C H E M 
retort with one part of charcoal in fine powder. Urge it 
with a violent heat j and the refults will be, i. A fmall 
quantity of water, 2. Some carbonic acid. 3. A cer¬ 
tain quantity of fulphuruted hydrogen gas. 4. There 
remains in the retort a red mafs, very foluble in water, 
giving out a fetid fmell of fulpliurated hydrogen, from 
which the acids difengage this matter in the ftate of gas, 
and precipitate home lulphur: hence is produced a true 
fulpliure of potalh. 
Put fome very dry fulphit • of potalh into a porcelain 
tube; put the tube into a furnace ; adapt to the upper 
end the apparatus for difengaging hydrogen gas, and to 
the lower end a tube which is to go into an empty bottle. 
Heal the tube gently ; as the hydrogen gas pafles, water 
is formed; and l'ulphure of potalh remains in the tube. 
Sulphit of potalh is lbluble in a quantity of water 
nearly equal to its own nrafs ; and this folubiiity is in- 
creafed -by heat. This fait is decompofed by lime and 
barytes, as may be Ihown by pouring lime-water, or wa¬ 
ter of barytes into a folution of fulpliit of potalh. A 
white precipitate is afforded, which is the fulphit of 
lime; and the potalh remains difengaged in the w'ater. 
The fulphureous acid does not, therefore, follow the 
fame laws of affinity as the fulphuric acid, fince this laft 
adheres more ffrongly to potalh than to lime. 
Alkalis do not change the nature of the fulphit of 
potalh. Among the acids, fome decompofe it, by fepa- 
rating the fulphureous acid; others change its nature 
without driving off - its acid, by affording a portion of 
oxygen, and converting it into fulphuric acid. The 
firit of thele effects is produced by the fulphuric, muri¬ 
atic, phofphoric, and fluoric, acids ; the fecond is ef¬ 
fected by the nitric and the oxygenated muriatic acids. 
The acids of borax and of carbon do not occafion any 
change in the cold. 
Several metallic oxyds aft upon this fait. Some are 
entirely reduced to the metallic Hate, luch as the oxyds 
of gold, filver, and mercury ; others are brought nearer 
to that ftate, fuch as thofe of lead, iron, and manganefe, 
at the maximum of oxygenation. There are others which 
change the nature of the fulphit of potafh in an oppo- 
fite direction to that which takes place in the foregoing 
cafes, that is to fay, which conveit it into fulphat, by 
depriving it of a certain quantity of lulphur, with which 
they form fulpliurated oxyds, fuch as the oxyds of arfe- 
nic and of iron flightly oxydated. But, in order that this 
operation may fucceed, it is neceffary to boil thele fub- 
ftances a long time in water, and afterwards to add to the 
lolution an acid which occafions a coloured precipitate, 
at the fame time that fulpliurated hydrogen gas is emit¬ 
ted. All the metallic folutions, except the carbonats, 
are decompofed by the iulphit of potalh; and, as molt of 
the metallic fuiphits are infolubie, different coloured 
precipitates are formed, according to the nature of the 
metal, and its ftate of oxydation, 
Sulphit of Soda. —This is prepared by putting 
into a Woulfe’s bottle one part of cryftallized carbonat of 
foda, and two parts of diltilled water, palling fulphurous 
acid gas, till the effervefcence ceafes. When the fatura- 
tion is nearly completed, a portion of cryftallized ful¬ 
phit of foda is found at the bottom of the liquor. This 
lalt is white, and perfectly tranfparent; its figure a four- 
fided prifm, two of the fides being very broad, and tw'o 
narrow, terminating in dihedral pyramids. Its taile is 
cool, and afterwards fulphureous. Its habitudes in the 
fire are abfolutely the fame as thofe of the fulphit of 
potalh ; except only that it commences its operations by 
the aqueous tufion. By expofure to the air it efflorefees, 
and is afterwards converted into fulphat, but lefs lpeedily 
than the fulphit of potalh. Mixed with a twellth part 
of its own weight of charcoal in powder, and heated in 
a retort, it furnilhes firit a little water ; then fome car¬ 
bonic acid mixed with a portion of fulphurated hydrogen 
gas; laftiy fulpliure of foda remains in the retort. 
Mineral acids have the lame effect with fulphit of foda 
I S T R Y. 235 
as with that of potalh. Barytes, lime, and potalh, de¬ 
compofe fulphit of foda: the precipitation is fulphit of 
barytes, of lime, or of potalh, according as one or other 
of thefe earths has been ufed. It contains, in 100 parts, 
i8-S of foda, 32-2 of acid, and 50 of water. 
Sulphit of Magnesia. —For the formation of this 
fait, put into a Woulfe’s bottle one part of carbonat of 
magnefia,. and two parts of diftilled water, introducing 
fulphurous acid gas as before. If no more of the lulphu- 
rous acid be ufed than is juft neceffary to faturate the 
magnelia, there will be no perceptible change in the vo¬ 
lume cf the mixture; and, were we not allured, by the 
difengagement of carbonic acid, which takes place du¬ 
ring the operation, and by the fixation of the fulphurous 
acid gas, that a combination has taken place, w'e might 
be tempted to believe that there was no adtion between 
this acid and the carbonat of magnelia. The greater 
part of the fulphit of magnefia which is produced, re¬ 
mains at the bottom cf the liquor ; but, by bringing a 
frelh quantity of fulphurous acid upon the mafs of the 
fulphit of magnefia, when the effervefcence has ceafed, 
it is diffolved entirely in the liquor, and part of the lalt 
is feparated in tranfparent cryftals as it grows cold. This 
lolution of fulphit of magnefia, expoied to the air in a 
jar, loles by degrees its excefs of fulphurous acid, and 
depolits tranfparent cryitals. 
This fait is white and tranfparent; Its figure a four-fi- 
ded prifm diminilhing at the top ; its tafte is fweetilh and 
earthy at firit, afterwards fulphureous. Expofed to heat, 
it foftens, fwells up, and becomes dudtile like a gum; 
by continuing to beat, after it has loft: its water of cry- 
Itallization, the fulphurous acid is feparated, and the 
magnefia remains pure. It becomes opaque in the air, 
and is converted into a fulphat by degrees, but it takes a 
long time. Powdered charcoal heated in a retort, with 
twelve parts of fulphit of magnefia, takes aw'ay the oxy¬ 
gen, and converts it into fulphure of magnefia. It is 
but little foluble in water. Mineral acids have the fame 
effect upon this as upon the other fuiphits. The ter- 
reftrial and alkaline iubltances already taken notice of, 
all decompole fulphit of magnefia. The earthy fub- 
ftances form in folution a depofit, compofed of newly- 
formed fuiphits and of magnefia, Potalh and foda work 
the lame effedls ; but the magnefia is precipitated pure 
in that cale, becaufe tliefe alkaline fuiphits are foluble. 
This fulphit coniilts of magnefia lixteen, fulphureous 
acid thirty-nine, and w'ater forty-five. 
Sulphit of Ammoniac. —To obtain fulphit of 
ammoniac cryftallized, pafs fulphurous acid gas, in the 
manner before diredted, into concentrated liquid ammo¬ 
niac. When the water is completely faturated with the 
ammoniac, there will be a depofition of tranfparent and 
very regular cryftals, formed by that portion of the ful¬ 
phit of ammoniac, which the water held in folution 
on account of its heat. This lalt has the form ot fix- 
fided priims terminated by pyramids with fix faces. Its 
tafte is cool and pungent, but becomes at length lome- 
wliat like fulphurous acid. It volatilizes with heat, but 
is not decompofed. It attracts the moifture of the air, 
and foon changes to a fulphat. Charcoal does not con¬ 
vert it into a fulphure, becaule it volatilizes too fait. It 
is very foluble in water, and cryltallizes in cooling. 
All the mineral acids, except the boracic and carbonic, 
decompofe this fait: this decompofition takes place with 
heat and effervefcence, and the fulphurous acid may be 
colledted in the ftate of gas over mercury. 
Barytes alfo decompoles this fulphit: if barytes in 
powder be pounded with this fait cryftallized, dried, or 
even diffolved in water, the ammoniac will be difen¬ 
gaged. Lime adts in the lame manner. Powdered niag- 
neila, heated with fulphit of ammoniac, decompoles it 
entirely: magnefia will alio decompole this fait diffolved 
in water, if the mixture be expoied to a boiling heat: 
in a mean temperature, the magnefia does not entirely 
decompofe the fulphit of ammoniac, but a triple lalt is 
produced 
