Page images
PDF
EPUB

:

Method of

pre

For this purpose the iodine may be introduced into a small flask, and the oxide of chlorine disengaged upon it, from a proper mixture of chlorate of potassa and sulphuric acid with the precautions above pointed out (217,) or 100 grains of chlorate of potassa may be introduced curing iodic into a small retort, with 400 grains of liquid muriatic acid of the sp. gr. 1. cid. 1.105: annex to the retort a small globular receiver, having a bent tube issuing from it, and passing to the bottom of a small flask, containing about 50 grains of iodine; carefully apply the heat of a lamp to the retort, by which oxide of chlorine will be disengaged, and which will be decomposed and absorbed by the iodine. A compound is then formed, which consists of chloriodic and oxiodic acids. The former is separable by a gentle heat, the latter remains as a white, semitranspa-composition. rent, sour, and inodorous body, very soluble in water. It consists of 125 iodine, 40 oxygen.)*

cid.

225. Chloriodic acid is easily obtained by the direct action of chlo-Chloriodic arine upon iodine. They unite and form crystals of a deep orange | colour, deliquescent, and easily fusible and soluble. The solution is

sour.

This compound contains (125 iodine, 36 chlorine.-Davy, Composition,

Phil. Trans. 1814.

It appears probable from the experiments of M. Gay-Lussac, that another chloride of iodine exists, in which 2 proportionals of iodine are united to 1 of chlorine; but these compounds have not yet been examined with sufficient precision, to enable us to speak certainly upon their composition.

CHAPTER IV.

OF SIMPLE ACIDIFIABLE AND INFLAMMABLE SUBSTANCES.

226. THE bodies belonging to this class are electro-positive, and Electro-posiconsequently, when separated from their combinations with the sub-tive. stances described in the last chapter, by Voltaic electricity, they are attracted by the negative surface. With very few exceptions, they combine with the three supporters of combustion, already described, and of these compounds, one or more are acids. They are six in

number:

1. Hydrogen.
2. Nitrogen.

3. Sulphur.

4. Phosphorus.

5. Carbon.

6. Boron.

SECTION I. Hydrogen.

227. HYDROGEN was first duly examined by Mr. Cavendish (Phil.

• The specific gravity of iodine vapour, as deduced from hydriodic acid, (oxygen being 1) 13=7.8125, near by and its atom is just double or 15.625, (the atom also, of oxygen being 1) -again 0.125 (atom hydrogen) × 125 = 15.625 (atom Iodine.)

gen.

Mode of pro Trans. Vol. lvi.) It may be obtained by the
curing hydro-
action of iron or zinc upon dilute sulphuric
acid. Some pieces of iron-wire, or of zinc,
may be introduced into the flask a, and co-
vered with sulphuric acid diluted with six
times its bulk of water. The gas escapes
by the bent tube b, which is inserted by
grinding into the neck of the flask, and may
be collected in the hydro-pneumatic ap-
paratus.

b

a

Hydrogen is an aëriform fluid, not absorbable by water. It has no Character and taste, a slightly disagreeable smell, and may be respired for a short Properties time, though it is instantly fatal to small animals. It is the lightest body known; and we therefore conveniently assume it as unity in speaking of the specific gravity of gases, as well as in referring to the proportions in which bodies combine. 100 cubic inches weigh at mean temperature and pressure 2.118 grains. Its specific gravity is 0.0694, when common air is taken as 1.00, and 0.0625 when oxygen is = 1.00*.

Weight.

Inflamable air pistol.

228. Hydrogen is inflammable, and extinguishes flame. When pure, it burns quietly with a lambent blue flame at the surface in contact with air; but, if mixed with thrice its volume of air, it burns rapidly, and with detonation. In making this experiment, a strong phial, capable of holding about 6 ounces of water, may be employed; or the inflammable air-pistol, which admits of the mixture being fired by the electric spark.

This instrument consists of a cylinder of brass, about three-fourths of an inch diameter, and six inches long, in the form of a small cannon or pistol-barrel, properly mounted, and having a wire, a, passing through a tube of ivory, b, and not quite touching the interior of the

a

*

eylinder, at the part usually occupied by the touch-hole; an electric spark communicated to this wire inflames the mixture of hydrogen and atmospheric air in its interior. It may be charged by previously filling it with dry sand, and emptying it out into a phial of hydrogen, which rises into the gun sufficiently mixed with air; the muzzle may be secured by a cork, which is expelled with much violence and a loud report, upon the inflammation of the gas.

229. The electrical air-gun, may be also charged, by holding it for a moment over the open jet of the following instrument always taking care that there is a due admixture of atmospheric air, otherwise the electric spark will not inflame it.

* We have seen that the specific gravity of hydrogen is 0,0625 when that of oxygen is taken 1.00 now 0,0625 is just 16 times as small as 1,00 for 0.0625 X 16 = 1, again to find the atom of hydrogen the atom of oxygen being a pound = 1, we have only to double the specifie gravity 0.0625 i. e. 0.0625 X 2 = 0.125 atorn hy drogen. (Sec. 236.)

:

a is a funnel shaped vessel, fitting by a ground-joint into the three-necked bottle ; to the stopper c is annexed a brass wire, with a cylinder of zinc screwed upon its lower end; d is a tube furnished with a stopcock and jet-pipe; the capacity of the vessel a should be nearly equivalent to that of b, and may contain 3 or 4 pints. To charge this apparatus with hydrogen, b is three fourths filled with water, and the stopper e being removed, a quantity of sulphuric acid, previously diluted with its bulk of water, is poured in by a long funnel, so that it may remain at the

[merged small][ocr errors][merged small]

bottom of the water which now fills the vessel. The stopper c, with its appended piece of zinc, is then put in, and the generated hydrogen forces the dilute acid into a, where its pressure serves to propel the gas through d whenever the stop-cock is opened; the acid, at the same time descending, produces a fresh portion of hydrogen by again acting upon the zinc. This instrument is useful where small quantities of hydrogen are required for burning, charging air-guns, and other purposes.

230. If 2 volumes of hydrogen and 1 of oxygen be burned in the phial or air gun, the explosion is extremely violent.

231. A current of hydrogen may be inflamed when issuing from a small aperture, and if a tube of 18 or 20 inches in length be held over the flame, a peculiar musical tone is produced. This effect is not peculiar to hydrogen, but is produced by a variety of other flames (FARADAY, Journal of Science and the Arts, Vol. v.) and is referable to the succession of explosions produced by the combustion of the gas in the tube.

232. The tendency which gaseous fluids have to become completely mixed under all circumstances, and as it were to penetrate each other, is well illustrated where hydrogen is employed. Thus, if two small phials, the one containing oxygen and the other hydrogen, be connected perpendicularly by a long glass tube, of small bore, it will be found, that although the hydrogen be uppermost, and much lighter than the oxygen, it will, in the course of a few hours, have perfectly mixed with the oxygen, and the gases will be found in equal proportions in both phials. Mr. Dalton has shown that gases, unlike other fluids, do not remain upon each other without admixture.-Manchester Memoirs, Vol. i. New Series.

233. Hydrogen, in consequence of its extreme lightness, is employed for filling air-balloons, and is elegantly applied to the purpose of obtaining instantaneous light in Volta's inflammable air-lamp.

Musical tones during the combustion of hydrogen.

Gases have a powerful tendency to mix together.

gen as a

234. The flame of hydrogen is occasionally employed for exciting intense heat; and it has been found, when mixed with oxygen and burn-Use of hydraed as the mixture issues from a small jet, to excite a temperature nearly pipe. equal to that of the arc of flame in the Voltaic circuit. A blow-pipe upon

this construction was first made by Mr. Newman, at the suggestion of Mr.

Union with

oxygen gas.

Brooks, and afterwards improved, as to its safety, by Professor Cumming, of Cambridge. Journal of Science and the Arts, i. 65 and ii. 380.

235. Hydrogen and oxygen. When two volumes of hydrogen gas are mixed with one volume of oxygen gas, and the mixture inflamed in a proper apparatus by the electric spark, the gases totally disappear, and the interior of the vessel is covered with drops of pure water, equal in weight to that of the gases consumed.

If pure water be exposed to the action of Voltaic electricity, it is Composition resolved into two volumes of hydrogen, disengaged at the negative pole, and one volume of oxygen, disengaged at the positive pole; so that water is thus proved by synthesis, and by analysis, to consist of two volumes of hydrogen, combined with one volume of oxygen. The specific gravity of hydrogen compared with oxygen, is as 1 to 16, therefore the component parts of water by weight are,

1 Hydrogen.
8 Oxygen.

[blocks in formation]

Apparatus for shewing the formation of

water.

So that 100 parts of water consist of
88.89 Oxygen.
11.11
Hydrogen.
100,00

236. The experiments illustrating the composition of water, may be divided into synthetic and analytic. Among these the following may be selected :

i. Burn a current of hydrogen under the funnel a, represented in the following wood-cut; by uniting with the oxygen of the atmosphere

b

a

it will produce aqueous vapour, which passing into the glass cylinder, 6, will condense in drops.

ii. The annexed woodcut represents an apparatus for showing the

[blocks in formation]

production of water by burning a current of hydrogen in an atmos

« PreviousContinue »