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Scientific Proceedings (126) 



Sodium phosphate at P H 7.0 completes the precipitation of 

 fibrinogen at an approximately molar P0 4 solution and the differ- 

 ence for subsequent fractions is 0.25 mol. By varying the pro- 

 portions of mono-sodium and di-sodium phosphate to obtain 

 solutions of similar molecular concentration with regard to the 

 P0 4 radicle, but with varying hydrion concentrations, it was 

 found that higher molecular concentrations were required for 

 the precipitation of the various protein fractions. By adjusting 

 the concentrations of the phosphate solution at each P H to con- 

 centrations of sodium which were equal to the sodium content of 

 solutions which were 1.0, 1.25, 1.50 and 1.75 molar with regard 

 to the phosphate radicle at P H 7.0, it was found that between ap- 

 proximately P H 8.0 and 5.8 essentially the same amount of pro- 

 tein was precipitated as at P H 7.0. If the precipitations be made 

 with concentrations of sodium phosphate at P H 7.0 which are 

 such that they are equal in sodium concentration to the sodium 

 sulfate solutions, essentially similar results are obtained with the 

 two salts for each protein fraction. In fact, the sodium concen- 

 trations of the fractional molar concentrations with relation 

 to the phosphate radicle given above differ only slightly from 

 those of concentrations found for sodium sulfate. 



When the proteins of serum were precipitated with the differ- 

 ent sodium phosphate solutions no precipitation occurred until 

 the equivalent of 1.25 molar phosphate at P H 7.0 was added, i.e., 

 no fibrinogen was present. If the serum of the new-born calf 

 was used, precipitation did not occur until the equivalent of 1.75 

 molar phosphate at P H 7.0 had been added, or only a slight pre- 

 cipitation occurred at 1.50 molar. On the other hand, if the 

 plasma of the new-born calf was used, precipitations occurred at 

 the equivalent of 1.0 molar phosphate and no increase was ob- 

 served until a concentration above 1.50 molar was reached, i.e., 

 fibrinogen, euglobulin and pseudoglobulin I were absent from 

 serum and fibrinogen was present in the plasma. 



In all of these cases we were dealing with a constant concen- 

 tration of sodium but with varying concentrations of the phos- 

 phate radicle — a range of approximately 0.8 mol. for any range 

 of the hydrion concentrations. It appears, therefore, that the 

 precipitation of the proteins of blood at hydrion concentrations 

 below the neighborhood of the isoelectric point is primarily due 

 to the cation. 



