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

by Pierre Joseph Macquer

OBSERVATIONS.

Sal Ammoniac, which consists of the Marine Acid united to a Volatile Alkali, is, with respect to the Vitriolic and Nitrous Acids, just the same as Sea-salt is with respect to those Acids; that is, the Vitriolic and Nitrous Acids, having a greater affinity, than the Marine Acid, with Volatile as well as Fixed Alkalis, will decompound the Sal Ammoniac, by expelling the Acid from its basis, and assuming its place, just as they do with regard to Sea-salt. Most therefore of what was said concerning the decomposition of Sea-salt, and the distillation of its Acid, by the two other Acids, must be applied here.

We shall only observe, that, when the Acid of Sal Ammoniac is to be distilled from it by the interposition of the Vitriolic or Nitrous Acid, great care must be taken to put but a very small quantity of this Salt into the retort; especially if the Acids to be added are concentrated: for, as soon as they mix with the Sal Ammoniac, a great effervescence arises, and the mixture swells to such a degree, that, unless the quantity in the retort be very small, it may run over altogether into the receiver. It is also proper to take notice, that this operation admits of but a small degree of heat, for two reasons; first, because the Acid of the Sal Ammoniac, being very easily dislodged by an Acid stronger than itself, rises also very easily; secondly, because the Sal Ammoniac which is to be decompounded, as well as the Ammoniacal Salts which result from its decomposition, are semi-volatile, and will sublime in substance if they be exposed to the smallest excess of heat. Moreover, the Nitrous Sal Ammoniac would be in danger of taking fire and exploding, for a reason frequently mentioned above.

The Nitrous Sal Ammoniac may be decompounded, as well as Sal Ammoniac, by the Vitriolic Acid. But, as the Nitrous Acid contained in the Salt is the strongest of all Acids next to the Vitriolic, no other Acid but this is able to expel it from its basis; in which respect this Salt resembles Nitre.

Instead of employing the Acids of Vitriol and Nitre to decompound Sal Ammoniac, we might make use of Neutral Salts consisting of these Acids combined with metallic or earthy bases: but then, as this decomposition cannot be effected without a greater degree of heat, there is reason to apprehend that some of the Sal Ammoniac would be thereby sublimed, before it could be decompounded.

PROCESS IV.

Sal Ammoniac decompounded by Fixed Alkalis. Volatile Salt. The Febrifuge of Sylvius.

Into a glass alembic or retort put Sal Ammoniac and Salt of Tartar, pulverized and mixed together in equal quantities. Set your vessel in a proper furnace, and immediately lute on a large receiver. A little volatile Spirit will ascend; and a volatile Alkali, in a concrete form, very white and beautiful, will sublime into the head, and come over into the receiver, in quantity near two thirds or three fourths of the Sal Ammoniac used. Continue the distillation, increasing the fire by degrees, till nothing more will sublime. Then unlute the vessels. Put up your Volatile Salt immediately into a wide-mouthed bottle, and stop it close with a crystal stopple. At the bottom of the retort, or cucurbit, you will find a saline mass, which, being dissolved and crystallized, will form a Salt nearly cubical, having the taste and other properties of Sea-salt. This is the Sal Febrifugum Sylvii.

OBSERVATIONS.

This decomposition of Sal Ammoniac is the reverse of that in the preceding process. In the former operation it was shewn that the Acid of Sal Ammoniac may be separated from its basis, by applying to that basis a stronger Acid: in the present operation, on the contrary, the basis of this Salt is separated from its Acid, by presenting to that Acid a Fixed Alkali, wherewith it hath a greater affinity than with the Volatile Alkali which serves it for a basis.