300 PHYSIOLOGICAL CHEMISTRY 



the protein derivatives, metaproteins, proteoses, peptones and 

 amino acids. 



As turbidity would interfere with the detection of small 

 amounts of protein, the urine should be clear before testing. 

 If necessary, filter, repeating the filtration and adding a 

 small amount of bismuth subnitrate if the filtrate did not 

 come through clear. If the urine still remains cloudy, add 

 a drop or two of barium chloride and then a drop or two of 

 sodium carbonate solution. Barium carbonate precipitates 

 and carries down with it the suspended material. 



a. ALBUMINS AND GLOBULINS. 



1. Heat Test. The heat test should be made in acid solu- 

 tion, as only in a weak acid solution will the proteins coagu- 

 late properly on boiling. The urine should be tested with 

 litmus and acidified if necessary with 0.5% acetic acid. Even 

 if the urine is acid, it is well to add a few drops of dilute 

 (0.5%) acetic acid to insure coagulation of proteins possibly 

 present. 



Boil a few cubic centimeters of acidified urine. If no pre- 

 cipitate forms, albumin and globulin are absent. If it becomes 

 cloudy or a precipitate forms, albumin or globulin is present. 



Do not add acetic acid before heating: (1) because albumin, 

 if present, may be converted into acid albumin; (2) because 

 acid tends to disintegrate cellular elements which may be 

 present, with the consequent separation of cell-proteins. The use 

 of strong mineral acids in this test is objectionable for simi- 

 lar reasons. 



2. Heller's Nitric Acid Test. To four c.c. of urine in a test 

 tube add, by means of a pipette, a few cubic centimeters of 

 concentrated nitric acid. Run in carefully, so that two distinct 

 layers may be formed. In the presence of albumin or globu- 

 lin, a distinct white ring will form at the junction of the 

 two layers. 



The following important facts should be taken into con- 

 sideration: Not over five minutes should be occupied in this 



