their folvents by other metallic matters, are precipitated 
■with all their properties. 
The muriatic acid does not immediately diffolve (jlver, 
but it perfe&ly diffolves its oxyd. Muriat of filver is 
obtained by decompofing the nitrat with muriatic acid, or 
muriat of foda : the very abundant precipitate which is 
inftantly formed, is muriat of filver. If the oxygenated 
muriatic acid be poured on leaves of filver, the filver 
will become oxydated by l'eparating oxygen from the 
oxygenated muriatic acid: the oxyd thus formed then 
diifolves in muriatic acid. 
The muriat of filver poffeffes many properties which 
deferve to be known; it is fo fufible, that it melts when 
expofed in an apothecary’s phial to a mild heat; even in 
that of hot allies. By this fufion it is converted into a 
grey and femi-tranfparent fubltance, refembling horn, 
and for that reafon has been called luna cornea. If it be 
poured on a done, it becomes fixed in the form of a fri¬ 
able matter, cryftallized as it were in fine filvery needles. 
When heated for a long time with contadl of air, it is 
decompofed; it pafies eafily through the crucibles: part 
is volatilized, and part is reduced into metal, affording 
globules of filver, interfperfed among the portions of the 
muriat of' filver which is not yet decompofed. This 
fait, expofed to light, lofes its white colour, ,andbecomes 
brown in a fhort time. It diifolves in water in but a ve¬ 
ry fmall quantity ; a pound of dillilled boiling water 
taking up only three or four grains, according to the ex¬ 
periment of Monnet. Alkalis are capable of decompo¬ 
sing muriat of filver, difl'olved in water, or in the dry 
way by heat; this method affords the pureft and fined 
filver known. A mixture of three partsof foda, with one 
part of muriat of filver,, is melted in a crucible : when it 
is in drong fufion it is taken from the fire, fuffered to 
cool, and lyoken ; the filver is found beneath the muriat 
of foda, formed in the operation, and the fuperabun- 
dant portion of alkali employed. Baume, the inventor 
of this procefs, affirms, that the quantity of alkali he 
direits prevents the muriat of filver from palling through 
the crucible, by ailing on all its parts, which it decom- 
pofes at once. Margraaf has given another procefs 
for reducing this fait, and obtaining perfectly pure fil¬ 
ver: Five drachms fixteen grains of muriat of lilver are 
triturated in a mortar, with one ounce and a half of am- 
moniacal carbonat, a fufficient quantity of didilled wa¬ 
ter being added to form apade ; this mixture is agitated 
t 11 the dwelling and effervefcence, which are excited, 
have fubfided. Three ouncesof purified merdury are then 
added, and triturated, till a perfect amalgam of filver is 
obtained: this is walhed with a large quantity of water, 
the trituration ftill being continued, and the wafhingre¬ 
newed, till the water pafies off very clear, and the amal¬ 
gam is very bright. The amalgam being then dried 
and didilled in a retort, till the vefiel has acquired a 
white heat, the mercury pafies into the receiver, and the 
filver is found pure at the bottom of the retort. In this 
way the metal is obtained in the mod' perfedt date of pu¬ 
rity, and without any fenfible lofs. This is the filver 
which ought to be ufed in the nicer chemical experiments. 
The water employed in waflring the mixture carries off 
two fubftances; a certain quantity of ammoniacal muri¬ 
at, which it holds in folution, and a white infoluble 
powder. When the latter is fublimed, a fmall quantity 
of filver is found at the bottom of the fublimatory vefiel. 
This experiment Ihews, that muriat of filver is not com¬ 
pletely decompofed unlefs by the double affinity. In 
fait, in the procefs of Margraaf, the ammoniac does not 
unite with the muriatic acid, but becaufe the filver com¬ 
bines on its part with the mercury, which attrails and 
tends tofeparate it from the acid, which the alkali alone 
could notdo. It is eafily feen, that this long and expen- 
five operation can only be ufed in the fmall works of a 
chemical laboratory. If muriat of filver in large quanti¬ 
ties be required to be reduced, either fixed alkalis, or 
Ibme metallic fubdance, mud be ufed, which have a 
S T R Y. 
dronger affinity than filver with the muriatic acid; fuels 
among others, are antimony, lead, tin, iron. See. If 
one part of muriat of filver be melted in a crucible with 
three parts of one of thefe metals, the filver will be 
found reduced at the bottom of the crucible, and the 
metal united to the muriatic acid. Silver precipitated in 
this manner is very impure, and always contains a por¬ 
tion of the metal ufed for the reduction ; and as lead is 
mod commonly employed, according to the advice of 
Kunckel, the filver obtained requires to be cupelled ; it 
cannot confequently be brought to the fame date of pu¬ 
rity with the filver reduced direilly by alkalis, or by the 
procels of Margraaf. 
The nitro-muriatic acid aits drongly on filver, and 
precipitates it in proportion as it is dilfolved : this efteit 
may eafily be underdood ; the nitric acid fird diifolves 
the metal, and the muriatic acid feizes it, forming mu¬ 
riat of filver, which falls down on account of its fmall 
degree of folubility. This procels may be ufed to fepa- 
rate filver contained in gold. 
This metal does not appear to be altered by neutral 
falts ; it is certain that it does not detonate with nitre, 
nor decompofe ammoniacal muriat. This unchangea- 
blenefs of filver with nitre, affords a good method of fe- 
parating it by detonation from the metals with which it 
may be united, fuch as copper, lead, &c. The alloyed 
metal mud be melted with the addition of nitre ; the fait 
detonates and burns the portion of foreign metal, and 
the filver remains at the bottom of the crucible, in a date 
of much greater purity than before. 
The oxyd of filver precipitated by cau'dic alkali, from 
its folution in nitric acid, is foluble in ammoniac. Ber- 
thollet difcovered that this combination poffeffes the pro¬ 
perty of fulminating in a degree fuperior to that of oxyd 
of gold. He remarks, that this fubdance fulminates 
with violence while diil humid, if it be preffed with a 
hard body. In this experiment the filver was found con- 
dantly reduced. In the dry date, the flighted touch, or 
friition of any kind, is fufficient to make it fulminate. 
If a fmall retort be filled with a folution of the oxyd of 
filver in ammoniac, and expofed to a boiling heat, bub¬ 
bles of azotic gas are difengaged, and fmall crydals are 
formed, which are opake, and have a metallic appear¬ 
ance. Thefe crydals detonate by the flighted touch, 
even when covered by the liquor, and, in large quanti¬ 
ties, produce dangerous^ explofioas. The detonation of 
the oxyd obtained by lime was much more powerful than, 
that by the .fixed alkalis. 
Silver is a metal highly ufeful, on account of its dua¬ 
lity, and its indedruitibity by fire and by air. Its bril¬ 
liancy renders it capable of ferving the purpofes of or¬ 
nament. It is applied on the fiijr'face of different bo¬ 
dies, and even on copper; and likewife enters into 
the texture of rich filks; but its mod confiderable ufe 
is that of affording a matter, proper, by its hardnefs 
and duitility, to form veffels of all forts. Silver 
plate is ufually alloyed with one twenty-fourth of cop¬ 
per, which gives it a greater degree of hardnefs and co¬ 
herence, and does not render it at all noxious, becaufe 
the twenty-three parts of filver cover the copper, and 
entirely,prevent its noxious effeits. It is univerlally em¬ 
ployed as a medium of exchange, in the form of money; 
in this cafe it is alloyed with one twelfth part of copper, 
and is confequently eleven penny-weights fine. 
Of GOLD. 
This metal, called Sol by the alchemids, is the mod 
perfeitand the lead changeable metal known; it is of a 
yellow brilliant colour; no other fubdance in nature isfo 
heavy, platina excepted, for it loles only between one 
nineteenth and one twentieth of its weight in water. 
Neither its hardnefs nor its eladicity are very confi¬ 
derable. Its- adonilhing duitility, which are well as¬ 
certained by the fmaiinefs- of gold wire, and the thin- 
nefs of gold leaf, is fuch, that an ounce of this metal is 
fufficient 
