534 



PHYSIOLOGICAL CHEMISTRY 



Procedure. Introduce into a wide-mouth bottle 200 c.c. of water, an accu- 

 rately measured excess of N/io iodine solution 1 and an excess of 40 per cent potas- 

 sium 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 2 inches in diam- 

 ter. This large test-tube should contain 20 c.c. of the urine under examination, 

 10 drops or a 10 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 apparatus is 

 arranged as described, it should be connected with a Chapman pump and an air 

 current passed through for twenty-five minutes. 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 

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

 acetone, as well as the preformed acetone, will have been removed from the urine 

 to the absorption bottle and there retained as iodoform. 



The contents of the absorption bottle should now be acidified with concen- 

 trated hydrochloric acid, 2 and titrated with N/io sodium thiosulphate and starch 

 as in the Messinger-Huppert method (see below). 



Interpretation. Normal adults on a mixed diet excrete on the 

 average 3-15 mg. of combined acetone and acetoacetic acid per day and 

 anything over 20 mg. is usually pathological. The amount is con- 

 siderably increased in fasting and on a carbohydrate-free diet due to the 

 development of acidosis. In severe diabetic acidosis values up to 6 

 grams per day or even higher may be noted. It is sometimes found in 

 large amounts in intoxications associated with pregnancy. It may be 

 found in increased amounts in the urine in a great variety of patho- 

 logical conditions. Quantitative estimation enables us to follow the 

 course of the acidosis. Ammonia excretion is also largely increased in 



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

 iodine solution to be used: Introduce into a test-tube 10 c.c. of the urine under examina- 

 tion and i c.c. of a solution of ferric chloride made by dissolving 100 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 10 c.c. 

 of N/io 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 N/io iodine 

 solution required may be roughly estimated by means of the following table: 



2 An excess of iodine is indicated by the development of a brown color. 



