GEM S&.. 
bifmuth are found fublimed with this falt. The os 
ammoniac till this falt 
balt which remains ‘in the 
Take fix ees af the fener bafe, the fame quantity of the 
calcined putty of tin, and forty-eight grains of manga- | 
nefe. 
8. From Antimony. Antimony is only fufceptible of 
eo in a certain ftate of oxydation, and then it pro- 
es uces a reddifh Dia clnanar ial glafs ; but if the antimony 
na ftate of abfolute calx, fuch as the diaphoretic an- 
eas then it isno longer vitrifiable, and may be fubiitu- 
ted for oxyd of tin, to make white ename . Fontanieu 
makes ufe | it 4: iene compofition of artificial topazes. 
g. Fro anefe.—Employed in a {mall ermeand this 
aes Hr eet ee fhe glafs whiter ; a larger quan- 
ne violet ag anda itilllarger ee 
Chere are two ke of 
re aring mangan 
i ep 0 a red heat t, Sand then quenching it with diftilled vinegar : 
it is afterwards dri 
fy and pulverize it 5 
calcine the mixture 
ip 
leys has er any tafte ; 
with it an n equal weight of it 
ture on a of porphyry with fulphuric acid, dilute 
with water ve os ftrengt 
t 
and introduce it into a cornute 5 diftil by a graduated fire ; 
and when the fal ammoniac is fublimed, ae ity a d 
to the mixture an equal quantity. Then diftil and fublime 
as before, and repeat a. operation = eee pag careful 
al ammonia i anganele 
deep, 
expofed. 
tain a gees deal of lead; but was not ane to 
old i in 
nieu obferves, that hee are three degrees of fre 
jor faBitiows gems, very different in their energy. 
‘kept up in the wind leee in ae laboratory “i chemi, 
i i means 
*perate aie, it is ecellary to turn about ie 
cible from time | to ha that the mafs may melt equally. 
; laced i 
be rep ac fumes 
towards the nozle of the bellows; for without ne precau- 
crue — 
pa we fhould run ane rifk of pa Sh ee — oppofite 
o the flame, and probably of cra hough ie 
is ae readieft way of melting, it ate en 7 employed: 
out of choice; for the crucible often breaks, or coals 
et into it, which may reduce the lead to the metallic 
ate. The wind furnace is either fquare or round. 
{mall cake of baked clay or brick, of the thicknefs of an 
inch, is placed upon the grate, and upon this cake is placed 
the enicible, {urrounded with coals. 
kel, of which ce ene part is fo difpofed, that we ma 
place crucibles at three ray heights; andthe name o 
e fteps on which the crucibles 
rhs 
uced. In order to conduct the fire well, only three billets 
of wood fhould be put into the furnace at a time for the 
firft twenty hours; four billets at a time for the next 
twenty hours ; and fix billets for the lait twenty hours ; 
in all fixty hours. The furnace is then left to cool, care 
being taken to flop the air me with fome lute; and in 
about forty-eight hours ena n the kiln is quite cold, 
the crucible is to be withdraw 
Compofitions.—To make ni wee diamond, take the above 
a or. oa of Mayence. This bafe is very pure, and has 
hie i is fir i - beautiful white pafte, fo gen 
y appellation of * Strafs,” which was 
For the yellow diamond.—To an ounce of the fourth bafe 
add, for colour, 24 grains of horn filver, or ten grains © 
glafs of antimon 
For the / spphire —To 24 ounces of the Mayence bafe 
add, for colour, two drachms, 46 grains of the calx o 
alt. 
ae the — ruby.—t1. sak 16 ounces of the Mayence 
ba our, a mixture oi 2 diachms 48 grains of 
the precipitate of Caffius, the fame ale led of crocus mar- 
tis prepared in ata the e of goiden fulphur of 
timony and of fufible manganele with the addition of 
two ounces of rock cryftal: or, 2. To ounces of the 
bafe made with flint, add half an ounce of fufible manga. 
nefe, and two ounces of rock cryftal. 
For the Balas ruby.—1.To 16 ounces of the Mayence bafe, 
add beats colouring powder, but diminifhed a fourth 
part ounces of the bafe made with flints, 
add ‘ie Gas colouring powder, but with a fourth lefs of 
the manganefe. 
or the oriental topaze.—-To 24 ounces of the firft or 
third bafe, add for colour five drachms of glafs of anti- 
mony. 
For the Brazil tocpaxe—To 24 ounces of the fecond or 
third bafe, add for colour 1 ou 2 ins of the 
glafs of antimony, oa 8 gra ins or the precipitate of 
OQ 
S) 
e 
Saxon topaxe.— 
24 ounces of the firft o 
the 
da bate, add, for colour, fix drachms of the glafs of an- 
timon 
For the 4 wacinth.——T'o 24 ounces of the bafe mzde with 
rock cryftal, add, for colour, 2 drachms 48 grains of glafs of 
antimony. 
y For 
