Excerpt from Discovery, 1920, Vol. 1: A Monthly Popular Journal of Knowledge

Since the supply of phosphorus was limited. And it was urgently needed by the army as a smoke-producing substance, the necessity arose of replacing it by some smoke-producing material which could be stored in appropriate floats on the decks of merchantmen or other vessels, the floats then being lit and thrown overboard when occasion demanded. The late Wing Commander Brock, Commanding Officer of the Royal Naval Experimental Station, Stratford, E devised a mixture which was really a firework com position, modified in such a way, by the addition of resinous and other carbonaceous material, that a dense smoke was produced on burning. This mixture was placed in tin canisters contained in a wooden box, each canister being connected by a fuse to a match composition (suitably protected) on the outside of the box, and which could be fired by friction. Near the top of the sides of the box were a number of small holes, that were plugged by a composition which would easily be blown out by the pressure set up in the box by the gases produced in the burning of the smoke mixture. The boxes were so arranged that they floated in water, the top side uppermost, and all that was necessary, in using them, was to strike the friction tab and then, when it was certain that they had started functioning correctly, throw them overboard. The results obtained were not very satisfactory, however, owing to the difficulty of keeping the boxes watertight, and the smoke-mixture free from moisture. Also, the smoke produced suffered from the same de feets as the fuel-funnel-smoke.

There are several chlorides of metals and non metals, such as stannic chloride, antimony penta chloride, silicon tetrachloride, etc., which give a good smoke when decomposed by the moisture of the atmo sphere, Or especially when a fine spray of the liquid is mixed with a fine spray of liquid ammonia; stannic chloride especially gives a very good cloud under such conditions (see English Patent To use these substances, however, they have to be stored in heavy steel cylinders under a considerable pressure of air, in order to force them out as a spray through a syphon tube; the dead weight of the containing-vessels is thus very large in comparison with the weight of smoke producing material. Moreover, the contents of a cylinder are discharged in the short time of 6 - 8 minutes. This method of producing smoke is therefore not very convenient on a large scale, but it has the advantage that smoke can be produced instantly, and in quantity, by the mere turning of a tap.

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