Abstract: A composition, eg a water-based polymer emulsion, cosmetics and the like, is preserved against microorganism growth, by incorporation of from 5-1000 ppm of an inorganic biocidal component which comprises a sparingly soluble silver compound deposited on a synthetic oxidic support.

Abstract: Novel solid antibacterial compositions suitable for use in an oil or gas well comprise at least 50% by weight of a solid antibacterial nitroalkanol compound active against sulphate-reducing bacteria and a carrier, the composition having a density of at least 1.2 g/cm.sup.3 and being adapted to dissolve, disintegrate or disperse in water but not in oil. A preferred antimicrobial compound is 2-bromo-2-nitropropane-1,3-diol. The antibacterial compositions are introduced into the aqueous layer in the sump at the bottom of the collecting system of the oil or gas well. This inhibits corrosion in the metal work of the oil or gas well, for example the pipe lines of the collecting system.

Abstract: A tablet for use in preserving samples of milk for analysis comprises bronopol (2-bromo-2-nitropropane-1,3-diol) and a water-soluble solid organic carboxylic acid, the amount of the organic acid being within the range 0.002-0.07 milli-equivalents per milligram of bronopol. The presence of the organic acid stabilizes the bronopol, thereby providing a tablet with an adequate shelf life. Suitable organic acids include citric acid, tartaric acid, malic acid, adipic acid, succinic acid and fumaric acid.