Abstract: A capsule 1 (FIG. 1) for the treatment of water in an aqueous heat transfer apparatus comprises open top compartments 2, 3 and luges 6 to bear against and grip the inside of a passage in which the capsule is located. The open tops of the compartments are closed by means of covers of controlled release glass which dissolve in water at different rates. The capsule can be arranged to release a first dose of corrosion inhibitor on exposure to water under relatively milder conditions and a second dose of corrosion inhibitor on exposure to water under relatively severer conditions.

Abstract: A device for the controlled release of an active material into an aqueous medium comprises a water soluble capillary tube (11) the bore (12) of which contains an active material (13). Dissolution of the active material is diffusion limited during a delay period while the capillary is dissolving. When dissolution of the tube is complete rapid dissolution of the remaining active material then takes place.

Abstract: A dispenser for use, for instance, as a rumen bolus is a generally cylindrical container (1) for material to be dispersed into the digestive tracts, etc. of a ruminant. The container has a closure (3) held in place by a controlled release glass (CRG) member (5). When this member is dissolved, the closure (3) comes out and the contents are released. The cylindrical container can be formed by a hole in a larger member which has several such holes so that different materials can be released, or materials released at different times.Variants include stacked arrangements in which several dispenser compartments are coupled so that as one is emptied a CRG member is dissolved to release material in the next compartment.In some cases the CRG member acts both as the release device, and as the closure for its compartment, and in others it also acts as a means of linking a number of detachable sections.

Abstract: A porous water soluble glass body is formed by sintering powdered glass, compacted to a predetermined density, at a temperature near the glass softening temperature (T.sub.s). The porous body may be impregnated with an organic material for subsequent release at a rate determined by the glass solubility.

Abstract: A device for the controlled release of an active material into an aqueous medium, e.g. body fluids, comprises a water soluble glass container in which the active material is sealed. The container wall has a region of reduced thickness which region dissolves before the remainder of the container wall to release the active material.

Abstract: A transparent glass article, e.g., for use as an inspection window in contact with water, including at least a surface layer of a glass which is adapted to dissolve at a preselected uniform rate. Slow dissolution of the glass provides a continuously renewable clear surface.

Abstract: A device for the controlled release of an active material into an aqueous medium comprises a porous sintered body of a water soluble glass (11). The pores of the body are filled with a composition (12) consisting wholly or partially of an active material. The device may be provided with a low solubility coating (13). On immersion in an aqueous medium the glass (11) dissolves to become a sponge-like structure having a plurality of convoluted capillaries and from which the active material is released.