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cipitated from copper salts; Pb is slowly precipitated from lead salts; Ag is precipitated from a slightly acid or neutral solution of AgNO3; Zn is readily precipitated from zinc salts.

NITRE.

Deville: Aluminium may be melted in nitre without undergoing the least alteration, the two materials rest in contact without reacting, even at a red heat, at which temperature the salt is plainly decomposed, disengaging oxygen actively. But if the heat is pushed to the point where nitrogen itself is disengaged, there the nitre becomes potassa, a new affinity becomes manifest, and the phenomena change. The metal then combines rapidly with the K2O to give aluminate of potash. The accompanying phenomenon of flagration often indicates a very energetic reaction. Aluminium is continually melted with nitre at a red heat to purify it by the oxygen disengaged, without any fear of loss. But it is necessary to be very careful in doing it in an earthen crucible. The SiO2 of the crucible is dissolved by the nitre, the glass thus formed is decomposed by the aluminium, and the silicide of aluminium formed is then very oxidizable, especially in the presence of alkalies. The purification by nitre ought to be made in an iron crucible well oxidized by nitre inside.

Fremy: At the melting point, aluminium is not

attacked by nitre; this property has been at times utilized to oxidize and then remove the metals alloyed with it, but it is now demonstrated that this mode of purification is very imperfect.

Mierzinski: Heated to redness with nitre, aluminium burns with a fine blue flame.

SILICATES AND BORATES.

Deville: By treating silicates and borates with aluminium silicon and boron may be obtained. The process is described at the end of Deville's book, but is too long and foreign to the subject in hand to be given here.

Tissier: Aluminium melted in an ordinary white glass vessel oxidizes itself at the expense of the SiO2, setting free silicon, and the alumina formed combines with the alkali forming an aluminate. In experiments which we have made, the metal became covered with a thin layer of silicon, while the metal which remained underneath was still malleable and did not appear to be combined with Si.

FLUORSPAR.

Tissier: This salt is without action on the metal and makes its best flux, especially so because of the property which it has of dissolving the alumina with which the metal may be contaminated and

which encrusts little globules. The fluorspar, by dissolving this crust, facilitates their reunion.

PHOSPHATE of Lime.

Tissier: We have heated to white heat a mixture of pure Ca (PO4)2 and aluminium leaf, without the metal losing its metallic appearance. This material thus appears to have no action on the metal.

SODIUM CHLORIDE (NaCl) AND CHlorides.

Deville: A solution of sodium or potassium chloride, in which is put a pure aluminium wire, seemed to me to exercise no sensible action on the metal, either cold or warm. It is not the same with the other metallic chlorides, and we may state that, as a general rule, these are decomposed by aluminium with greater facility as the metal which they contain belongs to a higher order. The chlorhydrate of Al itself dissolves aluminium forming a sub-chlorhydrate with evolution of hydrogen.

Tissier: NaCl is employed as a flux for Al in remelting it. It does not possess the property, like CaF2, of dissolving the A1203, and has the inconvenience of producing with the clay of the crucible a sensible quantity of Al2C16, which may on contact with the air act in promoting the loss of a certain quantity of metal.

METALLIC OXIDES.

Tissier: We made our experiments in this way: The Al leaf was mixed carefully with the oxide on which we experimented, then the mixture was placed in a small porcelain capsule and heated in a small earthen crucible which served as a muffle. Our results were as follows:

MnO2-Aluminium has no action on manganese

dioxide.

Fe2O3-By heating to white heat 1 equivalent of Fe2O3 and 3 of Al, the reaction took place with detonation, and by heating sufficiently we obtained a metallic button, well melted, and containing 69.3 per cent. Fe and 30.7 per cent. Al, being as hard and brittle as cast-iron. Its composition is nearly AlFe. It would thus appear that the decomposition of Fe2O3 will not pass the limit where the quantity of iron reduced is sufficient to form with the aluminium the alloy AlFe.

ZnO: A mixture of aluminium leaf and zinc oxide heated to whiteness did not appear to present the least indication of decomposition.

PbO: We mixed 2 equivalents of litharge with 1 of aluminium, and heated the mixture slowly up to white heat, when the Al reacted on the PbO with such intensity as to produce a strong detonation. We made an experiment with 50 grammes of PbO and 2.9 grammes of Al leaf, when the crucible was

broken to pieces and the doors of the furnace blown off.

CuO: 3 grammes of black oxide of copper mixed with 1.03 grammes of aluminium detonated producing a strong explosion when the heat reached whiteness.

Mierzinski: Aluminium reduces CuO and PbO with explosion, Fe2O3 only in part, forming the alloy AlFe. ZnO and MnO are not reduced by aluminium.

Bekétoff:* He reduced baryta (BaO) with metallic aluminium in excess, and obtained alloys of aluminium and barium containing in one case 24 per cent. in another 33 per cent. of Ba.

ANIMAL MATTERS.

Deville: Among the animal matters produced by the organism, some are acid, as sweat. These appear to have no sensible action on aluminium. Alkaline materials, as the saliva, have a greater tendency to oxidize it, but the whole effect produced is insignificant. M. Charrière has made for a patient on whom he practised tracheotomy a small tube of the metal, which remained almost unaltered although in contact with purulent matter. After a long time a little alumina was formed on it, hardly enough to be visible.

* Bull. de la Soc. Chem., 1857, p. 22.

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