196 



Scientific Proceedings (121). 



The mixture is immediately shaken and, after the precipitate has 

 darkened, it is filtered into another small test-tube, using a 2.5-3 

 cm. funnel and small thin filter paper. With a dry 1 c.c. pipette, 

 graduated in i/iooths, a definite volume of the filtrate is discharged 

 into one of the 5 c.c. graduated test-tubes with which the micro- 

 colorimeter is provided. It is convenient to take 0.5 c.c. but one 

 need not wait for this amount to filter through. Two volumes 

 of water are added and one volume of Nessler's solution (Bock- 

 Benedict formula diluted 1:5). After thorough mixing the tube 

 is placed in the micro-colorimeter, and matched to the standard 

 "nitrogen" wedge, described above. The reading is now made 

 on the scale and the amount of urea nitrogen per 100 c.c. blood 

 found directly by consulting Table L If the color is too deep, 



table 1. 



Dilution, — i Vol. Solution : 2 Vols. Water : 1 Vol. Nessler's Solution. 





Mg. N 





Mg. N 





Mg. N 





Mg. N 



Read- 



per 



Reading. 



per 



Reading. 



per 



Reading. 



per 



ing. 



100 c.c. 





100 c.c. 





100 c.c. 





100 c.c. 



10 



10 















11 



10 



36 



22 



61 



34 



86 



45 



12 



11 



37 



22 



62 



34 



87 



45 



13 



11 



38 



23 



63 



34 



88 



46 



14 



12 



39 



23 



64 



35 



89 



46 



15 



12 



40 



24 



65 



35 



90 



47 



16 



13 



41 



24 



66 



36 



91 



47 



17 



13 



42 



25 



67 



36 



92 



48 



18 



14 



43 



25 



68 



37 



93 



48 



19 



14 



44 



26 



69 



37 



94 



49 



20 



15 



45 



26 



70 



38 



95 



49 



21 



15 



46 



27 



71 



38 







22 



15 



47 



27 



72 



39 







23 



16 



48 



27 



73 



39 







24 



16 



49 



28 



74 



40 







25 



17 



50 



28 



75 



40 







26 



17 



51 



29 



76 



40 







27 



18 



52 



29 



77 



41 







28 



18 



53 



30 



78 



41 







29 



19 



54 



30 



79 



42 







30 



19 



55 



31 



80 



42 







3i 



20 



56 



3i 



81 



43 







32 



20 



57 



32 



82 



43 







33 



20 



58 



32 



83 



44 







34 



21 



59 



33 



84 



44 







35 



21 



60 



33 



85 



44 







