The Second International Standard for heparin.

The Second International Standard for Heparin is a hygroscopic powder which was obtained by purifying and drying a batch of commercial beef heparin powder. In an international collaborative assay it was compared with the First International Standard, which it will now replace. As a result of the assay the seven participating laboratories agreed that the potencies of the two preparations did not differ significantly and the definition of the International Unit for Heparin remains unchanged as the activity contained in 0.0077 mg of the Second International Standard for Heparin.