Aluminum. This is the metallic base of alumina, which is the plastic principle of certain kinds of clay. The color of aluminum is white, inclining to blue; it is very malleable, and ductile. Its specific gravity is only about 2.60; its melting point not less than 1000° Fahr. It is the most sonorous of all metals. It is thus obtained:- Make a thick paste of alumina, powdered charcoal, sugar, and oil, and heat it in a covered crucible until all the organic matter is destroyed; then transfer the product to a porcelain tube, and connect the one end with another tube containing dried chloride of calcium, and the other end with a small tubulated receiver. Then expose the porcelain tube to the heat of a small oblong furnace, and, having connected the chloride of calcium tube with a vessel disengaging chlorine, pass the gas through the apparatus, at the same time raising the heat of the tube to redness. In 1 or 2 hours, or as soon as the tube becomes choked, the whole must be allowed to cool, and taken to pieces, and the sesquichloride of aluminum thus formed collected. Then place 9 or 10 pieces of potassium, of about the size of peas, in a platina crucible, and upon them an equal number of similar pieces of the sesquichloride of alumina, formed as above; the cover is now to be put on and secured in its place with a wire, and the heat of a spirit lamp cautiously applied, until the spontaneous incandescence of the matter ceases. "When cold, throw the crucible into a large vessel of cold water, agitate and collect the gray powder deposited, and again wash it well and dry it. This gray powder consists of small metallic scales, resembling platina. It is not acted on by cold water, but is dissolved by the alkalies and some of the acids. Heated to redness, it catches fire and burns with great rapidity in the air, and in oxygen gas, with intense brilliancy. The powder, blown upon the flame of a candle, displays an immense number of inflamed points of great splendor.

3331. T6" Polish Aluminum

3331. T6" Polish Aluminum. The substances generally employed for polishing aluminum are of no utility. Mouray recommends the use of an emulsion of equal parts of rum and olive oil, made by shaking these liquids together in a bottle. "When the burnishing stone is used, the peculiar black streaks first appearing should not cause vexation, since they do not injure the metal in the least, and may be removed with a woolen rag. The objects in question may also be brightened in potash lye, in which case, however, care must be taken not to make use of too strong a lye. For cleaning purposes, benzole has been found best. Objects of aluminum can be electroplated without the least difficulty, and Mouray succeeded in imparting to them a bright, white lustre in passing them successively through a weak hath of hydrofluoric acid and aqua fortis. The effect thus obtained is said to he really surprising.

3332. To Frost Aluminum

3332. To Frost Aluminum. The metal is plunged into a solution of caustic potash. The surface, becoming frosted, does not tarnish on exposure to the air.