GB674476A - Improvements relating to fire-extinguishing compositions - Google Patents

Abstract

Sodium bicarbonate is rendered free-flowing by coating the particles thereof with a metallic salt of a fatty acid or a material equivalent to such a salt in its capacity to form a protective layer, and mixing the coated particles with porous silica capable of forming a paste with at least its own weight of water, such as kieselguhr, diatomite, fossil flour, infusorial earth, silica gel, adsorbent silica and silica aerogel. Up to 10 per cent of an inert filler such as clay, talc or calcium carbonate may be present. Aluminium, barium, calcium, lead, lithium and zinc salts of lauric, myristic, palmitic and stearic acids, beeswax or solid fatty acids such as palmitic acid may be used but magnesium stearate is preferred. Both the sodium bicarbonate and silica are preferably ground so that 99 per cent passes through a 200 mesh sieve. The preferred composition contains 97-98.25 per cent sodium bicarbonate, 1.25-2 per cent of the metallic salt and 0.5-1 per cent porous silica.