188 Aluminium. 



M. Hulot, director of the Mint at Paris, discovered that 

 aluminium may be used in the galvanic battery, instead of pla- 

 tina, zinc being employed as the electro-negative element. It 

 had long before been ascertained by Wheatstone, that it is as 

 strongly negative as that metal. It becomes soiled, however, 

 after a while, but may be cleansed by immersion for an instant 

 in nitric acid, and washing with water. 



Aluminium unites very imperfectly with lead, and only tem- 

 porarily with mercury. It combines with small quantities of 

 sodium, which changes its properties, and is with great diffi- 

 culty separated from it entirely. It alloys with iron, in all pro- 

 portions : but seven or eight per cent, makes it hard and brit- 

 tle. Cadmium, tin, and zinc, render it fusible. Two or three 

 per cent, silver, gives it a hardness and colour, equal to that 

 of the silver alloy which is commonly used ; a larger quantity 

 destroys its malleability. If any chlorine is present, which, 

 unless it is very pure, will probably be the case, the silver 

 alloy soon blackens. Aluminium containing ten per cent, gold 

 is softer than when pure, but not so malleable. Its most im- 

 portant combinations, however, are those which it forms with 

 copper : if it contains two or three per cent, of that metal, it is 

 aluminium bronze, a material well adapted for artistic, and 

 many other purposes : if it contains ten per cent, it is as 

 brittle as glass. Ten per cent, aluminium, and ninety per 

 cent, copper, gives an alloy which, though harder than com- 

 mon bronze, laminates extremely well — particularly if it is 

 heated, and is very ductile. The last is a definite compound, 

 since it is in the proportion of nine atoms copper to one of 

 aluminium, and great heat is disengaged during combination : 

 hence its constituents do not separate by fusion and cool- 

 ing. Its colour is that of green gold, which consists of gold 

 and silver : and it is capable of as fine a polish as steel. Its 

 tenacity is very great ; and, compared with that of copper and 

 iron, is found to be as follows — 



Copper 190 



Iron 280 



Aluminium Bronze 434 



It answers well for the material of axle-bearings, and similar 

 parts of machinery : after having been used for six months 

 with a steam-engine, it showed no wear ; and it lasted eighteen 

 months, in a machine which made two thousand two hundred 

 revolutions per minute, while any other substance, in the cir- 

 cumstances, was found to last only three months. Possessing 

 hardness without brittleness, it sustains shocks uninjured : and 

 is well adapted for artillery, or the barrels of firearms. 



It is difficult to gild or silver aluminium : baths of acid 



