iron wire, lengthened out with one of platinum be introduced within the tube, so that the latter metal only may be in contact with the mixed gases and let the end of this wire be distant about one-fourth of an inch from the extremity of the upper conducting one. When the apparatus is thus disposed, pass a series of electric sparks or shocks through the gases for several hours. The mixture will be diminished in bulk; will redden litmus paper when enclosed in it; and will exhibit distinctly the smell of nitrous acid. If the experiment be repeated with the addition of a few drops of solution of potassa in contact with the gases we shall obtain a combination of nitric acid with that alkali. The proportions which Mr. Cavendish found necessary for mutual saturation were five parts of oxygen gas and three of common air, or seven parts of oxygen gas to three of nitrogen gas. The acid says Dr. H., from whom we have extracted the above, thus obtained being constituted of 100 measures of nitrogen +233 oxygen, appears therefore to have been intermediate between nitrous and nitric acid, or more probably consisted of both those acids in a state of mixture. No evolution either of light or heat attends this combination, which is very slowly and gradually effected.

389. Pure nitric acid in a gaseous state is composed according to Davy of 29 nitrogen and 70 oxygen. The later experiments of this philosopher have led him to the conclusion that four in volume of nitrous gas, and two of oxygen gas, when condensed in water, absorb, in becoming nitric acid, one in volume of oxygen. Dr. Wollaston from his experiments and from those of Richter and Phillips infers that nitric acid contains by weight 50 of oxygen to 17.54 of nitrogen; in volume the proportions are 1 of nitrogen and 2 of oxygen.

390. This gas may be decomposed by causing it to pass through a porcelain tube heated to redness, and by this treatment it is resolved into nitrous acid gas, oxygen, and water.

391. For preparing the liquid nitric acid we are directed, in the last edition of the London Pharmacopoeia, to mix two pounds of nitrate of potass deprived of its water of crystallisation by heat with two pounds of sulphuric acid; a glass retort is to be used in the mixture and it is to be distilled in a sand-bath until a red vapor rises. The acid in the receiver is to be mixed with another ounce of nitrate of potassa and again to be distilled. This rectification Mr. Philips considers unnecessary.

392. The muriatic and sulphuric acids that generally contaminate the nitric acid of commerce may be separated from it by adding nitrate of baryta to precipitate the latter, and nitrate of silver, for the precipitation of the muriatic acid: This last the nitrate of silver may be put in solution, to the suspected acid, first and continued so long as it produces a white precipitate. When this ceases pour off the clear liquor and add in the same manner the nitrate of barytes; then if the acid be distilled it will pass off perfectly

tremely corrosive; its specific gravity is modified by the water it contains. At about 40° it congeals. It absorbs water from the air, increasing its bulk, and lessening its specific gravity. A sudden mixture of it with half its quantity of water occasions the evolution of heat. It retains its oxygen with little force; it is thus in part decomposed by the sun's rays, which separates oxygen from it, and all combustible bodies act the same upon it with more or less readiness, in proportion to their affinity for oxygen. With hydrogen, at as high temperature, detonation is occasioned, essential oils are inflamed by nitric acid when it is suddenly poured upon them.

394. Nitro Muriatic Acid.-This is the aqua regia of the alchemists. A mixture of nitric and muriatic acids, acquiring the power of dissolving gold, a power which neither of the acids possesses separately. The mixture of these two bodies occasions the evolution of chlorine; it would appear from the experiments of Sir H. Davy, that a mutual decomposition takes place, the hydrogen of the muriatic acid abstracts oxygen from the nitric, and in consequence the nitric becomes nitrous acid, water is formed, and, as we have said, chlorine evolves. The mode then in which this aqua regia affects gold, is by causing its combination with chlorine.

395. Nitro-muriatic salts cannot be formed, for when this combination acts upon alkalis or earths, the two acids as far as they combine do so separately; and metallic bodies dissolved in aqua regia only yield muriates.

396. Nitrogen and Chlorine. (Chlorine of Nitrogen.)-We are recommended by Mr.Brande to form this salt by filling a perfectly clean glass basin with a solution of about one part of salammoniac in twelve of water, and inverting it in a tall jar of chlorine. The saline solution becomes gradually absorbed and rises into the jar, a film forms upon the surface, and it acquires a deep yellow color. At length small globules, looking like yellow oil, collect upon its surface, and successively fall into the basin beneath, whence they are most conveniently removed by drawing them into a small and perfectly clean glass syringe, made of a glass tube drawn to a pointed orifice, and having a copper wire with a little tow wrapped round it for a piston. In this way a globule may be drawn into the tube, and transferred to any other vessel.

397. This is the most powerfully explosive and detonating substance that is known, so much so, that in experiments it is not safe to employ a quantity larger than a grain of mustard seed. It is especially thus combustible with phosphorus and the fixed oils. Dulong, who discovered the compound, was severely wounded in his first experiments with it, and Sir H. Davy had his eye injured by it.

398. The specific gravity of the fluid Sir H. Davy has determined to be 1653, water being 1. It is not congealed even by a very high degree of cold, it is said not to become solid at 16°. There are some bodies termed combustible with which it seemed to unite without decomposition; nor did metals, resins, or sugar, cause it to explode.

We are told by Mr. Brande, that it yields by decomposition one volume of nitrogen and four of chlorine, and as the specific gravity of nitrogen to chlorine is as 13 to 33,5, so it may be said to consist of one proportional of nitrogen, + 4 proportionals of chlorine, or 13" + 134e by weight,

and its number will be 147.

400. Nitrogen and Iodine.-If iodine be kept in a solution of ammonia in water, hydriodic acid is produced, and besides this, a brown powder which is an iodide of nitrogen, and which explodes with great violence upon the slightest touch. This compound evaporates spontaneously when exposed to the atmosphere. When it detonates it gives out the purple fumes of iodine; but, attempts having failed to collect the products, the proportions of its components have not been ascertained. Gay Lussac supposes it to consist of three atoms of iodine, and one atom of nitrogen.

CARBON.

For an account of this substance, and its product carbonic acid, see CARBON and CARBONIC ACID in the present work; see also the word DIAMOND.

401. Carbonic Oride.-The composition of this gas was first made known by Mr. Cruickshank of Woolwich, an account of which will be found in Nicholson's Quarto Journal, the fifth volume. It is usually obtained by subjecting carbonic acid to the action of substances which abstract from the acid a portion of its Oxygen. The mixture we are told which affords the gas in its purest state, is formed of equal parts of carbonate of baryta and clean iron filings; these should be introduced into a small earthen retort, so as nearly to fill it, and be exposed to a red heat.

Whether the gas be obtained by this or any other process, it must be washed with lime or a solution of potassa.

402. Carbonic oxide is lighter than common air. Its specific gravity being to hydrogen as 13-2 to 1, 100 cubic inches weighing about thirty grains. It is destructive of animal life. "When two volumes of carbonic oxide and one of oxygen are acted on by the electric spark, a detonation ensues, and two volumes of carbonic acid are produced. Whence it appears that carbonic acid contains just twice as much oxygen as carbonic oxide, which may be considered as a compound of one volume of oxygen and one volume of gaseous carbon; or of one proportional of carbon and one of oxygen, the latter being so expanded as to occupy two volumes. Brande.

403. Carbonic oxide is inflammable, and

burns with a blue flame; but when mixed with common air it does not explode as do other inflammable gases, but burns silently. A mixture, however, of two measures of it with one of common air, forms a composition which will explode by the introduction of red hot iron, or a lighted taper. When carbonic oxide, mingled with an equal bulk of hydrogen gas, is passed through an ignited tube, the tube becomes lined with charcoal. In this temperature, the hydrogen attacks oxygen more strongly than it is retained by the charcoal, and water is formed. It was found also by Gay Lussac to be decomposed by the action of potassium, which combines with the oxygen, and precipitates charcoal; and Dobeireiner, by bringing it into contact with sulphureted oxide of platinum, converted it into half its volume of carbonic acid. Henry.

404. Carbon with chlorine. When carbureted

hydrogen, mixed with a great excess of chlorine, is exposed to the action of light, a white crystalline substance is formed, which Mr. Faraday has termed perchloride of carbon. This substance has scarcely any taste; it resembles camphor in its odor; its specific gravity is about 2. It does not conduct electricity. It is not readily combustible, but burns with a brilliant light in oxygen gas. It is not soluble in water, but it freely dissolves in ether and alcohol; and the solutions deposit arborescent and quadrangular crystals. Volatile and fixed oils also dissolve it. It is not acted on by acids nor by alkalis; but at a red heat most of the metals decompose it. Chlorine has no action on it. Iodine abstracts from it part of its chlorine when applied to it at a high temperature. No water exists in it. Hydrogen gas when transmitted along with it through red hot tubes, decomposes it, muriatic acid and charcoal being produced. The composition of the perchloride seems to be about 10 of carbon, and 90 of chlorine, or the atomic composition is stated as

3 atoms of chlorine 108 2 atoms of carbon = 12 Weight of its atom

120

408. It is white, consists of small soft adhesive fibres, sinks slowly in water; is insoluble in it whether hot or cold; is tasteless; has a peculiar smell, somewhat resembling spermaceti; is not acted on by concentrated and boiling acids or alkalis, except that some of them dissolve a small portion of sulphur; dissolves in hot oil of turpentine, and in alcohol, but most of it crystallises in needles on cooling, burns in the flame of a lamp with a greenish blue flame, and a slight smell of chlorine; when heated melts, boils, and sublimes between 350°, and 450° or sublimes slowly at a heat of 250°, forming long needles. Potassium burns with a vivid flame in its vapor, and charcoal is deposited; and a solution of the residuum, in nitric acid, gives a copious precipitate with nitrate of silver.

409. Dr. Henry states the composition of this substance as follows:

And it is probable that another chloride of carbon will hereafter be found, consisting of two atoms of chlorine and one of carbon.

411. Carbon with chlorine and oxygen (chloro-carbonic acid).-This was termed by its discoverer, Dr. John Davy, phosgene gas, from its being produced through the agency of light. It is formed by mixing equal volumes of chlorine and carbonic acid gases, and exposing them to the sun's rays; condensation takes place to half their united volumes, and a gas is formed of intolerably pungent odor. When dissolved in water, it is changed into carbonic and muriatic acid gases. Chloro-carbonic acid is composed of an atom of carbon, an atom of oxygen, and an atom of chlorine. It condenses four times its volume of ammoniacal gas, and the product is a peculiar compound of a white color, from which the more powerful acids disengage muriatic and carbonic acids, but it is dissolved by acetic acid without effervescence. Several of the metals decompose it, and combine with the chlorine, evolving carbonic oxide, equivalent in volume to the original gas. Chloro-carbonic acid gas affords then an example of an acid with a simple base, and two acidifying principles, oxygen and chlorine, which are often united in the performance of this function. Henry.

412. BORON.-This substance was first procured by Sir H. Davy, in 1808, by means of vol

quently obtained in greater abundance and with more facility, by heating equal parts of potassium and boracic acid; in this experiment of Gay Lussac and Thenard, the oxygen of the boron is taken by the potassium and the boron is thus set free. Berzelius recommends the decomposition of an alkaline boro fluid by potassium, as the best method of obtaining the base. Boron appears in the form of a brown insoluble powder, burning with brilliancy when heated as high as 6000°, the combustion being more vivid in oxygen gas, or if the boron be mixed with substances which part freely with their oxygen. In this way boracic acid may be obtained; but this is usually procured by dissolving the salt called borax in hot water, and adding sulphuric acid. See BORACIC ACID. Boron is a non-conductor of electricity.

413. The experiments upon the composition of Boracic acid, says Brande, are much at variance. Berzelius's determination probably approaches nearest the truth; he regards it as containing 1 boron +3 oxygen. If therefore we consider it as consisting of 1 proportional of boron and 2 of oxygen, the number representing boron will be 5, and boracic acid will consist of

5 Boron 15 Oxygen

20 Boracic acid

PHOSPHORUS.

would inflame on taking them out of the water, and produce a painful and troublesome burn. It is usually formed into sticks, by pouring it, when fluid, into a funnel tube under water.

416. In performing this distillation a high temperature is required, so that the furnace should be sufficiently capacious to hold a body of charcoal piled up above the retort, which, as earthenware becomes permeable to the vapor of phosphorus at a red heat, must be coated with a mixture of slaked lime and solution of borax; this mixture may be laid on with a brush in two or three successive coats, and forms an excellent vitrifiable lute. Brande.

417. Phosphorus is an highly inflammable substance: its specific gravity 1770. When exposed to the air it exhales luminous fumes of a peculiar odor. It may be ignited by friction; in oxygen gas it burns very brilliantly, as also in nitrous oxide, nitrous and chlorine gases. Phosphoric acid is the product of a rapid combustion of phosphorus in oxygen.

418. The only information which we possess respecting the nature of phosphorus, is derived from the electro-chemical researches of Sir H. Davy. When acted on by a battery of 500 pairs of plates in the same manner as sulphur, gas was produced in considerable quantities, and the phosphorus became of a deep red brown color. The gas proved to be phosphureted hydrogen, and was equal in bulk to about four times the phosphorus employed. Hence hydrogen may probably be one of its components, but no confirmation of the truth of this view is derived from the recent experiments of the same philosopher, which, indeed, are rather contradictory to it. Henry.

419. Phosphorus is capable of being oxygenated in various ways. Oxide of phosphorus is formed on the surface of the material when it is kept for some time under water. This substance is inflammable, but not so volatile or fusible as is phosphorus itself. It is this which is generally employed in the phosphoric match boxes. But besides this oxide there are three acid combinations of phosphorus and oxygen, which have been named phosphorus, hypophosphorus, and phosphoric acids.

420. Phosphorus acid.-This is best obtained by subliming phosphorus through corrosive sublimate (a perchloride of murcury); then mixing the product with water, and heating it till it becomes of the consistence of a syrup. The resulting liquid is a compound of phosphorus acid and water, and it has therefore been named hydro-phosphorus acid.

421. The water is decomposed in the operation, its hydrogen, combining with the chlorine, forms muriatic acid; and its oxygen, uniting with phosphorus, forms phosphorus acid. Heat expels the muriatic acid from the mixture. According to Davy, 100 grains of phosphorus

acid consists of

of baryta, resulting from the action of phosphuret of baryta on water. The acid is to be added in just sufficient quantities to separate the baryta, and the solution which remains is the hypophosphorus acid, which, when evaporated to a certain extent, yields a sour viscid liquid, eagerly attractive of oxygen, and unsusceptible of crystallisation. It is doubtful whether this substance may not be a hydracid, or a triple compound of oxygen, phosphorus, and hydrogen; in this case, as Dr. Henry remarks, its proper appellation would be hydro-phosphorus acid.

423. Phosphoric acid.-This may be produced, of course, by the combustion of phosphorus in oxygen, or in atmospheric air, under a dry bell glass; but the following is given as the most economical method.

424. On 20 pounds of bone, calcined to whiteness and finely powdered, pour 20 quarts of boiling water, and add 16 pounds of sulphuric acid, diluted with an equal weight of water (in general much less of sulphuric acid is employed). Let these materials be well stirred together, and be kept in mixture about 24 hours. Let the whole mass be next put into a conical bag, of sufficiently porous and strong linen, in order to separate the clear liquor, and let it be washed with water, till the water ceases to have much acidity to the taste. Evaporate the strained liquor in earthen vessels, placed in a sand heat, and when reduced to about half its bulk, let it cool. A white sediment will form in considerable quantity, which must be allowed to subside; the clear solution must be decanted and boiled to dryness in a glass vessel. A white mass will remain, which is the dry phosphoric acid. This may be fused in a crucible, and poured out on a clean copper dish. A transparent glass is obtained, which is the phosphoric acid in a glacial state; not, however, perfectly pure, but containing sulphate and phosphate of lime. According to Fourcroy and Vauquelin, it is, in fact, a super-phosphate of lime, containing, in 100 parts, only 30 of uncombined phosphoric acid, and 70 of neutral phosphate of lime; but, when prepared with the full proportion of sulphuric acid, Mr. Dalton finds only from 8 to 12 per cent, of the calcareous phosphates. To separate the latter, Dr. Higgins neutralised the acid liquor, obtained by the action of sulphuric acid on bones, with carbonate of ammonia, the neutral liquor was decanted and evaporated, till a portion of it deposited crystals on cooling; and was then poured, while hot, into a thin glass balloon, which was placed on a sand-bed of a reverberatory furnace. The mouth of the balloon being covered with an inverted crucible, the fire was gradually_raised till the sand pot was obscurely red. way the sulphate of ammonia, and ammonia that neutralised the phosphoric acid, were both expelled, and the phosphoric acid remained in the form of a transparent colorless glass, still retaining a minute quantity of ammonia. The glacial acid may also be prepared from perfectly pure phosphoric acid, which has been made by acting on phosphorus with nitric acid. It is remarkable, that, according to the experiments

In this