If a solution of chloride of gold be precipitated by an excess of
ammonia, a yellow powder will be obtained, which, when heated, or only
bruised, explodes suddenly with a prodigious report. The force of this
aurum fulminans is terrible, and, in the hands of incautious persons,
has often occasioned much mischief. But, however powerful, it cannot,
as some have imagined, be employed instead of gunpowder, even were not
this impossible on account of the high value of the metal from which it
is made; for explosion does not take place when the powder is confined.
Phænomena of this kind are always of importance, and afford subject of
speculation to the philosopher, though no immediate use can be made of
them[1584]. Experiments, however, have rendered it probable that this
powder may possess some medicinal virtues, and we are assured that it
can be employed in enamel-painting.
He who attempts to trace out the invention of aurum fulminans is like
a person bewildered in a morass, in danger every moment of being lost.
I allude here to the immense wilderness of the ancient alchemists, or
makers of gold; to wade through which, my patience, though pretty much
accustomed to such labour, is not sufficiently adequate. Those who know
how to appreciate their time will not sacrifice it in endeavouring to
discover the meaning of books which the authors themselves did not, in
part, understand, or to comprehend passages in which the writer tells
us nothing, or, at any rate, nothing of importance. I have, however,
made my way through this labyrinth from Spielmann to the works which
are ascribed to Basilius Valentin[1585].
The period when this powder was invented is as uncertain as the
accounts given of its composition. It is however probable that the
discoverer was a German Benedictine monk, who lived about the year
1413[1586]; and there is reason to think that he may have made
many useful observations, of which we are yet ignorant. When new
observations have been made respecting gold, they have always been
found afterwards in the works of Valentin, in a passage which no one
before could understand. Such writings are of no more utility than
the answers of the ancient oracles, which were comprehended when a
knowledge of them was no longer necessary, and which misled those
who supposed that they comprehended them sooner. But the account of
aurum fulminans in Valentin is so uncommonly intelligible, that it
almost seems he either wrote in an explicit manner without perceiving
it, or that the words escaped from him contrary to his intention. As
the work in which it may be found is scarce, I shall transcribe the
prescription[1587]:--
“Take a pound of aqua regia made with sal-ammoniac; that is, take a
pound of good strong aquafortis, and dissolve in it four ounces of
sal-ammoniac, and you will thus obtain a strong aqua regia, which must
be repeatedly distilled and rectified until no more fæsces remain at
the bottom, and until it becomes quite clear and transparent. Take fine
thin gold-leaf, in the preparation of which antimony has been used;
put it into an alembic; pour aqua regis over it; and let as much of
the gold as possible be dissolved. After the gold is all dissolved,
add to it some _oleum tartari_, or _sal tartari_ dissolved in a little
spring-water, and it will begin to effervesce. When the effervescence
has ceased, pour some more oil into it; and do this so often till the
dissolved gold falls to the bottom, and until no more precipitate is
formed, and the aqua regia remains pure and clear. You must then pour
the aqua regia from the gold calx, and wash it well with water eight
or ten times. When the gold calx is settled, pour off the water, and
dry the calx in the open air when the sun shines, but not over the
fire; for as soon as this powder becomes a little heated or warm, it
explodes, and does much mischief, as it is so powerful and violent
that no man can withstand it. When the powder has been thus prepared,
take strong distilled vinegar and pour over it; keep it continually
over the fire for twenty-four hours, without stirring it, so that
nothing may fall to the bottom, and it will be again deprived of its
power of exploding; but take great care that no accident happens by
carelessness. Pour off the vinegar, and, having washed the powder,
expose it to dry.”
The latter part of the receipt shows that Valentin had made experiments
in order to discover how aurum fulminans might be deprived of its
power of exploding, and he found that this could be done by vinegar.
It appears from his writings that he had discovered also that the same
thing could be effected by sulphur[1588].
After the time of Valentin, Crollius, who lived in the last half of
the sixteenth century, seems to have been best acquainted with this
powder, and to have principally made it known[1589]: at any rate his
works are referred to by most of the modern writers. He calls it _aurum
volatile_, and speaks of its being useful in medicine. The name _aurum
fulminans_ was, as far as I know, first used by Beguin[1590]. The
method of preparing it is described by Kircher, who considers it as a
thing uncommon, and who calls it _pulvis pyrius aureus_[1591].