294 EARTHS. 



(/.) The mass in the crucible is found to be melted, and of a dark 

 gray color, and when put into water after it is cold, the saline matter 

 is dissolved, an offensive hydrogen gas is evolved, and metallic scales 

 remain, which after being thoroughly washed in cold water,* are pure 

 aluminium. 



3. PROPERTIES; 



(a.) A gray powder very simitar to that of platinum, in small me- 

 tallic scales or spangles, or in slightly coherent spongy masses, hav- 

 ing in some places a tin white lustre, rendered more distinct by pres- 

 sure on steel, or in an agate mortar. 



(b.) In fine powder, a non-conductor of electricity, but becomes a 

 conductor after fusion, f 



(c.) Fusible at a higher heat than that which melts cast iron. 



(d.) Ignited in the air, it burns vividly, and the product is alu- 

 minous earth, white and considerably hard ; sprinkled in powder, in 

 the flame of a candle, it gives bright scintillations, like iron in oxygen 

 gas. 



(e.) Ignited in pure oxygen gas, it burns with great heat and light, 

 and the resulting alumina is partially vitrified, yellowish, and hard as 

 corundum ; it even cuts glass. When burning in glass, it appeared 

 to reduce the silicium, producing a semi-fused brown spot. 



^/.) Near ignition, it burns in chlorine gas, and chloride of alu- 

 minium is formed. 



(g.) Not oxidized nor tarnished by cold water ; near ebullition, 

 hydrogen gas is feebly evolved, and scarcely any oxidizement is ob- 

 served. 



(h.) No action with strong sulphuric or nitric acid in the cold, 

 but with heat, the former is decomposed, and sulphurous acid gas 

 evolved ; it is dissolved in dilute muriatic and sulphuric acid, and 

 hydrogen gas extricated. 



(i.) Dissolved readily and entirely in dilute solution of potash, 

 and even in ammonia, hydrogen gas being evolved, and much alu- 

 mina held in solution.j 



4. COMBINING WEIGHT. Not accurately ascertained ; it has been 

 already stated, that the number 10 has been adopted, and that it 

 combines with one proportion of oxygen, 8, to form alumina, whose 

 equivalent is of course, 18* 



* The solution is neutral, and contains some alumina, formed, as it is said, in con- 

 sequence of a combination between chloride of potassium, and chloride of aluminium. 



t It is remarkable, as Dr. Wohler observed, that metallic iron, in fine powder, is 

 a non-conductor of electricity, so that this property of metals seems to depend on 

 their form, or, possibly, on intervening air. Perhaps if silicium were melted, it 

 might become a conductor, and thus be assimilated to the metals. 



J Dr. Brewster's Journal, No. 17, p. 178. 



