A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . rsions that have been indicated above. Estimation of the Urea from the Specitic Gravity ofthe Urine.—As urea is the chief solid constituent of theurine, the urea content can be approximately estimatedfrom the specific gravity. Empirically it has been deter-mined that urine of a specific gravity of containsabout one per cent, of urea; of to , aboutone and a half per cent.; of to , about twoto two and a half per cent.; of , about three
A Reference handbook of the medical sciences embracing the entire range of scientific and practical medicine and allied science . rsions that have been indicated above. Estimation of the Urea from the Specitic Gravity ofthe Urine.—As urea is the chief solid constituent of theurine, the urea content can be approximately estimatedfrom the specific gravity. Empirically it has been deter-mined that urine of a specific gravity of containsabout one per cent, of urea; of to , aboutone and a half per cent.; of to , about twoto two and a half per cent.; of , about three percent, of urea. In febrile and cachectic states, in whichthe urinary chlorides are reduced, this estimation mustbe corrected. For the chlorides in these diseases areexcreted in such small amounts that they exercise no ap-preciable influence on the urinary specific gravity. Con-sequently, a given specific gravitj indicates more ureathan is given in the above figures. Of the accurate methods for determining urea themethod of Hlifner is the most convenient for clinicalwork, the method of MOrner and Sjoquist the most accu-. FiG. 4856.—Hufners Apparatus. rate for scientific work. These two methods alone willtherefore be described. The titration method of Liebig-Pflilger, the method of Folin, etc., are all very good, butthey do not sur|)ass in convenience nor in accuracy thetwo methods mentioned and to be prescntlj described. The Hypobromite Method of Hiifner (Knop).—Thismethod is based on the fact that sodium hypobromite inalkaline solution decomposes urea into nitrogen, carbondioxide and water, according to the following formula: CO(NH,)g -f 3NaOBr = 3NaBr + CO, -f Urea. Sodium hypobromite. 2HS0 -\- 2N The COj that develops is absorbed liy the soda lyewhile the N passes through t he lye and is measured;from the volume of N liberated the amount of urea canbe calculated. This method is inaccurate in two respects:(1) of N liberated is never quite as large asthe the
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