25 8 C H E M I 
tion filtered, the barytic earth fhoots into Ana 11 cryftals, 
fome of which are evidently of an octahedral figure. 
This faft has been obferved by Klaproth, Vauquelin, 
and Pelletier. Like the carbonat of lime, it becomes fo- 
luble by an excels of acid. The fuper-faturated carbo¬ 
nat is an extremely ufeful fubftance in chemical experi¬ 
ments. It ferves to precipitate the fulphuric acid, by 
the infoluble compound which it forms with it. It 
ferves to purify the phofphoric acid from the fulphuric, 
and the carbonats oi potafhand foda from the fulphat 
which they contain. It is prepared with great care, by 
putting fome carbonat of barytes, or, which is the fame 
thing, barytes precipitated from muriatic acid by an al¬ 
kaline carbonat, into a bottle of water impregnated 
with carbonic acid. The bottle is inverted, and the 
mixture left to digeft in the cold for fome hours. The 
folution is filtered, and kept in inverted bottles, to pre¬ 
vent the efcape of the carbonic acid. By digefting fome 
of the fulphat of barytes in water impregnated with car¬ 
bonic acid, Morveau obtained fome carbonat of barytes 
with an excefs of acid. He conceives that a linall por¬ 
tion of the carbonat is mixed with the fulphat. 
Carbonat of Strontian. —This is found at 
Strontian, among the lead ore. It is of a light green co¬ 
lour, fome is tranfparent and colourlefsq fometimes it is 
ftriated in a regular cryftalline form. Its fpecific gra¬ 
vity is from 36-583 to j 6'750, confequently lighter than 
carbonat of barytes. It retains the carbonic acid gas ve¬ 
ry ftrongly; but with care, and by keeping up the fire, 
about five or fix parts of carbonic acid gas may be fepa- 
rated from 10a of carbonat of ftrontian, without putting 
the crucible in danger ; yet the fire muft not be too ftrong, 
for in that cafe the earth will attack the crucible, and 
form glafs, of a cryfolite colour. 
To an hundred parts of carbonat of ftrontian, add ten 
parts of charcoal in powder, and make it into a ftrong 
dough with ftarch ; and this fait may be decompofed in 
the following manner: put this dough into a crucible, 
with a little charcoalduft newly calcined : lay the dough 
over the charcoal} cover the whole with powdered char¬ 
coal ; adapt a head to the crucible, and lute it with 
earth. When the crucible is thus fecured, expofe it to 
a very ftrong heat for a full hour, which will luffice for 
difengaging the carbonic acid gas : when the crucible is 
cold, open it, and the lump will be fouqd preferved, 
weighing only feventy-two parts. If the remaining mat¬ 
ter be dilfolved in diftilled water, cryftallized ftrontian 
is produced. 
To manufaflure carbonat of ftrontian, expofe a folu¬ 
tion of this earth in water to the air, and a white pelli¬ 
cle will be formed over it, which is only a combination 
of the ftrontian with the carbonic acid gas it has attract¬ 
ed from the atmofphere. The mineral acids decompofe 
carbonat of ftrontian. This carbonat is neither vomit¬ 
ing nor deadly, as is the carbonat of barytes, both native 
and factitious ;, w'hich fliews a great difference between 
thefe carbonats. 
Carbonat of Lime.' —All calcareous matters in. ge¬ 
neral, are neutral falts, refulting from the combination 
of carbonic acid with lime. There are many fubftances 
of this kind, as chalk, fpar, marble, {hells, concretions, 
Sec. Each of thefe (alts is different in texture, tranfpa- 
rence, and grain;, variations which arife from their quick 
or flow combination, l'ublequent expofure to peculiar 
temperature, See. Thefe matters are commonly colour¬ 
ed by metallic fubftances, as iron, manganefe, Sec. The 
Icelandic fpar has the property of doubling the objeCt of vi- 
fion, a phenomenon which has never been truly explain¬ 
ed. Chalk., or calcareous carbonat, improperly called 
Spanifh white, is prepared in France at Marly, Mardon, 
Cavereau, See. But the moft tranfparent calcareous fpar 
only, fuch as white marble, {hould be ufed in. making 
experiments to eftablifti the properties of this earthy fait. 
When expol'ed to the action of heat, it loles its acid, 
and water of cryftallization. Take calcareous fpar or 
a. 
S T R Y. 
powdered marble; put it into a retort of porcelain or oft 
earth, or rather into a glafs tube well luted ; or a gun- 
barrel may be ufed, and laid through a furnace; (but in- 
this cafe the operator muft not be furprized at finding a 
little hydrogen gas in tjie courfe of his experiment; for 
this is produced by the afition of the water contained in 
the earthy fait with the iron.) Adapt a recurved tube 
offafety to its lower extremity, which tube is to go un¬ 
der a bell-glafs, or jar. Then heat the tube, and car¬ 
bonic acid gas will be found under the jar: the refidue 
in the tube or retort is quicklime, which no longer effer- 
vefees with acids. If the tranfparent calcareous fpar be 
fuddenly heated, it decrepitates and becomes opaque. 
The procefs for the fabrication of lime, is founded on 
the principles of the preceding experiments ; the object 
is always to feparate the acid from the calcareous fub¬ 
ftances. A kind of hard calcareous ftone, called Ivne-Jlone, 
is moft commonly ufed in making lime. Thefe ftones arc 
to be piled up in the form of an oven or vauit 5 under 
the arch a fire of wood is to be lighted, which muft be 
continued till a ftrong flame, without fmoke, rifes con fi¬ 
de rably above the furnace, and till the ftones are be¬ 
come very white. Still the fire muft not be too ftrong, for 
the furface of the ftones will vitrify, efpecially if they 
contain 15 lex and alumine : in that cafe the lime is- info- 
luble, and is called over-burnt lime. If the acid is net 
yet difengaged, the lime is ftill infoluble, which is often 
the cafe with the lime of commerce: fome pieces are 
found alfo which are not baked enough, and fome too 
much. The oxyd of iron contained in the ftone is pro¬ 
per alfo to excite fufion; fo that, for ochreous ftone, a 
more moderate heat fhould be employed, and longer 
continued. The oxyds of iron and manganefe render 
the lime better, efpecially the oxyd of manganefe. 
Sometimes lime-ftone is white in the quarry ; grows 
blackifli in the air, and even of a fine deep black : it is 
becaufe the oxygen of the air lays open the oxyd of iron 
or manganefe, which originally exifted as a white oxyd; 
water greatly favours the developement of'this oxyda- 
tion. Lime, to be good, (hould be fonorous and hard; 
Ihould heat quickly and ftrongly with water, and give 
out a thick fmoke. 
The calcareous carbonat is not changed by the air. It 
is not foluble in pure water, but in water loaded with 
carbonic acid : thus it is that nature diflblvea thofe cai 4 
careous mafies which the waters afterwards- carry away-. 
When the waters, by expofure to the air, lofe the acid 
which favoured the folution of the calcareous matters; 
depofits are formed and hence arife the ftalaftites and in- 
cruftations formed about fprings, &c. and even. beds of 
calcareous laminae, which no doubt have been kept in 
folution. If thefe waters, loft fuddenly the acid which 
favoured folution, there is an irregular precipitation: 
hence calcareous ftones which are loft, cellular, and 
fpongy. But, if the cryftallization was flow, we have 
cryftallizations, marble, ftalaftites, &c. 
If acidulated water, holding carbonat of lime in folu¬ 
tion, be boiled, the excefs of acid evaporates, and the 
calcareous carbonat is depofited. This procefs may be 
ufed with advantage in the analyfis of mineral waters. 
If an alkali,, as ammoniac for example, be poured into 
an acid folution of carbonat of lime, there will be a pre¬ 
cipitation. The precipitation thus, obtained gives fome 
trouble in analyling mineral waters ; for it is not known 
whether it comes from the lime, or from the magnefia : 
this therefore muft be tried s if it be a calcareous carbo¬ 
nat held in folution by the water, it will effervefee with 
acids ; if it be magnefia, it will not. If the excefs of car¬ 
bonic acid found in a folution of calcareous earth, be fatu- 
rated with lime, a precipitation will take place immedi¬ 
ately. All thefe experiments prove that lime cannot be 
diflblved in water, but by an excefs of acid. 
The fulphuric, nitric, and muriatic, acids, decompofe 
the carbonat of lime ; they feparate the carbonic acid 
with eifervefcence, The alkalis precipitate the. lime of 
thele 
