GB810816A - Process for the preparation of therapeutic magnesium aluminate hydrate - Google Patents

Abstract

A magnesium aluminate hydrate, probably having the formula <FORM:0810816/III/1> is prepared by reaction of an alkali metal aluminate solution and a magnesium salt solution at not above 50 DEG C. The aluminate solution contains 3-5 mols. of alkali metal oxide per mol. of Al2O3, and the quantities of reactants are such that the atomic ratio Al/Mg=0.9-3, preferably 2. The product is separated as a precipitate, washed until it contains not more than 0.5 per cent of water-soluble salts and left undried or dried at not above 120 DEG C. The magnesium salt may be the sulphate, chloride, bromide, iodide, nitrate or acetate, Examples of some of these being given. The alkali metal aluminate may be prepared by reacting an aluminium salt (such as a sulphate, chloride, bromide or nitrate, all of which are exemplified) and an alkali metal (e.g. sodium) hydroxide in solution, 6-8 mols. of the latter being employed for every gram atom of aluminium. It is preferred to add the alkali metal aluminate to the rapidly stirred magnesium salt solution in the form of one or more thin jets to facilitate even distribution; alternatively, both solutions may be introduced in the form of jets into stirred water or previously prepared magnesium aluminate hydrate. After filtering or centrifuging the solid, which in Example 1 is colloidal and washing, e.g. by decantation, the product may be dried, generally at below 70 DEG C., under vacuum if desired. Using short-drying times, a temperature of e.g. 110 DEG C. may be used (roller drying and spray drying with a 6-15 per cent by weight aqueous suspension at 60-100 DEG C. are mentioned). Thereafter, if necessary the product is comminuted in a ball or vibratory mill, e.g. to 0.10-0.12 mm. particle size. The product (which may be used as an antacid, see Group VI) has strong buffering properties for acids, in the pH range of 3-5, details being given in respect of hydrochloric acid. The pH value of a suspension in water is 9-11. British Specification 697,231, U.S. Specification 2,721,861, Swiss Specification 128,889 and German Specifications 70,175, 93,857, 244,211, 466,310, 506,146 and 508,460 are referred to.ALSO:A magnesium aluminate hydrate, suitable for use as an antacid, and probably having the formula <FORM:0810816/VI/1> is prepared by reaction of stated proportions of solutions of a magnesium salt and an alkali metal aluminate (see Group III). It may be used as a suspension in water, to which if desired other medication, inactive agents or aromatics may be added, or may be dried at not more than 120 DEG C. and if necessary comminuted, and used as a powder or formed into tablets containing at least 0.39 of the material. Specification 697,231, [Group III], and U.S.A. Specification 2,721,861 are referred to.