosphates, enough 

 of acetic acid must be added to cause a distinct acid reaction.) 

 The test-tube is then held over the flame in such a manner that 

 the heat acts upon the upper half of the urine only, heating this 

 portion gradually to the boiling-point. By thus operating, two 

 strata of fluid are obtained for comparison, and by holding the 

 test-tube against the light, or against a black background, any 

 difference in the appearance of the upper and lower strata may 

 easily be noticed. Any cloudiness or opacity seen may be due 

 to albumin, but may also be caused by phosphates. 



To decide this question, a few drops (10 to 15) of nitric acid 

 are allow r ed to flow gently down the side of the tube into the 

 urine. The precipitate will readily disappear when caused by 

 phosphates, but will be permanent when albumin is present. 



Instead of heating, as above described, merely the upper half 

 of the urine, the total quantity of the urine (acidulated by a few 

 drops of acetic acid) may be heated, and the test-tube set aside 

 for several hours (after having added 10 to 15 drops of nitric 



