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C H E M I 
form of gas, and that the oxygenated muriatic acid lofes 
its oxygen, fince it forms common muriat of ammoniac; 
that, in the fourth, nitric acid and water are produced, 
and that the oxyd of manganefe is difoxygenated, fince 
it no longer furnifhes oxygen gas with the help of fire. 
Hence it is very eafy to conceive, that ammoniac is com- 
poled of hydrogen and azot. Ammoniac may alf'o be 
decompofed by the oxyd of copper; in this cafe the me¬ 
tallic oxyd is received by means of the ammoniac: this 
Berthollet has proved, with this oxyd combined with 
ammoniac, and heated in the pneumatic apparatus. 
To this analyfis of ammoniac we may join fynthefis, 
by decompofing fimultaneoufly, or at the fame time, ac¬ 
cording to Guyton’s procefs, nitric acid and water, 
with the help of tin, zink, &c. then nitrat of ammoniac 
is formed which refults from the re-union of the azot 
of nitric acid, decompofed with the hydrogen of the wa¬ 
ter, equally decompofed by the metals. But ammoniac 
will never be fet free by this operation, becaufe, as fall 
as it is formed, it unites to the portion of nitric acid not 
yet decompofed, and even flops its decompofition. Prielt- 
ley has difeervered, that the eleftric fpark palling through 
smmoniacal gas, increafes its volume to three times its 
former quantity, and changes it into hydrogen gas. 
The caufe of this change is not yet well known. It ap¬ 
pears only that the alkali is decompofed in this experi¬ 
ment, and that its two component parts are feparated, 
and put into the Hate of elaftic fluidity. 
The experiments of Berthollet, as well as thofe of 
Prieltley, have proved that four meafures of ammoni- 
acal gas contained 2-9 of hydrogen gas and ri of azotic 
gas; or, taking the weights of thefe two fluids, that of 
the azotic gas contained in the alkali will be to that of 
the hydrogen gas in the proportion of izi to 29. 
For the purpofes of commerce and medicine, volatile 
alkali is prepared only from the animal kingdom. Being 
obtained by dillillation from the horns of animals, it has 
been long known in the (hops by the name of fpirit of 
hartfhorn. In this ftate it is very impure, containing 
fome oil and much carbonic acid. In order to obtain it 
free from thefe fubHances, it is necelfary to diffolve it in 
muriatic acid, and afterwards to difengage it from this 
combination by the addition of a fixed alkali, or of lime. 
Two parts of burnt lime, and one of the caultic alkaline 
fait, are the proportions to be added to one part of the 
muriat of ammoniac. This mixture is introduced into a 
retort, to which a feries of receivers, containing pure 
diftilled water, is to be adapted. The flighted heat is fuf- 
ficie'nt to difengage it in the ftate of gas. This gas paffes 
over into the receivers, combines with the water and fa- 
turates it. The quantity of gas which the water can ab- 
forb has not yet been accurately afeertained. In this 
ftate it is preferved in the Amps under the name of caultic 
volatile alkali, or fpirit of fal ammoniac with quicklime. 
Ammoniac, diluted with water, is ufed in a great 
number of diforders ; it is aperient, and powerfully in- 
cifive. It a£ts ftrongly on the lkin ; it is preferibed as a 
remedy for the bite of vipers, and for cutaneous and ve¬ 
nereal diforders, See. As this lubllance is acrid and 
caultic, it ought not to be ufed but with particular care. 
Externally applied, it is found exceedingly ferviceable in 
difeufling tumours, efpecially fuch as are formed by 
coagulated milk, lymph, &c. It readily cures burns, 
and is often and fuccefsfully employed in the cure of 
chilblains. It has been conftantly ufed under different 
names, as a very aftive ltimulant in fyncopes, apoplexies. 
Sec. Its life, in the latter cafe, ought to be in very mo¬ 
derate quantities; it is not prudent to adminiiter it in¬ 
ternally, without previous dilution in a confiderable 
quantity of water. Dangerous excoriations have been 
produced in the cefophagus, and the membranes of the 
llomach, by the volatile alkali being given without this 
precaution. See the article Ammoniac, in our firit vo¬ 
lume, p„ ^78, 
S T R Y. 
GENERAL PROPERTIES OF SULPIIATS. 
Sulphats are bitter; fome are foluble, fome not. They 
melt and volatilize by the adtion of heat, but are not de¬ 
compofed. All are decompofed by charcoal, forming 
fulphures, and carbonic acid. They all precipitate io- 
lutions of barytes. There are three fiinple rules for 
knowing a fulphat in diffolution in water : 1. By barytes. 
2. With the blow-pipe-a fulphure is formed. 3. Alco¬ 
hol precipitates immediately.all the folutions of fulpliats, 
and in a cryftallized form. The order of attraction of 
the bafes for fulphuric acid, is as follows : barytes, pot-' 
alh, foda, ftrOntian, lime, ammoniac, magnefia, glucine, 
alumine, and zircone, 
Sulphat of Barytes.—T he barytic fulphat has 
long been regarded as a ftone; it was called ponderous 
earth, and ponderous fpar. It is found in large quantities 
mixed with alumine, and the metallic ores ; it is cryftal¬ 
lized in rhombs or fix-fided prifins; it is often white, 
femi-tranfparent, grey, opaque, green, yellow, Sec. and is 
frequently found with fulphure of iron. It has neither 
tafte nor folubility ; its weight varies according to its 
texture, or the foreign bodies it contains. By fire it loies 
its water of cryftallization ; but can only be melted by a 
violent heat, fuch as that of the porcelain furnace, Sec. 
then it foftens and runs, but never in a liquid form ; it 
melts in globules with the blow-pipe. 
. Take fulphat of barytes in powder; mix with it one 
eighth of its weight of charcoal; heat the -whole in a cru¬ 
cible ; the produdl is a fulphure of barytes, which is to 
be cryftallized : then reduce the cryftals to powder, and 
pour over it nitric or muriatic acid: a nitrat or muriat 
of barytes is formed, which is to be decompofed with 
carbonat of potafh, the acid of which is driven oft' by 
heat, or by a mixture of charcoal. When the nitric 
acid is poured over the fulphure of barytes, water is de- 
compoled; fulpliurated hydrogen gas and nitrous gas are 
difengaged. The fulphur is almoll always mixed with 
charcoal in precipitation : to be certain that the.decom- 
pofition is complete, put an excefs of the acid. 
In preparing the fulphure of barytes, fulphurated hy¬ 
drogen is formed in a much larger proportion than in the 
other fulphures ; this arifes principally from the ftrong 
tendency which barytes has for combining with fulphuric 
acid, and from this arifes the brifle odour which is pro¬ 
duced in the decompofition of this fulphure more thaii 
in others. Hence is feen the reafon why, when we dil- 
folve a liilphure of barytes, a confiderable portion of 
fulphat of barytes remains, but it is a regenerated fulphat. 
The barytic fulphure is diftinguifhed by particular 
characters which deferve confideration. If a frefh folu- 
tion of barytic fulphure be evaporated, a confufed but 
plentiful cryftallization is produced. Strain quickly the 
cryftallized part, andprefs it in paper which may imbibe 
the moifture, a white cryltalline l'ubftance is produced, 
which is liydro-fulphure of baiytes ; the liquor which is 
feparated is fulphure of barytes, and contains, like all 
the diffolved fulphures, a confiderable portion of fulphu¬ 
rated hydrogen. 
The barytic fulphure, as well as the fulphat, if taken 
into the dark after it has been heated rather ltrongly, 
exhibits a vivid blueifti light. Lenifry fays, that~an 
Italian fhoemaker, named Vincenzo Cafciarolo, firit dif- 
covered the phofphoric light of the Bologna ftone. It 
is now however known, that this property is common to 
all the varieties of barytic fulphat. The procefs confifls 
in heating them red-hot in a crucible, reducing them to 
powder in a glafs mortar, and forming the fame into a 
palte, with a fmall quantity of mucilage of gum traga- 
canth, in pieces of the thicknefs of the blade of a knife. 
Thele being dried, are ftrongly calcined by placing them 
in the middle of the coals of a furnace which draws well. 
When the coal is all confumed, and the furnace grown 
cold, the pieces are cleanfed from the allies by means of 
„ a bel- 
