400 JPHYSIOLOGICAL CHEMISTRY. 



0.967 milligram 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 100 c.c. of urine 

 examined. 



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

 specimen. 



XV. Acetone. 



i. Folin's Method. The same type of apparatus is used in this 

 method as that described in Folin's method for the determination 

 of ammonia (see p. 380). The procedure is as follows: 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, 2 and a .little petroleum. Introduce into an absorp- 

 tion flask, 3 such as is used in the ammonia determination (see p. 

 380), 150 c.c. of water, 10 c.c. of a 40 per cent solution of potassium 

 hydroxide, and an excess of a -f-$ iodine solution. Connect 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 iodo- 

 form in the absorption flask. Add 10 c.c. of concentrated hydro- 

 chloric acid (a volume equivalent to that of the strong alkali orig- 

 inally added), to the contents of the latter and titrate the excess 

 of iodine by means of T ^- sodium thiosulphate solution and starch, 

 as in the Messinger-Huppert method (see p. 399). 



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 consideration for the clinician inas- 

 much as urines which contain acetone and diacetic acid are gener- 

 ally those from which the ammonia data are also desired. The pro- 

 cedure for the combination method is as follows : Arrange the 

 ammonia apparatus as usual (see p. 380), and to the aerometer of 

 the ammonia apparatus attach the acetone apparatus set up as de- 

 scribed above. Regulate the air current with special reference to 



1 Oxalic acid (0.2-0.3 gram) may be substituted if desired. 



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



3 Folin's improved absorption tube (see Fig. 123, p. 381) should be used in this 

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

 unsatisfactory because of the solvent action of alkaline hypoiodite on rubber. 



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

 sample is too small for the double determination. 



