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requiring a mercurial apparatus, by throwinginto any glafs receiver (previoufly filled overwater with carbonic acid gas), a ilream of am-moniacal gas proceeding immediately from amixture of quick lime and muriated ammoniain the manner defcribed under the articleammonia. A beautiful ftream of denfe whitevapour, which is the precipitated carbonat ofammonia, is feen to iffue from the point wherethe tube conveying the ammonia touches thecarbonic acid gas, and to fall down to the boh-tom of the receiver. At the fame time anabforption takes place, and the water rifes.

A very great variety is found in the relativeproportions of carbonic acid, ammonia, andwater, in this fait, even when the external ap-pearance is nearly the fame. Befides, a veryconfiderable change takes place by expofure toair. If a quantity of the hardeft and moltpungent frefh carbonat of ammonia of thefhops (which is femitranfparent and of a ftriatedor fibrous texture) be powdered and expofed tothe air on a (hallow plate in-doors or without, avery remarkable change begins to takes place ina few minutes. A large portion of the fait evapo-rates, filling the room with the pungent ammo-niacal odour, and the remainder becomes of anopake white, crumbly and veryfoft,and at laft per-fectly lofes the whole of its fmell and pungency.

This change is compleated in a few hours,and the lofs of weight is fo confiderable, that by(landing for a night ioo grains will be reducedto from 48 to 60, more or lefs, according to thequality of the fait ufed.

The nature of this change and the compofi-tion of thefe two kinds of carbonated ammoniaon an average calculation will appear by thefollowing experiments. 1 For diftintlion theymay be termed the pungent and the mild carbonat.of ammonia.

One hundred grains of the pungent fait, fe-lected from a quantity recently made and veryftrong, fuperfaturated with dilute muriatic acid,with due precaution, were found to lofe on anaverage about 54 grains of carbonic acid. An-other xoo grains diffolved in water was addedto- muriated lime, allowing an excefs of thelatter. A confiderable effervefcence took placewith the immediate lofs of 12.5 grains of car-bonic acid and a precipitation of carbonatedlime, which, waftied, dried, and gently ignited,weighed 89. grains. Of thefe 89 grains, ac-cording to the known proportions of this earthyfait, 49 grains were lime and 40 grains werecarbonic acid, very nearly. Now as there was

a copious difengagement of carbonic acid, alltire ammonia with which it was united mullhave paired to the muriatic acid of the de-compofed muriated lime, and none of it volati-lized. But 49 grains of lime were found tohave been feparated from the muriat, and thequantity of real muriatic acid requifite to fatu-rate 49 grains of lime is 41.12 grains, accordingto the known compofition of this fait. There-fore the quantity of ammonia contained in 100grains of the pungent carbonat is that which islufficient to convert 41.12 grains of muriaticacid into muriated ammonia, which, accordingto Kirwan, is about 25.8 grains. Hence 100grains of the recent, or pungent ammoniacalcarbonat may be reckoned to contain 54 grainsof carbonic acid, 25.8 grains of pure ammonia,and 20.2 grains of water. It may be added thatthe quantity of carbonic acid loll by the effer--vefeence on adding the carbonat of ammonia to ■the muriated lime is only 12.5, which added tothe 40 grains contained in the carbonat makesup only 52.5 inftead of 54, but the- remainingquantity of i-j of carbonic acid may well be fup-pofed to be entangled with the precipitate, andto be expelled during the walhing and ignition.

The mild carbonat of ammonia was then inthe fame manner examined. It was perfeftlywithout feent, and weighed only 49 per cent,of the pungent carbonat from which it hadbeen procured by expofure to air for twenty-four hours. One hundred grains loft alfo byeffervefcence with muriatic acid on an average54 grains of carbonic aoid, fo that the quantityof acid in equal weights of the two fpecies ofcarbonats appears to be very equal. On add-ing another 100 grains to muriated lime a muchmore violent effervefcence took place than inthe former cafe, with an immediate lofs of.26.5 grains. The carbonat of lime produced lwas only 58 grs. of which 26 were carbonicacid, and 32 grs. were lime; which, eftimatingas above, would require 26.9 grs. of muriaticacid, and would indicate about 16.2 grs. of pureammonia in the 100 grs. of the mild carbonat.Hence it may be concluded,, that 100 grs. ofthis fpecies of carbonat contain on an averageabout 54 grs. of carbonic acid—16.2 grs. ofammonia—and 29.8 grs. of water.

The change that takes place therefore whenthe pungent carbonat is expofed to air, may beprobably explained in the following way. . Allthe ammonia exceeding that which is containedin the mild carbonat may be fuppofed to beabove the true point of faturation, fo that the.

4 Own Experiments.

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