Page images
PDF
EPUB

Though Dr. VAN MARUM was convinced, by M. Lavifter's experiments, that metals, calcined in atmospherical air, absorb from it that principle, which renders it fit for respiration; yet he resolved further to investigate this point, by trying what would be the effect of a discharge of the battery through a piece of wire confined in phlogisticated air. For this purpose, he took air, in which a burning coal had been extinguished, and which had afterwards stood eight days upon water, that it might be entirely cleared from fixed air ; with this, he filled a glass cylinder, four inches in diameter, and fix inches high, closed at the upper end with a brass plate; from the center of this plate the wire was suspended, on which the experiment was made. The cylinder was set in a pewter dish filled with water, and, to prevent its being broken by the expansion of the air, its lower edges were supported by two pieces of wood half an inch high. The lower end of the wire rested on the dish, which was connected with the outfide coating of the battery.

On transmitting the charge, in this manner, through wires of lead, tin, and iron, of only half the length of those which were calcined by an equal explosion in atmospheric air, no calcination took place. The first was reduced to a fine powder, which, upon trial by spirit of nitre, appeared to be merely lead; the two other metals were melted into small globules.

The Doctor then tried the fame experiment in pure, or de phlogisticated air, obtained from red precipitate ; thinking that, in this, the metals would be more highly calcined, than in common air. His expectation was answered only by the lead, which was entirely reduced to a yellow calx, perfectly resembling masticot. The other metals were not more highly calcined in this, than in common air ; but the globules of iron acquired so great a heat, as to retain it for some seconds, even in the water, and to melt holes in the pewter dish into which they fell,

In nitrous air, calcination took place as easily as in common, or in dephlogisticated air; this was contrary to Dr. Van MARUM's expectation; but he accounts for it, by observing that, from the experiments of Mr. Cavendish, and of M. Lavsifier, pure air appears to be one of the component parts of the nitrous acid.

In order to illustrate M. Lavoisier's theory, Dr. Van MaRUM resolved to examine the phenomena resulting from the calcination of metals in water, This he tried with both iron and lead, and found that, in the moment of the explofion, a number of air-bubbles appeared on the surface, and the calx rose, like a cloud, through the water. This, he thinks, is not so eafily accounted for, by the theory of Stahl, as by that of M. Lavoisier, because, according to the former, water does not

readily

10

[ocr errors]

readily either receive, or part with phlogiston; whereas the lacter supposes this Auid to be composed of the oxiginous principle, united with that of inflammable air: if this be true, nothing more is necessary to calcination, than that the metal should acquire a greater affinity with the oxiginous principle, than subfifts between this, and that of inflammable air, united with it in the composition of water. To collect the air, generated by these calcinations, was no easy matter ; as the violence of the shock broke the glass receivers employed for this purpose ; at last, however, the Doctor contrived a method of receiving it in a glazed stone balon. From the first calcination of lead, about a quarter of a cubic inch of air was produced, which thewed no signs of inflammability; but, on every repetition of the experiment, a less quantity of air was generated ; and, on an accurate trial of that produced by the fourth calcination in the same water, it was found to consist of one part of infammable, and three of atmospherical air. Our author designs to repeat these experiments with water deprived of its air, by being boiled.

In order to imitate the phenomena of earthquakes, this ingenious philosopher followed Dr. PRIESTLEY's method, and made the electrical explofion pass over a board, floating on water, on which several columns of wood were erected ; but this succeeded only once. Reflecting that the electric explosion exerts the greatest lateral force when it passes through imperfect conductors, and that water is, probably, its principal fubterraneous conductor, he laid two smooth boards upon each other, moistening the sides in contact with water ; upon the uppermoft, he placed pieces of wood, in imitation of buildings, the bases of which were 3 inches long, and I } broad. When the charge of the battery was transmitted between the boards, all these were thrown down by the tremulous and undulatory motion of that on which they stood.

In the next chapter, Dr. Van MARUM gives an account of his attempt to repeat that interesting experiment, made by Mr. Cavendilh, in which he produced the nitrous acid, by a mix. ture of pure, with phlogisticated air * Instead of a syphon, the Doctor made use of a glass tube, one-fixth part of an inch in diameter, closed at one end, into which an iron wire, išo of an inch in diameter, had been inserted : into this tube, filled with mercury, and fixed in a vertical position, was introduced the air, with which the experiment was to be tried. The dephlogisticated air was obtained from red precipitate, and had been thorougbly purified, by alkaline salts, from any acid it might have contained. With a mixture of five parts of this, and

[ocr errors][ocr errors][ocr errors][ocr errors]

* See Monthly Review, vol. lxxiv. p. 321.

tbree

three of common air, the tube was filled to the height of three inches, to which was added 2 of an inch of lixivium, of the fame kind with that used by Mr. Cavendin. The result was, that, after cransmitting through the tube a continued stream of the electrical Ruid during fifteen minutes, two inches of the air were absorbed by the lixivium: more air being introduced into the tube, till it was filled to the height of three inches, it was again electrified. This process was repeated, till 8 inches of air had been absorbed by the lixivium : this was now examined, and found to be, in fome degree, impregnated with the nitrous acid; but it was very far from being faturated. With the same lixivium, of which a quarter of an inch remained in the tube, the experiment was continued till 14 inches more of air had been absorbed; but its diminution was not perceived to decrease, though the lixivium had now absorbed 77 measures of air, each equal to its own; whereas, in the experiment related by Mr. Cavendith, only 38 measures of air were absorbed by the alkali. But, not withstanding this greater absorption, the lixivium was yet far from being faturated.

The experiment was repeated with pure air, produced by minium, moistened with the vitriolic acid, and deprived of its fixed air; seven parts of this were mixed with three of phlogisticated air, and lixivium added to the height of į of an inch. Here, as in the former experiment, the diminution continued without any decrease; and the lixivium, after it had absorbed 224 inches, and consequently 178 times its own measure of air, was very far from being saturated with the nitrous acid.

On this, Dr. Van Marum wrote to Mr. Cavendish, and finding, by his answer, that this gentleman had used pure air, ob:ained from a black powder produced by shaking mercury with lead, he requefied to be informed of the process by which it is generated; but Mr. Cavendish, not chusing to communicate this at present, he determined to defer the repetition of the experiment, till this ingenious philosopher shall bave publithed his mode of obtaining the pure air used in it.

The following chapter contains a relation of some experiments made by suffering the electric fluid to pass in a continued stream through various kinds of air, inclosed, for this purpose, in the little glass rube used in the last experiments.

Pure air, obtained the week before from red precipitate, being placed over mercury, and electrified for thirty minutes, was die minished by one-fifth, the surface of the quicksilver soon began to be calcined, and, towards the end of the experiment, the glass tube was so lined with the calx as to cease to be transparent. By introducing a piece of iron, the electric stream was made to pass through the air without immediately touching the mercury; yet this was equally calcined. This phenomenon the Doctor

ascribes fifteen

[ocr errors][ocr errors]

ascribes solely to the diffolution of the pure air, the principle of which unites itself with the metal; as, in these experiments, the mercury had not acquired any sensible heat. Two inches and three-quarters of the same kind of air being placed over water, and electrified in the same manner during half an hour, loft a quarter of an inch; and being suffered to stand twelve hours in the tube, was found to have lost one-eighth of an inch more. This was very nearly the same diminution of the air that had taken place, when it was electrified over mercury; but, in this case, the process appears to be more flow, and the detached principle not so readily absorbed. The air remaining after these experiments, being tried by the eudiometer, did not differ from unelectrified pure air taken from the same receiver.

To determine whether the pure air retained any of the acid employed in its production, the Doctor repeated the experiment with air, obtained from red precipitate, confined by an infusion of turnsole, but could not perceive in it the least change of colour. He also electrified air, obtained from minium and the vitriolic acid, placed over some diluted vinegar of lead, but this was not rendered at all turbid.

Three inches of phlogisticated air being electrified, during the first five minutes, were augmented to 31 inches, and, in the next ten minutes, to 34 inches : some lixivium was then introduced to try whether this would absorb it; but, upon being electrified fifteen minutes, the column rose to the height of 31 inches. It was suffered to stand in the tube till the next day, when it was found to have sunk to its original dimension.

Nitrous air, confined by lixivium, being electrified during half an hour, lost three-quarters of its bulk; the lixivium appeared to have absorbed a great deal of nitrous acid; and the air remaining in the tube did not seem to differ from common phlogisticated air. Some of the same nitrous air, confined by lixivium, was, by standing three weeks, diminished to half its bulk, and this refiduum also proved to be phlogisticated air. Thus electricity very speedily effects that reparation of the nitrous acid from nitrous air, which is fowly produced by the lixivium alone.

Inflammable air, obtained from steel filings and the diluted vitriolic acid, being confined by an infufion of turnsole, was electrified for ten minutes without any change of colour in the infusion, or any alteration in the dimension of the air. The tube, being filled with the same air to the height of 2 į inches, and placed in diluted vinegar of lead, was exposed to the electric ftream during twelve minutes, in which time the inclosed air rose to five inches; but the vinegar remained perfectly clear. Three inches of inftammable air, obtained from a mixture of spirits of wine with oil of vitriol, on being electrified for

[ocr errors][ocr errors]

fifteen minutes, rose to ten inches; thus dilated, it loft all its inflammability, and when nitrous air was added, no diminution ensued.

A column of alkaline air, obtained by heat from spirit of fal ammoniac, three inches high, was electrified four minutes, and rose to fix inches, but did not rise higher when electrified ten minutes longer. It appears that this air is not expanded more by the powerful electric stream from this machine, than by the common spark. Water would not absorb this electrified air, which was in part in Aammable.

The tube, being filled, to the height of an inch, with spirit of fal ammoniac, and inverted in mercury, was electrified four minutes ; in which time, the tube was filled with eight inches of air, which proved to be equally inflammable, and as little absorbed by water, as the alkaline air. Hence Dr. Van Ma. RUM conjectures that this air is only the volatile alkali rendered elastic,

The last chapter contains an account of a very ingenious experiment to illustrate some phenomena observed in thunderstorms. Two balloons, made of the allantoides of a calf, were filled with infiammable air, of which each contained about two cubic feet. To each of these was suspended, by a filken thread about eight feet long, such a weight, as was just sufficient to prevent it from rising higher in the air ; they were connected, the one with the positive, the other with the negative conductor, by small wires about thirty feet in length, and being kept near twenty feet asunder, were placed as far from the machine, as the length of the wires would admit. On being electrified, these balloons rose up in the air as high as the wire allowed, attracted each other, and uniting, as it were, into one cloud, gently descended. The rising of these artificial clouds is ascribed to the expansion of the air they contained, in consequence of the repulfive force communicated to its particles by ele&tricity: when in contact, their opposite ele&rical powers destroyed each other, and they recovered their specific gravity, by losing the cause of iis diminution. In order to render this experiment more perfectly imitative, the Doctor suspended to the balloon which was connected with the negative conductor, a bladder filled with a mixture of inflammable and atmoípherical air, which, being kindled by the spark that took place on che union of these clouds, gave a confiderable explosion. From these experiments, the Doctor explains the sudden elevation of the clouds, and the violent showers of rain and hail, which often accompany thunder-storms.

Dr. Van MARUM intends to make considerable additions to his battery, as he finds that the machine is capable of charging a larger surface of coated glass; and designs, in his nexe pub

lication,

1

« PreviousContinue »