C H E M I 
opake white colour, by its interposition between the 
traniparent parts. This kind of vitreous frit is called 
enamel. Putty of tin, on account of its infufibility, de¬ 
prives all glalfes of their transparency, and converts them 
into coloured enamels. Thefulphats of potafh and foda 
are decompoled by jtin. Equal parts of fulphat of potafh 
and tin being heated in a crucible, afford a greenifh melt¬ 
ed mafs, which no longer exhibits any metal, and is a 
true fulphure of tin. The tin deprives the Sulphuric 
acid of its oxygen ; the fulphur difengaged by this de- 
compofition combines with the potafh, and this fulphure 
diffolves a portion of the oxyd of tin. 
This metal caufes nitre todetonate with rapidity. For 
this purpofe it is melted, and made obfcurely red-hot in 
a crucible. Dry nitre in powder being then thrown in, 
produces a white and brilliant flame. Add a frefh quan¬ 
tity of uitre, till there is no longer any detonation. 
Then take the crucible off the fire, and feparate its con¬ 
tents; wafh in water, and filtre the liquor, which will 
be found to contain the potafh of the nitrat, and there 
remains oxyd of tin, which contains a little alkali ren¬ 
dered cauftic by the tin. It fhould therefore be well 
wafhed; and, by the addition of an acid, all the oxyd 
of tin may be precipitated. 
The muriat of ammoniac is alfo decompofed by tin : 
Take of granulated tin, and of ammoniacal muriat in 
powder, nearly equal quantities ; putthe mixtureintoa re¬ 
tort, and adapt a receiver, with the mercurial .pneumatic 
apparatus; asi'oonas theretortisheated,caufticammoniac 
is difengaged in the ftate of gas. The refidue of tbede- 
compolition is a folid muriat of tin, decompofable by 
water, and flmilarto that which is formed by this metal 
with coiTofive muriat of mercury. 
The ufes of tin are very numerous. It is applied to ma¬ 
ny purpoies in the arts, in forming many veffels, organ pipes, 
decorations, &c. Bell metal, and bronze for flatues, are 
compounds of this metal, with copper. The pewterers mix 
tin with bifmuth, antimony, lead, and copper, to make 
utenfils of all forts, which are'very fubjeft to change by 
expofure to air. Tin is melted with oxyd of lead and 
fand, to make enamel, as well as to glaze pottery, &c. 
The cryftallized muriat of tin is ufeful in the art of calico 
printing. Its iolution in aqua regia, or nitro-muriatic 
acid, heightens the tindure of cochineal, of gum lac, 
&c. lb as to convert it into the molt lively fire colour. 
The dyers make ufe ofthisfolution, which they call com- 
poiition, 'to make fcarlet. When it is mixed in the dyers 
bath, it forms a precipitate, which carries down the co¬ 
louring matter, and depoiits it on the fluff which is to be 
dyed. This oblervation is due to Macquer, whole la¬ 
bours have greatly improved this art. 
Many, phyficians, who have directed their attention t,o 
metallic lubftances, confidered as medicines, have ac¬ 
knowledged the innocence of t.in, and have even advifed 
its filings to be taken in fubltance in diforders of the li¬ 
ver, of the matrix, and for worms. Schulz, in his dif- 
fertation on the ufe of Metallic Veffels, in the prepara¬ 
tion of food and medicines, recommends pure tin as very 
wholefome. La Poterie prefcribes oxyd of tin as one of 
the component parts of a preparation called antihedic, 
which conlifts of oxyds of antimony and tin, formed by 
detonation with nitre ; the alkali, which the water dif¬ 
folves, always retains a portion of the metallic oxyd. 
Tin is recommended as a vermifuge. Some people are 
in the habit of infufing fweet wine for four hours in the 
cold, in a tin veffel, and giving a glafs of this liquor to 
their children who are troubled with worms. It ads as a 
violent purgative. 
Of LEAD. , 
The ores of lead are found in lumps and in furrows, 
in mountains, foils, and rocks, and in ftones of all ages 
and kinds: its moft ordinary gangues are, quartz, hea¬ 
vy fpar, calcareous fpars, fluor, clay, l'chiflus, &c. fbme- 
S T R Y. ; 295 
times mixed with fulphure of iron, zink, calcedony, 
and even with jafper. Lead has little hardnefs, and (till 
lefs elafticity; it is the fweeteft of metals, having a pecu¬ 
liar fmell perceptible on rubbing, which arifes from a 
beginning of oxydation ; the fame may be faid of its tafle. 
The foftnefs of lead occafions it to be fo little fonorous. 
To this metal the alchemifts gave the name of Saturn. 
Its cohefion is manifefl by the adhefion of its parts re¬ 
cently divided, as loon as brought into contact : it isin- 
deed the only metal which can be brought perfectly in 
contad: if a leaden bullet be cut in two, and the parts 
immediately put clofe together, they will adhere very 
ftrongly. It eafily extends under the hammer, and may 
be reduced into plates or leaves thinner than paper. 
To obtain it in grains, it mull be melted, and then tri¬ 
turated in an iron mortar. 
Lead, expofed to heat, melts long before it becomes 
ignited. The heat neceffary to hold it in fufion, is fo 
inconfiderable, that the hand may be plunged in it when 
melted without pain; and in this ilate it does not burn 
vegetable fubltances. It is laid to melt at 540 0 of Fah¬ 
renheit. If it be fuffered to cool very flowly after being 
melted, and the melted portion be poured off from that 
which is become folid, it is found to be cryftallized in 
quadrangular pyramids. When melted with the contact 
of air, it foon becomes covered with a grey and dull pel¬ 
licle; this pellicle is carefully taken off, and reduced by 
agitation into an oxyd of a greenifh grey, verging towards 
yellow. When feparated by thefieve from the grains of 
lead with which it is mixed, and afterwards expofed to 
a more violent red heat, it becomes of a deep yellow, and 
in this ftate is named mafiicot. This laft, flowly heat¬ 
ed by a gentle fire, aflumes a beautiful red colour, and 
is known by the name of minium. If maflicot be ftrongly 
heated, fo as to produce a femi-vitrification, its parts ag¬ 
glutinate in little thin fcales* which preferve their red co¬ 
lour, but not fo bright: this oxyd takes the name of li¬ 
tharge of gold, and litharge of fiver when the colour is 
paler. This compofition is never made on purpofe : 
that which is found in the (hops is either procured from 
the purifying of gold and filver in the large way, or from, 
the works for converting lead intolitharge. If red oxyd, 
or litharge, be expofed to heat in a crucible, it will 
melt, but not fo eafily as lead, and is converted into 
glafs ; which glaf’s is fo fufible, that impenetrates the cru¬ 
cible, and efcapes. To avoid fill is inconvenience, add 
one part of fand to three parts of the oxyd ; put the mix¬ 
ture into a good crucible, place it on the muffle of a fur¬ 
nace, and keep it to a white heat for two or three hours, 
or till it melts; a fine amber-coloured glafs will be pro¬ 
duced. \ 
All the oxyds, and even the glaffes, of lead, are eafily 
decompofed by combuftible bodies. For this purpofe it 
is fuflicient to mix them with charcoal, foot, greale, oil, 
relin, or, in a word, any inflammable fubltance what¬ 
ever, and to heat them for a certain time, in order to ob¬ 
tain a button of lead. This reduction may be made ei¬ 
ther in a crucible, or witlxcharcoal under the blow-pipe. 
Hydrogen gas tinges the lurface of lead with rainbow 
colours; it even revives the oxyds of lead. If the red 
oxyd of lead be put in contact with this gas, it becomes 
black and dull. 
Lead mixed with fulphur produces a true fulphure : 
Melt three parts of lead and one of fulphur in an iron la¬ 
dle ; ftir the mixture; the fulphur quickly combines 
with the lead, and converts it into a black powder of a 
fcaly texture. If this be put into a crucible, it will not 
melt at lefs than a red heat; and the refult then is a 
black, brittle, fragile, mafs, difpofed in facets; this is 
fulphure of lead, or artificial galena. 
Phofphorus enters into fufion with lead : Melt in a cru¬ 
cible equal parts of lead filings and phofphoric glafs, 
with one-eighth part of charcoal: the product appears 
very little different from lead; it is malleable, eafily cut 
with 
