. 
GEM6S. 
of the firft bafe. 
This mixture being put into a Heffian 
crucible, and fubmitted to the fire 
converted into frit. 
ter for each 
renewal of the procefs be perfectly clear, and the lead 
which may ae to be revived be feparate it. 
‘Second —Two parts and‘a half of gue “ceruke, one 
part of prepared aie ‘one a ag of falt of tartar, and a 
quarter part of calcined This mixture is melted in 
a Heffian eracible, a ona nto cold water ; it is then t 
melted oo and wafhed a fecond and third ae as in the 
ace _ 
Third Ba i Two parts of minium, one part of rock- 
cryital, half part of nitre, and as much falt of tartar, being 
well mixed and melted, are poured in cold water, in the fame 
manner as the former. 
Fourth Bafe.—Three parts of calcined borax, one part of 
ct 
° 
After r being dried the mafs is mixed with an equal quantity 
as es melted and wafhed feveral times, as cireéted 
Fiji Bafe, or Mayence Bafe.—TVhis is one of the fineft 
cry ftalline compolitions our author is Rae with. Three 
partsof falt of tartar, and one aiid of prepar ed rock-cryftal, are 
mixed a nd made into frit 
Lo a? 
cible, \ warm water is pour a to vdiftve it. This ieee bein ig de- 
atta are pan 
redinto 
it, until it ceafes to effervefce. The water is again decanted. 
and the frit is wafhed in luke-warm water, until it has no 
muft be well aioe ae Geer at the 
fame ae me iftilled water. oe) 
— ces) of this po aie drie 
rax ; Tet the whole be well mee ina ar, then 
cae and poured into'cold water, as dec other bafes already 
defcribed. Thefe fufions and lotions having been repeated, 
you mix with the whole powdered compofition a twelfth part 
of nitre. ‘This new mixture being melted for the laft time, 
you will find in the crucible a beautiful cryttalline mafs, pof- 
fefing, as the author exprefies himfe!f, much of the 
Orien 
It Thould have been obferved before, that Mr. Fontanieu 
begins his operation with preparing the filiceous fubitances 
he gaa for the proceiles jult de decribed ; jhe ala them 
sant which 
¢} nd AAV in g 
dried the Ainty mal he pounds it, and. fis the me powder 
thr rough a a filk fieve ; he then digefts it during fome hours with 
muriatic sie which diffolves the oe matter often 
mixed with the fand; he then pours off the acid, wafhes the 
fand feveral poe to take away the acid remains ; dries it, 
and paffes it a fecond time through the fieve. 
The fubflances employe 
metallic oxyds ; and onthe proper p 
depends the vividnefs of the co ours. 
1, From Gold.—To obtain the purple colour known b 
the name of precipitate of Caffius, Mr. Fontanieu employs 
three different a of which the following, as he ac- 
quaints us, is by far the beft. 
Diftil in a ate retort, placed in a bath of athes, fome gold 
pau in aqua regia, made with three parts of nitrous, and 
e part muriatic acid ; when the acid is paffed over, and the 
ao contained in the ‘retort appears dry, leave the veffel to 
cool, then pour it into fome new aqua regia and proceed to 
Vou. XV. 
} +: foam mall epntae that 
re 
of ae oxyds 
for colour ing f 
’ 
diftil as before. Replace the aqua regia twice upon the 
gold, and diftil the fame. After thefe four pee pour 
by little and little into the retort rie of tartar per de- 
liquium, which will occafion a brifk efferve aver ; aie 
this ceafes, diftil the mixture till it become: dry, an 
fome warm water into the retort. Shake the whole, and put 
t intoa cucurbit, wren a precipitate is pone the colour 
of which is a brown and fometimes yellow. After 
having wa this precipitate, dry it. The mineral pur- 
ple thus een 1s faid to be much fuperior to that of the 
two other ie efles propofed by M. Fontanieu, fince two 
grains of it only ar 
whilft it requires of the ot 
bafe. 
Fro rom a Silver-—The oxyd of filver bene vitrified, 
produces a yellowifh-grey colour. This oxyd enters s only- 
into the compofition of the yellow ar tificial diamond and 
r. Fontanieu introduces it into the bafe in the form 
ef ick n filver (luna cornea In order to pre pare it, he dif- 
folv es the filver in nitrous acid and afterwards pours into it 
afolution of fea a white precipitate is obtained, which, 
being wafhed and decd, oat very readily in = fre, and is 
foon volatilized, if not m oe ae vtifiable matter, 
3. From Copper.— The o of copper aa to white 
glafs the fineft green eee ; e if this m etal be not ean 
ly in a ftate of oxydation it produces a brownifh-red colou 
Mountain blue verdigris, and the. refidue of its diltillation, 
are the preparations of copper which M. Fontanieu employs 
to make the artificial emerald. 
. From /ron.—Though it is commonly believed that the 
x iron communicate a very fine tran{parent red co- 
lour to white glafs, our author could only obtain from it a 
pale cde little opaque. 
h io 
Song 
i 
are various ways of pers the oxyd of iron called crocus 
Martis, or faffron of 
the bars of furnaces, which ferve to diftil aquafortis. B 
digefting filings of fteel with diftilled vinegar, then evaporat, 
ing and replacing the vinegar ten or twelve times upon thefe 
filings, and drying them alternately, an oxyd of iron is ob- 
tained, which muft be fifted through a filk fieve, and then 
calcined. The oxyd of iron, thus obtained by the vinegar, | 
our author fays, only introduced i into his bafes a green colour 
inclining to yellow. By the nore procefs one of the 
or the dr 
time, it is then cola with fpirits of wine, and afterwards 
wafhed with diftilled w 
From the Mague. fae is neceffary to calcine the mag- 
net befor eit be introduced into the vitrifications ; shaving, 
eek torrefied the magnet during two hours, it mutt 
be wa and dried. is only employed i in the compofi- 
tion ie ‘he common 
From Cobalt.—T h e > oxyd of cobalt i is made ufe of for 
bift aan 
