CHEMISTRY. 
Care mull be taken to divide the earth well, when it is 
to be melted with borax. When an earthy fubftance, in 
very fine powder, is to be united with borax by the blow¬ 
pipe, the earth (hould be laid at bottom, and the borax 
over it, that the wind may not carry it away : the wind 
nuilt not be too llrong till the matter begins to mix ; and 
put enough of the borax, that the glafs may be tranfpa- 
rent; for if the filex abounds, the glafs will be opaque. 
Borax gives a yellowifli colour to flame; this is one of 
its characteriftics. It diflblves filex with eafe; and the 
combination may be known to be perfedt when the glo¬ 
bule fliines bright. The makers of artificial fcones, or 
falfe gems, prefer borax, as a flux, to the boracic acid ; 
it melts eafier, and makes a very bright fixed glafs, clearer 
indeed than fome Hones ; but it has neither their denfity, 
hardne'fs, nor weight. 
Alumine combines with borax, and a brifk effervef- 
cence is produced, which probably arifes from the pre- 
ience of a little air or carbonic acid. Barytes and lime 
decompofe this fait; and, if quick-lime be ufed, the de- 
compofition is complete. Borax ftiews the prefence of 
metallic fubftances by the manner in which glafs is co¬ 
loured. 
The borax of commerce is loaded with excefs of foda; 
and Bergman found, that, to bring it to the ftate of a 
neutral ih.lt, it abforbed half its weight of boracic acid. 
This neutral borax is not foluble as the borax of the 
fhops. 
Potafti decompofes the borat of foda; but ammoniac 
does not alter it at all; fpr the folution, by fpontaneous 
evaporation, lets the ammoniac efcape, and at laft keeps 
nothing but the boracic acid. All the acids, except the 
•carbonic, decompofe borax in the cold way, and the bo- 
rats in general; they feparate the acid in form of fpan- 
gles. But, with a llrong heat, the boracic acid de¬ 
compofes all the acids whofe falts are lefs fixed. See the 
article Borax, in our third volume, page 210. 
Borat of Ammoniac. —To obtain this fait, difiolve 
very pure boracic acid in caullic volatile alkali or ammo¬ 
niac, until the faturation appears complete; then dilute 
with a fmall quantity of water, and about half the liquid 
is to be evaporated on a fand-bath ; a pellicle of united 
cryftals is formed, whofe furface exhibits the figure of 
polyhedral cryftals. Its tafte is penetrating and urinous; 
it converts fyrupof violets to a green, and gradually lofes 
its cryftalline form, and becomes brown by expofure to 
air. It is moderately lbluble in water, and is decompofed 
by barytes, lime, potalh, and foda. It differs from the 
other borats in this, that the ammoniac volatilifes, while 
the acid remains pure. 
Borat of Magnesia. —This name is given to the 
combination of boracic acid with magnefia ; it diffolves 
therein but flowly : the fluid, by evaporation, affords 
granulated cryftals. This fait has a. fweet faccharine 
tafte. It is fixed by heat; it melts, forming a tranfparent 
glafs, which becomes opaque in cooling, but which will 
continue clear, if there be an excefs of the boracic acid. 
Its degree of folubility is not known. Lime and barytes 
decompofe it; as do the alkalis. The acids take up the 
magnefia, and leave the boracic acid feparate. To pre¬ 
pare calcareous borat of magnefia, mix fulphat of mag- 
neiia with muriat of lime, and add borat of foda thereto. 
Borat of Gi.ucine. —This has never yet been defin¬ 
ed by any cbemift. 
Borat of Alumine. —The combination of bora¬ 
cic acid with the earth of alum, which we call alumi¬ 
nous borat, has not yet been obferved. It is only known 
■that if a folution of borat of foda be added to a folution 
of aluminous fulphat, a light and fleecy precipitate is 
formed. Tjie fulphuric acid quits the alumine to unite 
with the foda. This earth combines with the boracic 
acid, which is at the fame time feparated, and the new 
fait is gradually re-diflolved. The liquid precipitated by 
fixed alkali,- affords by evaporation a vilcid and ailrin- 
gent mafs, in which fulphat of foda and aluminous borat 
are confounded together. This fpecies of borat is deconi- 
Vol. IV. No. 194. 
257 
pofable by the fame fubftances as alum: its properties 
however have not yet been examined with fuflicient care. 
Borat of Zircon. —This yet remains for modern 
chemiftry to inveftigate. 
Borat of Silex, by fufion. —The nature and proper¬ 
ties of this fait has not yet been examined. 
Of CARBONATS. 
The following is the method of obtaining carbonats in 
general. In a large doubly-tubulated bottle, put a weak 
acid much diluted with water; to one of the apertures 
adapt along tube or conical conduit, the narrow end wi th¬ 
in the bottle, the broad part open upwards : through this 
tube diluted chalk is to be introduced: the neck of a 
matrafs narrowed at the end may be made fit for this pur- 
pofe. ’ This tube or neck muft be fo long that by help 
of.the liquid which dilutes the carbonat, the gas may 
be comprefied with a force fuperior to the preflure laid 
upon it by the other parts of the apparatus. This con¬ 
duit may be flopped at will, by means of a pillon, which 
is made with a folid tube of glafs, at one end of which 
fome glafs is roughly melted on with a lamp, and this 
extremity is covered with thread, or a bit of rag. To 
the other aperture of the bottle is adapted a bent tube, 
whofe aperture fhould be four inches wide; the fecond 
branch of this tube is to be plunged into a bottle fimilar 
to the full, and which is to contain a folution of potafh. 
Other bottles may be added, containing alkaline or earthy 
folutions ; but for thofe earths which are not foluble in 
water, they need only be diluted. The apparatus thus 
difpofed, lute the joinings ; then raife the tube or fyphon, 
introduce the diluted chalk by degrees, which falling on 
the acid is decompofed, and lofes its carbonic acid, wliich 
is force.d through the folutions, and thus becomes fatu- 
rated with acid gas. When the liquors are entirely fatu- 
rated, flrain, and evaporate them to obtain the cryftal- 
lifed carbonats. 
Carbonat of Barytes. —-Native carbonat ofbarytes 
has been known for fome years: Dr. Withering firft dis¬ 
covered it, in the mines of Alflon-moor in Cumberland 5 
it is found alfo in Scotland, at Strontian, in Argylefhire ; 
likewdfe in the vein of filver at Simcoff in the Altaic 
mountains, and between the Ob and Irlich in Siberia, 
This fubftance is extremely compadl, femi-tranfparent, 
and of the colour of horn ; it is of a fibrous texture, di¬ 
vided into irregular laminae, according to the direction of 
its fibres. When broken tranfverfely, it has a fatty look, 
and a form both convex and concave, like filiceous fub¬ 
ftances : outwardly its fibres are of an unequal texture, 
and lie in bundles, with intervals between them, which 
give it a cellular appearance : but this is not conftant or 
neceflary. That which comes from Strontian is in the 
form of agglutinated prifms, lying horizontally on the 
calcareous fpar: thefe prifms feem to have an hexagon 
form with parallel ftriae, and blunt tops. The fpecific 
gravity of thefe carbonats of barytes is very great, it is 
4_2’3Sa. This fait has neither fmell nor tafte ; it is neu¬ 
tral, and infoluble ; but, like carbonat of lime, it is fo¬ 
luble in water charged with carbonic acid. 
Carbonat of barytes is made artificially, for the native 
kind is very fcarce. Barytes is feparated from the fulphat, 
and then laturated with carbonic acid. The manner of 
obtaining the barytes is (hewn in our fedtion on Ear¬ 
thy Subfiances, page 223. But the native carbonat of 
barytes differs from that which is formed by art; the for¬ 
mer lofes not an atom of its acid by expofure to great 
heat; the latter lofes a fmall portion of it. 
Mixed with charcoal, and urged by a great heat, for 
two hours, in a crucible, the carbonic acid is difengaged, 
and the barytes remains pure ; but the procefs is uncertain, 
and flow. If native and artificial carbonat be mixed to¬ 
gether in powder, and heated, the mixture takes a green 
colour, which lafts for fome months; and then dilappears. 
All the mineral acids decompofe it. 
When this- fubftance, after having been long expoled 
to the fire, is wanned with boiling water, and the fiolu- 
3 U tion 
