Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . he carbonic acid, is then cooled,and titrated with tenth-normal sodium hydrateto determine the amount of acid which com-bined with the ammonia formed. Alizarin-red or methyl red are used as of tenth-normal sulphuric acid isequivalent to 0,001704 gram of ammonia(NH3), or gram of nitrogen. If thenitrogen value be multiplied by the result will be the amount of ureain the 5 of urine taken. From the total of n/io sulphuric acidneutralized must be
Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . he carbonic acid, is then cooled,and titrated with tenth-normal sodium hydrateto determine the amount of acid which com-bined with the ammonia formed. Alizarin-red or methyl red are used as of tenth-normal sulphuric acid isequivalent to 0,001704 gram of ammonia(NH3), or gram of nitrogen. If thenitrogen value be multiplied by the result will be the amount of ureain the 5 of urine taken. From the total of n/io sulphuric acidneutralized must be subtracted the n/io sulphuric acid values for the pre-formed ammonia as well as for the ammonia which may be present as animpurity in the 20 grams of magnesium chlorid used. iFolin advises (Handb. d. Biochem. Arbeitsmeth., 1911, V, 286) the use of small glassbulbs containing solid HgClI as an indicator of the proper temperature of this reaction. Thissubstance melts at 153° C., which is the optimum temperatiure to insure complete decomposi-tion of the urea. * See Folin, Jour. Biol. Chem., 1912, XI, Fig. 75 —Folins urea apparatus.{Hawk.) THE URINE. 225 It has been found by Schoorl that when carbohydrates and urea areheated together they form very stable condensation products (ureids). Forthis reason this method of Folin does not give accurate results with saccharinurine. A combination of this method with that of Morner, which will bedescribed later, will give absolutely accurate results. In the determinationof the ammonia values of the preformed ammonia and of the magnesiumchlorid, the later methods of Folin must be used. Morner-Sjoqvist Method. This method^ is an extremely accurate one, but no more so than that ofFolin, except in saccharin urines. If albumin be present it must, however,be removed by heat and acetic acid and the original volume of the urine re-stored. If the urine contains large amounts of hippuric acid this methodmay not give accurate results, as Salas
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