A composition which on being combusted in the atmosphere produces aerosols for the purpose of fog clearing, cloud seeding and weather modification, comprises one or more of the metals aluminum, magnesium, alkali metal and alkaline earth metal, at least one powdered oxidizing agent, and a solid, stable hygroscopic substance which is adapted, on combustion of the metal and oxidizing agent, to produce nuclei for condensation. The hygro-scopic substance, which may be mixed with the other materials or be in the form of a central core, is sodium or potassium metal (when it forms the core) or sodium or potassium chloride, or sodium azide, and the oxidizer may be a nitrate, (preferably of Na or K), sulphur or a sulphur-containing substance, an ammonium or alkali metal chlorate or perchlorate, or an unspecified peroxide. The hygroscopic substance and the metal in the combustible composition are preferably in powder form, and a mixture of the powdered components, including a binder if the mixture is to be extruded, is placed in a container made of aluminium, magnesium, or aluminium or magnesium alloy, or glass fibre-impregnated resin, and a fuze is placed in the charge. Examples are described, and one of them comprises powdered aluminium, sodium nitrate and sulphur, the aluminium sulphide formed on combustion acting as condensation nuclei.ALSO:A composition which on being combusted in the atmosphere produces aerosols for the purpose of fog clearing, cloud seeding and wheather modification, comprises one or more of the metals aluminium, magnesium, alkali metal and alkaline earth metal; at least one powdered oxidizing agent; and a solid, stable hygroscopic substance which is adapted, on combustion of the metal and oxidizing agent, to produce nuclei for condensation. The hygroscopic substance, which may be mixed with the other materials or be in the form of a central core, is sodium or potassium metal (when it forms the core) or sodium or potassium chloride, or sodium azide, and the oxidizer may be a nitrate (preferably of Na or K), sulphur or a sulphur-containing substance, an ammonium or alkali metal chlorate or perchlorate, or an unspecified peroxide. The hygroscopic substance and the metal in the combustible composition are preferably in powder form, and a mixture of the powdered components, including a binder if the mixture is to be extruded, is placed in a container made of aluminium, magnesium, or aluminium or magnesium alloy, or glass fibre-impregnated resin, and a fuze is placed in the charge. Examples are described, and one of them comprises powdered aluminium, sodium nitrate and sulphur, the aluminium sulphide formed on combustion acting as condensation nuclei.ALSO:A method of aerosolization in the atmosphere, for the purpose of fog clearing, cloud seeding and weather modification, comprises combusting a composition comprising one or more of the metals (preferably powdered), aluminium, magnesium, alkali metal and alkaline earth metal, and a powdered oxidizing agent, e.g. a nitrate (preferably of sodium or potassium) sulphur or a sulphur-containing substance, ammonium or alkali metal chlorate or perchlorate, or an unspecified peroxide. An additive comprising a hygroscopic salt (sodium or potassium chloride, or sodium azide) or sulphur, or sodium or potassium metal (where the additive forms a core embedded in the composition) is mixed with or juxtaposed near the composition to provide condensation nuclei on combustion of the composition. The composition and additive are located in containers which may be of alluminium or magnesium or alloys thereof, and the charge is provided with a fuze. The complete device may be combusted at ground level, or carried by rocket into the atmosphere, or towed behind or dropped from aircraft, or the composition may be charged with a mortar shell. Delayed aerosolization may be obtained by packing a primed charge (gunpowder) above the composition in the container.
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