Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (13)

_Prep._ 1. From GAS-LIQUOR:--The crude ammoniacal liquor of the gas-works is, either at once, or after distillation,[48] neutralised with hydrochloric or sulphuric acid, the choice being given to the one which is the cheaper and more accessible at the place where the works are situated. When hydrochloric acid is employed, the SATURATION is usually effected by allowing the acid to flow from a large wooden vessel or tank lined with lead or gutta percha into a large underground reservoir or tank containing the ammoniacal liquor, and having an exit-tube passing into the chimney or shaft of the steam-engine, to carry off the sulphuretted hydrogen and other offensive gases liberated during the mixture. Sometimes the gas-liquor is accumulated in enormous covered wooden tuns, capable of holding from 10,000 to 20,000 gallons, or more; and the acid is added by raising the gutta-percha carboys containing it by means of cranes, and then thoroughly mixing it with the liquor by means of powerful 'agitators,' whilst the offensive fumes are either passed off as before, or made to traverse the fire of the steam-engine before entering the chimney-shaft. The quantity of acid employed to effect saturation must, of course, depend on the ammoniacal strength of the gas-liquor operated on. The usual proportions are 1-1/2 to 2 _lbs._ of the former, to each gal. of the latter; but in all cases sufficient should be added to impart a very faint acid reaction to the mixture. This last having been effected, the saline solution, now containing hydrochlorate of ammonia, is, after repose, ready to be pumped or run off into the evaporators.

[Footnote 48: This is now generally conducted in a large wrought-iron boiler, connected with a rude modification of Coffey's still; the object being to obtain the liquor freer from tar and more concentrated.]

The EVAPORATION of the crude saline solution is usually carried on in large square or rectangular cast-iron vats, of very moderate depth, and capable of holding from 1000 to 1500 gallons, or more. These are encased in brickwork, and are heated by a furnace, of which the flues pass in a sinuous course beneath the lining of brickwork on which the vats or pans rest. During the concentration of the liquid, the tar, &c., which separates and floats on the surface, and which thus seriously impedes evaporation, is, from time to time, removed by skimming. As soon as the sp. gr. reaches 1·25, any excess of acid in the solution is exactly neutralised with a little fresh ammoniacal liquor; by which any waste of acid is prevented, at the same time that any ferric salt present, and which would contaminate the ultimate product, is precipitated as sesquioxide. After settling for a short time, the hot liquor is ready to be transferred to the crystallisers.

The vessels employed in the CRYSTALLISATION are pans or tubs, usually circular and about 7 or 8 feet wide, by 2-1/2 to 3 feet deep; and are generally set on the ground, or are embedded either partially or wholly in it. The saline liquor being pumped or run into them at a little below the boiling temperature, crystallises as it cools; the only interference being occasional stirring or agitation, to prevent the formation of large crystals, which would be inconvenient in the subsequent part of the process. The time occupied in the crystallisation varies, according to the size of the 'crystallisers,' and the weather, from 3 or 4 to 8 or even 10 days. The 'mother-liquor' of the 'crystallisers' is pumped back into the evaporating pans for further concentration. The crude blackish salt (hydrochlorate) thus obtained is contaminated with tarry and oleaginous matter, free acid, water, &c.; from part of which it is freed by exposing it in a layer about 4 inches deep, on a cast-iron plate gently heated by a zigzag flue of a small furnace, until all the water is expelled; care being taken that the heat never rises high enough to volatilise the salt. This operation is generally performed under a dome, or the expanded throat of a large chimney. The salt will now have become of a greyish-white colour, and is ready for the next operation.

The crude dried salt of the last process is finally purified by sublimation. For this purpose cast-iron-pots lined with clay, and heated from below and by flues round their sides, are employed. (See _engr._) The crude grey salt is beaten down into these pots until they are about 2-3rds filled, when the heads or capitols are fitted on, and heat applied. The latter are very heavy, being usually made of lead (sometimes of iron), and have the form of a dome, or a hemispherical cup, with a small tube or hole at the apex, in which a plug is loosely placed, to permit the escape of steam. These domes or heads are so made as to fit closely and firmly on the flat rim or flange of the 'sublimers,' and are retained in their places, during use, both by their weight, and by 2 or 3 clamps provided for the purpose. They are also furnished with 3 rings, set at equal distances, to allow of their being lifted off, or moved, by means of a pulley and chains. The due application and regulation of the heat is here of the utmost importance. If the temperature employed be too high, the sublimed salt will be contaminated with empyreumatic matter, while some of it will be carried beyond the dome and lost; and if it be extreme, the head may be altogether blown off, and the contents of the pan scattered about the building; whilst on the other hand, if the heat employed be too low, the resulting cake of sal ammonia will be soft, spongy, and either grey or yellowish. The proper temperature is said to be known by two or three drops of water readily boiling, and being dissipated in vapour, when placed on the head or cover of the sublimer; but it should not 'spit' or 'dance about,' or be raised by the heat out of contact with the metal. The usual practice is to keep the fires "briskly up until the sublimers and their surroundings attain a sufficient degree of heat; they are then slackened, and maintained at a mean temperature." (Muspratt.) The sublimation occupies from 5 to 9 days; but it is customary to raise the heads once, or even twice a week, to ascertain the progress made; the fires having been purposely neglected or checked for some hours previously. The process is finally stopped before the whole of the crude salt in the pots is volatilised; since the heat required for that purpose would lead to the decomposition of the carbonaceous impurities, and cause them to emit volatile hydrocarbons, which would materially lessen the purity and beauty of the product. The unsublimed portion in the pots forms a conical mass, which is technically called the 'yolk.' This is shown in the second engr. (see _below_), in which the latest improvements in the form of the subliming apparatus are also exhibited.

The sublimation having been carried to a sufficient extent, the fires are allowed to die out. The domes, after cooling, are lifted off, and the attached hemispherical cakes or 'bells' of SAL AMMONIAC or HYDROCHLORATE OF AMMONIA at once removed. These vary from 2 to 5 inches in thickness, and from 45 or 50 _lbs._ to 1000 _lbs._, and upwards, in weight, according to the size of the sublimers in which they have been produced. They are generally nearly pure, except in the outer part which has been in contact with the metal. From the subliming-house they are taken to the store or packing-house, and after having been scraped, to remove the discoloured portion before alluded to, are either preserved entire, or are broken up into convenient pieces, which are then packed in casks or barrels, and in either state are ready for the market.

When sulphuric acid[49] is used to neutralise the ammoniacal liquor, the process is generally, for the most part, the same as when hydrochloric acid is employed; but here the brown salt obtained by the crystallisation, and subsequent desiccation, is crude SULPHATE OF AMMONIA, instead of the hydrochlorate. It is intimately mixed with about an equal weight of chloride of sodium (common salt) before being put into the sublimers.

[Footnote 49: Sp. gr. 1·33 to 1·38.]

In some cases, particularly where the ammoniacal liquor is rich in carbonate of ammonia, gypsum is employed as a source of sulphuric acid. (See _below_.)

Another method is to convert the solution of the crude sulphate into a solution of the hydrochlorate, during the process, by the addition of chloride of sodium. Both these last methods are described below.

2. From BONE-LIQUOR, &c.[50]--The ammoniacal liquor technically called 'bone-liquor' or 'bone-spirit,' and formerly known under the name of 'spirit of hartshorn,' is essentially a solution of carbonate of ammonia more or less contaminated with volatile empyreumatic oil. Its conversion into SAL AMMONIA may be easily effected by saturating it with hydrochloric acid, evaporating the resulting neutral solution in lead or iron boilers until a pellicle begins to form, then pumping or running off the hot liquors into the crystallisers, and, lastly, draining and drying the crystals. The salt thus obtained may be purified either by sublimation or by recrystallisation. The whole series of processes closely resemble those already described, except in being less troublesome, owing to the absence of the tarry and other foreign matters which impede and complicate them when gas-liquor is employed.

[Footnote 50: That employed in England is chiefly obtained, as already mentioned, from the manufacturers of bone-black or animal charcoal; but, on the Continent, the liquor obtained by a like destructive distillation of various animal offals (blood, flesh, horn, hoofs, woollen rags and waste, hair, scrapings of hides, leather cuttings, &c.) is employed for the same purpose. The preparatory process by which this liquor is obtained is essentially the same in each case; except that with animal offal the temperature should not exceed a red-brown heat, in order that the resulting charcoal may afterwards serve to make ferrocyanide of potassium and Prussian blue. These liquors have usually a density ranging between 8° and 9° Baumé (Ure; = sp. gr. 1·056 to 1·063).]

Another method adopted, particularly on the Continent, and one equally applicable to any crude ammoniacal liquor rich in free ammonia or its carbonates, is to employ sulphate of lime instead of sulphuric acid to neutralise the alkali. For this purpose the ammoniacal liquor is passed through a series of three or four covered wooden filters lined with lead, each containing a layer of crushed gypsum to the depth of 3 or 4 inches. These filters are usually set on 'stages' one above another, and each communicates with a cistern placed beneath it by means of a leaden pipe furnished with a stop-cock. This last is not opened untill the liquor has remained some little time in the filter; and a pump throws back once, or oftener, upon each filter, what has already passed through it, before it is allowed to run into the next lower one. The 'liquor' in each filter is not allowed to stand higher than from 2 to 3 inches above the surface of the gypsum; and the lowest or last filter is supplied with fresh gypsum at each separate charge of fresh liquor. A little water is lastly passed through the filters to wash out the portion of ammoniacal liquor absorbed or retained by the filtering media. In this way the gypsum of the filters is converted into carbonate of lime at the expense of the carbonate of ammonia in the solution; whilst the ammonia of the latter decomposes the gypsum, and becomes converted into sulphate of ammonia, which, with some free ammonia, is found in the filtrate. Sulphuric acid is next added to the filtered liquor to completely neutralise the free and carbonated alkali still existing in it; after which it is evaporated in a leaden boiler, with frequent skimming to remove floating oil, until of the sp. gr. 1·160. Chloride of sodium (common salt), in sufficient quantity to convert all the sulphate of ammonia in the liquid into hydrochlorate, by double decomposition, is now added, with constant stirring; after which the clear portion is either pumped or syphoned off into a somewhat deep reservoir or tank, where it is allowed to settle. The liquid after sufficient repose is pumped from the reservoir to the boilers, and evaporated, with frequent agitation, so long as the sulphate of soda now existing in it falls to the bottom in granular crystals. These crystals are, at intervals, scraped to the cooler portion of the pan or boiler, whence they are removed by copper rakes and shovels, into draining-hoppers, placed near the edges of the pan. The liquor in the boiler is now a strong solution of sal ammoniac, but still containing a little sulphate of soda, from which it has to be freed by crystallisation. With this object it is further concentrated, and then run or pumped into the crystallisers. In 30 or 40 hours, or longer, the mother-liquor is run or pumped off. The mass of newly-formed crystals is then drained, and slightly washed, first with a little weak solution of sal ammoniac, and next with a very little cold water; after which they are again well drained. The crude HYDROCHLORATE OF AMMONIA, thus obtained, is converted into the pure salts, by desiccation and sublimation, as before.

In France, where this method is very generally employed, the sublimation is commonly conducted in stoneware or earthenware balloons or bottles coated with loam, of about 18 to 20 inches in height in the body, and either surmounted with inverted 'cups' or 'heads' 10 or 12 inches high, or simply covered with a tile, when (in the latter case) the sublimate collects in the upper part or neck of the balloon, which is above the action of the fire. A number of these vessels are set on the dome of a furnace, which is perforated with holes or slits, to allow the heat to pass through; whilst their necks or heads are sheltered from the action of the fire by plates of iron or earthenware, having semi-circular indentations on their edges, so that when placed together they form a level surface, through which the necks of the sublimers protrude, and fit closely. The fire is nicely regulated, so as to cause the salts to condense in the upper and cooler part of the vessels, or in the heads, as the case may be; and great care is taken to occasionally clear the necks with a skewer, to prevent choking, and consequent bursting.

In Scotland, where a similar process is also commonly pursued, the sublimers, according to Dr Ure, are generally "cast-iron pots, lined with fire-proof tiles; the condensation being effected in globular heads of green glass, with which each of the iron pots are capped."[51]

[Footnote 51: Ure's 'Dict. of Arts, M., & M.,' 5th Edn., i, p. 143.]

_Ratio._ Gas-liquor contains carbonate of ammonium (chiefly), with chloride, sulphate, hydrosulphate, cyanide, sulphocyanide, &c., of the same radical. On neutralisation with hydrochloric acid, or sulphuric acid, these are converted into chloride or sulphate of ammonium, according to the acid used. By sublimation with chloride of sodium, the sulphate of ammonium is converted, by double decomposition, into chloride of ammonium, which sublimes; and sulphate of sodium, which remains in the subliming pot. A similar change occurs when the solution of the sulphate, prior to crystallisation, is decomposed by the addition of chloride of sodium, or any other chloride. When the 'gas-liquor' is at once converted into chloride of ammonium by the addition of hydrochloric acid, the sublimation merely purifies the salt. Like changes occur when bone-spirit is employed.

_Comp._ Chemically considered, this salt consists of equal VOLUMES of gaseous ammonia and hydrochloric acid gas condensed into the solid form; or, by WEIGHT, according to the ammonia-theory, of--

Atoms. Equiv. wt. Per cent.
Ammonia (NH_{3}) 1 17· 31·78
Hydrochloric acid (HCl) 1 36·5 68·22
--- ----- ------
Hydrochlorate of Ammonia (NH_{3}HCl) 1 53·5 100·

Or, according to the 'ammonium-theory,' of--

Atoms. Equiv. wt. Per cent.
Ammonium (NH_{4}) 1 18· 33·65
Chloride (Cl) 1 35·5 66·35
--- ----- ------
Chloride of Ammonium (NH_{4}Cl) 1 53·5 100·

_Prop. &c._ The sal ammoniac of commerce is found under the form of large white hemispherical, cup-like cakes or masses (or in large fragments which are sections of them), possessing a tough, fibrous, semi-crystalline texture, and very difficult to powder. It is odourless, has a saline taste somewhat sharp or acrid, and sublimes without either fusion or decomposition. It slightly reddens litmus; dissolves in rather less than 3 parts of cold water, and in about 1 part of boiling water; is soluble in alcohol; and when crystallised from water, under favorable circumstances, forms distinct octahedra, or cubes, usually small and aggregated together in rays or feathery masses. By slowly evaporating its aqueous solution, it may be sometimes obtained in cakes an inch in thickness. It is anhydrous. Sp. gr. 1·450.

_Pur._ It should give a colourless solution with water; wholly sublime with heat; and neither chloride of barium, nor sulphuretted hydrogen, should affect its solution. A solution, to which a few drops of nitric acid have been added, should not yield a blue precipitate with ferrocyanide of potassium. It often contains sesquichloride of iron, and sometimes lead; both of which may be readily detected by the above tests. Its complete volatility may be easily determined by heating, in the flame of a candle, a small fragment held on the point of a knife.

_Tests._--1. It is known to be a salt of ammonium by its cooling ammoniacal fumes when triturated with lime, or when moistened with caustic potassa or soda:--2. It is shown to be a chloride by its solution yielding, with nitrate of silver, a white curdy precipitate, insoluble in boiling nitric acid, soluble in ammonia.

_Uses, &c._ In the _arts_, chiefly in the coating and soldering of metals, and the preparation of alloys; in dyeing; and in the manufacture of ammonia-alum; also, in large quantities, to give a factitious pungency to snuff. In _chemistry_, as a reagent; and, owing to the cold produced during its solution, to form frigorific mixtures. In _medicine_ it is chiefly used externally, as a stimulant and resolvent or discutient; and occasionally, internally, as a diuretic, stimulant, resolvent, alterative, tonic, &c., particularly in chronic inflammations of the mucous and serous membranes, in chronic glandular and visceral enlargements and indurations, and in amenorrh[oe]a. In rather large doses, frequently repeated, it is said to prove often highly beneficial in chronic enlargement and induration of the prostate gland (M. René Vanoye); and also in other like cases.--_Dose_, 5 to 20 gr., 3 or 4 times daily, either in powder or solution, mixed with some demulcent; as a discutient or resolvent lotion, 1 to 1-1/2 oz., to 1/2 pint of water, either with or without 4 or 5 fl. oz. of spirits or strong vinegar (often serviceable in chilblains); as a weak lotion, or a collyrium or injection, 1 to 4 dr., to water, 1 pint. In very large doses it is poisonous; the treatment is emetics and mucilaginous or demulcent drinks.

_Concluding remarks, Patents, &c._ The methods already described are those by which commercial hydrochlorate of ammonia is usually if not almost entirely obtained; the various improvements or modifications, from time to time introduced, affecting chiefly the minor details, and the form or size of the apparatus and machinery employed, and not the general principles on which the processes are based. One of the most important of these has for its object the entire removal of the iron present in the crude salt, some of which, if it be not removed before sublimation, is volatilised and contaminates the ultimate product. To obviate this evil, Mr Brewer passes a few bubbles of chlorine through the hot concentrated solution of the salt, previous to its crystallisation; by which the protochloride of iron is converted into the perchloride, which, being acted on by the ammonia always present in the liquor, is precipitated as ferric hydrate, with the formation of a small additional quantity of sal ammoniac. The only precaution necessary is to avoid employing more chlorine gas than is necessary to peroxidise the iron; as beyond this a portion of the ammonia-salt itself is decomposed, with the evolution of nitrogen. The temperature of the liquor is kept up, after the action of the chlorine, until the whole of the brown flocculent oxide of iron has subsided, when it is at once decanted or filtered into the crystallisers.

Another modification which has been adopted in two or three places is to effect neutralisation of the crude ammoniacal liquor by distilling it, and passing the fumes in at the lower end of a hollow shaft or column filled with coke, down which the acid trickles; the resulting solution of sulphate or chloride of ammonium being received in proper cisterns, conveniently situated near the base of the column.

In Mr Spence's method of obtaining ammonia-salts from gas-liquor or bone-spirit, a series of (usually four) cylindrical boilers, or reservoirs, so placed that the contents of each upper one may be drawn off into the one next below it are employed. Each boiler has an exit-pipe which carries the vapour generated in it to that next above it, whilst that of the highest boiler passes off to a trunk containing the acid necessary to form the salt. The top boiler is connected with the reservoir of gas-liquor (which is already mixed with milk of lime) by a charging pipe furnished with a stop-cock turned by a floating ball, so as to keep the surface of the liquor constantly at the same height. High-pressure steam enters the lower boiler, by which its ammonia is driven through the connecting pipe into the next boiler, and so on in succession, until it leaves the highest boiler in a concentrated state, and thus enters the acid-tank. When this last contains moderately strong hydrochloric or sulphuric acid, the resulting solution of CHLORIDE or SULPHATE OF AMMONIUM (as the case may be) is sufficiently concentrated to be at once run off into the crystallisers. As soon as the liquor in the lowest boiler is exhausted of its ammonia, its contents are drawn off, and replaced by that of the next boiler, which is followed by a like descent throughout the whole series.

Among improvements having for their object the substitution of cheap chlorides[52] for the more expensive commercial acids, may be mentioned those of--

[Footnote 52: Particularly such chlorides as are the 'waste or bye products' of other manufactures.]

1. Mr Laming (Patent dated 1843), who employs a strong solution of CHLORIDE OF CALCIUM for converting the ammonia of gas-liquor into the hydrochlorate.

2. Mr Hills (Patent dated 1846) employs CHLORIDE OF MAGNESIUM[53] in the same way; and by a subsequent patent proposes to convert the ammonia eliminated in the distillation of coal into the hydrochlorate, by mixing CHLORIDE OF MAGNESIUM with the coal in the retorts, or by introducing the chloride into a retort appropriated for the purpose. The heat dispels the chlorine of the chloride, in the form of hydrochloric acid, and this, uniting with the ammoniacal vapour, forms hydrochlorate of ammonia, which is retained in the liquor of the condenser. From this liquor the salt is obtained by evaporation, &c., in the usual way.

[Footnote 53: Of the Epsom-salt works, &c.]

3. Mr Croll (Patent dated 1849) converts the crude ammoniacal vapours that issue with the gas from the common retorts into the hydrochlorate, and obtains a solution of it by passing the gas through a solution of crude CHLORIDE OF MANGANESE[54] (1 cwt. of the salt to about 40 galls. of water), contained in one of the ordinary vessels used for purifying coal-gas. The manganic solution absorbs the ammonia and its salts, converting them into the hydrochlorate, whilst a corresponding proportion of oxide of manganese is precipitated. As soon as the liquor in the purifier is fully saturated, it is drawn off, and replaced by a fresh quantity; whilst the saturated liquor containing the hydrochlorate, after subsidence, or filtration, is evaporated, &c., as before. Crude CHLORIDE OF IRON may be substituted for the chloride of manganese, in the above process: as may also SULPHATE OF MANGANESE, but then the product, of course, will be sulphate of ammonia, instead of the hydrochlorate.

[Footnote 54: Obtained from the chloride-of-lime works. The portion of the precipitated oxide of manganese saved from the process may be reconverted into the chloride, by mixing 3 parts of it with 4 parts of common salt, and heating the mixture to low redness, scarcely perceptible in the dark, for 2 to 3 hours. 140 _lbs._ of the calcined mass, with 40 galls. of water, forms a solution that may be again pumped into the purifier.]

4. Mr Laming (Patent dated 1850) also proposes the use of various salts and mixtures for retaining and condensing the ammoniacal vapour of coal-gas as it passes from the retorts through the purifiers. Of these the principal are CHLORIDE OF CALCIUM obtained by decomposing chloride of iron by hydrate of lime; CHLORIDE OF IRON, obtained by decomposing sulphate of iron with chloride of sodium; CHLORIDE OF MAGNESIUM; a mixture of SULPHATE OF LIME and SULPHATE OF IRON; or of moist precipitated oxide of iron with carbonate of lime, carbonate of magnesia, or magnesian limestone; or one containing sulphate of magnesia, or chloride of magnesium or calcium, or one or more of them, in combination with oxide of copper, either with or without lime or magnesia, or with both or either of them or their carbonates. These salts, or compounds, are mingled with sawdust, or some other porous substance not acted on by the gas, before being put into the purifiers; and after they become saturated with the vapour, the newly-formed hydrochlorate or sulphate (according to the salt or mixture employed) is washed out of the mass with water.

Besides the usual sources of SAL AMMONIAC (and the other ammonia-salts of commerce) it has been proposed to obtain it from guano, peat, shale, &c., as noticed under SESQUICARBONATE OF AMMONIA (_suprà_); the substance employed to effect the neutralisation or decomposition of the ammoniacal liquor being, in this case either hydrochloric acid or a chloride.

In Young's Patent (1841) for 'obtaining AMMONIA and its SALTS,' a mixture of 2 parts of guano, and 1 part of hydrate of lime, is distilled in a retort placed vertically, at a moderate heat, gradually increased until the bottom of the retort becomes red hot. The ammoniacal portion of the fumes evolved are absorbed by the cold water contained in a suitable condenser; whilst the other gases eliminated by the process pass off uncondensed. By subsequently passing carbonic acid gas into the liquor of the condenser, a solution of CARBONATE, BICARBONATE, or SESQUICARBONATE of AMMONIA is formed. By nearly filling the condenser with diluted hydrochloric or sulphuric acid, instead of with water, a solution of HYDROCHLORATE or of SULPHATE OF AMMONIA is obtained.

Stale urine saturated with hydrochloric acid, or with sulphuric acid diluted with about twice its weight of water, yields SAL AMMONIAC, or SULPHATE OF AMMONIA (according to the acid used) on evaporation.

Hydrochlorate of ammonia is now wholly prepared on the large scale, and never by the dealer or retailer, by whom it is only occasionally refined or purified, in small quantities, for chemical and medical purposes. The sal ammoniac of commerce is found to be sufficiently pure for all its ordinary applications in the arts; but when wanted of greater purity, it is broken into pieces, and resublimed from an earthenware vessel into a large receiver of earthenware or glass. The product (REFINED SAL AMMONIAC, DOUBLE-REFINED S. A.; AMMONIÆ HYDROCHLO''RAS PU''RA, SAL AMMONI'ACUS DEPURA'TUS[dagger], L.) is popularly known as FLOWERS OF SAL AMMONIAC (flo'res sa'lis ammoni'aci, L.), from being in a finely divided crystalline state.

The chemically pure chloride of ammonium may be prepared by bringing its gaseous constituents--ammonia and hydrochloric acid--into contact. During the combination much heat, and even light, is generated, and the anhydrous solid salt is precipitated in a minutely divided state, which, under the microscope, is seen to be crystalline. It may be also more easily and conveniently prepared by saturating pure and moderately dilute hydrochloric acid with ammonia or its carbonates, and evaporating the solution until a pellicle forms, when crystals of the chloride separate as the liquid cools. A similar but rather more violent reaction occurs when gaseous chlorine is brought in contact with gaseous ammonia, or is passed into a nearly saturated solution of ammonia or its carbonates; but in this case nitrogen is evolved at the expense of the ammonia; moreover, the process is attended with danger.

The manufacture of sal ammoniac is usually a distinct business, and is carried on to a very great extent in the neighbourhood of London. Indeed, the London makers now supply the chief portion of that used in England. A large quantity is now, however, made at Manchester and Liverpool. A small quantity is imported from Germany. That from Brunswick is in the form of sugar-loaves. An inferior quality is also imported, in chests, from the East Indies.

The red bands frequently seen in the sal ammoniac of commerce are said to arise from the workmen falling asleep, and allowing the fire to go down, and then suddenly raising the heat too high. (Muspratt.) They consist chiefly of ammonio-chloride of iron.

=Ammonium, Citrate of.= (NH_{4})_{2}HC_{6}H_{6}O_{7}. _Syn._ DIAMMONIUM CITRATE, CITRATE OF OXIDE OF AMMONIA; AMMON''NIÆ CIT'RAS, L.

_Prep._ A concentrated solution of pure citric acid, gently heated, is saturated with sesquicarbonate of ammonium, in fine powder (about 7 parts to 6), and slightly in excess; and the resulting liquid is crystallised by refrigeration in close vessels, or by evaporation in vacuo. If heat be employed in the evaporation of the solution, an acid citrate will be formed.

_Uses, &c._ Chiefly as a chemical test. An extemporaneous citrate, made with lemon-juice and drunk effervescing, is employed as a saline draught, and a mild aperient and diaphoretic, in fevers, &c.

=Ammonium, Ferrocyanide of.= (NH_{4})_{4} FeC_{6}N_{6} . 3Aq. _Syn._ FERROCYANATE D'AMMONIAQUE, Fr. _Prep._ 1. Saturate a solution of hydroferrocyanic acid with sesquicarbonate of ammonium, in slight excess; evaporate the solution at a heat below ebullition, and crystallise by refrigeration.

2. Digest ferrocyanide of lead or of iron in a solution of sesquicarbonate of ammonium, at a gentle heat, for some time; then filter, evaporate, and crystallise.

_Prop., &c._ It is isomorphous with ferrocyanide of potassium; it is easily crystallisable, very soluble in water, and is decomposed by ebullition.

=Ammonium, Iodide of.= NH_{4}I. _Syn._ HYDRIODATE OF AMMONIA; AMMO''NII IODI'DUM, L.; HYDRIODATE D'AMMONIAQUE, Fr. _Prep._ An aqueous solution of hydriodic acid is neutralised with ammonia, or ammonium sesquicarbonate, in slight excess; and the resulting liquid is either carefully, but rapidly, evaporated to dryness over a water bath, or it is concentrated by the same means, and then caused to deposit crystals by refrigeration; in both cases care is taken to keep a slight excess of ammonia present during the evaporation. The crystals are dried by pressure between folds of bibulous paper; and the product, in either form, preserved in a stoppered bottle.

Pure iodine is triturated with a little distilled water, and solution of ammonium sulphydrate added, in small quantities at a time, with continued trituration, until the red colour of the iodine has entirely disappeared. The solution, after being gently boiled for a few seconds, to expel the sulphuretted hydrogen present, is filtered, slightly alkalised, with ammonia, and evaporated or crystallised, as before.

_Prop., &c._ Colourless; deliquescent; freely soluble in water, and in spirit; air and light turn it yellowish or brownish, with partial decomposition. It closely resembles iodide of potassium, than which it is more active, and thought to be better suited to irritable and relaxed habits.--_Dose_, 1 to 10 or 12 gr.

=Ammonium, Lac'tate of.= _Syn._ AMMO''NIÆ LAC'TAS, L. An uncrystallisable salt prepared by saturating ammonia, or its carbonate, with lactic acid. It has been found useful in rickets, and in dyspepsia and worms, when occurring in debilitated habits. For this purpose it is best taken fresh-prepared, as a draught, flavoured with syrup of orange-peel, 3 or 4 times daily. See LACTATE and LACTIC ACID.

=Ammonium, Nitrate of.= NH_{4}NO_{3}. _Syn._ AMMO''NIÆ NI'TRAS, L.; NITRATE D'AMMONIAQUE, Fr. _Prep._ Saturate nitric acid (diluted with 3 or 4 times its weight of water) with sesquicarbonate of ammonium, evaporate by a gentle heat, and crystallise. When not required in a crystalline form, it is usually evaporated to dryness at about 212° Fahr.; and the heat being carefully raised to about 250°, the fused salt is poured out on a polished slab of iron or stone, and when solidified broken up and put into bottles.

_Prop._ When the evaporation of the solution is conducted at a heat under 100° Fahr., the salt is obtained in beautiful hexagonal prisms; when at 212°, in long silky fibres; when by rapid evaporation and fusion, it forms a white, compact, and usually foliated mass. It dissolves in about twice its weight of water; is slightly deliquescent; melts at 230°, and is decomposed into nitrous gas and water at 460° Fahr. It deflagrates, like nitre, on contact with heated combustible matter.

_Uses, &c._ Chiefly to prepare nitrous oxide or laughing gas (of which nearly 4-1/2 cubic feet may be procured from every _lb._ avoir.); and with water, to form freezing mixtures, for which purpose it may be used for any number of times by simply evaporating the solution to dryness, when the salt, obtained unaltered, is ready for another operation. Care, however, should be taken not to expose it to too great a heat, as at a certain temperature it deflagrates with violence. It is occasionally employed in the laboratory to promote the combustion of organic bodies during incineration; and sometimes, though seldom, in medicine, as a diuretic and diaphoretic. It is said to reduce the frequency of the pulse, and the animal heat, without affecting the head, chest, or stomach. (Wibmer.)--_Dose_, 10 to 30 gr.

=Ammonium, Nitro-sulphate of.= _Syn._ AMMO''NIÆ NITRO-SUL'PHAS, L. Dissolve sulphite of ammonium, 1 part; in solution of ammonia, 5 parts; and pass nitric oxide gas through the solution; rapidly wash the crystals that form with solution of ammonia, dry in bibulous paper, without heat, and preserve them in a well-stopped bottle.--_Dose_, 10 to 20 gr.; in typhoid fevers, &c.

=Ammonium, Oxalate of.= (NH_{4})_{2}C_{2}O_{4}. _Syn._ AMMO''NIÆ OX'ALIS, L.; OXALATE D'AMMONIAQUE, Fr. Neutralise a hot solution of oxalic acid with sesquicarbonate of ammonia; evaporate and crystallise.

_Prop._ It forms beautiful, colourless, long, rhombic prisms, which effloresce in the air; slightly soluble in cold water; freely soluble in hot water; heated in a retort, it yields ammonia, carbonate of ammonia, cyanogen, and carbonic acid, together with oxamide, which sublimes.

_Uses, &c._ In _chemistry_, chiefly as a test for calcium (with which it produces a white precipitate soluble in nitric acid), and to separate lime from magnesium, solutions of the salt of which it does not precipitate. A BINOX'ALATE may also be formed; but it possesses no practical interest.

=Ammonium, Phosphate of.= (NH_{4})_{3}PO_{4}. _Syn._ AMMO''NIÆ PHOS'PHAS, L. _Prep._ Saturate a solution of phosphoric acid with sesquicarbonate of ammonium, in slight excess; gently evaporate and crystallise by refrigeration. Diuretic, discutient, and antilithic.--_Dose_, 3 to 10 gr., or 20 to 30 drops of a saturated solution, 3 or 4 times a day; in gout, rheumatism, and calculus, accompanied with the lithic-acid diathesis; also in rickets and certain forms of dyspepsia.

=Ammonium Suc'cinate.= _Syn._ AMMO''NIÆ SUC'CINAS, L. _Prep._ 1. Succinic acid, 1 part; water, 4 parts; dissolve, neutralise with solution of ammonia, or of ammonium carbonate, in slight excess, and evaporate, and crystallise as directed under the 'benzoate' or 'phosphate,'--_Dose_, 2 to 10 gr.

=Ammonium, Sul'phate of.= (NH_{4})_{2}SO_{4}. _Syn._ SULPHATE OF OX'IDE OF AMMONIA; AMMO''NIÆ SUL'PHAS, L,; SULFATE D'AMMONIAQUE, Fr.; SCHWEFELSAUER AMMONIUM SALZ, Ger.; Glauber's SECRET SALT[dagger], G. SECRET SAL AMMONIAC[dagger], SAL AMMONI'ACUM SECRE'TUM GLAUBE''RI[dagger], &c. Crude sulphate of ammonia exists in considerable quantity in the soot from pit-coal; and it is obtained, as a secondary product, from the ammoniacal liquor of gas-works and animal charcoal manufactories. These last are its chief sources. It is also found native, associated with sal ammoniac, in the neighbourhood of volcanoes, under the name of '_mascagnine_' or '_massagnine_,'

_Prep._ 1. (Medicinal.) Saturate dilute sulphuric acid with sesquicarbonate of ammonia, in slight excess; filter, gently evaporate, and crystallise.

2. (Commercial.) From gas-liquor or bone-spirit, saturated with weak oil of vitriol, and, the clear portion of the liquid, after repose decanted, concentrated by rapid evaporation, and crystallised, in the manner noticed under AMMONIUM, CHLORIDE OF.

_Prop._ Crystals, long, flattened, six-sided prisms; soluble in 2 parts of cold, and 1 of boiling water; fuses, with loss of one atom of water, at about 280° Fahr.; and is volatilised, with entire decomposition, at about 535°. Even its solution, by long boiling, becomes acid from loss of ammonia. The anhydrous salt does not exist.

_Uses, &c._ Pure sulphate of ammonia is diuretic, aperient, resolvent, and stimulant.--_Dose_, 10 to 30 gr. It is now seldom employed in medicine. The crude sulphate is principally used in the preparation of sal ammoniac and sesquicarbonate of ammonia, and for manure. "A mixture of 10% of this sulphate with 20% of bone-dust, some gypsum, and farm-yard manure, forms a very fertilising compost, applicable to a great variety of soils" (Ure); and we may add--greatly superior to a very large portion of what is now so commonly vended under the name of 'guano.'

_Concluding remarks, Patents, &c._ The manufacture of sulphate of ammonia, on the large scale, has been unavoidably explained in treating on the salts of that base already noticed. All that is necessary is to saturate with sulphuric acid the solution of ammonia, crude or otherwise, and obtained in any manner; and then to evaporate the solution until the salt crystallises out. At other times, however, instead of adding the acid to the ammoniacal liquor, the latter, either at once, or after treatment with lime, is submitted to distillation, and the evolved alkaline vapour is passed into the acid (previously somewhat diluted), contained in a large receiver or cistern, or a series of them; the salt being obtained from the resulting solution in the usual manner. By re-solution and a second crystallisation the sulphate is generally obtained sufficiently pure for all commercial purposes; but when the salt is intended for use as manure, or (unless very rough) for conversion into sal ammoniac, this need not be had recourse to.

Among modifications and improvements, not previously noticed, may be mentioned--

1. That of Dr Richardson (Patent dated Jan., 1850), who mixes SULPHATE OF MAGNESIA with the crude ammoniacal liquor, and thus forms a double sulphate of magnesia and ammonia, from which he obtains the SULPHATE OF AMMONIA by sublimation.

2. That of Michiel (Patent dated April, 1850), who prepares sulphate of ammonia by means of OXYSULPHATE OF LEAD obtained by roasting galena (sulphide of lead), by exposing it in a crushed state and thin layers for 2 or 3 hours, to the heat of a reverberatory furnace. The resulting mixture of sulphate and oxide of lead is reduced to the state of coarse powder, and well worked up with the ammoniacal liquor, when SULPHATE OF AMMONIA and sulphide and carbonate of lead are produced by the mutual reaction of the elements present. The first is removed by treatment with water; and the residuum serves for the manufacture of lead compounds, or may be reduced to the metallic state by fusion in the usual manner.

3. That of Mr Laming (Patent dated Aug., 1852), in which a stream of SULPHUROUS ACID GAS is transmitted through the liquor containing the ammonia, either in the free state or as carbonate, by which SULPHITE OF AMMONIA is formed. This salt he oxidises, and thus converts into the SULPHATE OF AMMONIA, by agitation and free exposure to the air.

Sulphate of ammonia, like the hydrochlorate, may also be obtained by saturating stale urine with the acid, and subsequent evaporation and crystallisation. See AMMONIA; AMMONIA, CARBONATES OF; AMMONIUM, CHLORIDE OF, and MANURES, &c.

=Ammonium, Sulphide of (neutral).= (NH_{4})_{2}S. _Prep._ Saturate strong solution of ammonia with pure sulphuretted hydrogen gas; then add a second portion of solution of ammonia, equal to that first used, and preserve it in a well-stoppered bottle.

=Ammonium, Sulphydrate of.= NH_{4}HS. _Syn._ SULPHIDE OF AMMONIUM, HYDROSULPHIDE OF AMMONIUM, HYDROSULPHATE OF AMMONIA. _Prep._ By passing sulphuretted hydrogen gas, to saturation, through a mixture composed of strong solution of ammonia, 1 part, and distilled water, 4 parts.

_Props._ Prepared as above, it has a very f[oe]tid odour. When pure it is wholly volatilised by heat, and does not disturb a solution of sulphate of magnesium. Mineral acids decompose it, with the evolution of sulphuretted hydrogen. By keeping, it decomposes and acquires a yellow colour. This yellow coloration does not, however, render it unfit for use as a reagent; but it must be borne in mind that it will now deposit sulphur when mixed with acids. In this state it proves valuable as a reagent to detect hydrocyanic acid, and as a solvent to separate metallic sulphides thrown down by sulphuretted hydrogen.

_Uses, &c._ It is principally employed by chemists as a reagent to precipitate metals, to separate metallic sulphides, &c.; and by the perfumers as a mordant in dyeing hair. In _medicine_ it has been used by Cruickshank, Rollo, and others, to check the morbid appetite, and to increase the action of the stomach and general tone of the system in diabetes mellitus. It has also been used by Brauw, Gruithuisen, and others, in old pulmonary and vesical catarrhs. It is a powerful sedative, lessening the action of the circulatory system, causing nausea, vomiting, vertigo, drowsiness, &c.--_Dose_, 3 to 6 drops, three or four times daily, mixed with pure water, and instantly swallowed. In large doses it is poisonous.

_Ant._ Very dilute solution of chlorine, or of chloride of lime or soda, followed by a powerful emetic, or the stomach-pump. When the vapour has been respired, free exposure to fresh air, with the head a little elevated, and copious affusions of cold water, with moderate draughts of brandy-and-water, and the use of the smelling-bottle (ammoniacal) should be adopted. If need be, artificial respiration should be attempted, and the air around the patient should be slightly impregnated with the fumes of chlorine or chloride of lime.

=Ammonium, Persulphide of.= _Syn._ BOYLE'S FUMING-LIQUOR, HOFFMAN'S VOL'ATILE SPIRIT OF SULPHUR, &c.; AMMO''NIÆ PERHYDROSUL'PHAS, A. PERHYDROSULPHURE'TUM, &c. Authorities differ as to the constitution of this liquid, which, since its introduction by Beguin in 1650, has passed under more 'aliases' than perhaps any other preparation. Its precise position amongst the ammonia-compounds is still undecided.

_Prep._ 1. (Beguin.) Sulphur, 1 lb; quick-lime, 1/2 lb; sal ammoniac, 4 oz.; mix and distil.

2. (Boyle.) Sulphur and sal ammoniac, of each, 5 oz.; quick-lime, 6 oz.; as last.

3. (Liebig.) Agitate the common hydrosulphate of ammonia with pure sulphur, until the latter ceases to be dissolved; and, after repose, decant the clear liquid.

_Prop., &c._ An orange-yellow, fuming, f[oe]tid liquid, of an oily consistence, having the characteristics of the common sulphydrate in a remarkable degree. It may prove an excellent medicine. "Useful for wounds and ulcers." (Beguin.) Diluted with three parts of spirit of wine, it formed the LIQUOR ANTIPODAG'RICUS of F. Hoffman; of which we are told that about 30 drops acted as a strong sudorific; and applied externally, mixed with camphor, "it relieved pain like a charm." (Hoffman.) The sulphides of ammonium are now scarcely ever employed as remedies.

=Ammonium, Sul'phite of.= (NH_{4})_{2}SO_{3}.7Aq. _Syn._ AMMONIÆ SULPHIS, L. Prepared by passing sulphurous acid gas into a solution of ammonia. It is crystallisable and very soluble in water.

=Ammonium, Sulphocyanide of.= NH_{4}CNS. _Prep._ 1. Neutralise hydrosulphocyanic acid with ammonia, and gently evaporate the solution to dryness, by the heat of a water bath.

2. Digest hydrocyanic acid with yellow sulphydrate of ammonium, and, after a time, evaporate as before.

A deliquescent, white, saline mass, very soluble in water, but seldom employed out of the laboratory in a pure state. Of late it has been obtained in quantity as a crude product of the gas-liquors.

=Ammonium, Tartrates of.= Of these there are two:--

=Ammonium, Neutral Tartrate of.= (NH_{4})_{2}C_{4}H_{4}O_{6}. _Syn._ AMMO''NIÆ TAR'TRAS, L. _Prep._ Saturate a solution of crystallised tartaric acid, 150 grs.; with sesquicarbonate of ammonium, 118 grs.; and either evaporate the solution at a gentle heat, and crystallise; or evaporate to dryness, and powder the residuum.

_Prop., &c._ Prismatic crystals, or a crystalline mass; soluble and efflorescent. Its medicinal properties and doses resemble those of citrate of ammonium.

=Ammonium, Bitartrate of.= NH_{4}HC_{4}H_{4}O_{6}. _Syn._ AMMO''NIÆ BITAR'TRAS, L. _Prep._ To a strong solution of tartaric acid add another of sesquicarbonate of ammonium, or of tartrate of ammonium, as long as a precipitate falls; which must be collected and dried.

_Prop., &c._ A crystalline powder, only slightly soluble in water, closely resembling ordinary cream of tartar. It is diaphoretic, diuretic, and deobstruent, and is frequently, though improperly, sold for the preceding preparation.

=Ammonium, Valerianate of.= NH_{4}C_{5}H_{9}O_{2}. _Syn._ AMMO''NIÆ VALERIA'NAS, L. _Prep._ Saturate valerianic acid with strong solution of ammonia, and evaporate the resulting liquid to a syrupy consistence at a heat under 175° Fahr.; then add twice its volume of alcohol, and, after agitation, allow it to crystallise by spontaneous evaporation.--_Dose_, 2 to 8 or 10 gr.; in neuralgia, epilepsy, hypochondriasis, hysteria, low fevers of an intermittent kind, &c.; also in dyspepsia and debility complicated with these affections.

=AMMONI'ACAL.= [Eng., Fr.] _Syn._ AMMONIACA'LIS, L. Pertaining to, or possessing the odour or properties of, ammonia. See AMMONIA, &c.

=AMMONI'ACUM.= _Syn._ GUM AMMONIACUM, G. AMMO''NIAC[dagger]; GOMME AMMONIAQUE, Fr.; AMMONIAK, Ger. A gummy-resinous exudation from the stem of _dorema ammoniacum_, in tears and masses, of a pale cinnamon colour, brittle, and when broken has a white and shining surface. Collected in Persia and the Punjaub. (B. P.)

Gum ammoniacum has an unpleasant odour, especially when heated, and a nauseous and slightly bitter taste. It is a mild, stimulating expectorant and emmenagogue; and its effects on the system resemble those of assaf[oe]tida except in being weaker. Externally, it is resolvent.--_Dose_, 10 to 30 gr. in pills or emulsion.

_Doses for Animals._ HORSE, 2 to 4 drachms. CATTLE, 2 to 4 drachms. SHEEP, 1/2 to 1-1/2 drachm. PIG, 1/2 to 1-1/2 drachm. DOG, 10 to 20 grains. Either by bolus or emulsion.

=Ammoniacum, Strained'.= _Syn._ PREPARED AMMONIACUM; AMMONI'ACUM PRÆPARA'TUM (Ph. L.), L. _Prep._ (Ph. L. 1851.) Boil ammoniacum in water just sufficient to cover it; strain the mixture through a hair sieve, and constantly stirring, evaporate in a water bath, until, on cooling, it becomes hard. The product, owing to a loss of volatile oil, is much weaker than the unprepared gum-resin. The process is only necessary with rough lump ammoniacum.

=Ammo''niated.= _Syn._ AMMONIA'TUS, L. In _pharmacy_, _perfumery_, &c., applied to preparations containing ammonia.

=AMMO'NIO-, Ammon'ico-.= In _chemistry_, a common prefix to double salts containing ammonia; as ammonio-citrate, a.-chloride, or a.-tartrate of iron, &c. See the respective metals.

=AMONTILLADO.= [Sp.] See SHERRY and WINE.

=AMORPH'OUS= (-morf'-us). _Syn._ AMORPH'US, L.; AMORPHE, INFORME, DIFFORME, Fr.; AMORPHISCH, MISGEBILDET, MISSGESTALTET, Ger. Shapeless. In _chemistry_ and _mineralogy_, applied to substances devoid of regular or crystalline form; as a lump of chalk, the majority of precipitates, &c. The corresponding substantives are AMORPH'ISM, AMORPH'OUSNESS* (_amorphis'mus_, L.; _amorphisme_, Fr.).

=AMPHIB'IA= (f[)i]b'-y'[)a]). [L. pl.; prim. Gr.] _Syn._ AMPHIB'IANS (-y[)a]nz), AMPHIB'IALS (-y'[)a]lz). Animals that possess the faculty of living both in water and on land. In _modern zoology_ it is restricted to those animals which possess both gills and lungs; as the _batrach'ia_ or frog tribe. The term is also often applied, colloquially, to otters, seals, walruses, crocodiles, &c., none of which can breathe under water, although, from the languid nature of their circulation, they are able to remain a long time in it.

=AMPHIB'IOUS= (y'[)u]s). _Syn._ AMPHIB'IUS, L.; AMPHIBIE, Fr.; BEYDLEBIG, Ger. In _botany_ and _zoology_, having the faculty of growing or living both on land and in water. See AMPHIBIA.

=AM'PHITYPE= (-fe-). See PHOTOGRAPHY.

=AMYGDALIN.= C_{20}H_{27}NO_{11}.3Aq. This substance exists in bitter almonds. It crystallises in pearly white plates, which are odourless and almost tasteless. It is nearly insoluble in hot and cold water and in cold alcohol, but soluble in boiling alcohol. To prepare amygdalin, boil well-pressed cake of bitter almonds twice in strong alcohol; strain through linen, and press the residue; remove any oil that may appear, heat the liquid again, and filter. In a few days part of the amygdalin crystallises out. Concentrate the residuary liquor to a sixth part, and add ether, which will throw down the amygdalin. Press it between blotting paper, wash it with ether, and set aside to crystallise.

=AMYG'DALOID= (-loyd). _Syn._ AMYGDALOID'AL; AMYGDALOÏ'DES (-d[=e]z), L.; AMYGDALOÏDE, Fr. Almond-shaped. In _mineralogy_, amygdaloid is 'toadstone.'

=AMYKOS= (Galen, Upsala). A cosmetic and mouth-wash. Claims to be prepared according to an English patent. It is an aqueous extract of 420 grms. cloves, boiled in a gallon of water, in which 420 grms. of pure glycerine are dissolved, and to which 210 grms. of borax are added. (Hager.)

=AMYKOSASEPTIN= is linen saturated with a hot solution of borax. (Nyström.)

=AMYLA'CEOUS= ([)a]m-e-l[=a]'-sh'[)u]s). _Syn._ AMYLA'CEUS, L.; AMYLACÉ, Fr. Of or like starch; consisting of or abounding in starch; starchy. See FOOD, NUTRITION, STARCH, &c.

=AM'YL= (-[)i]l). C_{5}H_{11}. The radical of the fusel-oil compounds (AMYL-SERIES).

=Amyl, Acetate of.= C_{5}H_{11}C_{2}H_{3}O_{2}. _Syn._ PEAR-OIL. _Prep._ From fusel-oil, 1 part; acetate of potassa (dry), 2 parts; concentrated sulphuric acid, 1 part; distilled, with the usual precautions, from a glass retort into a cool receiver. The distillate is purified by washing it with very dilute solution of potassa, and redistilling it from fused chloride of calcium. A little litharge added to the liquid in the retort, before rectification, will remove any sulphurous odour, should it be present.

_Prop., &c._ Liquid, limpid, colourless; insoluble in water; soluble in alcohol; boils at 272° Fahr.; alcoholic solution of potassa converts it into an acetate of that base, with reproduction of fusel-oil.

_Obs._ The odour and flavour of this preparation are those of the Jargonelle pear. It is now extensively manufactured, and, after dilution with alcohol, is sold under the name of ESSENCE OF JARGONELLE PEAR, for flavouring liqueurs and confectionery.

=Amyl, Vale'rianate of.= C_{5}H_{11}C_{5}H_{9}O_{2}. _Syn._ APPLE-OIL, A.-ESSENCE, &c. This compound is abundantly formed during the preparation of valerianic acid from potato oil, and is recognised by the offensive odour of rotten apples evolved during the process. By treating the crude product of the distillation with a weak solution of pure potassa, the valerianic acid is removed, and the volatile oil obtained nearly pure. Dissolved in rectified spirit it forms the 'APPLE-ESSENCE' now so much employed as a flavouring ingredient for confectionery and liqueurs. See FRUIT ESSENCES, VALERIANIC ACID, &c.

=AMYL NITRITE.= _Syn._ AMYL NITRIS, B. P. Produced by the action of nitric or nitrous acid on amylic alcohol.--_Dose._ By inhalation, the vapour of 2 to 5 minims. To be used with caution. It may be produced by passing a stream of nitrous acid gas through purified amylic alcohol at a temperature of 132° C.

For other methods of preparing it consult 'Wood and Bache's United States Dispensatory, 1877.' Mr Umney ('Pharm. Journal') says that true nitrite of amyl should be made by passing nitrous acid into amylic alcohol which has been previously submitted to a fractional distillation, until the portion retained for use has a boiling point of 132° C. A nitrate so prepared, when deprived of any excess of acid it may contain by rectification over fused carbonate of potash, will have a boiling point of 98°-99° C.

=AM'YLENE= (-e-l[=e]ne). C_{5}H_{10}. [Eng., Fr.] _Syn._ AM'ILENE*; AMYLE'NA, AMYLE'NUM, L. A peculiar volatile, liquid hydrocarbon, discovered by Cahours.

_Prep._ From fusel-oil repeatedly distilled along with either anhydrous phosphoric acid, or a concentrated solution of chloride of zinc; the product being repeatedly rectified at a low temperature, until the boiling point sinks to 102° Fahr.

_Prop., Uses, &c._ An ethereal liquid, lighter than water, having an aromatic odour, slightly alliaceous. Sp. gr. of vapour, 2·68. Its vapour was several times successfully employed, by the late Dr Snow, as a substitute for ether and chloroform in producing anæsthesia, being, though less agreeable, also less pungent, and consequently easier to breathe, than either of them; but its use has since been given up owing to doubts as to its safety, two or three deaths having followed its inhalation.

=ANADOLI= (Kreller, Nuremburg). An oriental tooth-powder. Powdered soap, 42 parts; starch powder, 44 parts; levantine soapwort, 12 parts; oil of bergamot and lemon to flavour. (Wittstein.)

=ANÆMIA.= Deficiency of blood.

=ANÆSTHE'SIA= ([)a]n-[=e]z-the'-zh'[)a]; -sh'[)a]; -th[=e]ze'y'[)a]r). [L.; prim. Gr.] _Syn._ ANESTHÉSIE, Fr. In _pathology_, diminished or lost sense of feeling.

In _surgery_ and _obstetrics_, the production of temporary anæsthesia, for the purpose of rendering operations painless, relieving the pangs of childbirth, &c., is effected by the use of--

=ANÆSTHET'ICS.= _Syn._ ANÆSTHET'ICA, L.; ANESTHÉTIQUES, Fr. In _pharmacology_ and _surgery_, substances or agents which diminish or destroy sensibility, or which relieve pain. In its full extent this term includes both anodynes and narcotics; but it is now more generally confined to those substances which greatly diminish common sensibility, or entirely remove susceptibility to pain. Among the most useful, safe, and powerful of this class are chloroform, ether, nitrous oxide, and intense cold; besides several chlorinated compounds, such as the bichlorides of ethylen, methylen, and carbon.