326 PHYSIOLOGICAL CHEMISTRY. 



run about 2-3 c.c. of concentrated sulphuric acid carefully down 

 the side and note the red ring at the point of contact. Upon slightly 

 agitating the contents of the tube the whole solution gradually as- 

 sumes a reddish color. As the tube becomes warm, it should be 

 cooled in running water in order that the temperature may not 

 rise above 70 C. 



2. Mylius's Modification of Pettenkofer's Test. To approx- 

 imately 5 c.c. of urine in a test-tube add 3 drops of a very dilute 

 (i: 1,000) aqueous solution of furfurol, 



HC CH 



HC C-CHO. 

 \/ 

 



Now incline the tube, run about 2-3 c.c. of concentrated sulphuric 

 acid carefully down the side and note the red ring as above. In 

 this case also, upon shaking the tube, the whole solution is colored 

 red. Keep the temperature below 70 C. as before. 



3. Neukomm's Modification of Pettenkofer's Test. To a few 

 drops of urine in an evaporating dish add a trace of a dilute 

 sucrose solution and one or more drops of dilute sulphuric acid. 

 Evaporate on a water-bath and observe the development of a violet 

 color at the edge of the evaporating mixture. Discontinue the 

 evaporation as soon as the color is observed. 



4. v. Udransky's Test. To 5 c.c. of urine in a test-tube add 

 3-4 drops of a very dilute (i : 1,000) aqueous solution of furfurol. 

 Place the thumb over the top of the tube and shake until a thick 

 foam is formed. By means of a small pipette add 2-3 drops of con- 

 centrated sulphuric acid to the foam and observe the dark pink col- 

 oration produced. 



6. Hay's Test. This test is based upon the principle that bile 

 acicls have the property of reducing the surface tension of fluids 

 in which they are contained. The test is performed as follows : 

 Cool about 10 c.c. of urine in a test-tube to 17 C. or lower, and 

 sprinkle a little finely pulverized sulphur upon the surface of the 

 fluid. The presence of bile acids is indicated if the sulphur sinks 

 to the bottom of the liquid, the rapidity with which the sulphur 

 sinks depending upon the amount of bile acids present in the urine. 

 The test is said to react with bile acids when the latter are present 

 in the proportion i : 120,000.. 



