Philosophical Magazine

globule is made to touch a globule of mercury about twice as large, they combine with considerable heat; the compound is fluid at the temperature of its formation; but when cool it appears as a solid metal, similar in colour to silver. If the quantity of the basis of potash is still further increased, so as to be about 'th the weight of the mercury, the amalgam increases in hardness, and becomes brittle. The solid amalgam, in which the basis is in the smallest proportion, seems to consist of about one part in weight of basis and 70 parts of mercury, and is very soft and malleable.

When these compounds are exposed to air, they rapidly absorb oxygen; potash which deliquesces is formed; and in a few minutes the mercury is found pure and unaltered.

When a globule of the amalgam is thrown into water, it rapidly decomposes it with a hissing noise; potash is formed, pure hydrogen disengaged, and the mercury remains free.

The fluid amalgam of mercury and this substance dissolves. all the metals I have exposed to it; and in this state of union, mercury acts on iron and platina.

When the basis of notash is heated with gold, or silver, or copper, in a close essel of pure glass, it rapidly acts upon them; and when the compounds are thrown into water, this fluid is decomposed, potash formed, and the metals appear to be separated unaltered.

The basis of potash combines with fusible metal, and forms an alloy with it, which has a higher point of fusion than the fusible metal.

The action of the basis of potash upon the inflammable oily compound bodies, confirms the other facts of the strength of its attraction for oxygen.

On naphtha colourless and recently distilled, as I have already said, it has very little power of action; but in naphtha that has been exposed to the air it soon oxidates, and alkali is formed, which unites with the naphtha into a brown soap that collects round the globule.

On the concrete oils, (tallow, spermaceti, wax, for instance,) when heated, it acts slowly, coaly matter is depo

sited, a little gas is evolved, and a soap is formed; but in these cases it is necessary that a large quantity of the oil be employed. On the fluid fixed oils it produces the same effects, but more slowly.

By heat likewise it rapidly decomposes the volatile oils; alkali is formed, a small quantity of gas is evolved, and charcoal is deposited.

When the basis of potash is thrown into camphor in fusion, the camphor soon becomes blackened, no gas is liberated in the process of decomposition, and a saponaceous compound is formed; which seems to show that camphor contains more oxygen than the volatile oils.

The basis of potash readily reduces metallic oxides when heated in contact with them. When a small quantity of the oxide of iron was heated with it, to a temperature approaching its point of distillation, there was a vivid action; alkali and gray metallic particles, which dissolved with ef fervescence in muriatic acid, appeared. The oxides of lead and the oxides of tin were revived still more rapidly; and when the basis of potash was in excess, an alloy was formed with the revived metal.

In consequence of this property, the basis of potash readily decomposes flint glass and green glass, by a gentle heat; alkali is immediately formed by oxygen from the oxides, which dissolves the glass, and a new surface is soon exposed to the agent.

* When a globule of the basis of potash is introduced into any of the fixed oils heated, the first product is pure hydrogen, which arises from the decomposition of the water absorbed by the crust of potash during the exposure to the atmosphere The gas evolved, when the globule is freed from this crust. I have found to be carbonated hydrogen, requiring more than an equal bulk of oxygen gas for its complete saturation by explosio I have made a great number of experiments, which it would be foreign to the cbject of this lecture to give in minute detail, on the agencies of the basis of potash on the oils. Some anomalies occurred which led to the inquiry, aud the result was perfectly conclusive. Olive oil, oil of turpentine, and naphtha, when decomposed by heat, exhibited as products different proportions of charcoal, heavy inflammable gas, empyreumatic oily matter, and water, so that the existence of oxygen in them was fully proved; and accurate indications of the proportions of their elements might be gained by their de composition by the basis of potash. Naphtha of all furnished least water and carbonic acid, and oil of turpentine the most.

Vol. 32. No. 125. Oct. 1808.

At a red heat, even the purest glass is altered by the basis of potash the oxygen in the alkali of the glass seems to be divided between the two bases, the basis of potash and the alkaline basis in the glass, and oxides, in the first degree of oxygenation, are the result. When the basis of potash is heated in tubes made of plate glass filled with the vapour of naphtha, it first acts upon the small quantity of the oxides of cobalt and manganese in the interior surface of the glass, and a portion of alkali is formed. As the heat approaches to redness, it begins to rise in vapour, and condeuses in the colder parts of the tube; but at the point where the heat is strongest, a part of the vapour seems to penetrate the glass, rendering it of a deep red brown colour; and by repeatedly distilling and heating the substance in a close tube of this kind, it finally loses its metallic form, and a thick brown crust, which slowly decomposes water, and which combines with oxygen when exposed to air forming alkali, lines the interior of the tube, and in many parts is found penetrating through its substance*.

In my first experiments on the distillation of the basis of potash, I had great difficulty in accounting for these phænomena; but the knowledge of the substance it forms in its first degree of union with oxygen, afforded a satisfactory explanation.

[To be continued.]

II. On the Opinions that have prevailed respecting the Nature of Alkalis and Earths. By a Correspondent.

SIR,

To Mr. Tilloch.

I HAVE not been a little amused by the manner in which your correspondent O. begins his lettert.

"Messrs. Davy, Berzelius, and Pontin, have only verified

This is the obvious explanation in the present state of our knowledge; but it is more than probable that the silex of the glass likewise suffers some change, and probably decomposition. This subject I hope to be able to resume on another occasion.

Phil. Mag. vol. xxxi. p. 273.

what

what Lavoisier suspected, that the alkalis and earths are metallic oxides."

This "only verifying" seems to him a matter of very little importance, and the guess much more curious than the discovery. Reasoning in this way, it may be said, that Newton only verified what Seneca suspected, and that Columbus had only rediscovered Plato's Atalantis.

From such a writer accuracy is not to be expected. His first assertion is incorrect. Lavoisier never supposed the fixed alkalis to be metallic oxides. In his time there were no analogies which led to such an opinion. This sagacious philosopher, on the contrary, has stated the idea that they may contain azote; which O. may see in the very book he quotes, Kerr's Translation of Lavoisier's Elements, second edition, page 213.

Before Lavoisier, even as early as Van Helmont jun. and Beccher, it was conceived that metals were capable of being produced from earths. Bergman, in later times, but before. Lavoisier, published the opinion with respect to barytes; and Baron, with respect to alumine: but this kind of reading cannot be familiar to O., a person who seems to believe in the results of the experiments of Toudi and Ruprecht, on the metallization of the earths, and merely says, that their accuracy was called in question by Klaproth and Tihawski; whereas the fact is, that the metallic substances obtained by Toudi and Ruprecht were proved by Tihawski and by Klaproth to be phosphurets of iron: and the question was laid at rest by the elaborate researches of Savaresi, who showed that they could not be obtained except in cases when materials which furnished phosphuret of iron were present. See Annales de Chimie, tome ix. p. 275, and tome x. p. 118.

Mr. Kerr, in his Translation of Lavoisier's Elements, second edition, has reasoned upon the experiments of Toudi and Ruprecht as if they were correct; stating that if magnesia be a metallic oxide, then soda, being a modification of magnesia, "according to some experiments published in the Transactions of the Turin Academy," must be also a metallic substance. He might have gone further, and said, that as M. Guyton de Morveau has proved potash to be

At a red heat, even the purest glass is altered by the basis of potash the oxygen in the alkali of the glass seems to be divided between the two bases, the basis of potash and the alkaline basis in the glass, and oxides, in the first degree of oxygenation, are the result. When the basis of potash is heated in tubes made of plate glass filled with the vapour of naphtha, it first acts upon the small quantity of the oxides. of cobalt and manganese in the interior surface of the glass, and a portion of alkali is formed. As the heat approaches to redness, it begins to rise in vapour, and condenses in the colder parts of the tube; but at the point where the heat is strongest, a part of the vapour seems to penetrate the glass, rendering it of a deep red brown colour; and by repeatedly distilling and heating the substance in a close tube of this kind, it finally loses its metallic form, and a thick brown crust, which slowly decomposes water, and which combines with oxygen when exposed to air forming alkali, lines the interior of the tube, and in many parts is found penetrating through its substance*.