A RAPID AND EASY METHOD OF E S T I M A T I N G U R E A
I N URINE.
1 % E. ~ H. BARTLEI., M. D. T h i s apparatus wiis designed for the use of physicians rather t h a n chemists. Tlie process is a modification of the well known liypobromi te process, by mliicli t h e urea is decomposed, with the formation of CO,, H,O and free nitrogen. T h e first two of these remain i n solution, while tho nitrogen escapes and is mea s 11red Tlic hypobromite solution is usually prepared by dissolving 2 5 C.C. of bromine and 100 grms. of sodium hydroxide i n 250 C.C. of mater. To avoid this tcdions a n d disagreeable preparatioii I prepare t h e solution as needed by mixing, in the apparatus, a 20$ so1ntio:i of potassium bromide and sodium hypochlorite (T>abarnquc’s solution), in the proportion of one of t h e former to about t h e e of t h e latter. Tlie result of this mixture is a solution of sodium hypobromite and potassium chloride, answering in every wily the requirements of the process. The two solutioiis keep well, while t h e hypobromite solution does not. T h e apparatus consists of two parts: First-A graduated pipette delivering 1 C.C. Second-A graduated tube about 1 am. in diameter :tiid 30 C I ~ . long, closed a t one end, wid graduated from this closed end throughout its entire length. T h e graduntion is made R S follows: A s t m d n r d solution of urea is prepared containing 10 grains t o t h e fluid ounce. With a n ordinary gas tube it was fonnd that 1 C.C. of this solution gave 5.3 C.C. of nitrogen.
.
2b3
T h i s is :ibont tlie a r e i ~ a g eu i w t strciigtii 0 , iioriiitii urine. Each 8.2 C.C. on the new t u b e :ire then tlivided i n t o t c i i I>riiicip:tl tlivisions, siid e x l i of these into four sni:kllt!i, divisions. Each of t h e principni divisioiis t h i ~ i ii ~ ~ p r c ~ r egrains nts per fluid ounce, when 1 C.C. of the u r i n e is t:tkt*ii. By :t siinilar method tlic gradu:it i o n tiiiiy be iii:icic t o represent grams 1wr litre. The process is conducted as follows:
Holding tile ~ i i w m e t e rin tlie left Iiaiiil p o u r iii eiiougli of the 20 1)er ceiit. soitition of potassium 1)roriiidc: to fill it to the fifth divisioii: t l i c i i t ~ d d 11ypoc:liloritt~ soliitioii to tlic eigliteeiitli or tmeiitietli i i i x i , k . T l i ( ~tnlie is i i o w inc:liiicci ant1 water added to about t h e tivciity-fifth tlivisioii. \Yith t h e sniaii pipette 1 C.C. of nriiie is now atitled. ailowing i t to 1,1111 tiown t i i t > side of t h e tube so that it s1i:iIl mix w i t h t h e w t e r floating tipon tliit licnvier solution tielon.. ‘l‘lie ol)eii oiitl o f t l i t , iirc.oineter is now firmly closcil wit11 tlie tliiinib, and its coiltent6 tlicirougl~ly mixed by inverting i t ;t few times. \Vlien tlie effervesceiic(L c w s e s , which ris~i;iliyt:tl~w hiit it two o r t l i r w tninntes: invert ; u i d r t ~ ~ off r l the height of tlic! liiiiiicl i i i the tube. ‘I’lic t l i l i i i i l ) is I I O I V renioved niicler n.:itcbr> tlie tubi: ile1)ressw.l to bring tlicb l i q i i i c l i l l thtt tribe t o a level with tlic: \vnter in the outer vesscl. atit1 ii secoiitl rc:tcling talc( l’lie clifft!retice bc.twecn thc, t w m t d i i i p givcl; :it t j ! i r ~ ’tlie iiiinibfr of gritiiis of iiwa iii e:wli flnidoiiiicc, orgritmrncs per litre, :iccordinq to t h e construction of tllC eCrLl(1. T h i s iiiiriiber niiiltiplietl by tlie iinmber of oiinccs passed in twoiity-four Iiotirs. in tlic one caset 0 1 ’ litrcs i n t h e otli(:r>gives t h e nrrioiint of iirw piissetl in t w i i t y - f o u r hours, wliicli slionld be abont 600 grains, or 30 t o :;:; gyms. The instrument may be had of Eimci. S: A\niencl. So.rr;.-Esi,criiileiitj iiiade t o deteriiiiiic whetbei tlie np]u~ratiiscciiiid he used t u drterriiiiic total nitrogeu, after c1ecoinpo~itioi1i n the Kjeldalll flask with sulpliuric w i d , yavc good results. Exl~erimuiits with amiiioiiiuni chloride slio\ved t h a t h u t tme-tliird of t h e iiitrogeo was set frce from tlii.; s i l t , whilc t h e sulphate seems to j i e l d all of its iiitrogeii.
