URINE 557 



In fasting the decomposition of fat is increased due to the lack 

 of carbohydrate material and acidosis develops. The same holds true 

 for a carbohydrate-free diet. Apparently, also, fat is much less 

 readily oxidized in the presence of a carbohydrate deficiency. 



Acetone 



Folin's Method. Principle. The preformed acetone is aspirated 

 from the urine mixture at room temperature to prevent decompo- 

 sition of acetoacetic acid. The acetone is collected in alkaline 

 hypoiodite solution as in the Folin-Hart method. lodoform is formed 

 quantitatively and the excess of iodine is titrated with sodium thio- 

 sulphate. 



Procedure. The same type of apparatus is used in this method as that 

 described in Folin's method for the determination of ammonia (see page 519). 

 Introduce 20-25 c.c. of the urine under examination into the aerometer cylinder 

 and add 10 drops of 10 per cent phosphoric acid, 1 8-10 grams of sodium chloride. ? 

 and a little petroleum. Introduce into an absorption flask, 3 such as is used in the 

 ammonia determination (see page 519), 150 c.c. of water, 10 c.c. of a 40 per cent 

 solution of potassium hydroxide, and an excess of a N/io iodine solution. Con- 

 nect the flask with the aerometer cylinder, attach a Chapman pump, and permit 

 an air current, slightly less rapid than that used for the determination of ammonia, 

 to be drawn through the solution for 20-25 minutes. All of the acetone will, at 

 this point, have been converted into iodoform in the absorption flask. Add 

 10 c.c. of concentrated hydrochloric acid (a volume equivalent to that of the 

 strong alkali originally added), to the contents of the latter and titrate the 

 excess of iodine by means of N/io sodium thiosulphate solution until a light 

 yellow color is obtained. At this point add a few cubic centimeters of starch 

 paste and titrate the mixture until no blue color is visible. This is the end 

 reaction. 



Calculation. Subtract the number of cubic centimeters of N/io thiosulphate 

 solution used from the volume of N/io iodine solution employed. Since i c.c. of 

 the iodine solution is equivalent to 0.967 mg. of acetone, and since i c.c. of the 

 thiosulphate solution is equivalent to i c.c. of the iodine solution, if we multiply 

 the remainder from the above subtraction by 0.967 we will obtain the number 

 of milligrams of acetone in the volume of urine employed. 



Calculate the quantity of acetone in the twenty-four-hour urine specimen. 



Interpretation. See Van Slyke's Methods, page 556. 



Folin has further made suggestions regarding the simultaneous determination 

 of acetone and ammonia by the use of the same air current. 4 This is an important 



1 Oxalic acid (0.20.3 gram) may be substituted if desired. 



* Acetone is insoluble in a saturated solution of sodium chloride. 



3 Folin's improved absorption tube (see Fig. 168, p. 520) should be used in this connec- 

 tion inasmuch as the original type embracing the use of a rubber stopper is unsatisfactory 

 because of the solvent action of alkaline hypoiodite on rubber. 



4 These determinations may even be made on the same sample of urine if the sample is 

 too small for the double determination. 



