IRON IN BLOOD 197 



and completed in the incubator at 110 C. The residue is then 

 heated to constant weight by the method of Stolte and the sodium 

 and potassium are weighed as the chlorides. When combined with 

 the cobalti-nitrite method for potassium, this procedure may be 

 used as a rapid method for the indirect determination of sodium. 

 It is also possible to weigh the combined chlorides of sodium and 

 potassium, determine the total chlorides, and calculate the amount 

 of potassium and sodium. 



IRON IN BLOOD 



Method of Berman 1 



Principle. The iron held in combination in blood is split off 

 by the action of concentrated hydrobromic acid. The iron is 

 oxidized to the ferric condition and the organic matter is destroyed 

 by potassium permanganate. The resultant solution is mixed 

 with a solution of ammonium sulphocyanate in water and acetone 

 and the color is compared with that of a standard iron solution 

 similarly treated. 



Procedure. Blood is obtained in the usual manner for deter- 

 mining hemoglobin with the Sahli apparatus, by pricking the finger 

 or ear lobe. To 0.040 c.c. of blood, measured in a calibrated pipette, 

 mixed with 2 c.c. of water and 0.2 c.c. of 0.1 N HC1, 2 c.c. of 0.1 N 

 KMn04 are added. Then the mixture is placed in a water bath 

 for about two minutes, when a brownish red coagulum results, 

 supernatant above a colorless or slightly yellowish fluid. To this 

 two drops of concentrated hydrobromic acid are added. The 

 tube is returned to the water bath for another two minutes. 

 The product should be a water-clear fluid containing a few whitish 

 flakes. The solution is filtered through acid-washed filter paper 

 into a long narrow graduate. Washings are added until the 

 filtrate has reached the 5 c.c. mark. Then 5 N NH^CNS is added 

 up to 10 c.c., and acetone up to 20. The graduate is stoppered, 

 and the fluids are mixed. A shrinkage of volume occurs. Acetone 

 is added again to the 20 c.c. mark, and the graduate is stoppered. 

 A salmon-red color is produced. 



The standard, which may be prepared at the same time as the 

 blood, is made by adding two drops of concentrated hydrobromic 

 1 Berman: Jour. Biol. Chem., 1918, 35, 231. 



