Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (12)

=Amber, Sol'uble.= _Prep._ Fragments of amber are cautiously heated in an iron pot, and as soon as it becomes semi-liquid, an equal weight of pale boiled linseed-oil, previously made hot, is very gradually stirred in, and the whole thoroughly blended. Used as a cement for glass and earthenware, and thinned with oil of turpentine to make varnishes. It will keep any length of time if preserved from the air.

=AMBER-CAM'PHOR.= See PYRÉTINE (Crystalline).

=AM'BER DRINK=[dagger]. Amber-coloured malt liquor.

=AM'BER-SEED.= Musk-seed (which _see_).

=AM'BER-TREE.= The popular name of a species of anthospermum, an evergreen shrub, of which the leaves, when bruised, emit an agreeable odour.

=AM'BERGRIS= (-gr[)i]s; gr[=e]se[double-dagger]). _Syn._ GREY AMBER*; AMBRAGRI''SEA (gr[)i]zh'-e-[)a]), L.; AMBREGRIS, Fr.; AMBRA, AMBAR, Ger. An odorous, solid substance, found floating on the sea in tropical climates, and in the cæcum of the cachalot or spermaceti whale (physeter macrocephalus). It has been supposed by some to be a morbid secretion of the liver or intestines, analogous to biliary calculi; but according to Mr Beale, it consists of the mere indurated fæces of the animal, perhaps (as suggested by Brande and Pereira) somewhat altered by disease. "Some of the semifluid fæces, dried with the proper precautions, had all the properties of ambergris." (Beale.) It is occasionally found in masses weighing from 60 to 225 _lbs._

_Prop., &c._ Solid, opaque, ash-coloured, streaked or variegated, fatty, inflammable; remarkably light; highly odorous,[40] particularly when warmed, cut, or handled--the odour being peculiar and not easily described or imitated, of a very diffusive and penetrating character, and perceptible in minute quantities; rugged on the surface; does not effervesce with acids; melts at 140° to 150° Fahr. into a yellowish resin-like mass; at 212° flies off as a white vapour; very soluble in alcohol, ether, and the volatile and fixed oils. It appears to be a non-saponifiable fat, analogous to cholesterine. Sp. gr. 0·780 to 0·926.[41]

[Footnote 40: It has a "pleasant musk-like odour, which is supposed to be derived from the squid ('sepia moschata') on which the animal feeds," the "horny beaks" of which "are often found imbedded in the masses." (Pereira.) It has a smell resembling that of dried cow-dung." (Redwood, 'Gray's Supplement,' 1857, p. 606.)]

[Footnote 41: Sp. gr ·780 to ·896--Brande; ·908 to ·920--Pereira.]

_Pur._ From the high price of genuine ambergris it is very frequently, if not nearly always, adulterated. When quite pure and of the best quality, it is--1. Nearly wholly soluble in hot alcohol and ether, and yields about 85% of ambreine:--2. It almost wholly volatilises at a moderate heat, and when burnt leaves no notable quantity of ashes; a little of it exposed in a silver spoon melts without bubble or scum; and on the heated point of a knife it is rapidly and entirely dissipated:--3. It is easily punctured with a heated needle, and on withdrawing it, not only should the odour be immediately evolved, but the needle should come out clean, without anything adhering to it (Normandy):--4. The Chinese are said to try its genuineness by scraping it fine upon the top of boiling tea. "It should dissolve (melt) and diffuse itself generally." Black or white is bad. The smooth and uniform is generally factitious.[42]

[Footnote 42: Ure's 'Dict. of A., M. & M.,' 5th Ed., i, 128.]

_Uses, &c._ It is highly prized for its odour, which is found greatly to improve and exalt that of other substances; hence its extensive use in perfumery. In _medicine_ it was formerly given as an aphrodisiac, in doses of 3 to 10 gr. "A grain or two, when rubbed down with sugar, and added to a hogshead of claret, is very perceptible in the wine, and gives it a flavour, by some considered as an improvement." (Brande.)

=Ambergris Facti''tious.= An article of this kind, met with in the shops, is thus made:--Orris-powder, spermaceti, and gum-benzoin, of each, 1 _lb._; asphaltum, 3 or 4 _oz._; ambergris, 6 _oz._; grain-musk, 3 _dr._; oil of cloves, 1 _dr._; oil of rhodium, 1/2 _dr._; liquor of ammonia, 1 _fl. oz._; beaten to a smooth hard mass with mucilage, and made into lumps whilst soft. This fraud is readily detected.

=AM'BREINE= (-bre-[)i]n). _Syn._ AMBREI'NA, L.; AMBREINE, Fr.; AMBARSTOFF, Ger. The fatty, odorous principle of ambergris.

_Prep._ Digest ambergris in hot alcohol (sp. gr. 0·827) until the latter will dissolve no more, then filter. The AMBREINE will be deposited as the solution cools, in an irregular crystalline mass, which may be purified by recrystallisation in alcohol.

_Prop., &c._ Melts at about 90°; volatilises at 212° to 220° Fahr.; nitric acid converts it into AMBREIC ACID. It closely resembles cholesterine.--_Prod._ 85%.

=AMBRETTE'= (-br[)e]t'). [Fr.] Musk-seed.

=AMBROSIA, RING'S VEGETABLE= (Tubbs, Peterborg, U.S.). A liquid with a sediment, containing 1 per cent. of lead. (Chandler.)

=AMEISEN BALSAM.= Von Dr Livingstone (Ahnelt, Charlottenburg). Balsam of ants. Castor oil, 72 grms.; balsam of Peru, 2 grms.; bergamot, 5 drops. (Hager.)

=AMERICAN PILLS= (A. H. Boldt, Lexington). For full-blooded, corpulent persons, and for those of sedentary habits, for irregular menstruation, and against contagious diseases. Made of scammony, rhubarb, and soap. (Schädler.)

=AMERICAN MEDICINES, Dr SAMPSON'S= (New York). Two kinds of pills of coca:--No. 1. 85 pills composed of coca extract and coca powder, and each pill containing about 0·006 grm. of a morphia salt. No. 2. 50 pills, also of coca, and each containing 0·05 grm. of powdered iron. Both kinds are rolled in lycopodium. (Hager.)

=AMERICAN PILLS FOR ASTHMA.= Gilded pills made of gum ammoniacum.

=AMERICAN SCHAMPOO-FLUID FOR PROMOTING THE GROWTH OF THE HAIR.= Spirit of wine and rum, with some carbonate of ammonia and potash.

=AMERICAN DROPS FOR TOOTHACHE= (Majewsky, Warsaw) have been found of various composition. Some which profess to have taken a prize at the Vienna Exhibition were composed of French brandy, containing common salt, and coloured with cochineal. The first was a spirituous solution of an ethereal oil with some oil of cloves, coloured rather reddish; No. 2 was a similar solution with some oil of peppermint and tincture of rhatany; and No. 3 was merely a diluted solution of No. 2. (Hager.)

=AMERICAN UNIVERSAL BLOOD-PURIFYING HERB TEA= (Dr Kuhr), for women's diseases, hysteria, nervous debility, epilepsy, stomachic complaints, asthma, hæmorrhoids, gout, rheumatism, worms, and much besides. White horehound, marsh mallow, liquorice wood, and sassafras, of each, 10 parts; anise, coriander and fennel, of each, 5 parts; red poppy petals, 4 parts; lavender flowers, 2 parts; senna, peppermint, millefoil flowers, and valerian root, of each, 1 part. (Kuhr and Selle.)

=AM'ETHYST= (-th[)i]st). _Syn._ PURPLE ROCK-CRYSTAL; AMÉTHYSTE, Fr.; AMETHYS'TUS, L. A beautiful sub-species of quartz or rock crystal, of a violet-blue colour of varying intensity, in great request for cutting into seals, brooches, and other like articles of ornament. It was known and prized in the earliest ages of antiquity. Among the ancients, cups and vases were made out of this mineral; and it was an opinion of the Greeks and Persians, that an amethyst bound on the navel would counteract the effects of wine, and that wine drank out of an amethystine vessel would not intoxicate. See GEMS.

=Amethyst.= In _chromation_, _dyeing_, &c., a rich variety of deep violet colour. Hence, AMETHYST'INE ([)i]n), &c.

=Amethyst, Orient'al.= A rich violet-blue variety of transparent, crystallised corundum.

=AM'IANTH= (-e-[)a]nth). _Syn._ AMIANTH'US, AMIAN'TUS, L.; AMIANTE, Fr. The whiter and more delicate varieties of asbestos, particularly those which possess a satiny lustre.

=AM'IDIN= (-e-d[)i]n). [Eng., Fr.] _Syn._ AM'YDINE; AMIDI'NA, L. A substance noticed by Saussure in starch-paste, when long kept. According to Caventou, it is formed at once by the action of boiling water on starch. It forms the interior substance of the starch-grains, and its properties are intermediate between those of starch and gum. It is, indeed, the soluble part of starch, of which a perfect solution can only be obtained by prolonged ebullition in a large quantity of water.

=AMID'OGEN.= NH_{2}. Literally, the generator of amides; in _chemistry_, the name given by Kane to an hypothetical body, composed of two atoms of hydrogen and one of nitrogen. It forms AMIDES by combining with other bodies.

=Amidogen Ba'ses.= In _chemistry_, 'amines' in which only one equiv. of hydrogen is replaced by an organic radical; and hence called PRIMARY MON'AMINES.

=AMMONIA.= NH_{3}. _Syn._ AMMONIA GAS, AMMONIACAL GAS, ANHYDROUS AMMONIA, TERHYDRIDE OF NITROGEN; AMMONIAQUE, Fr.; AMMONIAK, Ger. At the present day the ammonia of commerce is chiefly prepared from the ammoniacal liquor of the gas-works and the manufactories of ivory black, animal charcoal, &c. Lant or stale urine is also an important source of ammonia. In these places a large quantity of crude ammoniacal liquor is produced; to which either sulphuric or hydrochloric acid is added, by which it is converted into a salt, which may be obtained nearly pure by evaporation, and one or more crystallisations, and, in the case of the hydrochlorate and carbonate, subsequent sublimation. Other sources and processes have been sought out and occasionally adopted for the preparation of the principal salts of ammonia (its sulphate, carbonate, and hydrochlorate); some of which have been patented, but few of them have got into general use, or have been carried out on the large scale. For many years the manufacture of ammonia and its compounds has incessantly engaged the attention of European chemists.

Many unsuccessful attempts have been made to directly convert the nitrogen of the atmosphere into ammonia. Of these we may mention one which consisted in passing a mixture of nitrogen, carbonic oxide and steam over red-hot hydrate of lime, whereby ammonia and carbonic acid are formed. A plan for the indirect application of atmospheric nitrogen in the preparation of ammonia was suggested by Margueritte, in which it was proposed that cyanide of barium should be prepared, and its nitrogen converted into ammonia by the aid of a current of superheated steam at 600° C. According to the description of this process in a patent, not, however, in practice, native carbonate of baryta is calcined with about 30% of coal-tar, for the purpose of rendering the mass porous as well as more readily converted into caustic baryta at a lower temperature. The carbonaceous mass is, after cooling, placed in a retort, and kept at a temperature of 300° C., while air and aqueous vapour are forced in, the result being the formation of ammonia in considerable quantity, and carbonate of baryta, which is again used.

Ammonia is evolved from ball soda while cooling; during the formation of cyanogen and cyanide of potassium in blast furnaces; and the formation of sal-ammoniac in the process of iron smelting.

Ammonia, in a state of combination, is found, in variable quantities, among the saline product of volcanoes, in sea and rain water, in bituminous coal, in urine, in guano, and in the atmosphere, especially that of large towns. The minute stellated crystals sometimes found on dirty windows in London, and other populous cities, consist of sulphate of ammonia. It is also found in clayey and peaty soils, and in minute quantity in good air and water. (Brande; Fownes; Letheby.) In the free state it exists in the juices of some plants, and in the living blood of animals, and it is freely developed during the decomposition of azotised vegetable substances, and during the putrefaction of animal matter.

_Prep._ A mixture of fresh hydrate of lime with an equal weight of sal ammoniac (both dry and in fine powder) is introduced into a glass flask or retort, the beak of which communicates with one end of a U-shaped tube filled with small fragments of recently burnt quick-lime, and from which extends another glass tube, about 18 inches long, having its further end bent up ready to be placed under a gas-jar, on the shelf of a mercurial pneumatic trough. (See _engr._) The joints being all made air-tight by collars of india rubber, heat is applied by means of a spirit-lamp, and as soon as the air contained in the apparatus is expelled, the gas is collected for use. It cannot be dried by means of chloride of calcium. Powdered quick-lime may be substituted for the hydrate in the above process; in which case the evolved gas is anhydrous, but a much greater heat is then required for its liberation.

_Comp._ Ammonia is a compound of 3 volumes of hydrogen, and 1 vol. of nitrogen, condensed into two volumes; and by weight of 82·35 parts of nitrogen, 17·65 parts of hydrogen, or, in other words, of one atomic weight of nitrogen and three of hydrogen, having the formula NH_{3}.

_Prop._ Gaseous, colourless, invisible; highly pungent, acrid, irritating and alkaline; irrespirable, unless very largely diluted with air; extinguishes combustion; burns slowly in oxygen; sp. gr. 0·589; 100 cub. inches weigh 18·26 gr. Under a pressure of 6·5 atmospheres, at 50° Fahr., it forms a transparent, colourless liquid of the sp. gr. 0·731; at 60° Fahr. this liquid expanded into 1009 times its volume of ammoniacal gas; at -40° Fahr., and the ordinary atmospheric pressure, it forms a subtle colourless liquid, which at -103° Fahr. freezes into a white, translucent, crystalline substance. (Faraday.) It is highly basic; all its salts are either volatilised or decomposed at, or under, a red heat--those with a volatile acid sublime unchanged--those with a fixed acid lose their ammonia. It is decomposed into its elements by transmission through a red-hot tube; and when in contact with metallic oxides or spongy platinum, at the same temperature, the newly evolved hydrogen unites with the oxygen of the oxide or of the atmosphere, forming water. Water at 50° Fahr. absorbs 670 times its volume of this gas, and the solution has the sp. gr. 0·875. Its concentrated aqueous solution boils at 130°, and freezes at -40° Fahr.

_Tests, &c._ Ammonia is recognised by--1. Its pungent odour:--2. By turning vegetable blues green, and vegetable yellows brown; but which soon regain their previous colours, especially on the application of heat:--3. By producing dense white fumes when brought in contact with those of hydrochloric acid:--4. By the Nessler test (see WATER, QUANTITATIVE AND QUALITATIVE ANALYSIS OF):--5. If a saturated solution of arsenious acid is mixed with a solution of nitrate of silver (strength 2%) a trace of ammonia causes the formation of try-argentic arsenite:--6. Böttger says a very delicate test for ammonia is afforded by an aqueous solution of carbolic acid. On adding to a liquid containing the smallest quantity of ammonia, or an ammoniacal salt, a few drops of this solution, and then a small quantity of a filtered solution of chloride of lime, the liquid becomes green, especially when warmed.

_Phys. eff., &c._ Inhaled, undiluted with air, it is an irritant poison, producing spasms of the glottis, convulsions, and death; even when diluted it acts as a powerful acrid, and local irritant; applied to the skin it causes vesication. The use of the pungent odour of common 'smelling salts,' in syncope, headache, &c., is well known. Largely diluted with air, it has been recently highly extolled in chronic hoarseness, asthma, &c.; and as an antidote to the fumes of bromine, chlorine, and hydrocyanic acid. (Smee.)

_Ant., &c._ The vapour of acetic acid or common vinegar, freely inhaled. It may be produced by sprinkling a little on a piece of hot iron, as a heated shovel. If bronchial inflammation follows, it must be treated by purgatives and a low diet; and, if severe, and the patient be plethoric or robust, by venesection or cupping.

_Uses._ Ammonia is employed in numerous processes in _chemistry_ and the _arts_; but chiefly in the form of 'liquor of ammonia,' 'spirits of hartshorn,' &c., and in combination, under the form of salts. In its pure or gaseous state it possesses little practical interest.

=Ammonia, Solution of.= _Syn._ SOLUTION OF AMMONIA, LIQUOR AMMONIÆ, AMMONIUM HYDRATE, AMMONIA, Eng.; AMMONIAQUE LIQUIDE, DISSOLUTION D'AMMONIAQUE, ESPRIT DE SAL AMMONIAC, Fr.; ATZENDER AMMONIUM-LIQUOR, SALMIAK-GEIST, Ger.; LIQUORE DI AMMONIACO, Ital. Ammonia gas readily dissolves in water, one volume of water absorbing about 670 volumes of ammonia, much heat being liberated, and the solution increases greatly in volume.

This solution is regarded in two very different lights; firstly and most generally as simply a solution of gaseous ammonia, a view rendered most probable by its general physical and by many chemical reactions; by a few, however, it is looked upon as a solution of ammonium hydrate.

Prepared by distilling, in a tubular retort, equal parts of sal ammoniac, hydrated lime, or slaked lime and water, and passing the gas evolved through a set of Wolff's bottles partially filled with water, as in the figure above.

_A_, Cylindrical Iron Retort.
_B_, Furnace for ditto.
_C C C C_, Stoneware Receivers.
_D D D D_, Connecting Pipes.
_E F_, Waste Pipe and Receiver.
_G_, Safety Tube. ]

Commercially this article is prepared on the large scale, from a mixture of about equal parts of fresh-slaked lime and sal-ammoniac or sulphate of ammonia, which is heated in an iron cylinder or retort connected with a set of 'refrigerators,' the latter consisting of a row of stoneware bottles with double necks, containing water, and kept very cold. The general arrangement of the apparatus used in this manufacture is exhibited above, and with the accompanying references, will be easily understood. The 'condensers,' when in use, are surrounded with cloths (not shown in the _engr._) kept wet with very cold water, whilst constant current of cold air is commonly made to pass over them. The pipe (_D_) leading from the retort is also several feet long, and is advantageously passed through a wooden screen in order that the radiated heat of the retort and brickwork of the furnace may be intercepted as much as possible.

Two different methods of proceeding are adopted in this process. In the one the dry pulverulent ingredients are mixed together, and the resulting gas distilled over into the water placed in the receivers. In the other the lime is made into a 'pap' with water, and the ammonia-salt, in coarse powder, being added, the whole is rapidly blended together, before closing the retort, and applying heat. In either case a proportionate quantity of water is put into the condensers, and the operation is nearly similar; but the latter method requires the least heat, and so far as the receivers and refrigerators are concerned, is, perhaps, the one most easily managed. It is that which is always, and necessarily followed, when sulphate of ammonia is employed.

_Prop., Uses, &c._ Highly pungent, caustic, and alkaline; lighter than water, and presenting in a liquid form most of the characteristics of pure ammonia. When strongest has a sp. gr. of ·875, and contains about 39 per cent. of ammonia, but the usual strong ammonia of commerce has a sp. gr. of but ·88. The liquor ammonia fortior, B. P., has a sp. gr. of about ·893, and contains 32·5 per cent. of ammonia, while the liquor ammoniæ B. P. has a sp. gr. of about ·940, and contains about 10 per cent. of ammonia. As a medicine it is antacid, diaphoretic, rubefacient, stimulant, and counter-irritant; and is used in various affections in which these remedies are indicated. As a vesicant it is superior to cantharides, and as a caustic it is used with advantage in the bites of rabid animals, especially those of serpents and insects. Its vapour is a common nasal stimulant in faintings, epilepsy, &c. In its concentrated form it is a corrosive poison.--_Dose_, 5 to 25 drops, in cold water, or milk and water. It enters into the composition of several valuable external remedies, and is in constant employment in the _chemical laboratory_, both as a reagent and for the preparation of other compounds.

_Ant., &c._ When the fumes have been inhaled, the patient should be exposed to a current of fresh air; and when the liquid has been swallowed, vinegar or lemon-juice mixed with water may be administered; followed by an emetic, or, on its failure, by the stomach-pump.

_Estim._ The quantity of gaseous ammonia in pure water of ammonia is easily determined from the specific gravity of the liquid, or from its saturating power. When impure or mixed with other substances, a given weight of the sample is placed in a small retort, the end of which is made to dip into a vessel containing dilute hydrochloric acid. A strong solution of caustic potassa is then poured into the retort, and heat applied by means of a small spirit lamp. When _all_ the ammonia is distilled over, the acid solution is evaporated to dryness, by the heat of a water bath, and the residuum (chloride of ammonium) weighed. Each grain of the chloride thus found represents ·31804 gr. of pure ammonia; 53·5 parts of the former being equivalent to 17 of the latter. If the article for examination be a solid substance (as a salt), it may be dissolved in water, or in dilute acid, before being put into the retort.

In accurate experiments in the laboratory, ammonia is usually WEIGHED either as chloride of ammonium (see _above_), or as ammonio-bichloride of platinum (NH_{4}Cl, PtCl_{2}); every gr. of the latter representing ·07614 gr. of pure ammonia. Sometimes, though rarely, the quantity of ammonia is determined from the volume of nitrogen eliminated from it, of which 14 gr. represent 17 gr. of ammonia.

_Concluding remarks, Patents, &c._ Whatever form or process may be adopted for the preparation of liquid ammonia, it is absolutely necessary to keep the receivers as cool as possible, by means of snow, ice, or a current of very cold water, for the purpose of promoting the absorption of the gas, and to prevent its loss. On the small scale, the glass receivers or bottles may be most conveniently surrounded with ice, or a freezing mixture, and two, or more of them, should be furnished with safety-tubes, to prevent accidents. On the large scale, a capacious oblong retort, usually of iron (but sometimes, though seldom, of lead), with a large opening or tubulature conveniently situated for inserting the 'charges,' and withdrawing the residuum of the distillation, is employed. The tubulature, or opening, is closed by means of a large and accurately ground iron stopper, or with a door secured by screws, as the case might be. The stopper is well greased before insertion, and is removed by means of a powerful lever. Should it become so firmly fixed that it cannot be displaced in the usual manner, a cloth moistened with cold water, and carefully wrapped round it, without touching the neck of the retort, will generally cause it to contract sufficiently to enable the operator to remove it with facility. Sometimes a large iron kettle, with a moveable and accurately fitting lid secured in its place like that of a 'Papin's digester,' and having a large and long tubulature in its centre, is employed instead of a retort, over which it has the advantage of exposing a larger opening for the removal of the residuum of the process. In either case the distillatory vessel is imbedded in sand supported by fire-brick, and is not exposed directly to the heat of the furnace. Before commencing the distillation the joints are all well luted, to avoid leakage. An excellent plan is to pass the gas, as it leaves the retort, through a silver or pewter 'worm' or 'refrigerator' set in a tub supplied with a stream of very cold water; by which it will be sufficiently cooled before it reaches the 'receivers' to obviate the necessity of any further attention to them than keeping the cloths wrapped round them constantly moistened with cold water. The lower end of the 'worm' should be connected, by means of a balloon-shaped 'adopter,' with the 'still,' and the upper end with the first 'receiver,' the use of the balloon being to intercept any volatilised ammonia-salt that might be accidentally driven over by the heat being too high, or too suddenly raised.

The heat should be gradually applied, and very gradually raised, to prevent any of the sal ammoniac or sulphate being volatilised undecomposed; and even towards the end of the process it should not even approach redness.

The lime is best 'slaked' and 'papped' with about 4 parts of water; as a lower heat is then required to expel the gas, and it passes over more easily and fully than when less water is employed. This is absolutely necessary when the sulphate is the ammonia-salt used; as otherwise the residuum of 'sulphate of lime' would become so hard that it could not be easily removed from the retort.

The gas being wholly expelled from the retort, or other distillatory vessel, it is disconnected from the receivers, and (when sal ammoniac has been employed) the heat is raised sufficiently high to fuse the residual chloride of calcium, which is then at once baled or poured out. Glass retorts often suffer fracture at this point; but if they escape now, it generally happens that they are broken when heat is applied for a second operation. Hence, according to Prof. Muspratt, it is rare to find a retort, even when carefully handled, that will stand two operations.

When crude sulphate of ammonia is employed it is advisable to have only a little water in the first receiver, which is placed there merely to purify the gas which passes through it, and to retain any traces of volatile empyreumatic or oily matter which may be carried over with it.

Pure solution of ammonia is most easily obtained from 'sal ammoniac,' but crystallised sulphate of ammonia, often crude, is more commonly employed, on account of its lower price.

The preparation of pure solution of ammonia admits of no other improvements than such as merely affect the form of the apparatus employed to produce it; and hence, unlike the ammonia-salts of commerce, has been little meddled with by inventors and patentees. Among the plans having for their object the production of an ammoniacal solution, more or less concentrated, fitted for many of the purposes of the arts, and for the preparation of salts, but not for chemical and medical use, besides those of Reece, Spence, Crane and Jullien, &c., already noticed, may be mentioned--

1. That of Watson (Patent dated 1838) in which gas-liquor mixed with a proper quantity of fresh-slaked lime is distilled from a spacious retort or still into a receiver containing cold water, until much steam passes over with the gas, when the strong alkaline liquor forming the distillate, and called the first portion, is drawn off. The distillation is then continued, when a weaker and impurer solution is obtained, called the second portion. The first portion is then reintroduced into a retort or still with a small quantity of fresh lime, and the distillation repeated. The product the patentee calls the first portion of the second distillation. The latter is a strong ammoniacal liquor sufficient for all the purposes of scouring, cleaning, conversion into commercial ammonia-salts, &c. It may be further purified by a third distillation; the second portion of each operation being transferred again to the still with the next fresh charge of gas-liquor.

2. A modification of Coffey's still,[43] patented by Mr W. E. Newton (1841), under the name of the 'AMMONIA STILL,' is now extensively and successfully employed in this manufacture. By its use ammonia may be obtained from 'gas-liquor,' 'bone-spirit,' or any other ammoniacal liquor or solution, and even from solutions of the salts of ammonia, of almost any density, and of considerable purity; and this by a process which is continuous and inexpensive. The body of the apparatus is formed of wood, the chambers are lined with lead, and the diaphragms are of perforated sheet iron. The management of the apparatus varies with the form in which it is desired to obtain the product. When the ammonia is required to leave the upper chamber of the rectifier in the form of gas, either pure or impure, the steam which ascends, and the current of 'ammoniacal liquor' which descends, are regulated in such relative proportions that the latter remains at or near the atmospheric temperature during its passage through some of the upper chambers, becoming successively hotter as it descends, until at length it enters into ebullition; in which state it passes through the lower chambers, either to make its escape, or to enter a cistern provided to receive it. If, on the contrary, the ammonia is required to leave the upper chamber in combination with the vapour of water, the supply of steam entering below must be in such proportion to that of the ammoniacal liquor supplied from above, that the latter may be at or near the boiling temperature in the upper part of the apparatus. Crude liquor and ammonia-salts, before being thus submitted to distillation, are, of course, first treated with a proper quantity of quick-lime--in the one case to remove most of the impurities, and in the other to set the ammonia free by seizing on its acid.[44]

[Footnote 43: An _engr._ and description of this still, as employed for spirit, is given under DISTILLATION (which _see_).]

[Footnote 44: For a full description of the "AMMONIA-STILL," _see_ Newton's 'Patent Journ.,' 'Pharm Journ.,' xiii, 64; &c.]

The water or solution contained in the first bottle or the first receiver is found to be the strongest, provided it has been kept well cooled; and that in the others, of progressively decreasing strength. By mixing the contents of one bottle with another a solution of almost any strength may be made. It is also easy to prepare liquor of ammonia of any required strength, or to ascertain the strength of that in the receivers, by observing the expansion of the liquid. Water, when fully saturated with ammonia, expands from 3 volumes to 5 vols.; and in less, but corresponding proportion, according to the quantity absorbed. All that is necessary in practice is, that each receiver be furnished with a gauge-pipe by which the degree of expansion may be noted. On the small scale, graduated glass receivers may be used.

3. Mallet's Apparatus. This, which is employed in many of the large gas works, is shown in vertical section in the accompanying woodcut. Steam is forced into large receptacles, which are filled with gas water, by which means the carbonate of ammonia is volatilised. When lime, as is sometimes the case, is added, ammonia gas is evolved, and this being conveyed into weak sulphuric acid, sulphate of ammonia is the result.

The apparatus consists of two cylindrical boiler-plate vessels, A and B. A is heated directly by the fire, and has a leaden tube, _c_, which dips into the liquid contained in B, this vessel being so placed as to catch the waste heat from the fire. _b_ and _e_ are man-holes; _a_ and _a'_ are stirrers. By means of the tube _d_ the fluid from B can be run off into A. Gas-water is poured into both vessels, and lime added; ammonia is liberated, whilst carbonate of lime and sulphide of calcium are formed, and these latter remain in the vessels after the volatilisation of the ammonia. The vessel D is also filled with ammoniacal water, and when the operation is in action this water, already warmed, is run by the aid of the tube _h_ from D into B. E is a gas-water tank, from which D is filled by means of _g_. The ammonia set free in A is, with the steam, conveyed by the pipe _c_ into B, thence through _c'_ into the wash-vessel C, and thence again through _c''_ into the first condenser, D. The partially condensed vapour now passes into the condensing vessel F, the worm of which is surrounded by cold water. The dilute ammonia is collected in G, and forced by means of the pump (R) into C, from whence it is occasionally removed by means of a syphon into either A or B. The non-condensed ammoniacal gas is carried from G through a series of Wolfe's bottles, the first bottle (H) containing olive oil, with the object of retaining any hydrocarbons that may be present in the gas; the bottle J contains caustic soda-ley, in order to purify the ammonia and retain impurities; the bottle K is half filled with distilled water. The ammoniacal gas having passed through K, is conveyed to the large wooden tank (lined with lead) L, filled with diluted sulphuric acid, if it is intended to prepare sulphate of ammonia, or with water, if solution of ammonia be required. The vessel L is placed in a tank of water; _i_ is a small pipe for introducing acid, while the tube leading to M serves to carry off any unabsorbed ammonia, M being likewise filled with acid.

4. By means of Rose's apparatus, the ammoniacal gas-liquor mixed with one third of slaked lime is heated in a boiler to a temperature of from 96° to 100°, the ammoniacal gas evolved being passed into hydrochloric acid, and thence through charcoal into vessels containing from 120 to 150 litres of water, which is converted into liquid ammonia of a sp. gr. 0·920.

5. In Lunge's apparatus the gas-water is heated in a boiler, and the liberated ammoniacal gas passed into sulphuric acid.

Solution of ammonia is now seldom made by the druggist, or on the small scale, the large manufacturing chemists supplying it at a very low rate, and of very superior quality. In the shops it is kept of two or three strengths.

The estimation of the strength of ammonia solutions in commerce is known as ammonimetry, and depends upon their specific gravities. The per-centage richness of solutions of ammonia, or of its carbonates, may be most accurately determined, by ALKALIMETRY. For all the ordinary purposes of commerce, and of the laboratory, the strength of pure solutions of ammonia may, however, be inferred, with sufficient correctness, from their density; and to this the term AMMONIOMETRY is usually restricted.

The specific gravity of the sample being found either by the hydrometer[45] or specific gravity bottle, in the usual manner, its per-centage strength may be seen by inspection of the following _Table_ and the _Table_ on p. 127.

[Footnote 45: An hydrometer specially weighted and graduated for this purpose is called an AMMONIM'ETER, AMMONIOM'ETER, or AMMO'NIA-ME'TER (AMMONIM'ETRUM, AMMONIOM'ETRUM, &c., L.)]

TABLE I.--_Showing the per-centage of_ PURE AMMONIA,
_and of_ AMMONIA-WATER _of_ ·9000, _in Water of
Ammonia, of the given specific gravities, at_ 60° Fahr.
By Dr URE.

------------+------------+----------------+------------
Sp. Gr. by | Water of | Pure | Water,
experiment. | Ammonia | Ammonia, per | per cent.
| of 900, | cent. |
| per cent.| |
------------+------------+----------------+------------
·9000 | 100 | 26·500 | 73·500
·9045 | 95 | 25·175 | 74·825
·9090 | 90 | 23·850 | 76·150
·9133 | 85 | 22·525 | 77·475
·9177 | 80 | 21·200 | 78·800
·9227 | 75 | 19·875 | 80·125
·9275 | 70 | 18·550 | 81·450
·9320 | 65 | 17·225 | 82·775
·9363 | 60 | 15·900 | 84·100
·9410 | 55 | 14·575 | 85·425
·9455 | 50 | 13·250 | 86·750
·9510 | 45 | 11·925 | 88·075
·9564 | 40 | 10·600 | 89·400
·9614 | 35 | 9·275 | 90·725
·9662 | 30 | 7·950 | 92·050
·9716 | 25 | 6·625 | 93·375
·9768 | 20 | 5·300 | 94·700
·9828 | 15 | 3·975 | 96·025
·9887 | 10 | 2·650 | 97·350
·9945 | 5 | 1·325 | 98·675
------------+------------+----------------+------------

[asterism] Strengths corresponding to sp. gr. which are not in the above _Tables_ may be found by the 'method of differences' explained under ALCOHOLOMETRY.

[asterism] The sp. gr. of any sample of liquid ammonia, expressed in three integers, deducted from ·998, and the remainder divided by 4, gives a number which represents the per-centage strength, nearly. (Ure.) This rule may be sometimes conveniently employed for rough calculations, in the absence of _Tables_.

=Ammonia, Carbonates of.= (B. P.) _Syn._ AMMONIÆ CARBONAS. See AMMONIUM, SESQUICARBONATE OF.

TABLE II.--_Exhibiting the relations between the_
SPECIFIC GRAVITY _of Solution of Ammonia and the_
PER-CENTAGE STRENGTH, _for every variation of ·00125
sp. gr., from ·87500 to 1·00000, at_ 62° Fahr. Abridged
from the larger _Table_ of Mr J. J. GRIFFIN.

----------+------------+----------+------------+----------+------------
Sp. Gr. of|Pure Ammonia|Sp. Gr. of|Pure Ammonia|Sp. Gr. of|Pure Ammonia
the Liquid| per cent., |the Liquid| per cent. |the Liquid| per cent.,
Ammonia. |by Weight. | Ammonia. |by weight. | Ammonia. |by weight.
----------+------------+----------+------------+----------+------------
·87500 | 34·694 | ·91750 | 21·837 | ·96000 | 10·119
·87625 | 34·298 | ·91875 | 21·477 | ·96125 | 9·790
·87750 | 33·903 | ·92000 | 21·118 | ·96250 | 9·462
·87875 | 33·509 | ·92125 | 20·760 | ·96375 | 9·135
·88000 | 33·117 | ·92250 | 20·403 | ·96500 | 8·808
·88125 | 32·725 | ·92375 | 20·046 | ·96625 | 8·483
·88250 | 32·335 | ·92500 | 19·691 | ·96750 | 8·158
·88375 | 31·946 | ·92625 | 19·337 | ·96875 | 7·834
·88500 | 31·558 | ·92750 | 18·983 | ·97000 | 7·511
·88625 | 31·172 | ·92875 | 18·631 | ·97125 | 7·189
·88750 | 30·785 | ·93000 | 18·280 | ·97250 | 6·867
·88875 | 30·400 | ·93125 | 17·929 | ·97375 | 6·547
·89000 | 30·016 | ·93250 | 17·579 | ·97500 | 6·227
·89125 | 29·633 | ·93375 | 17·231 | ·97625 | 5·908
·89250 | 29·252 | ·93500 | 16·883 | ·97750 | 5·590
·89375 | 28·871 | ·93625 | 16·536 | ·97875 | 5·273
·89500 | 28·492 | ·93750 | 16·190 | ·98000 | 4·956
·89625 | 28·133 | ·93875 | 15·846 | ·98125 | 4·641
·89750 | 27·736 | ·94000 | 15·502 | ·98250 | 4·326
·89875 | 27·359 | ·94125 | 15·158 | ·98375 | 4·011
·90000 | 26·984 | ·94250 | 14·816 | ·98500 | 3·698
·90125 | 26·610 | ·94375 | 14·475 | ·98625 | 3·386
·90250 | 26·237 | ·94500 | 14·135 | ·98750 | 3·074
·90375 | 25·865 | ·94625 | 13·795 | ·98875 | 2·763
·90500 | 25·493 | ·94750 | 13·456 | ·99000 | 2·453
·90625 | 25·123 | ·94875 | 13·119 | ·99125 | 2·144
·90750 | 24·754 | ·95000 | 12·782 | ·99250 | 1·835
·90875 | 24·386 | ·95125 | 12·446 | ·99375 | 1·527
·91000 | 24·019 | ·95250 | 12·111 | ·99500 | 1·220
·91125 | 23·653 | ·95375 | 11·777 | ·99625 | ·914
·91250 | 23·288 | ·95500 | 11·444 | ·99760 | ·609
·91375 | 22·924 | ·95625 | 11·111 | ·99875 | ·304
·91500 | 22·561 | ·95750 | 10·780 |1·00000 | { 0
·91625 | 22·198 | ·95875 | 10·449 | | {or Water.
----------+------------+----------+------------+----------+------------

[asterism] The specific gravity of mixtures of pure solution of
ammonia and pure water is precisely the mean of the specific
gravities of their constituents. (Davy; Dalton; Christison.) In
all solutions of ammonia, a quantity of anhydrous ammonia,
weighing 212-1/2 gr., displaces exactly 300 gr. of water, and
reduces the sp. gr. of the liquid to the extent of ·00125.
(Griffin.) The strongest solution of ammonia which it is
possible to prepare at 62° Fahr. has the sp. gr. ·87500, and
contains 34·694% of pure ammonia, by weight, or 21,251 gr. per
gallon. (Griffin.)[46]

[Footnote 46: Mr Griffin, in his 'System of Ammonimetry,' calls every 212-1/2 gr. of anhydrous ammonia a TEST-ATOM; and every 7 water gr. measure, a SEPTEM. Thus, a gallon of water (= 10 _lbs_) contains 100,000 septems. The degrees of his AMMONIA-METER range from 1 to 100, and indicate the number of test-atoms of ammonia in one _gal_. of the liquid.]

=AMMONIUM.= The name given to a group of atoms, which play the part of a compound basic, radical, or metallic element. This substance, whose formula is NH_{4} or (NH_{4})_{2}, has never been isolated, although capable of forming most stable salts with the various acid radicals. Several attempts have been made, however, to obtain this compound radical, or group of elements, in a free state, and with more or less success, but on account of its great instability it invariably decomposes when set free into ammonia and hydrogen.

Ammonium salts are some of the most important chemical agents, and are usually recognised as follows, ammonia solution, however, usually acting in exactly the same manner as a solution of ammonium hydrate:--By imparting a deep blue tint to solutions of salts of copper. By exhalation of ammoniacal gas (recognised by its odour), when triturated or mixed and heated with caustic potassa, soda, or lime. Added to a solution of bichloride of platinum, they produce a heavy yellow, crystalline precipitate, consisting of minute octahedrons easily discernible under the microscope. With protonitrate of mercury, a black precipitate. With bichloride of mercury, a heavy, white precipitate. With a concentrated solution of tartaric acid, a crystalline, white precipitate, nearly similar to that given with salts of potassa. They are nearly all soluble in water, volatile, and crystallisable.

Except the carbonate, they are almost invariably estimated by conversion into ammonia, and estimation by volumetric analyses, as in alkalimetry. In the laboratory, however, for exact purposes, they are converted into the double chloride of ammonium and platinum.

=Ammonium Salts:--=

=Ammonium, Acetate of.= NH_{4}C_{2}H_{3}O_{2}. _Syn._ AMMO''NIÆ ACE'TAS, L.; ACETATE D'AMMONIAQUE, Fr.; ESSIGSÄURES AMMONIAK, Ger. _Prep._ 1. Take of acetate of lime or of potassa and sal ammoniac, equal parts; mix and distil at a gentle heat. The oily liquid (BINACETATE OF AMMONIUM, HNH_{4}(C_{2}H_{3}O_{2})_{2}), in the receiver forms a radiated crystalline mass on cooling. Dry gaseous ammonia passed into this salt, melted by a gentle heat, transforms it into the solid and inodorous neutral acetate, NH_{4}C_{2}H_{3}O_{2}.

2. Strong acetic acid is saturated with ammonia or carbonate of ammonium, and the solution evaporated over sulphuric acid in vacuo; the resulting crystals, after being carefully drained, are dried by pressure between bibulous paper.

_Prop., &c._ Long, slender crystals, or a crystalline mass, freely soluble in both alcohol and water, and deliquescent in the air; taste sharp and cooling, and somewhat sweetish. Its solutions cannot be evaporated without loss of the ammonia; even the salt passes off in large quantities with the vapour of water. Its aqueous solution becomes alkaline on keeping, from decomposition of the acid. Distilled with anhydrous phosphoric acid, it is converted into ACETONITRILE. An aqueous solution of this salt was introduced into the Materia Medica by Boerhaave, and has since been extensively used as a diaphoretic and febrifuge, under the popular name of MINDERERUS SPIRIT, after Minderer or Mindererus, who extensively employed it and extolled its virtues. When pure, both the salt and its solutions are neutral to test-paper, and are wholly volatilised by heat. See SOLUTIONS.

=Ammonium, Arseniate of.= (NH_{4})_{3}AsO_{4}. _Syn._ AMMONIÆ ARSE'NIAS, L. _Prep._ 1. (NEUTRAL.) Saturate a warm concentrated solution of arsenic acid with carbonate of ammonium in slight excess; evaporate by a gentle heat, that crystals may form on cooling.

2. =Ammonium, Binarseniate of.= H(NH_{4})_{2}AsO_{4}. As above, but adding an additional equiv. of the acid, as soon as any excess of ammonia has been expelled by the heat employed to evaporate the solution.--_Dose_ (of either). 1-24th to 1-12th gr.; in phthisis, certain skin diseases, &c. See SOLUTIONS (and _below_).

=Ammonium, Arsenite of.= NH_{4}AsO_{2}. _Syn._ AMMONIÆ AR'SENIS, L. _Prep._ From a hot concentrated solution of arsenious acid, and sesquicarbonate of ammonium, as the last.--Used (chiefly) to make arsenite of iron. The properties and physiological effects of the above arsenical preparations are for the most part similar to those of arseniate and arsenate of potassa. They are all poisonous.

=Ammonium, Benzoate of.= _Prep._ 1. Dissolve benzoic acid in ammonia solution to saturation, then further add ammonia in slight excess, and crystallise by refrigeration, or in vacuo.

2. (LIQUID; SOLU'TIO AMMONIÆ BENZOA'TIS, L.) As the last, but without evaporating the solution.

_Prop., &c._ Very soluble and very difficult to crystallise. If the solution is boiled for a short time and then abandoned to spontaneous evaporation, crystals of ACID BENZOATE OF AMMONIUM are deposited. It is used chiefly as a chemical test; but has been recently recommended in chronic bronchitis, old coughs, &c.; and to check the formation of chalk-stones and urinary calculi.--_Dose_, 10 to 15 gr.; (of the solution) 15 drops to 1 fl. dr., or more. See BENZOIC ACID.

=Ammonium, Bromide of.= NH_{4}Br. _Syn._ AMMO''NII BROMI'DUM, A. BRO'MIS, L.; HYDROBROMATE D'AMMONIAQUE, BROMURE D'AMMONIUM, Fr. A salt which is obtained from hydrobromic acid, bromide of iron, &c., by similar processes to those adopted for the iodide. The following process for the preparation of bromide of ammonium is from the formula for the new medicaments adopted by the Paris Pharmaceutical Society: "Add bromine very slowly to a solution of ammonia, with continual stirring, until the liquid remains faintly and persistently coloured by a slight excess of bromine." It forms white prismatic crystals; and, in its general properties, resembles bromide of potassium. It is volatile, and easily decomposed.

Used as a nervine in hysterics; especially useful for sleeplessness where there is no organic disease; given in epilepsy when bromide of potassium fails.--_Dose_, 2 to 20 grains.

=Ammonium, Carbonates of=[47]--

[Footnote 47: For complete information respecting the various carbonates of ammonia consult Dr Divers' papers in the 'Journal of the Chemical Society.']

=Ammonium, Carbonate of.= _Syn._ NEUTRAL CARBONATE OF AMMONIUM. Equal parts of dry sal ammoniac and sodium carbonate are heated to form the neutral ammonium carbonate of commerce, which sublimes. Solid crystalline substance, with a strong ammoniacal odour, volatile and soluble.

_Uses, &c._ In the solid form it is not now used in medicine; but it is indirectly employed in several liquid preparations in which the sesquicarbonate is ordered. It is superior to any other preparation of ammonia for filling smelling bottles; as it is not only more pungent, but does not lose its pungency by keeping. It volatilises more quickly than the sesquicarbonate, and the residuum, unlike that of the latter salt, continues as odorous as ever. It is the basis of several of the most popular and esteemed advertised smelling salts of the shops. Spirit of hartshorn is an impure solution of this salt, originally obtained by distilling hartshorn or bones.

=Ammonium, Sesquicarbonate of.= Probably 2NH_{4}HCO_{3} + NH_{4}NH_{2}CO_{3}, _i. e._ a mixture or compound of bicarbonate of ammonium and carbamate of ammonium. _Syn._ (CARBONATE OF AMMONIA, AMMONIÆ CARBONAS. B. P.). CARBONATE D'AMMONIAQUE, Fr.; KOHLENSAURES AMMONIAK, Ger. It is prepared on a very large scale commercially as follows:--Sal ammoniac or sulphate of ammonia, and chalk, equal parts, both dry and in powder, are mixed as before, and sublimed from a series of iron retorts or iron pots, into a well-cooled and capacious receiver lined with lead or earthenware; or, more generally, into such a receiver connected, by iron or lead pipes, with a second and similar one containing a stratum of water, to absorb the free ammonia evolved during the process.

The so-called "Volcanic Ammonia" is evolved during the manufacture of borax, from carbonate of soda and boracic acid. It is largely used in pharmacy.

_Prop._ The carbonate of ammonia, of commerce, usually occurs in the form of white, fibrous, translucent, or semi-translucent cakes, generally about two inches thick. It is less volatile and pungent than the neutral carbonate; soluble in 4 parts of water at 55° Fahr., 3·3 parts at 62°, 2·5 parts at 96°, and 2 parts at 120°; boiling water and alcohol decompose it, with the evolution of carbonic acid gas and ammonia; by age or exposure to air, the surface assumes an opaque white colour, from its carbonate flying off, and the remaining bicarbonate being less volatile. Unlike the carbonate, it can neither be resublimed nor digested or distilled with either alcohol or water, without suffering decomposition. Sp. gr. 0·966.

The exact composition of this salt varies, according to its method of preparation.

_Uses, &c._ It is commonly employed by bakers to give lightness to their fancy goods, and to make extemporaneous bread and pastry; by the chemist and pharmaceutist, for the preparation of other salts of ammonia, and in analysis, &c. In _medicine_ it is used as a stimulant, antispasmodic, antacid, and diaphoretic, in acidity of the stomach, dyspeptic affections, gout, scrofula, hysteria, lowness of spirits, epilepsy, &c.; and in the convulsions attending dentition. It has been recently recommended, by Dr Barlow, in diabetes. It is also employed to make effervescing draughts; and externally as a counter-irritant and stimulant. Its use as a nasal stimulant in headaches, fainting, &c., is well known. In large doses it is emetic; in excessive doses poisonous. Its long-continued use, in quantity, is often productive of very serious consequences--slow fever, debility, emaciation, scurvy, loss of teeth, hæmorrhage, general cachexy, and even death. The antidote and restorative treatment are, the free use of lemon-juice, wine or malt-liquors, new milk, and antiscorbutic vegetables, with a generous diet, of which the red meats form a large proportion.--_Dose._ As a stimulant or diaphoretic, 5 to 15 gr., dissolved in cold water; as an emetic, 20 to 30 gr., in tepid water, repeated if necessary; as an effervescing saline draught, 15 to 30 gr. A few grains (8 or 10) dissolved in a tumbler of cold water is an excellent 'refresher' in lowness of spirits, or after fatigue; and is highly esteemed by drunkards; being, in each case, preferable to 'spirit of sal volatile,'--_Doses for Animals._ HORSE: 1 to 2 drachms. CATTLE: 2 to 4 drachms. SHEEP: 20 grains to 1 drachm. PIG: 20 grains to 1 drachm. DOG: 3 to 10 grains; in bolus, pill, or cold gruel.

_Concluding remarks, Patents, &c._ In extension of the above it may be added that, on the large scale, the distillation is usually carried on in cast-iron retorts, similar in size, shape, and character to those employed in the manufacture of coal-gas, and of which five, or more, are commonly set horizontally in the same furnace. (See _engr._) Each retort has its mouth (_a_), through which the 'charge' is introduced, closed with a movable door, which is securely fastened in its place, in the manner shown in the engr.; and is furnished, at the upper part of its further end, with an iron pipe (_c_), to carry off the evolved vapours to the condenser or receiver. The latter consists of two large square wooden chambers (_B, C_), lined with lead, and either fitted with movable covers, secured by water-joints, or with doors in the side, to permit of the easy removal of the sublimed salt. The first receiver communicates with the second by means of a large lead tube (_d_) near its centre, and by another tube (_d'_), somewhat smaller, and nearer the bottom, but above the surface of the stratum of water in the second receiver, before alluded to. These chambers have also a lead pipe (_e, e_), stopped during the process with a plug or cock of lead, to allow of the liquid product of the distillation, &c., to be drawn off, or run into another receiver or cistern, at will. Both chambers are placed on strong wooden supports, or scaffolding, to bring them on a level with the retorts. When the impure sulphate or other ammonia-salt is used in the manufacture of the sesquicarbonate (which is generally the case), the resulting salt being impure and discoloured, is resublimed in iron pots (_f, f, f_), furnished with movable leaden heads, which are kept cool by a current of air passing over them; a little water being introduced into the subliming pots to render the product translucent. The heat is applied either by means of a flue passing from the retort-furnace (_A, b_), or by a water bath heated in the same manner; the latter being the preferable method, as the temperature should not be greater than about 200° Fahr., and need not exceed 150° to 155°. These pots are arranged in sets, as shown at _D_ in the engraving.

The charge of a retort usually consists of about 70 to 72 _lbs._ of sulphate of ammonia or 57 to 58 _lbs._ of the hydrochlorate to 1 _cwt._ of chalk; or in these proportions. The product is about 40 _lbs._ of the crude salt, which, by careful resublimation, yields about 39 _lbs._ of marketable carbonate of ammonia.

Carbonate of ammonia, like the chloride and sulphate, is now scarcely ever prepared on the small scale, that of commerce being not only cheaper, but sufficiently pure for all the purposes of medicine and the arts.

=Ammonium, Bicarbonate of.= HNH_{4}CO_{3}. _Prep._ By digesting cold water on sesquicarbonate of ammonia in considerable excess, until the whole of the pungent neutral carbonate is dissolved out. If the salt is reduced to powder the operation is facilitated.

To powdered sesquicarbonate of ammonia add boiling water just sufficient to dissolve it, and immediately close the vessel; crystals form as the liquid cools, containing 2-1/2 equiv. of water.

_Prop., &c._ For the most part similar to the sesquicarbonate, except in having a taste and smell which is only faintly ammoniacal, and hence more palatable. Crystallises in oblique prisms, which, as usually obtained, contain about 23% of water. It requires 8 parts of cold water to dissolve it. It is distinguished from the previous carbonates by the almost entire absence of ammoniacal odour, and by its solution giving no immediate precipitate with chloride of barium, but by standing, or on the addition of a little liquor of ammonia, a white earthy precipitate, accompanied with the evolution of carbonic acid gas. A saturated solution of this salt, evaporated by a very gentle heat, or refrigerated, gives small prismatic crystals having neither smell nor taste.

_Uses, &c._ Similar to those of the other carbonates.--_Dose_, 6 or 7 to 20 or 25 gr.

=Ammonium, Chloride of.= NH_{4}Cl. _Syn._ MURIATE OF AMMONIA, SAL AMMONIAC, HYDROCHLORATE OF AMMONIA; CHLOROHYDRATE D'AMMONIAQUE, SEL AMMONIAC, &c., Fr.; SALMIAK, Ger. A substance which, as already noticed, appears to have been originally obtained, by sublimation, from the soot of camels' dung, in Egypt. In this country, at the present day, it is manufactured chiefly from the crude ammoniacal liquors obtained as secondary products in the manufacture of coal-gas and animal charcoal.