39^ PHYSIOLOGICAL CHEMISTRY. 



acetone and diacetic acid in terms of acetone. It is, however, much 

 simpler and less time consuming. The method includes the 

 transformation of the diacetic acid into acetone and carbon dioxide 

 by means of heat and the subsequent removal of the acetone thus 

 formed as well as the preformed acetone by means of an air current 

 as first suggested by Folin (see p. 400). The procedure is as fol- 

 lows: Introduce into a wide-mouthed bottle 200 c.c. of water, an 

 accurately measured excess of ^ iodine solution 1 and an excess of 

 40 per cent potassium hydroxide. Prepare an aerometer cylinder 

 containing alkaline hypoiodite solution to absorb any acetone which 

 may be present in the air of the laboratory and between the cylinder 

 and bottle suspend a test-tube about two inches in diameter. This 

 large test-tube should contain 20 c.c. of the urine under examina- 

 tion, 10 drops of a ten per cent solution of phosphoric acid, 10 

 grams of sodium chloride, and a little petroleum, and should be 

 raised sufficiently high to facilitate the easy application of heat to 

 its bottom portion. The connections on the side of the tube should 

 be provided with bulb tubes containing cotton. When the appa- 

 ratus is arranged as described, it should be connected with a Chap- 

 man pump and an air current passed through for twenty-five min- 

 utes. During this period the contents of the test-tube are heated 

 just to the boiling-point and after an interval of five minutes again 

 heated in the same manner. By this means the diacetic acid is con- 

 verted into acetone and at the end of the twenty-five minute period 

 this acetone, as well as the preformed acetone, will have been re- 



1 Proceed as follows in order to obtain a rough idea regarding the amount of 

 T ^j- iodine solution to be used : Introduce into a test-tube 10 c.c. of the urine 

 under examination and I c.c. of a solution of ferric chloride made by dissolving 

 loo grams of ferric chloride in 100 c.c. of distilled water. After permitting the 

 mixture to stand for two minutes, compare the color with that of an equal 

 volume of the ferric chloride solution in a test-tube of similar diameter. If 

 the two solutions be of approximately the same color intensity, 20 c.c. of the 

 urine under examination will yield sufficient acetone to require nearly TO c.c. 

 of -^j. iodine solution. In case the mixture is darker in color than is the 

 ferric chloride solution, the former should be diluted with distilled water until 

 it is of approximately the same intensity as the ferric chloride solution. From 

 this data the amount of y ^ iodine solution required may be roughly estimated 

 by means of the following table: 



