188 AMMONIA. —Chloride of Ammonium.
Chloride of Ammonium. — Sal-ammoniac, ammoniumchloride, muriate of ammonia. CMorure d'ammonium, orchlorure ammoniaque, French ; chlorammonium, salmiak,salzsaures ammoniak, German. Formula, NII 4 C1.—The manufacture of chloride of ammonium was firstprafctised by the Arabians, although it has been attri-buted to the Egyptians. The term sal-ammoniacusis very ancient; but whether the ancients, at theperiod in which this term was used, applied it to ourchloride of ammonium is doubtful. Pliny and hiscontemporaries were unacquainted with sublimationin any shape; and it is a fact, that even the processof lixiviating earths, or crystallizing saline substancesfrom their solutions, was so ill understood that thenative compounds, however impure, were employedin the manufacture of inks, colours, &c. From themany evidences adduced by Beckmann, it is almostcertain that the sal-ammoniacus of the ancients wascommon rock salt. Indeed, the uses to which it isstated the sal-ammoniacus was applied, leaves nodoubt that the chloride of ammonium was not meant.The Arabian philosophers were the first to furnishan account of true sal-ammoniac. Geber describesits preparation and its purification by sublimation.
Sal-ammoniac was an article of trade about theyear 1410; but the purposes to which it was applied,or the mode of its preparation in Egypt at that period,have not been recorded. In the sixteenth centurymany of its properties were known, particularly itsbehaviour with nitric acid, by which aqua-regia isformed.
The younger Geoffroy was the first to show thatsal-ammoniac consisted of hydrochloric acid and vola-tile alkali, and that it could therefore be produced inEurope by sublimation. An account of the sal-ammoniac—ammonium chloride—manufactories atDamayer, in the Delta , was given in 1720 by aJesuit named Sicard. It is uncertain at what periodthe manufacture became general in Europe . Largemanufactories of this article were at work in Scotland so early as 1750.
Chloride of ammonium was discovered in themineral products of volcanic districts in the fifteenthcentury. It is generally met with, sublimed amongother volatile bodies, in the fissures of lava, particu-larly at Vesuvius, Etna , in the Island of Volcano,and at the Solfatara, near Naples . Small quantitiesof it have been found in the vicinity of ignited coal-fields, as at St. Etienne in France, in Scotland , and atNewcastle. A variety, possessing a greyish-white■ colour, of a conchoidal fracture, has been mentionedas occurring in Bucharia . The native salt is generallymassive, has a fibrous texture, is sometimes feathery,in crusts, and in minute cubic and octahedral crystals;its colour, when pure, is white. It is sometimes trans-parent, sometimes opaque; externallydull or glistening,and internally shining or vitreous. This salt has nosmell, butapungentandsalinetaste; its specific gravityis 1‘5. It is soluble in 2-72 parts of water at 66° Fahr.(18°'8 C.), with great reduction of temperature, andin its own weight of water at 212° Fahr. (100° C.); itdoes not attract moisture on exposure to the air.Ammonium chloride is, when exposed to the air,
partially decomposed, it loses ammonia, and becomesacid to test paper. When heated it completely vola-tilizes in white fumes without fusing. After subli-mation it forms very tough crystalline masses, whichcan scarcely be powdered, and emits, when trituratedwith lime, a strong ammoniacal odour.
according to Klaproth the following
results:—
Ammonium chloride,....
.... 99-5 .
. 97-5
Ammonium sulphate,.
. 2’5
100-0
100-0
Chloride of ammonium is prepared in the labora-tory by neutralizing pure ammonia with hydrochloricacid: or by transmitting a stream of ammonia gas intohydrochloric acid till saturated, and then evaporatingthe solution and crystallizing out the salt. Theproperties of the chloride, in a chemical point ofview, are not very distinctive, though in a manu-facturing light the compound is highly important.Its chief characteristics will be mentioned after thereader becomes familiar with the chief methodsfollowed in its preparation on a large scale.
In Egypt , which undoubtedly was the great seatof its manufacture from the thirteenth to the middleof the seventeenth century, and from whence all theEuropean markets were supplied, it was obtained bythe following process, which indeed is still in use.
The great source of sal-ammoniac in Egypt isthe dung of the camel, which is dried by plaster-ing it upon the walls, and then used for fuel,which is very scarce in that country. A fire ofthis material evolves a thick smoke charged withchloride of ammonia, a large part of which is con-densed in the soot. The latter is carefully collectedthroughout the country, particularly in the Delta district, and brought to the sal-ammoniac factoriesfor the purpose of distillation. The first accurateaccount of the manner of manufacturing the salt inEgypt was transmitted thence to Europe by Lemere,French consul at Cairo , in 1770. The soot was putinto large round glass bottles, which were externallycoated with loam, in order that they might the betterbear the heat, and were then ranged in a long ridgeor terrace, in such a way that only their necks wereexposed to the air, while the flue from the furnacecirculated freely round each of them. These bottles,or globes, were generally 1J foot in diameter, andthe neck about 2 inches long : 40 lbs. of soot
formed the charge, filling each of them to within 4inches of the neck. From this weight of materialabout 6 lbs. of the salt were obtained. A fire,made of dry camel’s dung, heated the range of bottles;on the second day, when the bottles became heated,the salt commenced subliming, and much care thenbecame necessary on the part of the attendant tokeep their necks free for the passage of the uncon-densed vapours. Towards the conclusion of theoperation, the fire was urged to bring the globes toincipient redness, that the last portions of the saltmight be disengaged. At the end of the third daythe fire was extinguished, and as soon as the globes