of Berthier, it contains at least one-fourth its weight of water, a proportion which could scarcely have been expected in so hard a substance.' Henry.

425. Phosphate of ammonia, exposed to a red heat in a platinum crucible, affords also a phosphoric acid, which is very pure.

426. Phosphoric acid is deliquescent and soluble. It is not susceptible of decomposition by the action of heat merely. When distilled in an earthern retort, with about half its weight of charcoal powdered, the glacial acid is decomposed; its oxygen, uniting with the carbon, forms carbonic acid, and part of the phosphorus rises in a separate state; another, and the larger part, escapes in combination with hydrogen. In this way phosphorus is best obtained.

427. Phosphorus and chlorine.-These elements combine in two proportions, constituting two definite compounds, viz. the perchloride, or bichloride, and the chloride, or proto-chloride.

428. When phosphorus is treated with chlorine, it burns with a pale flame, and produces a white volatile compound, which condenses on the sides of the vessel. This is the perchloride of phosphorus, a substance which was for some time confounded with phosphoric acid; but its volatility is sufficient to mark the difference. It rises in vapor at a temperature considerably below 212°. It acts violently on water, a mutual decomposition being effected, muriatic and phosphoric acids being the result. When transmitted through a red hot porcelain tube, with oxygen, phosphoric acid is formed and chlorine evolved; this fact is in proof, that the affinity of oxygen for phosphorus, is stronger than chlo

rine.

429. The chloride, or proto-chloride of phosphorus.-Sir H. Davy recommends the preparation of this compound, by passing the vapor of phosphorus over corrosive sublimate, which is a perchloride of mercury. By this process calomel, or proto-chloride of mercury is formed, and the phosphorus unites with one proportional of chlorine.

430. Chloride of phosphorus is a liquid of the specific gravity 145. It soon, upon standing, deposits a portion of phosphorus, and becomes limpid and without color. It is converted into the perchloride by chlorine. Ammonia separates phosphorus, and produces a triple compound.

431. It acts upon water with much energy, and produces muriatic and phosphorus acids; while the perchloride produces muriatic and phosphoric acids, for as, in the perchloride, there are two proportionals of chlorine, so in acting upon water, two of oxygen must be evolved, which, uniting to one of phosphorus, generate phosphoric acid. The chloride of phosphorus, on the contrary, containing only one proportional of chlorine, produces muriatic acid, and phosphoric acid, when it decomposes water. But the phosphorus acid thus produced, always contains water, which it throws off when heated in ammonia, forming, with that alkali, a dry phosphate. This experiment shows that the hydro-phosphorus acid consists of two proportionals of phosphorus acid, = 37 +1 water =8.5,'

432. Phosphorus with Iodine.-Iodide of phosphorus is formed by the simple combination of iodine with phosphorus; the compound is of a reddish brown color, and if the components be quite dry when they are made to come into contact, their combination produces no evolution of gas; but if they be moistened, then hydriodic acid is formed from the union of iodine with the hydrogen of the water, a little subphosphureted hydrogen is also produced, and phosphorus remains in solution.

SULPHUR.

433. Sulphur, or brimstone, is met with either as a compact solid body, usually in the shape of long rolls, or in the form of a light powder, called flower of sulphur. It is principally a mineral product. The sulphur of commerce is generally purer than that which is met with in this country, which is usually combined with a portion of the metal from which it has been separated.

434. Sulphur volatilises at about the temperature of 180°, if the heat be carried up to 225° it liquifies; by a rapid increase of temperature up to from 350 to 400°, it becomes viscid, and of a deep brown color. It sublimes at 600°, and after fusion it forms a crystalline fibrous mass.

435. If sulphur be converted into vapor in close vessels, it is again collected in a solid form; what remains has been named sulphur vivum.

436. For pharmaceutical purposes it is occasionally precipitated from its alkaline combinations by an acid, and is then the milk of sulphur, or precipitated sulphur of the pharmacopoeia. This precipitated sulphur is considered by Dr. Thomson as a compound of sulphur and water.

437. We may judge of the purity of sulphur by heating it gradually upon a piece of platinum leaf; when, if free from impurities, it will totally evaporate. Boiling oil of turpentine will also dissolve sulphur completely, if it be pure.

438. That sulphur contains hydrogen was proved by the experiments of Sir II. Davy, who produced sulphureted hydrogen from it by powerful voltaic influence; and the action of potassium upon it demonstrates the same thing, these two bodies enter energetically into combination, and sulphureted hydrogen is evolved with intense heat and light.

439. But whether hydrogen be an incidenta! or inherent ingredient of sulphur is considered as still doubtful, both by Davy and Berzelius; the latter chemist found, upon heating oxide of lead with sulphur, that the quantity of water produced was not sufficient to indicate any definite proportion of hydrogen in sulphur.

440. Sulphur and Oxygen.-Two well-defined compounds are formed by the combination of sulphur with oxygen, viz. sulphurous and sulphuric acid. The first may be obtained by several processes: 1. By burning sulphur in oxygen gas. 2. By heating mercurial oxide with sulphur. 3. By boiling mercury in sulphuric acid; and, 4. By burning sulphur, at a low temperature, in common air, under a glass bell.

441. Sulphurous acid has a suffocating smell, resembling that which attends the burning of sulphur itself. It is more than twice as heavy as atmospheric air. In a gaseous state it extinguishes burning bodies; and it is fatal to animal life, when exclusively respired.

442. Water absorbs about thirty-three times its bulk, or one-eleventh its weight, and caloric is evolved by the union. The watery solution does not, as acids in general do, redden an infusion of litmus, but it entirely destroys its color. Hence its use in bleaching several substances; it is employed sometimes to check fermentation in wines.

443. Sulphurous acid may be converted to the state of sulphuric, by imparting oxygen to it. If water, impregnated with sulphurous acid, be exposed to oxygen gas, the oxygen gradually becomes absorbed, and thus is sulphuric acid formed. By the addition of a little oxide of manganese to water saturated with sulphurous acid gas, sulphuric acid will be produced. This gas is likewise formed into sulphuric acid by admixture with chlorine, if the gases are in contact with water; the hydrogen of the water in this case combines with the chlorine, and the oxygen with the sulphurous acid. The contact of water is also necessary to the formation of the sulphuric acid, when the decompositions are effected by means of nitrous acid gas.

444. Sulphurous acid gas is decomposed by the application of heat, in contact with some combustible substances. A mixture of sulphurous acid and hydrogen gases, passed through a redhot porcelain tube, will be attended by the following decomposition and result; the oxygen of the acid will combine with the hydrogen, and form water, while sulphur will be deposited in a separate form.

Sulphurous acid, we are told, consists of
1 atom of sulphur
2 atoms of oxygen

16

16

32

448. Sulphuric acid is largely consumed in a variety of manufactures. It is used by the makers of nitric, muriatic, citric, and tartaric acids; by bleachers, dyers, tin-plate makers, brass-founders, and gilders. For these purposes it is generally sufficiently pure as it comes from the wholesale manufacturer; but as traces of lead, lime, and potassa are usually found in it, it often requires to be purified by distillation, for the use of the experimental chemist.

449. The distillation of this acid in glass retorts, requires some precaution, in consequence of the violent jerks which the production of its vapor occasions, and which often break the vessel; this may be prevented by putting some strips of platinum into the acid; it then boils quietly, and it is only necessary to take care that the neck of the retort and receiver are not broken, in consequence of the high temperature of the condensing acid. This very useful contrivance, says Mr. Brande, was first shown me by Mr. James Smith.

450. If the acid of commerce contain dissolved sulphate of lead, it becomes turbid, on dilution, so that its remaining clear when mixed with water, is some proof of its purity, as far, at least, as lead is concerned.

451. When sulphuric acid was procured by the distillation of green vitriol it was frequently observed that a portion concreted into a white mass of radiated crystals. The same substance has also been remarked as occasionally formed in the acid of the English manufacturers. It has been called glacial or fuming sulphuric acid, and is by Dr. Thomson considered as the pure or anhydrous acid; that is sulphuric acid free from

In volumes, it is constituted of

1 vol. of vapor of sulphur condensed into 1 vol. 1 vol. of oxygen

445. Sulphuric acid was formerly obtained from sulphate of iron (green vitriol) by distillation. It is now generally formed by burning a mixture of about eight parts of sulphur with one of Ditre, in close leaden chambers, containing water. See Parkes' Chemical Essays, vol. ii. See also the first part of the present essay.

446. Sulphuric acid is a limpid and colorless fluid; it is oily in its consistence, hence the vulgar name of oil of vitriol. A very considerable heat is evolved when sulphuric acid and water are suddenly mixed. It is acrid and caustic; it is nearly twice as heavy as water. It may be frozen by a sufficient reduction of temperature; and when, at the specific gravity of 1780, it requires for its congelation even a less degree of cold than is sufficient to freeze water. All combustible matters decompose sulphuric acid, it is therefore necessary in preserving it, to VOL. V.

of sulphuric acid combined with a portion of sulphurous acid.

452. It has long been an object with the manufacturer to obtain sulphuric acid without the aid of nitre, and a patent has been obtained for a process of this kind, invented by Mr. Hill. It consists in submitting coarsely powdered iron pyrites (sulphuret of iron) to a red heat, in cylinders communicating with a leaden chamber containing water. The sulphur, as it burns out of the pyrites, appears at once to pass into the state of sulphuric acid. Brande.

453. The theory of the formation of sulphuric acid, when it is procured from sulphur, is generally that of sulphur acquiring a certain quantity of oxygen, either from the atmosphere or from the bodies with which the sulphur is made to come in contact; when the acid is formed by burning nitre and sulphur together, sulphurous acid is generated, while the nitre occasions the production of nitric oxide, which produces nitrous acid gas. 'When these gases, i. e. sulphurous and nitrous acids, are perfectly dry they do not act 2 D

upon each other, but moisture being present in small quantities they form a white solid, which is instantly decomposed when put into water. The nitrous acid reverts to the state of nitrous oxide, having transferred one additional proportional of oxygen to the sulphurous acid, and with water producing the sulphuric acid; while the nitric oxide by the action of the air again affords nitrous acid, which plays the same part as before.'

454. Sulphuric acid is susceptible of decomposition, by being treated with combustible substances at high temperatures. Indeed heat alone will decompose it. If the vapor of the acid be passed through a red hot tube of glass or porcelain it is resolved into sulphurous acid gas and oxygen gas. Platinum wires, communicating with the extremities of a galvanic pile, will also decompose the acid, and it will be found that, at the end of the negative wire, floculi of sulphur make their appearance, while at the positive end oxygen gas is evolved. In this experiment some sulphate of platinum is said to be formed, produced by the action of the acid upon the platinum, and indicated by the presence of a brownish tinge.

455. The hypo-sulphurous acid does not exist, as do the two acids just mentioned, separable from a base; nor does hypo-sulphuric acid.

It

456. Sulphur with chlorine.-Chloride of sulphur was first described by Dr. Thomson, in Nicholson's Journal. Upon sulphur being heated with chlorine more than twice its weight of the gas is absorbed, the product is a greenish yellow fluid, which exhales suffocating fumes when exposed to the air; its specific gravity is 1.6. is volatile below 200° of Fahrenheit. It does not affect vegetable blues when they are in a dry state, but upon water being added, it instantly reddens them, sulphur becomes deposited, and sulphurous, sulphuric, and muriatic acids are formed from the decomposition of the water, its hydrogen uniting with the chlorine, and its oxygen combining with a portion of the sulphur to form the sulphuric and sulphurous acids, while another portion of sulphur is, as above stated, thrown down.

457. Sulphur and iodine readily combine at a gentle heat and form a black compound, not unlike the sulphuret of antimony. This was first described by Gay Lussac in the An. de Chim, 91. Its precise composition does not seem to be

known.

SELENIUM.

458. Berzelius detected this substance in the sulphur of Fahlun in Sweden, and he at first supposed it to be tellurium. The process of extracting it is described in the 13th volume of the Annals of Philosophy. This material has since been discovered in the volcanic rocks of Lipari; and more recently several minerals from the east have been found to contain it by the analysis of Mr. Henry Rose (See An, de Chim. et de Phys. xxix. 113.) A seleniuret of lead has also been analysed from the Lawrence Mine at Clausthal, which bore a considerable resemblance to galena, and from which selenium was sublimed by heating the material in a glass tube.

459. The color of selenium is gray, but it varies considerably; it has a bright metallic lustre, and by most chemists is arranged among the metals. When heated before a blow-pipe it exhales fumes, with a smell like that of horse-radish, which is so powerful that it is said a fragment not exceeding 1-50th of a grain is sufficient to impregnate the air of a large apartment.

460. Selenium combines with the oxygen of the air when heated. The selenic oxide gas is but sparingly soluble in water. It does not unite with liquid alkalis. It seems to belong to the same class of oxides as the carbonic oxide.

461. Selenic Acid.-If selenium be heated to dryness in combination with nitric acid, a volatile and crystallisable compound is formed, which is the selenic acid. This may likewise be obtained by dissolving selenium in nitric and nitro-muriatic acid, and evaporating the solution in a retort. This acid unites with most bases in two proportions, forming a class of salts called seleniates, biselianates, &c. See Annales de Chimie et Physique, tom. vii. Thomson's Annals, ii. and xii.

462. Selenium absorbs chlorine gas, with which it forms a brown liquid, that by the addition of more chlorine is changed into a white solid mass. Berzelius states this to be a compound of muriatic and selenic acids, but it is probably composed, says Dr. Henry, of chloride of selenium and the latter acid.

After treating of the acidifiable bodies (not metallic), and their combination with oxygen, chlorine, iodine, and fluorine, the author, whose arrangement we hitherto adopt, proceeds to consider their combination with each other.

NITROGEN AND HYDROGEN. (Ammonia). 463. Ammonia in a gaseous form may be obtained by mixing equal parts of muriate of ammonia and dry quicklime, or two of the former and one of the latter; they are to be introduced into a small glass retort, a gentle heat applied, and the gas that is evolved collected over mercury.

464. This gas has a strong pungent smell; it has a specific gravity to hydrogen of 8 to 1, 100 cubical inches weighing a little more than 18 grains. It extinguishes flame, and is fatal to animal life; it converts most vegetable blues to green, and yellows to red; thereby establishing its alkaline properties, and it has obtained the vulgar appellation of volatile alkali. It is readily absorbed by water, and when the liquid is saturated with the gas, liquid ammonia is produced; which may be formed in the way recommended by Mr. R. Phillips. Remarks on the London Pharmacopeia, for an account of this process see AMMONIA and PHARMACY.

465. Ammoniacal gas may be analysed by applying an electric spark to a mixture of ammonia and oxygen gas, which inflames it, in the same way that the electric spark fires a mixture of hydrogen and oxygen gases. Dr. Henry first observed this, and published the announcement in the Philosophical Transactions for 1809.

466. To obtain accurate results we are directed to use less oxygen at first than is sufficient to saturate the whole hydrogen of the alkali, for is

481. Ammonia with carbonic acid.-The ammonical and carbonic acid gases readily combine to form carbonate of ammonia. One volume of the latter and two of the former, being mixed in a glass vessel over mercury, undergo a complete condensation, and carbonate of ammonia is the result. This is one of the most useful of the ammoniacal compounds.

482. A bi-carbonate is engendered if water be present, for this so far overcomes the elasticity of the gas as to enable the salt formed to take up another volume of carbonic acid.

483. Carbonate of ammonia is generally met with in cakes which are broken away from the vessel in which the salt sublimes, when it is made by treating muriate of ammonia with carbonate of lime. This salt ought indeed to be called hydrated carbonate of ammonia, since the

result of the combination is carbonate of am

monia, water, and chloride of calcium, the two first being in union; and, even supposing the materials of the compounds to be dry, water comes to be formed by the union of the hydrogen abstracted from the muriatic acid, with the oxygen taken from the lime.

484. Under the name of the sub-carbonate of ammonia, another compound is met with in the shops, produced by mixing one part of muriate of ammonia with one and a half of dry carbonate of lime, and exposing them to heat in a proper

apparatus.

solves rather less than four ounces. This solution is the liquor ammonia sub-carbonatis of the London Pharmacopoeia.

486. Borate of ammonia is formed by saturating boracic acid with ammonia; it is formed in crystals. Phosphate of ammonia is very soluble, but does not easily crystallise. Hypophosphite of ammonia. Composition unknown. Phosphate of ammonia is a common ingredient in urine, especially of the carnivorous animals. It may be formed by saturating the superphosphate of lime, which results from the action of monia; or by at once saturating phosphoric acid sulphuric acid on bones, with carbonate of amwith ammonia.

It crystallises in four-sided pyramids with square bases, which are soluble in twice their weight of water at 6°. Hyposulphite of ammonia is strictly, according to Mr. Herschell, a bi-salt. It may be formed by passing sulphurous acid through the aqueous solution of the sulphuret. This salt does not freely crystallise. Its taste is exceedingly bitter and pungent. Sulphate of ammonia may be formed by passing ammonia into sulphuric acid; but it with the sub-carbonate; or by decomposing is usually prepared by dilute sulphuric acid, muriate of ammonia by sulphuric acid. This salt crystallises in six-sided prisms, which have quescent, and are soluble in an equal weight of a bitter and pungent taste; are slightly deliboiling water. Seleniates of ammonia exist in biseleniates, and quadrisileniates. three different proportions, forming seleniates,

HYDROGEN WITH CARBON.

487. Carbon and hydrogen combine so as to form carbureted hydrogen gas; this union is effected in several natural processes, especially those of putrefaction; it cannot, however, be effected by heating charcoal at once in hydrogen gas, since the cohesive attraction existing between the particles of the charcoal prevents the free chemical combination between the two sub

stances.

488. Another combination of these substances is generally known by the name of olefiant gas, which was first noticed by the chemists of Holland, and termed by them olefiant, and to a third combination Mr. Dalton has given the provisional name of super-olefiant; this last, however, has never been exhibited in a separatę form.