186 METHODS FOR THE ANALYSIS OF BLOOD 



bismuth nitrite is quickly carried out. Speed during the filtration 

 and washing is essential for good results. Ten c.c. of the 50 per 

 cent acetone are used; 2 c.c are blown from a miniature wash bottle 

 (made from a 10 c.c. graduated cylinder) into the precipitation 

 flask. The suction is stoppered and the liquid poured onto the 

 mat. This is repeated four times. Ten c.c. of pure acetone are 

 used to complete the transfer of the precipitate to the Gooch. 

 If the volumetric or colorimetric procedure is used, complete 

 transference of the precipitate is not necessary. 



The Gooch is dried in an air bath at 100 C. until a constant 

 weight is obtained. 



Weight of precipitate X 0.03675 = Weight of sodium in solution. 



Volumetric Procedure. The Gooch crucible and contents 

 are placed in a tall 200 c.c. beaker. A large excess of standard 

 permanganate (at least twice the amount necessary for oxidation) 

 and enough water to cover the crucible are added. The precipitate 

 is stirred loose from the crucible and asbestos. Ten c.c. of 1:1 

 sulfuric acid are poured in while the liquid is being stirred. After 

 a few minutes the solution is heated to 75C., an excess of standard 

 oxalic acid added, and the titration finished with permanganate. 

 A blank must be run on the reagents under similar conditions. 



C.c. KMnO4X normal f actor X8 = Mg. O used 



Mg. Ox7.82 = Mg. precipitate 



Mg. precipitate X 0.03675 = Mg. sodium. 



Colorimetric Procedure. For those who prefer a colorimetric 

 method a suitable technique follows. The precipitate is com- 

 pletely transferred to a beaker and 10 c.c. of the alkaline tart-rate 

 are added. Upon warming, the salt rapidly dissolves. The solu- 

 tion is quantitatively transferred to a 100 c.c. volumetric flask, 

 cooled, made up to volume, and mixed. A further dilution is made 

 so that a volume containing approximately 0.01 mg. of N can be 

 taken for colorimetric comparison. 



The standard and unknown in 100 c.c. volumetric flasks are 

 diluted to about 90 c.c. Two c.c. of the sulfanilic acid and naph- 

 thylamine solutions are added to each. The flasks are made up 

 to volume, mixed, and allowed to stand twenty minutes for the 

 full color development. There is a very wide range of propor- 



