Tons        Value
Silicon carbide       8,323       $1,074,152
Aluminum oxide       48,463        6,969,387

A new use for carborundum was found during the war when Uncle Sam assumed the role of Jove as “cloud-compeller.”  Acting on carborundum with chlorine—­also, you remember, a product of electrical dissolution—­the chlorine displaces the carbon, forming silicon tetra-chloride (SiCl_{4}), a colorless liquid resembling chloroform.  When this comes in contact with moist air it gives off thick, white fumes, for water decomposes it, giving a white powder (silicon hydroxide) and hydrochloric acid.  If ammonia is present the acid will unite with it, giving further white fumes of the salt, ammonium chloride.  So a mixture of two parts of silicon chloride with one part of dry ammonia was used in the war to produce smoke-screens for the concealment of the movements of troops, batteries and vessels or put in shells so the outlook could see where they burst and so get the range.  Titanium tetra-chloride, a similar substance, proved 50 per cent. better than silicon, but phosphorus—­which also we get from the electric furnace—­was the most effective mistifier of all.

Before the introduction of the artificial abrasives fine grinding was mostly done by emery, which is an impure form of aluminum oxide found in nature.  A purer form is made from the mineral bauxite by driving off its combined water.  Bauxite is the ore from which is made the pure aluminum oxide used in the electric furnace for the production of metallic aluminum.  Formerly we imported a large part of our bauxite from France, but when the war shut off this source we developed our domestic fields in Arkansas, Alabama and Georgia, and these are now producing half a million tons a year.  Bauxite simply fused in the electric furnace makes a better abrasive than the natural emery or corundum, and it is sold for this purpose under the name of “aloxite,” “alundum,” “exolon,” “lionite” or “coralox.”  When the fused bauxite is worked up with a bonding material into crucibles or muffles and baked in a kiln it forms the alundum refractory ware.  Since alundum is porous and not attacked by acids it is used for filtering hot and corrosive liquids that would eat up filter-paper.  Carborundum or crystolon is also made up into refractory ware for high temperature work.  When the fused mass of the carborundum furnace is broken up there is found surrounding the carborundum core a similar substance though not quite so hard and infusible, known as “carborundum sand” or “siloxicon.”  This is mixed with fireclay and used for furnace linings.