Preparation. This salt is prepared on a large scale from the ammoniacal liquors obtained in the destructive distillation of coal and bones; these contain ammonia chiefly in the form of carbonate; they are decomposed either by sulphuric acid or by sulphate of lime, in the former case, with evolution of carbonic acid, in the latter, with precipitation of carbonate of lime; the liquid containing the sulphate of ammonia is then evaporated to crystallization; the crystals thus obtained are gently heated, to destroy various organic matters with which they are contaminated, and are then recrystallized.

Properties-Sulphate of ammonia is isomorphous with sulphate of potassa, crystallizing in flattened six-sided prisms, which contain no water of crystallization; it becomes slightly moist when exposed to air. When heated, the crystals decrepitate, afterwards fuse, and finally disappear entirely, sulphite of ammonia subliming, and water, ammonia, nitrogen, and sulphurous acid, passing off.

Sulphate of ammonia dissolves in 2 parts of cold and 1 part of boiling water. It has lately been proposed to employ this salt in order to render certain fabrics less combustible; it is also employed in the manufacture of artificial manures, and for the preparation of ammonia, alum, and other ammoniacal salts.

Bisulphate of Ammonia (NH,O.SO,,HO.SO,) may be obtained by the addition of sulphuric acid to the neutral salt.

§ 181. The Phosphates of Oxides of Ammonium possess but little practical interest; when heated, they disengage ammonia and water, leaving phosphoric acid. Gay-Lussac has proposed the use of phosphate of ammonia for rendering stuffs incombustible.

PHOSPHATE OF SODA AND AMMONIA, PHOSPHORUS SALT, MICROCOSMIC SALT. NaO.NH,O.HO.PO,=NaO.AmO.HO.PO,.

This salt occurs in the urine. It is prepared by dissolving 6 or 7 parts of phosphate of soda (2NaO.HO.PO,) and 1 part of chloride of ammonium in hot water, and allowing the solution to crystallize. It forms large transparent prisms, of the formula NaO.NH,O.HO.PO,+8Aq. The crystals effloresce slightly in air, and evolve a little ammonia. When gently heated, they fuse easily, and lose, at first, water and ammonia, being converted into NaO.HO.PO,; if this last be further heated, it is, of course, converted into NaO.PO,. Microcosmic salt is easily soluble in water; the solution evolves ammonia when evaporated. This salt is much used as a flux in blowpipe experiments. SESQUICARBONATE OF AMMONIA, SAL VOLATILE, COMMERCIAL CARBONATE OF AMMONIA, 2NH,0.3CO,.

§ 182. This compound has been alluded to above, as produced in the destructive distillation of coal and bones; when obtained from these sources, it is generally purified by one or two sublimations with animal charcoal, which retains the empyreumatic matters; the ordinary process, however, by which the sesquicarbonate of commerce is prepared, consists in subliming a mixture of sulphate of ammonia (or chloride of ammonium) and 2 parts of chalk, in an earthen or iron retort, furnished with a receiver of earthenware or lead; the salt distils over in the liquid form, and solidifies in the receiver, which is broken up when the mass is removed. The decomposition is represented by the following equation :3NH,Cl+3(CaO.CO,)=3CaCl+2NH ̧0.3CO,+NH,+HO; or, 3(NH,O.SO,)+3(CaO.CO,)=3(CaO.SO,)+2NH,O.3CO,+NH +HO.

cent solid, produced by the action of dry ammonia upon chlorosulphuric acid (SOCI), which is obtained when a mixture of chlorine and sulphurous acid is exposed to the action of solar light. Phosphamide, see & 116. Carbamide (NII.CO) is obtained when ammonia acts upon chlorocarbonic acid gas.

The salt obtained by this process, however, is a mixture consisting chiefly of the sesquicarbonate with varying proportions of other carbonates.

Properties. When freshly prepared, sesquicarbonate of ammonia forms a transparent fibrous mass, which, when exposed to air, soon becomes covered with an opaque, friable crust, into which the whole mass is gradually converted, the salt, meanwhile, exhaling a powerful odor of ammonia. This white crust consists of the bicarbonate of ammonia, and appears to be formed from the sesquicarbonate by the abstraction of ammonia and carbonic acid:

2NH,O.3CO,=NH,O.CO,HO.CO,+NH,+CO..

This change takes place much more rapidly if the salt be powdered; when it is completed, the residue has lost its pungent odor. When sesquicarbonate of ammonia is heated, carbonic acid is evolved at first, and part of the sesquicarbonate of ammonia sublimes unchanged, whilst the remainder enters into fusion, and is decomposed into compounds containing different proportions of ammonia and carbonic acid. The sesquicarbonate of ammonia dissolves in about 3 parts of cold water; if the salt be treated with a small quantity of water, it appears to suffer a partial decomposition, the solution containing chiefly the neutral carbonate, NHO.CO,, and the residue the bicarbonate. If a warm saturated solution be allowed to cool, large crystals of bicarbonate of ammonia are deposited. The latter salt also appears to be precipitated when the aqueous solution of the sesquicarbonate is mixed with alcohol.

The aqueous solution has an alkaline reaction, and an ammoniacal odor;1 if exposed to the air, it is gradually converted into solution of the bicarbonate; when the solution is boiled, carbonic acid, and traces of ammonia, are disengaged with effervescence, and the neutral carbonate remains in solution; if this be further evaporated, the latter salt is also volatilized.

The Bicarbonate of Ammonia may be obtained by passing carbonic acid through a concentrated solution of the sesquicarbonate; it is deposited in crystals of the formula NH2O.CO,,HO.CO,, which have the same form as those of bicarbonate of potassa. They are inodorous, permanent in the air, and volatilize when heated; this salt is much less soluble in water than the neutral carbonate. When the solution is boiled, it disengages carbonic acid, and neutral carbonate of ammonia (NH2O.CO,) remains in solution.

When sesquicarbonate of ammonia is dissolved in boiling water, in a flask, which is afterwards closed to prevent the escape of carbonic acid, the solution deposits, on cooling, large prismatic crystals of the formula 2(NH,O.HO.2CO2)+ Aq.

Sesquicarbonate of ammonia is employed as a smelling-salt, and, to a considerable extent, medicinally.

In the laboratory it is very useful as a reagent, and as a source of many other ammoniacal salts.

Other carbonates of ammonia, of more complicated composition, have been obtained, but present no points of interest.

The Borates of Ammonia are devoid of practical interest.

CHLORIDE OF AMMONIUM, HYDROCHLORATE OF AMMONIA, SAL-AMMONIAC. NH,Cl=AmCl.

§ 183. This salt is formed, in thick white fumes, when hydrochloric acid gas and ammoniacal gas are brought into contact; it is sometimes found in the neighborhood of volcanoes.

If an aqueous solution of sesquicarbonate of ammonia be exposed to a temperature approaching the freezing point, it deposits crystals of the formula 2NH,0.3CO,+3Aq. 2 Bicarbonate of ammonia has been found in considerable quantity, forming crystalline masses, in a bed of guano on the western coast of Patagonia.

Preparation.-Chloride of ammonium was formerly prepared chiefly in Egypt, where the inhabitants collected the soot arising from the imperfect combustion of the dung of camels; this soot was afterwards heated in large glass flasks, when the chloride of ammonium sublimed in the upper part, and was extracted by breaking the flask.1

A large quantity of sal-ammoniac is now prepared from the ammoniacal liquors obtained in the distillation of bones for the preparation of animal charcoal, and of coal in the gas-works. These ammoniacal liquors are neutralized with hydrochloric acid (which decomposes the carbonate of ammonia and sulphide of ammonium, with evolution of carbonic and hydrosulphuric acids), evaporated, and allowed to crystallize; the salt is then gently heated to destroy the tarry matter which it contains, dissolved in water, and purified by animal charcoal; the pure crystals are afterwards sublimed in large earthen bottles, or in iron vessels, lined with clay, and provided with leaden domes.

Chloride of ammonium is also prepared by subliming a mixture of sulphate of ammonia and chloride of sodium, when

NH2O.SO,+NaCl-NaO.SO,+NH ̧CI.

The sulphate of ammonia is obtained from the ammoniacal liquor of the gasworks, or of the bone-black factories, either by neutralizing them with sulphuric acid, or by double decomposition with a sulphate (of lime or oxide of iron).

The chloride of ammonium is also sometimes prepared from mixed solutions of sulphate of ammonia and chloride of sodium; on evaporation, the chloride of ammonium crystallizes out, and sulphate of soda remains in the mother-liquor.

Properties. The sublimed chloride of ammonium of commerce forms a very tough, translucent, fibrous mass, generally retaining the shape of the vessel into which it was sublimed, and often of a brown color where it has been in contact with this vessel. It is not altered by exposure to air. At a red-heat it volatilizes in thick white clouds, without previously fusing. It may, however, be fused in a tube, which is hermetically sealed.

Chloride of ammonium dissolves in 2.7 parts of cold water, and in an equal weight of boiling water. The solution, on cooling, deposits anhydrous crystals of a peculiar feathery appearance and consisting of an assemblage of minute octohedra.

When an aqueous solution of chloride of ammonium is evaporated, a little of the salt passes off with the vapor.

The solution of chloride of ammonium is capable of dissolving many metallic oxides and salts insoluble in water. Chloride of ammonium is sparingly soluble in alcohol.

Many metals, at somewhat elevated temperatures, decompose chloride of ammonium, metallic chlorides being formed, while ammonia and hydrogen are evolved.

Uses of Chloride of Ammonium.-This salt is the source from which ammonia is always prepared in the laboratory, and is also very useful in analysis.

It is employed occasionally in soldering, to cleanse the metallic surfaces to be united; its action in this case appears to depend upon the principle which Rose has recently turned to account in analytical operations.

Rose found that when the arseniates, arsenites, antimoniates, and stannates of the alkalies were heated with several times their weight of chloride of ammonium, the arsenic, antimony and tin were volatilized in the form of chlorides. The alkaline phosphates were entirely converted into chlorides by the same treatment. Alumina was partly, and sulphate of alumina entirely, volatilized when heated

At Liège, sal-ammoniac is prepared by burning, in peculiarly constructed ovens, a mixture of coal, common salt, clay, and animal matter, collecting the soot, and separating the chloride of ammonium from it by sublimation.

with sal-ammoniac. Sesquioxide of iron was also partly volatilized. The oxides of nickel, cobalt, and bismuth, were reduced to the metallic state. Oxide of zinc, oxide of lead, sulphide of lead, and sulphate of zinc, were completely volatilized. These reactions have been applied by their discoverer to facilitate the quantitative analysis of various substances.

Chloride of ammonium is also employed in medicine.

The bromide (NH,Br) and the iodide (NHI) of ammonium, much resemble

the chloride.

SULPHIDE OF AMMONIUM, HYDROSULPHATE OF AMMONIA.

NH,S=AMS.

§ 184. This compound is obtained when hydrosulphuric acid gas is mixed with excess of ammoniacal gas in a vessel which is cooled down to 0° F. (— 18° C.); it may also be obtained by distilling a mixture of single equivalents of chloride of ammonium and sulphide of potassium, the receiver being cooled to the above temperature.

When thus prepared, it forms colorless crystals, which decompose at the ordinary temperature, into ammonia and bydrosulphate of sulphide of ammonium :

2NHS=NH2+NH,S.HS.

A solution of sulphide of ammonium is prepared by saturating a solution of ammonia with hydrosulphuric acid, and afterwards adding a quantity of the same solution equal to that originally employed; hydrosulphate of sulphide of ammonium (NHS.HS) is first produced, and is converted into sulphide of ammonium (NHS) by the additional equivalent of ammonia.

Properties.-The solution thus obtained, which is frequently employed in analysis, is colorless, possesses a strongly alkaline reaction, and a disagreeable odor of ammonia and hydrosulphuric acid. When exposed to air, it soon becomes yellow, from the formation of the bisulphide :

2NH S+O (from the air)=NH,S,+HO+NH ̧;

a small quantity of hyposulphite of ammonia is also formed :—

NHS,+0,=NHO.S,O,.

A solution of pure sulphide of ammonium remains clear when mixed with excess of acid, whilst, if one of the higher sulphides be present, sulphur is deposited.

Sulphide of ammonium is a sulphur-base, like the sulphides of potassium and sodium; it hence dissolves the sulphides of arsenic, antimony, and other sulphur-acids.

The Hydrosulphate of Sulphide of Ammonium (NH,S.HS), may be obtained, by passing equal volumes of ammonia and hydrosulphuric acid into a vessel surrounded with ice; it forms colorless needles, which are very volatile and soon decomposed in the air. Its solution is alkaline to test-papers.

Bisulphide of ammonium (NH,S,) is obtained in yellow crystals when vapors of sulphur and sal-ammoniac are passed through a porcelain tube, heated to redness, and connected with a cooled receiver.

It is very deliquescent, and is readily decomposed by acids, sulphuretted hydrogen being evolved, and sulphur deposited.

The compounds NHS,,NHS,NHS, and NHS, have been obtained.

The solution known as Liquor fumans Boylii, is obtained by distilling a mixture of 1 part of sulphur with 2 parts of chloride of ammonium, and 2 or 3

1 At ordinary temperatures, or when an excess of hydrosulphuric acid is employed, the compound NH S.HS is obtained.

parts of lime; it appears to be a mixture of different sulphides of ammonium, especially of NHS and NHS,, with water. The reaction by which it is produced may probably be thus expressed :

4CaO+3NH,Cl+S,=CaO.SO,+3CaCl+3NH ̧S.

The liquid is obtained, even when the ingredients are anhydrous, in which case, water must be formed by a secondary decomposition between the lime and chloride of ammonium.

It is of a yellow color and disagreeable odor; it fumes in the air. Liquor fumans Boylii is sometimes, though rarely, used in medicine.