The ferrohemoglobin solubility test; its accuracy and precision together with values found in the presence of some abnormal hemoglobins.

METHODS A 2.8M phosphate buffer is prepared by dissolving 21.7 Gm. dibasic potassium phosphate (K2HPO4) and 16.9 Gm. monobasic potassium phosphate (KH2PO4) in distilled water free of CO2. The volume is adjusted to 100 ml. To 1.8 ml. of this buffer, 20 mg. of sodium hydrosulfite (Na2S2O4) and 0.2 ml. of buffered hemolysate (3) are added in a small test tube. After 15 minutes or longer the mixture is filtered through Whatman paper No. 5, and 0.2 ml. of ifitrate is added to 3.8 ml. of the same phosphate buffer containing 20 mg. sodium hydrosulfite. A control is prepared by adding 0.1 ml. of hemolysate to 20 ml. of distilled water. Readings of the control and the test sample are made in a spectrophotometer at 415 mjs. Solubility (expressed as per cent) is calculated by dividing the absorbancy of the test sample by the absorbancy of the control and multiplying the result by 100.