Abstract: Purification of aqueous hydrogen peroxide solutions using conventional ion-exchange techniques can result in the hydrogen peroxide decomposing explosively. Much safer processes are obtained by restricting the contact between the resin bed and the hydrogen peroxide solution to a very short contact time, by employing a treatment chamber that is vented to the atmosphere and also by slurrying the resin bed. The bed is conveniently retained on a mesh that acts as a filter (13) preferably conical having an aperture (17) at its apex through which is introduced a small fraction of the solution countercurrent (10) to the main solution flow (9) in order to slurry the bed (19). The solution can be recycled through the same bed or a plurality of beds. Very high purification can be achieved and combined with improved safety of operation.

Abstract: Strontium-modified aluminium alloys may be produced by using strontium peroxide as the source of strontium. The strontium peroxide may be mixed with molten aluminium or molten aluminium alloy in a quantity sufficient to give the desired strontium metal content in the alloy being produced. The temperature of the molten aluminium or aluminium alloy with which the strontium peroxide is mixed is preferably at least 1000.degree. C.The strontium peroxide alloys produced may be master alloys for use in the production of casting alloys, or may be casting alloys. Strontium acts as a grain refiner in such alloys.

Abstract: A .delta.- or .epsilon.- lactone is heated in the vapour phase and the presence of a cracking catalyst to form a monounsaturated acyclic carboxylic acid. For example .epsilon.-caprolactone gives .delta. - .epsilon. hexenoic acid. This acid is then cyclised by heating with a strong protonating agent. In the example the product is .gamma.-caprolactone or 4-hexanolactone.

Abstract: A feed material containing the group --O--(CR.sub.2).sub.n --CO-- in a macrocyclic ring or acylic chain is heated to between 300.degree.C and 500.degree.C in the absence of a catalyst to give a mono-unsaturated acyclic carboxylic acid. For example polymeric .epsilon.-caprolactone gives .delta.-.epsilon. hexenoic acid. This acid is then cyclised by heating with a strong protonating agent. In the example the product is .gamma.-caprolactone or 4-hexanolactone.