Abstract: A gaseous contaminate personal dosimeter which comprises a container; an inert porous thin barrier element forming one side of the container, the barrier element adapted to permit the diffusion of the gaseous contaminates that are to be determined into the interior of the container; and a gaseous contaminate-collecting medium within the container and positioned opposite the barrier element to collect gaseous contaminate diffused from the ambient atmosphere through the barrier element; and means to inhibit convection movement of the diffused gases within the container, whereby the dosimeter permits the determination of gaseous contaminate in proportion to ambient concentrations independent of ambient convection patterns.

Abstract: A process of concentrating an aqueous polyvinyl-chloride emulsion employing a membrane device comprising a feed zone and a permeate zone, the zones separated by an ultrafiltration semipermeable membrane, which process comprises: introducing the polyvinyl-chloride emulsion to be concentrated into the feed zone; removing a concentrated polyvinyl-chloride emulsion from the feed zone and removing an aqueous fraction from the permeate zone; interrupting the process of concentration periodically when the flux rate of the process falls below a desired flux rate value; and contacting the semipermeable membrane with a solution containing a solvent, such as tetrahydrofurane, for the polyvinyl-chloride for a time sufficient to restore the flux value to its desired level, the semipermeable membrane employed characterized by being solvent-resistant to the solvent employed in contacting the membrane.