2 9 o C H E M I 
to feparate it entirely from the platina by roafting. Zink 
precipitates platina from its foiution in aqua regia. Four 
hundred and lixteen parts of zink are required, accord¬ 
ing to Bergman, to precipitate feventy-l’even parts of 
platina. Silver forms a brittle mat's with zink, which, 
like that with gold, may be decompofed in the fire. The 
iilver is precipitated by zink from its foiution in nitric 
acid, partly in an oxydated, and partly in a metallic, ftate. 
A portion of the zink, however, falls along with the 
filver. To combine lead with zink it is neceflary to co¬ 
ver the mixture with charcoal, and to exclude from it 
carefully the external air. Zink precipitates lead from 
acids. Very beautiful metallic ^vegetations , as they have 
been termed, may be produced by fufpending a bit of 
zink in a foiution of -acetat of lead. It does not appear 
to be determined whether zink can be made to combine 
with bifmuth. It precipitates thebilmuth in its metallic 
ftate from acids. Zink unites with nickel. It occafions 
no perceptible precipitation of nickel from acids. Zink 
unites difficultly with arfenic, not taking up more than 
2 -5th of that metal. The mixture is of a grey colour, 
and brittle. If oxyd of arfenic be melted with zink, the 
zink is oxydated, and a portion of the arlenic rifes in its 
metallic ftate. Chemifts differ in opinion with regard 
to the poffibility of combining zink with iron, but the 
difficulty feems to arife chiefly from the volatility and 
eafy oxydation of the zink. Iron is precipitated by this 
metal from its folutions in acids; the precipitate ap¬ 
proaches more or lefs to the metallic ftate, according to 
the previous degree of its own oxydation, and the oxy¬ 
dation of the zink. Zink melts difficultly with cobalt. 
It does not precipitate this metal from acids, nor change 
the red colour of its folutions. A very beautiful green 
paint is produced in precipitating by potafli from a mix¬ 
ture of cobalt diffolved in aqua regia, and nitrat of zink, 
the oxyds of thefe metals. The prefence of iron deftroys 
the beauty of the colour. Zink unites eafily with tin, 
and renders it harder and more brittle. It precipitates 
tin from its folutidn in acids. With the muriatic and 
acetic folutions it produces metallic vegetations. 
Zink, in filings, or in powder, caufes nitre to detonate 
with Angular rapidity. The mixture being very 
dry, and thrown by fpoonfuls into a red-hot crucible, 
produces a white and red flame. The activity of the 
inflammation is fuch, that portions of burning matter 
are thrown to a difta-nce out of the crucible, in fuch a 
manner as to require fome precaution on the part of the 
operator. The zink burns by the afliftance of the oxy¬ 
gen afforded by the nitre, and is afterwards found in the 
ftate of an oxyd, more or lefs perfect, according to the 
quantity of nitre ufed. One part of the’refidue is folu- 
ble in water. It confifts of the potafli combined with a 
portion of the oxyd of zink, which may be precipitated 
from its foiution by the addition of acids. Refpour at¬ 
tributed to this foiution the property of difl'olving all the 
metals, if Hellot may be credited, who gives it as the al- 
kaheft of that alchemift. 
Zink, according to the experiments of Pott, appears 
capable of decompoftng muriat of foda. It efpecially 
decompofes ammoniacal muriat with great facility. 
Monnet affirms, that this metal triturated with ammo¬ 
niacal muriat, difengages the ammoniac. Bucquet has 
obferved, that when this fait and zink are diltilled toge¬ 
ther, much ammoniac gas and hydrogen gas are pro¬ 
duced by the combination of the muriatic acid with this 
metal: and he was fynfible that the facility with which 
the zink difengages the ammoniac, is a confequence oft 
its ftrong action on the muriatic acid. The oxyd of zink 
likewile difengages it, according to Hellot. The refidue 
of this decompofition is muriat of zipk, which may be 
fublimed. 
Zink is of great ufe in the arts. It is employed in, 
many alloys, efpecially in topibac, ruchbec, or prince’s 
meta}. Fine filings of zink are ufed to produce the 
white and brilliant ftars in fire-works. The German 
S T R Y. 
pliyficians employ the fublimed oxyd of zink with fuc- 
cefs as an antifpafmodic in convuliions and epileptic fits. 
Pompholix, tatty, or the different oxyds of zink, are ufed 
as excellent deficcative medicines, to be externally ap¬ 
plied in diforders of the eyes. 
Of TIN. 
Mod mir.eralogifts doubt the exiftence of native tin ; 
fome authors however affirm that it has been found in 
Saxony, in Bohemia, and in the peninfula of Malacca. 
It is ftrongly affirmed, that it exifts in the mines of Corn¬ 
wall 5 and Sage has defcribed a fpecimen of this tin gi¬ 
ven him by Mr. Woulfe, a chemift of London. This 
piece is grey and brilliant in its frafture; and, when 
beaten on the anvil, it forms brilliant and flexible lami¬ 
nae; There have as yet been no mines of tin difcovered 
in France. Baume, however, fufpe&s, that it might be 
found in the neighbourhood of Alengon, and in fome 
cantons of Britany, becaufe rock cryllals are found, 
which appear to be coloured by that metal. The coun¬ 
tries where they are the mod abundant, and are worked, 
are the counties of Cornwall and Devonfhire, in England; 
alfo in Germany, Bohemia, Saxony, the ifland of Banca, 
and the peninfula of'Malacca, in the Eall Indies. 
To make the allay of an ore of tin, it muft be grofsly 
pounded, after dividing it into different parcels, wafhed 
and roafted in a covered capfule of earth, care being 
taken to uncover it from time to time, in order to diflir 
pate the tin as little as poffible ; for, if it be roafted in an 
open-fire, much of that metal is loft, as Cramer remarks. 
It muft likewile be roafted with expedition, left the tin 
fliould be too much oxydated. Baume, to obviate thefe 
two inconveniences, propoles to mix a quantity of rofin 
or pitch, which reduces a portion of the oxyd formed in 
this operation. After the ore is roafted, it is to be quick¬ 
ly fufed in the crucible, with three parts of black flux, 
and a fmall quantity of decrepitated marine fait. B.y 
comparing the weight of the wafhed and roafted ore with 
that of the metallic button obtained, the quantity of fo¬ 
reign matter, and the proportion of tin it will afford in 
the hundred, is known. Cramer propofes to make this 
affay in a more expeditious manner, and perhaps with 
lefs lofs, by making ufe of two large pieces of charcoal: 
one of them muft have a cavity,, to ferve inltead of a 
crucible, into which the ore is put, with a lufficient 
quantity of pitch ; the other is perforated with a fmall 
opening, to give iffue to the vapours. This is applied 
on the former to cover it, and they are tied together with 
iron wire, after having luted the joinings. Thefe are fet 
on fire before the noozle of a pair of forge bellows, and 
kept there by means of charcoal placed round them. As 
foon as a fufficient heat has been given to fufe the tin, 
the charcoal is to be extinguifhed with water, and the 
tin is found within them in the form of a button or 
globule. 
Bergman propofes to affay the ores of tin by foiution 
in fulphuric acid, to which the muriatic acid is afterwards 
added ; and to precipitate it by fixed alkali. If the tin 
be pure, one hundred and thirty-one grains of the pre¬ 
cipitate wiil be equal to one hundred and fix of tin. If 
it be mixed with copper and iron, thefe foreign metals 
are to be removed by means of the nitric and muriatic 
acids. 
The working of ores of tin in the large way is fimilar 
to the procefs before defcribed; it is often neceflary to 
make fires of wood in the mine, to calcine and l'often 
the gangue, which is very hard, by which very dangerous 
vapours are difengaged. This procefs is ufed in the mines 
of Geyer. In other places the ores are found in land, at a 
very fmall depth, as at Ebenftock. The pounded ore is 
is waxed in boxes, with little partitions of cloth, to re¬ 
tain the metallic particles; it is then rohfted in reverbe¬ 
ratory furnaces, to which a horizontal chimney is adapt¬ 
ed, to collect the fulphur and arlenic; after which it is 
fufed and poured into moulds, to give it the form of 
blocks. 
