C H E M I 
little oxydated ; red vapours fly off, and the metal be¬ 
comes of a lighter colour. 
Of TUNGSTATS. 
Tungstat of Lime. —This fubftance is found in the 
iron mines of Bitzberg, in the tin mines of Schlecken- 
walde in Bohemia; and moll of the white tin cryltals of 
Sauberg near Ehrenfrienderfdorf, are tungftat of lime. 
This tungftat is not ienfibly altered by heat; it de¬ 
crepitates, but it does not melt. It has a fparry ap- 
.pea ranee. 
To diftinguilh this from other native faline fubftances, 
pour over it fome weak nitric acid, or muriatic acid, and 
dig-ell with a gentle heat: with the muriatic acid more 
efpeciall'y, the powder affumes, at the end of the opera¬ 
tion, a fine clear yellow colour. 
There are various methods of decompofmg this cal¬ 
careous tungftat: i. One part of native calcareous tung¬ 
ftat in powder is fufed in an iron crucible, with four 
parts of carbonat of potalh; this mafs is lixiviated with 
twelve parts of boiling water, and nitric acid is poured 
on, which unites with the potalh, for which it has a 
greater affinity, and difengages the tungftic acid. More 
nitric acid may be poured in, which may be evaporated 
to drynefs, and thus continue till no more red vapours 
arife: then we are lure it is fufficiently oxygenated. 2. 
About twelve parts of nitric acid, in the ftate of ordinary 
aqua-fortis, are required for the complete decompofition 
ot one part of calcareous tungftat. Scheele performed 
this operation at feveral repeated times. After the ac¬ 
tion of three parts of weak nitric acid upon one part of 
this neutral lalt, he pours two parts of cauftic ammoniac 
upon the powder, which the nitric acid had changed to a 
yellow colour; it becomes white by the aftion of the alka¬ 
li; and he repeats this fucceffive adfion of the acid and the 
alkali, until the whole-of the calcareous tungftat is en¬ 
tirely diffolved. By precipitation from the nitric, acid 
employed in this folution, by the addition of the pruffiat 
of potalh, and afterwards by potafli itlelf, he obtained a 
little prufiiat of iron, or Pruifian blue, and fifty-three 
grains of chalk : the ammoniac, by the addition of nitric 
acid, afforded an acid precipitate. In this experiment, 
the nitric acid decompofes the calcareous tungftat, by 
feizing the lime; and the tungftic acid, which is fet at 
liberty by this decompofition, is leized by the ammoniac. 
The ammoniacal fait formed by this laft folution is de- 
compofed by the nitric acid, which has a ltronger affinity 
with the ammoniac than this laft has with the tungftic 
acid. As this laft acid is much lefs foluble than the am¬ 
moniacal tungftat, it falls down, in-proportion as it is fet. 
at liberty, in the form of a white powder. This powder 
is lixiviated with cold diftiiled water, in order to have 
the tungftic acid in a ftate of purity. 
Sulphuric acid has very little action upon tungftat of 
lime; it decompofes but a very final! part of it. The 
muriatic acid adds upon calcareous tungftat in the fame 
manner as the nitric acid does, and decompofes it with 
the fame energy. 
Tungstat of Iron, or Wolfram. —Wolfram is 
one of thofe minerals whofe equivocal effeft occaiioned it 
to be often ranked with different fpecies, to which it 
l’eemed to have fome refembiance; l'o that it was long 
before it obtained a permanent place. Henckel fays, that 
at Altenbury in Milnia, it was erroneoufly called anti¬ 
mony ; hence, perhaps, the name of wolf's foam , or wol¬ 
fram. Many naturalifts regarded it as afchorl abounding 
in iron ; others conlidered it as an arfenical ore of iron ; 
Wallerius thought it a fpecies of manganefe. But d’El- 
huyar, Vauquelin, and Hecht, put an end to thele con¬ 
jectures, by proving that wolfram contains a metal of a 
peculiar nature, which is tungften. 
.Wolfram is drawn from the mines of Saxony, Bohe¬ 
mia, and Sweden. It often accompanies cryltals of tin, 
which are alfo of a blackifh colour, but differs materially 
from it. It bas been found in France alio, in the de- 
Vol, IV. No. 195. 
S T R Y. 265 
partment of Haute-Vienne, in the canton and commune 
of St. Leonard, and at Puy-les-Mines. It is of a brown- 
ifli black colour; eafily yields to the file, and then exhi¬ 
bits a brown colour, (lightly tinged with violet, where 
the file has paffed : the dull, rubbed upon paper, exhi¬ 
bits. fpots of the fame colour. It is compofed of brilliant 
laminae, which are eafily feparated by percuffion. Its 
fpecific gravity is confiderable, according to M. Haiiy, 
73-333. Laftly, It is very (lightly eieCtric, and does not 
attradt the magnetic needle. 
Chemical Properties .—It is not fufible with the aCtion 
of the blow-pipe. With borax it diffolves, running into 
a greenifli globule. With phofphat of loda and ammo¬ 
niac, it runs into a tranfparent globule of a deep red co- 
cour. D’Elhuyar and Vauquelin have feveral proceffes 
for decompofing of wolfram: 1. With nitrat of potafh,, 
2 With carbonat of potalh. 3. With muriatic acid. 
To make this decompofition by means of nitrat of pot- 
affi, introduce by degrees into a porcelain crucible, made 
red -hot, three parts of nitrat of potafh, and one part of 
wolfram, in powder; it is neceflary that the crucible be 
large, to prevent the matter from running over, in con- 
fequence of the ftrong ebullition occafioned by the ni¬ 
trous acid, which comes up in red vapours. Having 
kept the mixture in fuiion for about half an hour, pour 
it on an iron-plate, where it collects into a green mafs, 
cryltallized in needles on the furface; this mafs diluted 
with water, leaves a brown infoluble powder : the drained 
liquor retains a green colour, which may be taken away 
by boiling, after which it again depofits a brown fedi- 
ment. The acids precipitate from this tranfparent liquor 
a white powder, which is tungftic acid combined with 
potafli, and which has retained a certain quantity of the 
acid ufed in the precipitation of this fubftance. The 
brown powder which the liquor precipitates in,boiling, 
as well as that which is inloluble in water, are a mixture 
ofoxyd of iron, and oxyd of manganefe. 
Wolfram may in like manner be decompofed, by ex- 
pofing to the abtion of heat one part of wolfram, and 
two parts of carbonat of potafh. The liquor obtained 
in this procefs is likewife a mixture of tungftic acid and 
potafh. But the analyfis of wolfram by the muriatic acid 
is to be preferred, becaufe the pure acid may thereby be 
obtained with expedition and facility ; whereas, in the 
preceding experiments, the triple fait mult be firft de¬ 
compofed. Let one hundred parts of wolfram be boiled 
for a quarter of an hour, with three times its weight of 
muriatic acid; as loon as the liquor begins to heat, a 
yellow dull appears, and the liquor affumes a brown co¬ 
lour. When cold, decant the liquor, and lixiviate the 
depofit; digeft this for fome hours with ammoniac, 
which diffolves a part of it. Repeat the operation 
upon the refidues, till the matter, undergoing no far¬ 
ther change, is reduced to about fix parts, and is in¬ 
foluble. By thus repeating the procefs, the wolfram is 
entirely decompofed ; the ammoniacal liquor being eva¬ 
porated to drynefs, and the fait it furnifhed calcined, a 
yellow powder is obtained which anfwers to thirty-four 
parts. Put into the acid liquor, containing iron and 
manganefe, fome fulphuric acid, and evaporate to diy- 
nefs; diffoive lulphats of iron and manganefe in the wa¬ 
ter; three parts of filex will be gained by filtration. Sa¬ 
turate the excefs of acid of the liquor with carbonat of 
potafh ; the liquor affumes a brown colour, but does not 
become turbid ; by boiling, it lofes its brown colour, and 
throws down a red powder. The tranfparent liquor, 
mixed with carbonat of potafli, itill precipitates a yel- 
lovviih matter, compofed ofoxyd of manganefe and oxyd 
of iron. By treating the precipitate as laid down in the 
foregoing experiment, the oxyd of manganefe may be 
feparated. By this operation, Vauquelin obtained from 
100 parts of wolfram, 67 parts of calcined tungftic acid, 
18 of black oxyd of iron, 6-25 of black oxyd of manga¬ 
nefe, and 1-50 of filex; making in all yi’i5, fo that 5 25 
only were loft, 
' 3 .Y fungjlic 
