Chap. III. Alkalies and Alkaline Salts.

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operation for several days successively ; only unluting thehead occasionally, to put in fresh materials. When the up-per jar becomes entirely filled with carbonate of ammonia, itcracks. It is then to be removed, the salt to be taken out ofit, and a fresh one substituted in its place.

When only a small quantity is wanted, a common iron pot,such as is usually fixed in sand furnaces, may be employed,an iron head being fitted to it. The receiver ought to belarge, and a glass, or rather tin, adopter inserted between itand the head of the pot.

The distilling vessel being charged with pieces of horn, amoderate fire is applied, which is slowly increased, and rai-sed at length almost to the utmost degree. At first water a-rises, which gradually acquires colour and smell, from the ad-mixture ofempyreumaticoil and ammoniacal salts; carbonateof ammonia next arises, which at first dissolves, as it comesover, in the water, and thus forms what is called the spirit.When the water is saturated, the remainder of the salt con-cretes in a solid form to the sides of the recipient. If it berequired to have the whole of the salt solid, and undissolved,the water should be removed as soon as the salt begins to a-rise, which may be known by the appearance of white fumes ;and that this may be done the more commodiously, the re-ceiver should be left unluted, till this first part of the processbe finished. The white vapours, which now arise, sometimescome over with such vehemence as to throw off or burst thereceiver : to prevent this accident, it is convenient to have asmall hole in the luting, which may be occasionally stopt witha wooden peg, or opened, as the operator shall find proper.Lastly, the oil arises, which acquires greater colour and con-sistency as the operation advances. Carbonate of ammoniastill comes over, but it is partly dissolved in the hot oily va-pour. At the same time, there is a considerable disengage-ment of gas, consisting of a mixture of carburetted hydro-gen, often containing sulphur and phosphorus, and of car-bonic acid.

All the liquid matters being poured out of the receiver, thesalt, which remains adhering to its sides, is to be washed outwith a little water, and added to the rest. It is convenientto let the whole stand for a few hours, that the oil may thebetter d's ngage itself from the liquor, so as to be separatedfirst by a funnel, and afterwards more perfectly, by filtrationthrough wet paper.

None of these products, except perhaps a small quantity ofthe carbonic acid, exist ready formed in the matter subjected

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