Discovery of Fulminating Compounds
Fulminating gold, silver, and platinum (Latin, fulmen, lightning
flash, thunderbolt) are formed by precipitating solutions of
these metals with ammonia. They are perhaps nitrides or hydrated
nitrides, or perhaps they contain hydrogen as well as
nitrogen and water of composition, but they contain no carbon
and must not be confused with the fulminates which are salts of
fulminic acid, HONC. They are dangerously sensitive, and are
not suited to practical use.
Fulminating gold is described in the writings of the pseudonymous
Basil Valentine,1 probably written by Johann Thölde (or
Thölden) of Hesse and actually published by him during the
years 1602-1604. The author called it Goldkalck, and prepared
it by dissolving gold in an aqua regia made by dissolving sal
ammoniac in nitric acid, and then precipitating by the addition
of potassium carbonate solution. The powder was washed by
decantation 8 to 12 times, drained from water, and dried in the
air where no sunlight fell on it, "and not by any means over the fire, for, as soon as this powder takes up a very little heat or
warmth, it kindles forthwith, and does remarkably great damage,
when it explodes with such vehemence and might that no man
would be able to restrain it." The author also reported that warm
distilled vinegar converted the powder into a material which was
no longer explosive. The name of aurum fulminans was given to
the explosive by Beguinus who described its preparation in his
Tyrocinium Chymicum, printed in 1608.
Fulminating gold precipitates when a solution of pure gold
chloride is treated with ammonia water. The method of preparation
described by Basil Valentine succeeds because the sal ammoniac
used for the preparation of the aqua regia supplies the
necessary ammonia. If gold is dissolved in an aqua regia prepared
from nitric acid and common salt, and if the solution is
then treated with potassium carbonate, the resulting precipitate
has no explosive properties. Fulminating gold loses its explosive
properties rapidly if it is allowed to stand in contact with sulfur.
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Fulminating silver was prepared in 1788 by Berthollet who
precipitated a solution of nitrate of silver by means of lime water,
dried the precipitated silver oxide, treated it with strong ammonia
water which converted it into a black powder, decanted the
liquid, and left the powder to dry in the open air. Fulminating
silver is more sensitive to shock and friction than fulminating
gold. It explodes when touched; it must not be enclosed in a
bottle or transferred from place to place, but must be left in the
vessel, or better upon the paper, where it was allowed to dry. |
