Xvi. the Ultrafiltration of Proteins through Graded Collodion Membranes

THE behaviours of protein solutions when filtered through membranes of graded porosities under different conditions of PH and dispersion medium have been further studied in the case of haemocyanin (Helix pomatia), edestin and egg albumin. The particle sizes of these proteins in dilute solution have been determined by Svedberg and his co-workers by the method of ultracentrifugal analysis, the respective values being 24, 8 and 4 34m,u. The purpose of our present study has been to ascertain the conditions most favourable for the filtration of these proteins in a manner similar to that followed for the serum proteins [Elford and Ferry, 1934], and to establish for each the filtration end-point. A means is then provided of checking further the value of the empirical correction factor adopted by Elford [1933] for deducing the particle size of a suspension from the pore diameter of the limiting membrane by which it is just completely retained. The experimental ultrafiltration technique has been exactly as described in the earlier paper dealing with the serum proteins [1934]. The analyses of filtrates have been based upon refractometric measurements and controlled precipitation tests with salicylsulphonic acid. The stock protein solutions were always sterilised by filtration through a suitable membrane.