Abstract: A membrane for hemodialysis is prepared by casting, extruding or spinning a solution of a polyether-polycarbonate block copolymer and a swelling agent having a molecular weight of about 1,000 to about 20,000 Daltons, then partially evaporating the solvent, gelling and washing. The membrane has a top cut-off value less than about 68,000 Daltons, and hence is substantially impermeable to albumin, but nonetheless provides high permeability to water and to other small molecules.

Abstract: A filtration membrane is disclosed which has an ultrafiltration rate of between 200.times.10.sup.-4 and 500.times.10.sup.-4 ml/sec..times.cm.sup.2 .times.bar at 20.degree. C. and which is substantially impermeable to albumin of a molecular weight of about 44,000 or greater. A process for producing a filtration membrane is also disclosed in which a polymer solution is extruded with a center liquid under conditions such that the ratio of the volume of polymer solution to the volume of center liquid is within the range of from about 2:1 to about 4:1 to form a membrane extrudate.

Abstract: Apparatus for hemofiltration is disclosed, including a reverse osmosis module for purifying an impure supply of water, a container for adding concentrate thereto and preparing a replacement liquid, a semipermeable hemofiltration membrane filter for filtering the supply of blood and the replacement liquid in order to produce an ultrafiltrate stream and a filtered blood stream from the supply of blood and a filtrate stream from the replacement liquid so that the filtered blood and filtrate streams can be mixed and returned to the patient.

Abstract: Apparatus for separating a liquid, such as whole blood, into fractions having different densities includes a separation chamber and a transfer device, such as a continuous piece of flexible tubing, for supplying the liquid to the separation chamber and discharging the liquid fractions therefrom. The separation chamber and the transfer device are conjointly rotated about a first axis which passes through a stationary end of the transfer device, while being simultaneously and conjointly rotated about a second axis which is coincident with a medial longitudinal axis of the rotating end of the transfer device so as to prevent the transfer device from twisting as a result of its rotation about the first axis.