noun
also grad·a·col membrane ˈgradəˌkȯl-, -käl-
Etymology: German gradokol, from grado- (from International Scientific Vocabulary grade ) + kollodium collodion
: a collodion membrane prepared from a solution of collodion in alcohol and ether in such a way as to have a predetermined average pore diameter and used especially in ultrafiltration (as of a virus suspension)