exchange for 0 05m tris hydroxymethyl aminomethane 0 15m sodium chloride buffer at ph 6 3 12 grams of plyethylene glycol peg 4000 100 ml eluate 10 grams of peg 6000 100 ml eluate was then added and the mixture stirred for 30 minutes at room temperature the precipitate so formed was isolated by centrifugation dissolved in 0 05m tris 0 15m nacl buffer at ph 7 25 at 1 10 the volume of the initial g 25 eluate the vwf activity was present in this solution as measured by the platelet ristocetin assay analytical characterization of vwf solution showed that platelet agglutination activity gradually increased at room temperature and this increase was amplified by increasing the temperature and prolonging the time of incubation analytical characterization has also shown that the molecular distribution and binding properties of vwf were unaltered under these conditions the data shown in tables i and ii are representative of that obtained according to the present invention table i______________________________________yield and specific activity of vwf vwf specific total activitysample units yield units mg______________________________________cryoprecipitate 44 451 100 0 498solutionunbound pool 10 373 23 34 0 118vwf bound to 34 078 76 66 moab columnlyophilized vwf 18 990 42 72 48 20product______________________________________ table ii______________________________________increase in vwf activityat recovery at incubation specific specific at at unit activity unit activity u00b0 c time sample ml unit mg ml unit mg temp hrs ______________________________________1 2 49 3 77 46 50 70 45 37 25 34 80 52 72 rt 25 54 36 82 31 37 302 1 77 12 33 37 243 1 70 11 50 37 244 1 50 3 00 16 75 33 50.