Abstract: A water purification device comprises a compartment for holding a supply of impure water; a purified water collection zone; and a dense hydrophilic membrane between the compartment and the purified water collection zone. The membrane is capable of functioning by membrane distillation. A water vapour condensing surface is provided in the purified water collection zone. The condensing surface is spaced from the membrane.

Abstract: The invention provides a method for the solvent-extraction of .beta.-carotene from an aqueous algal biomass suspension, whereby a vegetable oil which is immiscible with water is mixed with an aqueous biomass suspension, the biomass containing the .beta.-carotene, to form a mixture of the organic phase and the aqueous suspension, whereby the .beta.-carotene is caused to dissolve in the organic phase. This is followed by separation of the organic phase from the aqueous phase by passing the organic phase containing the dissolved .beta.-carotene through a semi-permeable membrane to effect microfiltration or ultrafiltration of the organic phase. The membrane is of a material which is hydrophobic and the organic phase is passed through the membrane with a pressure drop across the membrane which is lower than that which causes the aqueous phase to pass through the membrane.

Abstract: A method of preparing a semi-permeable membrane suitable for reverse osmosis includes contacting a porous artifact with an hydrated metal oxide, to form an hydrated metal oxie coated artifact. Thereafter the hydrated metal oxide coated artifact is contacted with at least one polyelectrolyte selected from the group listed in claim 1, thereby to form a polyelectrolyte layer in or on the hydrated metal oxide layer.

Abstract: The invention provides a method of coating a surface comprising the application of one or more layers to a substrate to be coated, one of the layers being a barrier layer containing stainless steel flakes. The invention also provides an article having a surface coated according to the method. The layers include, in addition to the barrier layer, one or more of an impregnant, an undercoat and a reinforcement layer. The layers are applied in the order of the impregnant, the undercoat, the reinforcement layer, and the barrier layer.