Elements of the Theory and Practice of Chymistry, 5th ed.

by Pierre Joseph Macquer

He also justly looked on Acids as an effectual means of procuring the separation, or decomposition, he was in quest of. We know that, with the Volatile Alkali, they form Ammoniacal Salts, which, though they are not so light as the Volatile Alkali, sublime nevertheless with a moderate heat; and that, on the contrary, the same Acids with Fixed Alkalis, or Absorbent Earths, form Neutral Salts, which resist the violence of fire. On this principle Mr. Duhamel poured Acids, to the point of saturation, upon Volatile Alkalis containing much Fixed Alkali, or Chalk. But this experiment succeeded no better than the foregoing; for the mixture being put to distil, sublimed wholly in Sal Ammoniac. Indeed a little fixed matter was left at the bottom of the retort; but the quantity thereof was too small to merit notice.

At last, the only way Mr. Duhamel could think of, for separating, from a Concrete Volatile Alkali, the fixed parts which that Salt had rendered Volatile, was to expose it to the air, covered with a piece of gauze only; but in its dry state, without dissolving it in water. The Volatile Urinous Salt was by this means dissipated; having deserted the fixed part, which remained at the bottom of the bason, and, being exposed to the fire, retained its fixed nature. But it took more than a year to effect this separation; nor are we sure that it was complete; for it is not certain that all the fixed part was left behind, and that some of it was not dissipated with the Volatile Urinous Salt.

This volatilization, this kind of metamorphosis of a Fixed Alkali and an Absorbent Earth into a Volatile Alkali, is a very curious phenomenon, and deserves to be considered by the best Chymists.

We shall finish our observations on the decomposition of Sal Ammoniac by Lime, with some reflections on the nature of the caput mortuum that remains after this distillation.

This residuum is only Lime impregnated, but not saturated, with the Acid of Sea-salt. If the distillation be urged at last with a violent fire, the caput mortuum will be found formed into a mass, seeming to have been half-melted. This matter is a kind of Phosphorus, and emits light in the dark, when struck with any hard body. Mr. Homberg was the first who discovered it to have this property. Having calcined, and melted together in a crucible, one part of Sal Ammoniac and two parts of Lime, with a design to fix that Salt, he observed the mass remaining after the fusion to have the property just mentioned.

Lime, thus impregnated with the Acid of Sal Ammoniac, is very improperly called by the name of Fixed Sal Ammoniac. This compound attracts the moisture of the air, and even runs wholly into a liquid, if it be impregnated with much Acid. It hath almost all the properties of Fixed Alkalis. This liquid is called Oil of Lime, for the same reason that deliquated Salt of Tartar is called Oil of Tartar.

PROCESS VI.

Volatile Alkalis combined with Oily matters. A Volatile Oily Aromatic Salt.

Pulverise and mix together equal parts of Sal Ammoniac and Salt of Tartar: put the mixture into a glass or stone cucurbit: pour on it good Spirit of Wine, till it rise half an inch above the matter. Mix the whole with a wooden spatula; apply a head and a receiver, and distil in a sand-bath, gently heated, for two or three hours. A Volatile Salt will rise into the head; and then the Spirit of Wine will distil into the receiver, carrying with it a portion of the Volatile Salt.

When nothing more will come over, let your vessels cool; then unlute them, separate the Volatile Salt, and weigh it directly. Return it into a glass cucurbit, and for every ounce thereof add a dram and a half of Essential Oil, drawn from one or more sorts of aromatic plants. Stir the whole with a wooden spatula, that the Essence may incorporate thoroughly with the Volatile Salt. Cover the cucurbit with a head, fit on a receiver, and, having luted it exactly, distil in a sand-bath, as before, with a very gentle heat. All the Volatile Salt will rise, and stick to the head. Let the fire go out, and when the vessels are cooled take your Salt out of the head. It will have an odour compounded of its own proper smell, and the smell of the Essence with which it is combined. This is an Aromatic Oily Salt. Put it into a bottle stopped close with a crystal stopple.