271 
s C H E M I 
talllzed in fjnall needles, very deliquefcent, which be¬ 
comes green when heated, and is foon after decompofed. 
If the folution be not evaporated, it forms what is 
called Jympathetic ink. This ink may be prepared alfo 
with nitro-muriatic acid; or thus: Put into a matrafs 
one part of cobalt, or rather zaffre, with four parts of ni¬ 
tric acid; let the mixture digeft in a hot fand-bath for 
three or four hours, or till the diffolution is almoft com¬ 
plete : then add as much rnuriat of foda as was ufed of 
of cobalt, and of water four times the quantity of the ni¬ 
tric acid; filter the liquor through paper, and you have 
a fympathetic ink, with which, if you write upon white 
paper, no mark will be vifib'le ; but, by (lightly warming 
it, the charafters will appear of a beautiful fea-green co¬ 
lour; as the paper gets cold, the colour difappears, but 
may be revived again by heat. 
The aflion of the other acids on cobalt is not known. 
The boracic acid is the only one which feems capable of 
combining with it; and this muft be by the aftion of 
double affinity: Mix a folution of borat of foda and a 
folution of cobalt in one of the foregoing acids, and a 
double decompofition takes place. The foda unites with 
the acid which held the metallic oxyd in folution, and the 
boracic acid, combined with that acid, forms a fait which 
is precipitated. The borat of cobalt is feparated by fil¬ 
tration. 
Nitrat of potalh oxydates cobalt: Mix one part of co¬ 
balt with three of nitrat of pota(h: make the mixture 
detonate by throwing it in fpoonfuls into a red-hot cru¬ 
cible ; a fmall detonation is heard each time. When all 
the mixture is in the crucible, urge it with a ftrong heat; 
then take the crucible off the fire, pour out the contents, 
wa(h them in plenty of boiling water, and drain the li¬ 
quor. The powder remaining after filtration is oxyd of 
cobalt, which has different degrees of red, but is often 
greenifh. Cobalt detonates under the hammer, when 
mingled with the fuper-oxygenated rnuriat of potafli: if 
this mixture be brought in contact with fulphuric acid, 
it burns with great rapidity, and the fmoke rifes in the 
air affuming the form of a crown, in the fame manner as 
phofphorated hydrogen gas burning fpontaneoufly in a 
tranquil atmofphere. 
Cobalt unites by fufion with gold; but the poperties 
of the mixture are little known. It precipitates gold 
from its folution in aqua regia. £obalt alfo melts with 
platina, and precipitates it from its folution in aqua re¬ 
gia. Silver does not unite by fufion with cobalt. The 
folution of filver in nitric acid is precipitated by cobalt, 
thirty-feven parts of cobalt only being required to pre¬ 
cipitate one hundred of filver. Mercury does not appear 
to amalgamate with cobalt. It is precipitated from ni¬ 
tric acid by cobalt in its metallic (late. Lead, accord¬ 
ing to Gmelin, unites by fufion with cobalt, and is pre¬ 
cipitated by this metal from its folution in acids. Bif- 
muth does not unite by fufion with cobalt. It alfo is 
precipitated by the cobalt from its folutions in acids. 
Nickel unites readily by fufion with cobalt, and is fepa¬ 
rated from it withgreatdifficulty. Thisfeparation iseffeft- 
ed by melting it with a fulphure of potafli, which aiffolves 
the cobalt more eafily than the nickel. The affinity of 
thefe two metals for acids has not been determined, 
though there is reafon to think that the affinity of the 
cobalt is ftrongeft. When a bit of nickel is introduced 
into a folution of nitrat of cobalt, a change in the colour 
is produced, but without any evident precipitation of 
cobalt. Copper melts with cobalt. They may be fepa¬ 
rated by fublimation with rnuriat of ammoniac. Copper 
is precipitated from its folution in acids by cobalt. From 
a folution of copper and cobalt in aqua regia, the copper 
may be precipitated by zink, which produces no change 
in the folution of cobalt. Arfenic and its oxyd unite 
with cobalt. They may be feparated by roalting them 
with charcoal. The ari'enic does not precipitate cobalt 
from acids, though it feems to have a greater affinity 
with thefe lubltances than cobalt. Iron melts eafily with 
S T R Y. 
cobalt. Neither of thefe metals feem to precipitate the 
other from its folution in acids. Tin produces a flight 
precipitation from rnuriat of cobalt. 
The oxyd of cobalt diflolves in cauftic ammoniac, but 
not without the affiftance of heat; and the liquor af- 
fumes a beautiful rofe colour. Onlv the oxyd of cobalt 
is employed in the arts, not the metal. It is ufed in 
painting earthen ware and porcelain ; former painters 
ufed it ground with oil, hence that very rough blue vifi- 
bie in the ground-work and draperies of old piffures; 
for the colour grows darker with age by contaft with air. 
It is a colouring matter for glafs and enamel. Azure is 
ufed in dying cloth, in making ftarch, &c. 
Of MANGANESE. 
This was long unknown as a metal, though much ufed 
in the arts; it has been employed in glafs works for 
more than two thoufand years. This mineral has the 
property of whitening glafs, or rendering it colourlefs; 
whence it has been called foap of glafs Only Scheele,, 
and the chemifts of his day, have (hewn that this fub- 
ftance is a metal of a peculiar nature. Native manganefe 
is laid to have been found by Picot la Peyroufe, in iron- 
mines in the valley of Vicdelos, in the ci-devant county 
of Foix, in France. It was in globules, fomewhat flat¬ 
ted, malleable, and of a lamellated texture. 
Manganefe, however, is generally in the oxyd Hate, 
prefenting feveral varieties. The oxyd is either black, 
red, or white, compaft, friable, in long four-fided cry(- 
tals like needles, particularly in the heavy fpar; fome is 
globulous, ftala&iceous, and pulverulent, like black duff: 
which foils the fingers. The white is the molt weakly 
oxydated ; it is found in iron-mines, but not mixed with 
the iron. The black oxyd of manganefe is often found 
among hematites. The carbonat of manganeie contains 
a good deal of iron, carbonic acid, lime, &c. Scheele 
has proved that the afhes of vegetables contain manga¬ 
nefe ; it is feparated by treating with nitrat of potafh; 
urging the mixture to fufion, a coloured glafs, either blue 
or green, is obtained. 
To reduce manganefe to the metallic ftate, line a cru¬ 
cible; put in at the hole a globule of oxyd of man¬ 
ganefe foftened with oil or gum-water, and cover the 
whole with a layer of charcoal; fix another crucible over 
this, and urge the fire very ftrongly for an hour, or an 
hour and a half. The metal which refults generally has 
inequalities on its lurface. The redufition is rather 
difficult; this metal is very refractory, and requires a 
llrong heat ; it is, befides, much difpofed to vitrify, 
which is another difficulty: fo vitrifiable indeed is it, 
that Guyton, who enclofed a button of this fubffance in 
a fmall crucible well luted, and urged it with a (trong 
fire in Macquer’s furnace, could obtain but one-half me¬ 
tal ; the reft was fcoria and vitreous matters. It is faid 
in Crell’s Journal, that, by mixing carbonat of magnefia 
with charcoal, pouring in nitric acid, and then evapo¬ 
rating to drynefs, a dry matter would be produced, 
which, being well wafhed and feparated, would give a 
complete metal, very beautiful, which is metallic man¬ 
ganefe. If this be true, it is a reduftion in the humid 
way. Gah.n is one of the firft who fucceeded in reducing 
the oxyd of manganefe. 
The metal manganefe is white; its frafture is granu¬ 
lated, irregular, of a metallic whitenefs, (hining, but loon 
growing dull in the air. Reduced to powder, it is eafily 
oxydated by air. If it'be heated in contaft with air, it 
is converted into an oxyd, at firft whitifh, but which be¬ 
comes more and more black in proportion as the calci¬ 
nation proceeds, and finally turns green. It requires an 
exceflive degree of heat to melt it. The fulphuric acid 
attacks this metal. Scheele and Bergman fay, that, dur¬ 
ing the folution, there is an effervefcence which ariles 
from the difengagement of a certain quantity of hydro-, 
gen gas. Fourcroy, on the contrary, affects, that the 
Sulphuric acid is decompofed by the manganefe: this, 
therefore. 
