| 摘要 |
Fire-fighting foam effective against burning hydrophilic or polar liquids like lower alcohols, ketones, etc. is made from concentrate containing thixotropic thickener dissolved in large amount, up to 1.5% or more, yet has a tolerable viscosity so that it can be poured or pumped. Heteropolysaccharide-7 or chain-shortened modifications of it are particularly suitable for this purpose. Higher concentrations are made practical by including in the concentrate urea, thiourea, ammonium cyanate or ammonium thiocyanate, to reduce the concentrate's viscosity and keep the polysaccharide from separating out upon freezing. Magnesium salts can also be dissolved in concentrate to improve fire extinguishing action when diluted with fresh water.
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