THE enormous amount of heat evolved during the combustion of aluminium has been applied, in recent years, to several industrial operations. The following easily performed eXperiment shows in a striking manner the possibilities of the new thermic agent. The amateur is warned, however, that the mixture is highly explosive and must be handled with care, preferably in the open, out-of-doors. An egg-shell furnace. Most people would think that the melting of a large gold or silver coin requires some pounds of coal, a furnace and some time. The idea is not unreasonable, as gold melts at 1,064 deg. C. and silver at 960 deg. C. As a matter of fact, however, a sil ver quarter can be changed within a few seconds into a liquid sphere with the amount of combustible contained in one half of an egg shell, and in a furnace which is the egg shell itself, no blast whatever being used. The feat requires the use of the Ifollowing mixture: Al umini um P'Owder ............................. 17 Flowers of sulphur ............................. 15 Potassium nitrate ............................. 52 100 The saw dust and tbe powdered potassium nitrate are dried separately on the kitchen stove. When cold they are mixed with the other two ingredients. The mixture is then compressed into one half of a dry egg shell. The silver quarter is laid over it, as sbown in the accompanying figure, and a match is applied to the composition. The molten silver coin always collects itself into one single lump, which remain” highly luminous some time after the combustion is over.
This article was originally published with the title "An Experiment with Aluminium Powder" in Scientific American 105, 5, 103 (July 1911)