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The line of contact of the tube, when the weights were Change of pofirst suspended, traversed the poles of the centre bar of the duced no almagnet only; but while they remained attached, I turned teration in the the tube till it stood in a diagonal direction with the extreme angles of the outside bars; but no difference of attraction was indicated, as it would not sustain more, or separate with less weight, than in its first position.


traction dimi nished:

but a solid cy

than a flat bar.

I then increased the width of the line of contact in the On increasing tube, with a file, to about, of an inch, and found that it the contact by filing the sur separated with nearly a pound less weight: l'increased its face, the width still more, and the attraction was proportionably less. This led me to suppose, that the extraordinary degree of attractive force, by which the tube was held to the magnet linder adhered in the first instance, depended entirely on the minuteness more feebly of the line of contact; and of course, that a solid piece of sound iron of the same diameter, would be similarly attracted. To prove this however, I procured a solid cylinder of iron the same length and diameter as the tube; but upon applying the weights, I was surprised to find it sepa rate with less than half what was necessary to displace the conductor belonging to the magnet.

These hitherto unexplained, and probably unobserved, phenomena, are submitted for explanation to such of your philosophic readers, as may have paid more attention to this subject, than I have had an opportunity of doing; in hopes of being gratified with some communications, which will not fail to be interesting, while they elicit a more extensive inquiry into that mysterious and neglected princi ple of nature, magnetism.

London, April the 10th, 1811.

Yours, &c.



An Answer to Mr. MURRAY's Observations on the Nature of
Potassium and Sodium: by Mr. JOHN DAVY.



MR. Berthollet has estimated the proportion of water in Quantity of

common fused potash at 13.9 per cent; and Mr. Davy, from water in por

Ꭰ ?


an experiment on the action of silex on this hidrate, has concluded in his Bakerian lecture for 1809, that it contains, taking the potash formed by the combustion of potassium as a standard, about 16 or 17 per cent.

Mr. Davy's In the same lecture he has shown from the quantity of standard pot fused muriate, produced from a given weight of potassium in muriatic acid gas, that his standard potash has a much greater saturating power, than the hidrate of potash; that 100 of the former will neutralize the same quantity of acid as 120 of the latter.

Combined with boracic

eid without evolution of


Common pot

He has since ascertained, that, when potassium and powdered boracic acid glass are heated together in a tube of platina, both with and without red oxide of mercury, no water or inflammable gas is produced; and that the result is the same, when potash formed by the combustion of potassium is combined with boracic acid.

On the contrary, substituting the hidrate, or common ash does not. fused potash, he has in one experiment actually collected about 15 per cent of water; and the loss of weight after the combination of the acid and alkali, in other similar experiments, indicated from 15 to 20 per cent.


Combustion of He has found too, that the only product of the combuspotassium in oximuriatic tion of potassium in oximuriatic gas is fused muriate of potash; that the same salt is formed; and oxigen gas evolved, without the least appearance of water, when potash from the combustion of potassium is used; and that water as well as oxigen is separated when hidrate of potash is employed.

Difference be tween the pure alkalis

and their hidrates.

Perexides of potash and soda.

In addition to these circumstances, which are stated in Mr. Davy's last Bakerian lecture, a copy of which he has allowed me to peruse, there are physical properties also pointed out, distinguishing potash and soda from the hidrates; the former for instance require a much higher temperature for fusion than the latter, and possess greater hardness and apparently greater specific gravity.

It is well known to those who have attended to the late progress of chemical discovery, that potash and soda are only to be procured by the rapid combustion of the alkaline metals, or by the after application of a red-heat; and that per●xides are formed when the combustion is feeble either in *xigen gas or common air. Messrs. Gay-Lussac and The


nard first distinctly pointed out the nature of these peroxides, and described their properties. According to their statement, the peroxide of potassium contains three times the quantity of oxigen that exists in potash, and the peroxide of sodium half as much more as exists in soda*. These oxides have also been examined by Mr. Davy, and the general results of his experiments are conformable to those of the French chemists.

Messrs. Gay-Lussac and Thenard, using the same test Trials of the as Mr. Davy had before applied to their hypothesis, making saturating power of the comparative trials of the saturating powers of the alkalis alkalis. formed from the metals and of the common hidrates, were convinced, that potassium and sodium are not hidrurets; and consequently they adopted Mr. Davy's opinion, that they are simple bodiest.

Mr. Murray controverts this opinion in his paper, published in the last number of your Journal: Finding that potash from the combustion of potassium, has much the same sa turating power as hidrate of potash, he infers, that the metals of the fixed alkalis are compounds of unknown bases and hidrogen. As this gentleman does not describe the manner in which he formed his potash; there is every rea son to conclude it must have been by combustion in the atmosphere, in which case, it would have been principally peroxide; and an equal weight of it ought to have less satu→ rating power than an equal weight of common potash. Since, therefore, Mr. Murray's hypothesis appears to be unfounded, since it is contradicted by the ample statement of clear and decisive facts already made, I shall conclude without examining the speculations connected with it.

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At the end of this paper will be found a notice of these gentlemen's experiments; it is part of a Report of the Institute, published in the Moiteur already referred to,


Peroxides of the alkalis treated with acids.


Quantity of water in the alkalis examined.

Extract from the Moniteur of July the 5th, 1810, referred to in the preceding paper. Translated from the French by T. O.C.

THESE oxides [the peroxides] present with some acid

gasses phenomena worthy of attention. Messrs. GayLussac and Thenard observed, that with carbonic acid gas the results were, an alkaline carbonate and an evolution of oxigen gas that with sulphurous gas and oxide of potassium a sulphate and oxigen were obtained; and that with this gas and oxide of sodium the produce was only a great deal of sulphate and a little sulphuret: that not the slightest trace of moisture was given out in any case; and that the weight of the products obtained corresponded precisely to those of the oxide employed and the acid absorbed: Now as in the combustion of potassium and of sodium nothing is evolved, or no volatile product formed; we perceive, that, if these metals be hydrurets, it is a necessary consequence, that the sulphates and carbonates of potash and soda, and no doubt all the salts that have these alcalis for their base, contain as much water, as the hidrogen of these hidrurets can form by combining with oxigen, and that they retain it at a very high temperature; which is possible, but which nothing has hitherto proved. If it were so, a farther consequence would be, that potash and soda contain much more water, than Messrs. d'Arcet and Berthollet admit in them: for these alkalis would contain not only the water which is extricated on combining them with acids, but likewife that which the falt formed is capable of retaining. It was of fome use to determine directly the first of these two quantities of water; and this Messrs. Gay-Lussac and Thenard have done. For this purpose they converted into alkali, gradually and by means of humid air, several grammes of potassium and sodium, and saturated them with sulphuric acid diluted with water. On the other hand, having enployed the same acid to saturate pure potash and soda that had been heated red hot; and having taken an account, in all the saturations, of the acid employed, as well as of the


metal or alkali employed also; it was easy for them to de duce the consequence they sought. Thus they found, that 100 parts of potash contain 20 of water, and that 100 of sođa contain 24, supposing potassium and sodium to be simple substances. They have even verified this quantity of water with respect to soda, by treating over mercury in a curved jar a given quantity with a quantity, also given, of dry carbonic acid gas. The soda was placed on a small plate of platina, and gave out so much water the moment the tem perature was raised, that this water trickled in abundance down the sides of the jar. We can even by these means, or by sulphurous acid gas, render the water sensible in 2 millig. [0.03 of a grain] of soda or of potash."


On the Nature of Orimuriatic Gas, in reply to Mr. MURRAY



strictly tical.

MR. Murray, in his answer to the remarks which I ven- Mr. Murray tured to make on his former paper, appears principally de- considers Mr. Davy's theory sirous of showing, that what my brother, Mr. Davy, has as hypothe advanced as a theory respecting oximuriatic gas, is strictly an hypothesis. The conclusiveness therefore of Mr. Murray's answer depends on his success in proving Mr. Davy's views hypothetical; if he fails in this respect, he fails altogether, and the old hypothesis loses its asserted claims to


Mr. Murray first affirms, that Mr. Davy's theory is not This not the a simple expression of facts, as I have represented it; that fact. it is not a fact, that muriatic acid gas is a compound of oximuriatic gas and hidrogen, but an inference; and that the compositions of all the oximuriates are similar infer ences. This I cannot admit. In the formation of muriatic açid gas, no substances, but those just mentioned, are concerned; the weight of the compound is the exact weight


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