UREIN, CARBAMIC ACID. 657 



HASKINS has changed FOLIN'S method, as he precipitates the urine 

 first with phosphomolybdic acid and after a further preparation pro- 

 ceeds according to FOLIN. According to GLASSNER 1 the MORNER-SJOQVIST 

 method cannot be used in the presence of large quantities of amino- 

 acids, as they remain in part in the alcohol-ether solution. 



KNOP-HUPNER'S method 2 is based on the fact that urea, by the action of 

 sodium hypobromite, splits into water, carbon dioxide (which dissolves in the 

 alkali), and nitrogen, whose volume is measured (see page 653). This method 

 is less accurate than the preceding ones, and therefore in scientific work it is dis- 

 carded. It is of value to the physician and for practical purposes, because of 

 the ease and rapidity with which it may be performed, even though it may not 

 give very accurate results. For practical purposes a number of different appa- 

 ratus have been constructed to facilitate the use of this method. 



For the quantitative estimation of urea in blood or other animal 

 fluids, as well as in the tissues, SCHONDORFF has proposed a method 

 where the proteins and extractives are first precipitated by a mixture 

 of phosphotungstic acid and hydrochloric acid, and then the filtrate 

 made alkaline with lime. The quantity of ammonia formed on heating 

 a part of this filtrate to 150 C. with phosphoric acid and the amount 

 of carbon dioxide produced by heating the other part to 150 C. are 

 determined. In regard to the principles of this method, as well as to 

 the details, we refer to the original article (PFLUGER'S Arch., 62). See 

 also HOPPE-SEYLER-THIERFELDER'S Handbuch, 8. Aufl. SALKOWSKI 3 

 has recently suggested a method for estimating the urea in tissues. 



Urein is the name given by OVID MOOR to a product which he obtained by 

 extracting urine, which had been evaporated to a syrup, with absolute alcohol 

 and precipitating the urea with alcohol containing oxalic acid, or by cooling and 

 treatment with alcohol. Urein is a golden-yellow oil which is poisonous; it 

 reduces permanganate in the cold, and it forms the chief portion of the nitro- 

 genous extractives of urine. Tkere is no doubt that urein is a mixture of several 

 substances. According to MooR, 4 the amount of urea in the urine is only about 

 one-half that ordinarily given, and he has suggested a new method for the deter- 

 mination of the true quantity of urea. The possibility that in the urine we have 

 other bodies besides urea which have been determined with the urea cannot be 

 denied a priori. From the investigations published so far it must be said that 

 MOOR'S assertions are not sufficiently grounded. 5 



/NH 2 



Carbamic Acid, CH 3 N0 2 = CO<^ . This acid is not known in the free 



X)H 



state, but only as salts. Ammonium carbamate is produced by the action of dry 

 ammonia on dry carbon dioxide, but also after the addition of Na,C0 3 to a 



1 Haskins, Journ. of biol. Chem., 2; Glaessner, Zeitschr. f. exp. Path. u. Therap., 4. 



2 Knop, Zeitschr. f. analyt. Chem., 9; Hufner, Journ. f. prakt. Chem. (N. F.), 3. 

 In regard to the extensive literature, see Huppert-Neubauer, 10. Aufl., 304, and follow- 

 ing. 



3 Arbeiten aus dem pathol. Institute, Berlin, 1906. 



4 O. Moor, Bull. Acad. de St. Petersbourg, 14 (also Maly's Jahresber., 31, 415), 

 and Zeitschr. f . Biologic, 44 and 45, and Zeitschr. f. physiol. Chem., 40 and 48. 



5 See Kubiabko, Maly's Jahresber., 31, 415; Erben, Zeitschr. f. physiol. Chem. 

 38; Folin, ibid., 37; Gies, Journ. Amer. Chem. Soc., 25; Haskins, Amer. Journ. of 

 Physiol., 12; Lippich, Zeitschr. f. physiol. Chem., 48 and 52. 



