and their size

to that of the bore or number of pumps.

Exp. 15.

of whatever size. But as, in taking the water at the same level, a pump of 30 feet will bring it three times as high as three pumps of 10 feet; so in the above experimeut, the column of 600 groups produced probably three times as much change of density in the electric fluid, with a proportional divergence, as did the three columns of 200 groups, individually acting on the same low level, or degree of density, that of the standard of plus or minus.

But if in this case the size of the plates, or the multiplication of their number at the same numerical distances from the extremities, be indifferent, it is not the same in some other cases, as I shall illustrate by the same analogy. In the above case, the height to which the water was to be raised being the only object, the number or size of the pumps was indifferent; but if a current is to be produced at that level, either with a certain degree of rapidity, or of a certain volume, then the diameter of the pumps comes in as a condition. The following experiment will show the analogy of this case, with the effects of the different sizes of plates in the column.

Exp. 15. I made two other columns of 200 groups each; but these I only cut square, for one of, and for the other of of an inch, still zinc and Dutch gilt paper. These two columns produced sensibly the same divergence as the former, in the same electroscope; but in this was already shown the difference in other respects; the time for producing this divergence was in the inverse ratio of the size of the plates.

This experiment gives a clear idea of the effect produced by a greater size of the plates, both in the pile and in the column. In the circuit of the former, with the same number of groups, the effects are proportional to the size of the plates, because the current of the electric fluid becoming denser and more rapid in passing through the wires used in these operations, the effects are greater, in proportion to the number of equal parts of surface, either in a few or many plates, concurring to produce the motion of the electric fluid which arrives at the entrance of this narrow channel. That difference in the rapidity and density of the current cannot be discovered in the circuit of the column,

because

because the condition to which chemical effects are owing is wanting in it, as I have explained in my former paper; but the size of the plates influences the frequency of the strikings of the little electroscopic pendula, when their simple divergence is exceeded; because each time that one of them strikes, either at the negative or the positive side, that instantaneous communication of the column with the ground changes in some degree its electric state; and the same state is sooner restored, to produce another striking, in proportion to the size of the plates, with the same number of groups. This effect will enter as an essential circumstance into the Ild part of this paper, concerning the aerial electroscope.

II.

The Bakerian Lecture for 1809. On some new Electrochemical Researches, on various Objects, particularly the metallic Bodies from the Alkalis, and Earths, and on some Combinations of Hidrogen, By HUMPHRY Dayy, Esq. Sec. R. S. F. R. S. E. M. R. I. A.

(Concluded from p. 55.)

IV. On the Metals of Earths.

I HAVE tried a number of experiments, with the hopes Metals of the of gaining the same distinct evidences of the decomposition common of the common earths, as those afforded by the electrochemical processes on the alkalis, and the alkaline earths.

tartas

iron.

I find, that, when iron wire ignited to whiteness, by the apparently power of 1000 double plates, is negatively electrified and combined with fused in contact with either silex, alumine, or glucine, slightly moistened and placed in hidrogen gas; the iron becomes brittle and whiter, and affords by solution in acids an earth of the same kind, as that which has been employed in the experiment.

I have passed potassium in vapour through each of these Potassium in earths, heated to whiteness in a platina tube: the results vapour were remarkable, and perhaps not unworthy of being fully detailed.

passed through

silex,

alumine, and

ucine.

When silex was employed, being in the proportion of about ten grains to four of potassium, no gas was evolved, except the common air of the tube mingled with a little inflammable gas, not more than might be referred to the moisture in the crust of alkali formed upon the potassium. The potassium was entirely destroyed; and glass with excess of alkali was formed in the lower part of the tube; when this glass was powdered, it exhibited dark specks, having a dull metallic character not unlike that of the protoxide of iron. When the mixture was thrown into water, there was only a very slight effervescence; but on the addition of muriatic acid to the water, globules of gas were slowly liberated, and the effect continued for nearly an hour; so that there is great reason to believe, that the silex had been either entirely or partially deoxigenated, and was slowly reproduced by the action of the water, assisted by the slight attraction of the acid for the earth.

When the potassium was in the quantity of six grains, and the silex of four grains, a part of the result inflamed spontaneously as it was taken out of the tube, though the tube was quite cool, and left, as the result of its combustion, alkali and silex. The part which did not inflame was similar in character to the matter which has been just described, it did not act upon water, but effervesced with muriatic acid.

Potassium, in acting upon alumine and glucine, produced more hidrogen than could be ascribed to the moisture present in the crust of potash; from which it seems probable, that, even after ignition, water adheres to these earths.

The results of the action of the potassium were pyrophoric substances of a dark gray colour, which burnt, throwing off

* The results of this experiment are opposed to the idea, that potassium is a compound of hidrogen and potash, or its basis; for, if so, it might be expected, that the hidrogen would be disengaged by the attraction of the alkali for silex. In my first experiments on this combination, I operated in an apparatus connected with water, and I found, that the potassium produced as much hidrogen, as if it had been made to act upon water; in this case the metal had rapidly decomposed the vapour of the water, which must have been constantly supplied.

brilliant

1

brilliant sparks*, and leaving behind alkali and earth; and which hissed violently when thrown upon water, decomposing it with great violence. I examined the products in two experiments, one on alumine, and one on glucine, in which naphtha was introduced into the platina tube, to prevent combustion; the masses were very friable, and presented small metallic particles, which were as soft as potassium, but so small, that they could not be separated, so as to be more minutely examined; they melted in boiling naphtha. Either a part of the potassium must have been employed in decomposing the earths in these experiments, or it had entered into combination with them, which is unlikely, and contrary to analogy, and opposed by some experiments which will be immediately related.

form alloys

Supposing the metals of the earths to be produced in ex- Attempt to periments of this kind, there was great reason to expect, with them. that they might be alloyed with the common metals, as well

as with potassium. Mercury was the only substance, which it was safe to try in the tube of platina. In all cases in which the potassium was in excess, I obtained amalgams - by introducing mercury while the tube was hot; but the alkaline metal gave the characters to the amalgam: and though, in the case of glucine and alumine, a white matter separated during the action of very weak muriatic acid upon the amalgam, yet I could not be entirely satisfied, that there was any of the metals of these earths in triple combination. Mixtures of the earths with potassium, intensely ignited Mixtures of in contact with iron filings, and covered with iron filings in the earths, a clay crucible, gave much more distinct results. Whether and irou filings, silex, alumine, or glucine was used, there was always a formed alloys. fused mass in the centre of the crucible; and this mass had perfectly metallic characters. It was in all cases much whiter and harder than iron. In the instance in which silex was used, it broke under the hammer, and exhibited a crystalline texture. The alloys from alumine and glucine were imperfectly malleable. Each afforded by solution in

potassium,

* The pyrophorus from alum, which I have supposed in the last Homberg's Bakerian lecture to be a compound of potassium, sulphur, and char- pyrophorus. coal, probably contains this substance likewise.

Amalgams formed with the alkaline earths.

Lime, and magnesia.

Amalgam of magnesia.

metal in the

earths may be obtained.

acids, evaporation, and treatment with reagents, oxide of iron, alkali, and notable quantities of the earth employed in the experiment.

Though I could not procure decided evidences of the production of an amalgam from the metals of the common earths, yet I succeeded perfectly by the same method of operating in making amalgams of the alkaline earths.

By passing potassium through lime and magnesia, and then introducing mercury, I obtained solid amalgams, which consisted of potassium, the metal of the earth employed, and mercury.

The amalgam from magnesia was easily deprived of its potassium by the action of water. It then appeared as a solid white metallic mass, which by exposure to the air became covered with a dry white powder; and which, when acted upon by weak muriatic acid, gave off hidrogen gas in considerable quantities, and produced a solution of magnesia.

Proportions of By operations performed in this manner, there is good reason to believe, it will be possible to procure quantities of the metals of the alkaline earths, sufficient for determining their nature and agencies, and the quantities of oxigen which they absorb; and by the solution of the alloys containing the metals of the common earths, it seems probable, that the proportions of metallic matter in these bodies may likewise be ascertained.

Hypothetical calculation.

On an hypothesis which I have before brought before the Society, namely, that the power of chemical attraction and electrical action may be different exhibitions of the same property of matter; and that oxigen and inflammable bodies are in relations of attraction, which correspond to the func tions of being negative and positive respectively; it would follow, that the attractions of acids for salifiable bases would be inversely as the quantity of oxigen that they contain; and supposing the power of attraction to be measured by the quantity of basis which an acid dissolves, it would be easy to infer the quantities of oxigen and metallic matter from the quantities of acid and of basis in a neutral salt. On this idea I had early in 1808 concluded, that barytes must contain the least oxigen of all the earths; and that the order, as to

the