138 SAL- AMMONIAC. 
Aqua-fortiS) or nitric acid (30) as it is denominated by 
chemists, is prepared from this mineral. The mode of 
obtaining it in large manufactories is by distilling a 
mixture of nitre and clay in glass or stone retorts, each 
capable of containing seventy or eighty pounds' weight 
of this mixture. But the acid thus procured being weak 
and impure, chemists, for nicer purposes, generally pre- 
pare it by distilling, in a glass apparatus, a proportion of 
three parts of nitre and one of sulphuric acid (24-). The 
uses of aqua-fortis are various and important. All kinds 
of metals,, except gold and platina, are capable of being 
dissolved in it. Hence, among other uses, it is em- 
ployed by dyers, for dissolving tin, and forming with 
madder a scarlet colour ; and, by hatters, for dissolving 
mercury (228) for some processes in the preparation of 
hats. Jewellers use it for several purposes. 
AMMONIA FAMILY. 
20?. SAL-AMMONIAC, or MURIAT OF AMMONIA, 
is a salt compounded of ammonia and muriatic acid (22). It is 
occasionally found in a state of powder, sometimes in a massive 
form, and sometimes in very irregularly shaped crystals, the 
primitive form of which is an octohedron(Fig. 5). It is, how- 
ever, more frequently an artificial production from the soot of 
burned animal matter. 
The name of sal-ammoniac was acquired by this sub- 
stance from its having been found by the ancients in. 
great abundance amongst sand near the temple of Jupi- 
ter Ammon, in Africa. It is at present found in Per- 
sia; and, accompanying sulphur, amongst volcanic 
matter near Mount Vesuvius. 
This salt was formerly imported from Egypt in the 
form of conical loaves, or of round cakes, which were 
convex on one side and concave on the other ; but it is 
now made in Europe, by burning at the same time soot, 
bones, oil, and salt. The deposit formed by the vapour 
consists of sal-ammoniac, in conjunction with other sub- 
stances, which are separated from it by a subsequent 
process. When good, it is white, transparent, and dry 
