to the surface. The air is then expelled by a stream of carbonic acid gas and the tube is heated, without interrupting the current of gas, till the metal is all dissolved.

Aluminium amalgam decomposes in contact with air or water more quickly than sodium amalgam. When a few drops of an amalgam containing but a small proportion of aluminium are left in contact with moist air, gelatinous, opalescent excrescences of pure hydrated alumina are seen to form on their surfaces, exhibiting both in their form and mode of growth considerable resemblance to the so-called Pharoah's serpents. This hydrated alumina is perfectly soluble in acids and alkalies. Water has the same effect as moist air. Watts, in vol. viii., states that aluminium oxidizes when its surface is rubbed with a piece of soft leather impregnated with mercury. The rubbed surface becomes warm, and in a few seconds whitish excrescences appear, consisting of pure alumina. The presence of mercury appears necessary to produce the result.

Fremy says that Tissier has proven that aluminium previously contaminated with caustic potash or soda combines easily with mercury. The alloy which results is very brittle, the aluminium in it decomposes water, oxidizes easily in the air, and behaves as a metal of the alkaline earths.

Gmelin* states that potassium amalgam intro

* Hand Book, vi. 3.

duced into a hole bored in a crystal of alum immediately acquires a rotary motion, which lasts sometimes half an hour. At the same time, it takes up a considerable quantity of aluminium and becomes more viscid.

ALUMINIUM AND COPPER.

Tissier Bros., 1858: "Just as copper increases the hardness of aluminium, so aluminium in small proportions increases the hardness of copper. However, aluminium does not injure its malleability, but makes it susceptible of taking a beautiful polish, and, according to the proportions, varies its color from red gold to pale yellow. These facts were announced some time back by Dr. Percy, in England, who made the alloy by introducing copper into the mixture of cryolite and sodium which he was reducing. We have made large quantities of these alloys, and we may say that they leave nothing to be desired in regard to lustre or color to make them perfect imitations of gold. They alter much less by successive fusions than the alloys of copper with zinc and tin employed for the same object. A ten per cent aluminium alloy was harder than our gold coin, took a fine polish by burnishing, and had the color of pale jeweller's gold; it could be forged and worked the same as copper. The five per cent. aluminium alloy was less hard than the preceding, but, like

it, takes a fine polish, and in tint approaches nearly to pure gold. The twenty per cent. aluminium alloy much resembles bismuth, having a whitish-yellow tint. This alloy crystallizes in large leaves and pulverizes in the mortar like bismuth or antimony. Alloys with five to ten per cent. of aluminium may have their color changed at will, either by leaving in nitric acid, which takes away the copper and leaves the aluminium, or in hydrochloric, which leaves the copper. The resistance, hardness, and elasticity, which are communicated to copper by introducing small quantities of aluminium, will certainly make these important industrial alloys."

Deville, 1859: "The aluminium and copper alloys with two to three per cent. aluminium are used by M. Christofle, who employs them for large castings of objects of art. They are harder than aluminium, and work well under the burin and chisel. The alloy with ten per cent. aluminium had its useful properties first described by M. Debray. It is very hard, can be beaten out cold, but with remarkable perfection when hot, and may be well compared to iron, which it resembles in all these physical properties. It is also very ductile. This ten per cent. aluminium alloy is usually known as aluminium bronze. It behaves as a true alloy, and, in consequence, will not liquate into different combinations. It is formed of

This is proven by the fact that, when in making the alloy the pure copper is in the crucible and a bar of aluminium is added, the combination takes place with such disengagement of heat that if the crucible is not of good quality it will be fused, for the whole becomes white hot.

"The color of the ingot of bronze is exactly that of 'green gold,' an alloy of gold and silver. The bronze receives a beautiful polish, being comparable in this regard only to steel. Its chemical properties do not differ much from those of most of the alloys of copper. However, in numerous experiments, we have noticed that it resists most chemical agents much better than these, especially sea-water and sulphuretted hydrogen. Its tenacity is equal to that of steel. M. Lechatelier made the following determinations on the metal cast into cylinders:

"A. Gordon made some experiments recently, in

which the strength of the aluminium bronze which

he tested was 84.00 kilos per square millimetre. I made the test on some wire, and the result I reached was 85.00 kilos; under the same conditions iron gave 60.00 and best steel 90.00 kilos. According to experiments as to its wear as journal boxes, it is found to wear away less than any other journal metal yet tried.

"Its malleability is almost perfect, as is seen by the following report of M. Boudaret, a practical engineer: First, aluminium bronze is malleable at all temperatures, from bright red to cold; second, it is perfectly malleable at red heat, breaking less and elongating more than pure copper; third, it is hard to roll in the cold, after several passes it ceases to elongate and must then be annealed very often or it will break quickly; fourth, it results from the foregoing that it is best to roll it at as high a heat as possible below fusion; fifth, annealing and tempering render it softer than simple annealing. If after having annealed at bright red heat it is let cool in still air to redness and then plunged into cold water, it is ductile and malleable enough in the cold to stand all industrial working."

Mierzinski, 1885: "Two points are to be attended to in making aluminium bronze. First, a very pure copper must be used, the best is that electrically deposited, but it generally costs too much. The next best is the Lake Superior brand. The usual commercial copper gives all sorts of poor results, owing to the antimony, arsenic, tin, zinc,