URINE: QUANTITATIVE ANALYSIS. 401 



the determination of acetone and at the end of 20-25 minutes dis- 

 connect the acetone apparatus and complete the determination of 

 the acetone as just described. The air current is not interrupted 

 and after having run one and one-half hours the ammonia apparatus 

 is detached and the ammonia determination completed as described 

 on page 380. 



If data regarding diacetic acid are desired, the result obtained by 

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

 Messinger-Huppert method (see p. 399), inasmuch as the latter 

 method determines both acetone and diacetic acid. Under all con- 

 ditions the determination of acetone should be as expeditious as 

 possible. This is essential, not only because of the fact that any 

 diacetic 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. 



XVI. Diacetic Acid. 



1. Folin-Hart Method. Arrange the apparatus as described 

 under the Folin-Hart method for the determination of acetone 

 and diacetic acid (see p. 397). Start the air current in the usual 

 way and permit it to run 25 minutes without the application of 

 heat to the urine under examination. Under these conditions the 

 preformed acetone present in the solution is all removed (see p. 

 398). Immediately attach a freshly prepared absorption bottle or 

 introduce fresh alkaline hypoiodite solution into the original bottle. 

 Apply heat to the large test-tube as already described (see p. 398), 

 in order to convert the diacetic acid into acetone, permit the air 

 current to continue for the usual 25 minute period, and determine 

 the diacetic acid value in terms of acetone by the usual titration 

 procedure (seep. 399). 



2. Folin-Messinger-Huppert Method. Determine the com- 

 bined acetone and diacetic acid, in terms of acetone, by the Mes- 

 singer-Huppert method (see p. 399) and subsequently determine the 



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