MISCELLANEOUS AGENTS.

Tissier: Only 2.65 grammes of aluminium introduced into melted red hot sodium sulphate (Na2SO1) decomposed that salt with such intensity that the crucible was broken into a thousand pieces, and the door of the furnace blown to a distance. Heated to redness with alkaline carbonate, the Al was slowly oxidized at the expense of the CO2, C was set free, and an aluminate formed. The reaction takes place without deflagration.

Mierzinski: Heated to redness with potassium or sodium sulphate, aluminium gives a strong detonation. Potassium carbonate quickly destroys the metal with separation of carbon. Hydrogen, nitrogen, sulphur, and carbon are without any influence on aluminium, but chlorine, iodine, bromine, and fluorine attack it rapidly.

GENERAL OBSERVATIONS ON THE PROPERTIES OF ALUMINIUM.

Deville: Aluminium, at a low temperature, conducts itself as a metal which can give a very weak base; in consequence, its resistance to acids, HCl excepted, is very great. It conducts itself with the alkalies as a metal capable of giving a quite energetic acid, it being attacked by K2O and Na2O dissolved in water. But, this affinity is still insufficient to determine the decomposition of

melted KOH. For a stronger reason it does not decompose metallic oxides at a red heat. This is why, in the muffle, the alloy of aluminium and copper gives black CuO, and this also accounts for the alloy of aluminium and lead being capable of being cupelled. But, by a strange exception, and which does not appertain solely, I believe, to aluminium, as soon as the heat is above redness the affinities are quickly inverted, and the metal takes all the properties of silicon, decomposing the oxides of lead and copper with the production of aluminates.

From all the experiments which have been reported and from all the observations which have been made, we can conclude that aluminium is a metal which has complete analogies with no one of the simple bodies which we consider metals. In 1855 I proposed to place it along side of chromium and iron, leaving zine out of the group with which aluminium had been until then classed. Zinc is placed very well beside magnesium, there being intimate analogies between these two volatile metals. There may be found at the end of a memoir which M. Wöhler and I published in the Compt Rendu and the Ann. de Chem. et de Phys.' the reasons why we are tempted to place aluminium near to silicon and boron in the carbon series, on grounds analogous to those on which antimony and arsenic are placed in the nitrogen series.

PART V.

METALLURGY OF ALUMINIUM.

As has been remarked in the historical section, Davy was the first to try to isolate aluminium. His attempts were unsuccessful. The next chemist to publish an account of attempts in this direction was Oerstedt, who published a paper in 1824 in a Swedish periodical.* Oerstedt's original paper is thus translated into Berzelius' Jahresbericht:'†

"Oerstedt mixes calcined and pure alumina, quite freshly prepared, with powdered charcoal, puts it in a porcelain retort, ignites and leads Cl gas through. The coal then reduces the alumina, and there results A12C16 and CO, and perhaps also some phosgene, COCI2; the Al2C1 is caught in the condenser and the gases escape. The Al2C1 is white, crystalline, melts about the temperature of boiling water, easily attracts moisture, and evolves heat when in contact with water. If it is mixed with a concentrated potassium amalgam and heated quickly, it is transformed; there results KCl, and

* Oversigt over det K. Danske Videnskabemes Selkabs Forhandlingar og dets Medlemmers Arbeider. May, 1824, to May, 1825, p. 15.

Berz. Jahresb. der Chemie, 1827, vi. 118.

the aluminium unites with the mercury. The new amalgam oxidizes in the air very quickly, and gives as residue when distilled in a vacuum a lump of metal resembling tin in color and lustre. In addition, Oerstedt found many remarkable properties of the metal and of the amalgam, but he holds them for a future communication after further investigation."

I have not been able to find any other paper by Oerstedt, but the next advance in the science is by Wöhler, and all agree in naming him as the true discoverer of the metal. The following is taken from Poggendorf.*

Wöhler reviews the article which we have just given, and then continues as follows:

"I have repeated this experiment of Oerstedt, but achieved no very satisfactory result. By heating potassium amalgam with AlCl and distilling the product, there remained behind a gray melted mass of metal, but which, by raising the heat to redness, went off as green vapor and distilled as pure potassium. I have therefore looked around for another method or way of conducting the operation, but, unpleasant as it is to say it, the reduction of the aluminium fails each time. Since, however, Herr Oerstedt remarks at the end of his paper that he did not regard his investigations in aluminium as yet ended, and already several years

* Pogg. Ann., 1827, ii. 147.

have passed since then, it looks as if I had taken up one of those researches begun auspiciously by another (but not finished by him) because it promised new and splendid results. I must remark, however, that Herr Oerstedt has indirectly by his silence encouraged me to try to attain to further results myself. Before I give the art how one can quite easily reduce the metal, I will say a few words. about Al2C1 and its production.

"I based the method of reducing aluminium on the reaction of Al2C16 on potassium, and on the property of the metal not to oxidize in water. I warmed in a glass retort a small piece of AlCI® with some potassium, and the retort was shattered with a strong explosion. I tried then to do it in a small platinum crucible, in which it succeeded very well. The reaction is always so violent that the cover must be weighted down, or it will be blown off; and at the moment of reduction, although the crucible be only feebly heated from outside, it suddenly glows inside, and the platinum is almost torn by the sudden shocks. In order to avoid any mixture of platinum with the reduced aluminium, I next made the reduction in a porcelain crucible and succeeded then in the following manner: Put in the bottom of the crucible a piece of potassium free from carbon and oil, and cover this with an equal volume of pieces of A12C1. Cover, and heat. over a spirit lamp, at first gently, that the crucible be not broken by the production of heat inside,