68 METHODS FOR THE ANALYSIS OF URINE 



hours the ammonia apparatus is detached and the ammonia 

 determination completed as described on page 42. 



If data regarding acetoacetic acid are desired, the result 

 obtained by Folin's method may be subtracted from the result 

 obtained by the Van Slyke method for acetone and acetoacetic 

 acid. Under all conditions the determination of acetone should 

 be as expeditious as possible. This is essential, not only because 

 of the fact that any acetoacetic acid present in the urine will 

 become transformed into acetone, but also because of the rapid 

 spontaneous decomposition of the alkaline hypoiodite solution 

 used in the determination of the acetone. It has been claimed 

 that alkaline hypoiodite solutions are almost completely converted 

 into iodate solutions in one-half hour. Folin states, however, 

 that the transformation is not so rapid as this, but he nevertheless 

 emphasizes the necessity of rapidity of manipulation. At the 

 same time it should be remembered that the air current must not 

 be as rapid as for ammonia, inasmuch as the alkaline hypoiodite 

 solution will not absorb all the acetone under those conditions. 



INDICAN 



Ellinger's Method l 



Principle. This method for the quantitative determination of 

 indican is based upon the principle underlying Jaffe's qualitative 

 test for indican. The urine after removal of interfering substances 

 with basic lead acetate is treated with Obermayer's reagent to 

 oxidize the indican to indigo. The indigo is extracted with 

 chloroform, the chloroform evaporated off and the residue titrated 

 with potassium permanganate. The method is not very accurate 

 but is as satisfactory as any. 



Procedure. To 50 c.c. of urine in a small beaker or casserole 

 add 5 c.c. of basic lead acetate solution, mix thoroughly, and filter. 

 Transfer 40 c.c. of the nitrate to a separately funnel, add an equal 

 volume of Obermayer's reagent and 20 c.c. of chloroform, and 

 extract in the usual manner. This extraction with chloroform 

 should be repeated until the chloroform solution remains color- 

 less. Shake up the combined chloroform extracts two or three 

 times with distilled water in a separating funnel and complete the 



1 Hawk: Practical Physiological Chemistry, Sixth Edition, 1918. 



