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

by Pierre Joseph Macquer

From this history of the preparation of Sal Ammoniac it appears that Soot, and particularly the Soot of animal matters, either contains abundance of this Salt perfectly formed, and waiting only for sublimation to separate it therefrom, or, at least, that it contains the proper materials for forming it; and that during the operation, which is a kind of distillation of Soot, these materials combine together and sublime.

We shewed, in our analysis of Soot, that this substance yields by distillation a great deal of Volatile Alkali; and this is an ingredient which makes at least one-half of Sal Ammoniac. As to the other principle of this Salt, I mean the Marine Acid, this also must needs exist in Soot: but it is not so easy to conceive how it should come there.

It is very true that vegetable and animal substances, the only ones that produce Soot in burning, contain some portion of Sea-salt: but then this Salt is very fixed, and seems unfit to rise with the Acid, the Oil, and the subtile Earth, of which the Volatile Alkali is formed. Therefore we must suppose either that its elevation is procured by the force of the fire, aided by the volatility of the matters that exhale in burning; or that, being decomposed by the violence of the combustion, its Acid alone rises with the other principles above-mentioned. The latter seems probable enough: for though in the common operations of Chymistry the bare force of fire doth not seem sufficient to decompose Sea salt; yet the example of Sea-plants, which, before burning, contain this Salt in abundance, and whole ashes contain scarce any at all, but are replete with its fixed part, that is, with its Alkaline basis, seems to prove that, when this Salt is intimately mixed with inflammable matters, it may be destroyed by burning; so that its Acid shall desert its basis, and fly off with the Soot.

Before the exact method of procuring Sal Ammoniac was known, it was generally imagined that the manufacturers, mixed Sea-salt, and even Urine, with the Soot; because these two substances contain the principles of which this Salt consists. But, besides that the contrary now certainly appears from the above-mentioned Memoirs, it hath been shewn by Mr. Duhamel, who hath published several Memoirs and experiments concerning the composition and decomposition of Sal Ammoniac, from which we have partly taken what we have already said on this subject, and which will furnish us with some more curious observations; it hath been shewn, I say, in the first of Mr. Duhamel's Memoirs, printed with those of the Academy for 1735, that the addition of Sea-salt to the Soot, from which Sal Ammoniac is to be extracted, contributes nothing to its production, and cannot increase its quantity. That alone, therefore, which was originally contained in the matters that produced the Soot, enters as a principle into the composition of Sal Ammoniac. We observed also, in treating of the analysis of Soot, that Mr. Boerhaave obtained from it a considerable quantity of an Ammonical Salt without any additament.

Sal Ammoniac is sometimes found perfectly formed in the neighbourhood of Volcanoes. This Salt is probably produced from the fuliginosities of vegetable or animal matters consumed by the fire of the Volcano.

Sal Ammoniac is often impure, because it carries up with it, in sublimation, some of the black charred matter which ought to be left at the bottom of the vessel: but it is easily purified. For this purpose you need only dissolve it in water, filter the solution, then evaporate and crystallize; by which means you will have a very white and very pure Sal Ammoniac. You may, if you please, sublime it again in a cucurbit and blind head, with a fire not too brisk. Some of it will rise in the form of a light white powder, called Flowers of Sal Ammoniac. These Flowers are no other than true Sal Ammoniac, which hath suffered no decomposition; because the bare action of fire is not capable of separating the Acid and the Volatile Alkali, of which this Neutral Salt consists. When you intend to decompose it, you must use the means to be mentioned hereafter.

Though Sal Ammoniac be only semi-volatile, and requires a considerable heat to sublime it, yet it hath the property of carrying up with it matters that are very fixed and ponderous; such as metallic substances, and some kinds of earths. For medicinal uses we sublime therewith Iron, Lapis Hæmatites, the Copper in blue Vitriol, &c. and then it takes different names, as Martial Flowers of Sal Ammoniac, Ens veneris, and other such denominations, which it borrows from the matters sublimed with it.

PROCESS III.

Sal Ammoniac decompounded by Acids.

Into a large tubulated glass retort put a small quantity of Sal Ammoniac in powder: set your retort in a furnace, and lute on a large ballon, as in the distillation of the smoaking Acids of Nitre and Sea-salt. Through the hole in your retort pour a quantity of Oil of Vitriol, or Spirit of Nitre, equal in weight to your Sal Ammoniac. An effervescence will instantly follow. The mixture will swell, and discharge white vapours, which will come over into the receiver. Stop the hole in the retort immediately, and let the first vapours pass over, together with some drops of liquor, which will distil without fire. Then put a few coals into the furnace, and continue the distillation with a very gentle heat; which however must be increased, little by little, till nothing more will come off. When the operation is finished, you will find in the receiver a Spirit of Salt, if you made use of Oil of Vitriol; or an Aqua regis, if Spirit of Nitre was employed: and in the retort will be left a saline mass, which will be either a Glauber's Secret Sal Ammoniac, or a Nitrous Sal Ammoniac, according to the nature of the Acid used to decompound the Sal Ammoniac.