Experiments and Observations on Different Kinds of Air. Joseph Priestley

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СКАЧАТЬ offered them water several times, they would never taste it; and yet they continued in perfect health and vigour. Two or three of them will live very peaceably together in the same vessel; though I had one instance of a mouse tearing another almost in pieces, and when there was plenty of provisions for both of them.

      In the same manner in which a mouse is put into a vessel of any kind of air, a plant, or any thing else, may be put into it, viz. by passing it through the water; and if the plant be of a kind that will grow in water only, there will be no occasion to set it in a pot of earth, which will otherwise be necessary.

      There may appear, at first sight, some difficulty in opening the mouth of a phial, containing any substance, solid or liquid, to which water must not be admitted, in a jar of any kind of air, which is an operation that I have sometimes had recourse to; but this I easily effect by means of a cork cut tapering, and a strong, wire thrust through it, as in fig. 4, for in this form it will sufficiently fit the mouth of any phial, and by holding the phial in one hand, and the wire in the other, and plunging both my hands into the trough of water, I can easily convey the phial through the water into the jar; which must either be held by an assistant, or be fastened by strings, with its mouth projecting over the shelf. When the phial is thus conveyed into the jar, the cork may easily be removed, and may also be put into it again at pleasure, and conveyed the same way out again.

      When any thing, as a gallipot, &c. is to be supported at a considerable height within a jar, it is convenient to have such wire stands as are represented fig. 5. They answer better than any other, because they take up but little room, and may be easily bended to any shape or height.

      If I have occasion to pour air from a vessel with a wide mouth into another with a very narrow one, I am obliged to make use of a funnel, fig. 6, but by this means the operation is exceedingly easy; first filling the vessel into which the air is to be conveyed with water, and holding the mouth of it, together with the funnel, both under water with one hand, while the other is employed in pouring the air; which, ascending through the funnel up into the vessel, makes the water descend, and takes its place. These funnels are best made of glass, because the air being visible through them, the quantity of it may be more easily estimated by the eye. It will be convenient to have several of these funnels of different sizes.

      In order to expel air from solid substances by means of heat, I sometimes put them into a gun-barrel, fig. 7, and filling it up with dry sand, that has been well burned, so that no air can come from it, I lute to the open end the stem of a tobacco pipe, or a small glass tube. Then having put the closed end of the barrel, which contains the materials, into the fire, the generated air, issuing through the tube, may be received in a vessel of quicksilver, with its mouth immersed in a bason of the same, suspended all together in wires, in the manner described in the figure: or any other fluid substance may be used instead of quicksilver.

      But the most accurate method of procuring air from several substances, by means of heat, is to put them, if they will bear it, into phials full of quicksilver, with the mouths immersed in the same, and then throw the focus of a burning mirror upon them. For this purpose the phials should be made with their bottoms round, and very thin, that they may not be liable to break with a pretty sudden application of heat.

      If I want to expel air from any liquid, I nearly fill a phial with it, and having a cork perforated, I put through it, and secure with cement, a glass tube, bended in the manner represented at e fig. 1. I then put the phial into a kettle of water, which I set upon the fire and make to boil. The air expelled by the heat, from the liquor contained in the phial, issues through the tube, and is received in the bason of quicksilver, fig. 7. Instead of this suspended bason, I sometimes content myself with tying a flaccid bladder to the end of the tube, in both these processes, that it may receive the newly generated air.

      In experiments on those kinds of air which are readily imbibed by water, I always make use of quicksilver, in the manner represented fig. 8, in which a is the bason of quicksilver, b a glass vessel containing quicksilver, with its mouth immersed in it, c a phial containing the ingredients from which the air is to be produced; and d is a small recipient, or glass vessel designed to receive and intercept any liquor that may be discharged along with the air, which is to be transmitted free from any moisture into the vessel b. If there be no apprehension of moisture, I make use of the glass tube only, without any recipient, in the manner represented e fig. 1. In order to invert the vessel b, I first fill it with quicksilver, and then carefully cover the mouth of it with a piece of soft leather; after which it may be turned upside down without any danger of admitting the air, and the leather may be withdrawn when it is plunged in the quicksilver.

      In order to generate air by the solution of metals, or any process of a similar nature, I put the materials into a phial, prepared in the manner represented at e fig. 1, and put the end of the glass tube under the mouth of any vessel into which I want to convey the air. If heat be necessary I can easily apply to it a candle, or a red hot poker while it hangs in this position.

      When I have occasion to transfer air from a jar standing in the trough of water to a vessel standing in quicksilver, or in any other situation whatever, I make use of the contrivance represented fig. 9, which consists of a bladder, furnished at one end with a small glass tube bended, and at the other with a cork, perforated so as just to admit the small end of a funnel. When the common air is carefully pressed out of this bladder, and the funnel is thrust tightly into the cork, it may be filled with any kind of air as easily as a glass jar; and then a string being tied above the cork in which the funnel is inserted, and the orifice in the other cork closed, by pressing the bladder against it, it may be carried to any place, and if the tube be carefully wiped, the air may be conveyed quite free from moisture through a body of quicksilver, or any thing else. A little practice will make this very useful manœuvre perfectly easy and accurate.

      In order to impregnate fluids with any kind of air, as water with fixed air, I fill a phial with the fluid larger or less as I have occasion (as a fig. 10;) and then inverting it, place it with its mouth downwards, in a bowl b, containing a quantity of the same fluid; and having filled the bladder, fig. 9, with the air, I throw as much of it as I think proper into the phial, in the manner described above. To accelerate the impregnation, I lay my hand on the top of the phial, and shake it as much as I think proper.

      If, without having any air previously generated, I would convey it into the fluid immediately as it arises from the proper materials, I keep the same bladder in connection with a phial c fig. 10, containing the same materials (as chalk, salt of tartar, or pearl ashes in diluted oil of vitriol, for the generation of fixed air) and taking care, lest, in the act of effervescence, any of the materials in the phial c should get into the vessel a, to place this phial on a stand lower than that on which the bason was placed, I press out the newly generated air, and make it ascend directly into the fluid. For this purpose, and that I may more conveniently shake the phial c, which is necessary in some processes, especially with chalk and oil of vitriol, I sometimes make use of a flexible leathern tube d, and sometimes only a glass tube. For if the bladder be of a sufficient length, it will give room for the agitation of the phial; or if not, it is easy to connect two bladders together by means of a perforated cork, to which they may both be fastened.

      When I want to try whether any kind of air will admit a candle to burn in it, I make use of a cylindrical glass vessel, fig. 11. and a bit of wax candle a fig. 12, fastened to the end of a wire b, and turned up, in such a manner as to be let down into the vessel with the flame upwards. The vessel should be kept carefully covered till the moment that the candle is admitted. In this manner I have frequently extinguished a candle more than twenty times successively, in a vessel of this kind, though it is impossible to dip the candle into it without giving the external air an opportunity of mixing with the air in the inside more or less. The candle c, at the other end of the wire is very convenient for holding under a jar standing in water, in order to burn as long as the inclosed air can supply it; for СКАЧАТЬ