272 PHYSIOLOGICAL CHEMISTRY 



concentrated sulphuric, hydrochloric, and nitric acid respectively 

 drop by drop to the three tubes, and record the results in each. 

 The coagulation with nitric acid may be used to detect extremely 

 small amounts of protein. Dilute 1-2 c.c. of albumin solution 

 with several volumes of water. To a few cubic centimeters of 

 this dilute solution in a test tube, add concentrated nitric acid 

 carefully from a pipette. Caution. In taking up concentrated 

 acids in a pipette, great care should be exercised to avoid draw- 

 ing the acid into the mouth. Be sure the point of the pipette 

 is kept well below the surface of the acid, which should have 

 been poured into a clean test tube before being drawn up into 

 the pipette. Do not fill the pipette more than half full of acid. 



Run the nitric acid slowly into the albumin solution from the 

 pipette, keeping the point of the pipette at the bottom of the 

 test tube. This facilitates the formation of two layers. 



Observe the cloudy ring at the juncture of the two liquids. 

 Performed in this way, the test is known as the Heller King test, 

 and is used to detect the presence of protein in urine. 



8. Dilute the albumin solution used, and determine the smallest 

 concentration of albumin which will give a positive Heller test. 



9. Alcohol. To a few cubic centimeters of albumin solution 

 add alcohol. 



10. Heavy Metals. To small portions of albumin solution add 

 solutions of copper sulphate, mercuric chloride and lead acetate. 

 Egg white is used as an antidote in cases of poisoning by "blue 

 vitriol," "corrosive sublimate," etc., since it forms insoluble 

 compounds with these metal salts which then can be pumped 

 from the patient 's stomach with a stomach pump, or removed by 

 vomiting. The salts of most heavy metals will precipitate pro- 

 teins, in the same way as those tested above. 



11. Acetic Acid and Potassium Ferro cyanide. To a few cubic 

 centimeters of albumin solution add 5-10 drops of 10% acetic 

 acid (why?) and then, drop by drop, potassium ferrocyanide. 

 A precipitate forms. Avoid an excess of the reagent, as the 

 precipitate may be redissolved. This test is very delicate. Zinc 

 also will give a similar precipitate with ferrocyanide, a fact 



