C H E M I 
lie acid and ammoniac. It was termed fecret anmoniacal 
fait of Glauber, becaufe this chemiil was the firft who dit- 
covered it. 
It is faid to have been found in a white efflorefcence 
in the environs of volcanos, and in cryftals about the 
mouth of Veiuvius, and that it has been extrafted from 
fome of t he waters of Tufcany; it has been faid alto to . 
have been feen on the furl ace of the earth, like nitre, 
about Turin; but all this appears doubtful. Bergman 
found none in the waters which lie examined ; however, 
as there is much fulphur and ammoniac in nature, this 
combination may be formed ; but, being very foluble in 
water, and even attracting moifture, it may by that means 
difappear. 
To prepare this fait, put carbohat of ammoniac into 
a ballon ; let it diffolve in a fufficient quantity of water; 
into the folution pour fulphuric acid, by little and little, 
till the mixture attains the point of faturation; a bri.lk 
eiferveicence is produced each time. When the mixture 
is faturated, {train the liquor; let it evaporate in a gen¬ 
tle heat to a thin pellicle; or this fait may be made to 
cryftallize fpontaneoufly ; but it mult be at a low tem¬ 
perature,- and kept quite {till, covering the veffel with 
. gauze, or a paper pricked with little holes. 
This fait, when very pure, appears under the form of 
needles, which, when carefully examined, are flattened 
priiins with lix fid.es, two of which are .very large, termi¬ 
nated by pyramids with fix faces, more or lefs irregular ; 
but this form exhibits varieties which are different from 
thofe we have deferibed ; it lbmetim.es occurs in the form 
of quadrangular prifms, and often in fquare and very 
thin plates. The form i'eems to depend, as in every in- 
ftance of cryftailization, on the manner in which tlie la- 
line particles are depofited, which is either lets regularly 
on each other, or according to the law of their decreale. 
The tafte of this fait is bitter and urinous; it is very 
light, and very friable. As it contains much water of 
cryftailization, it melts at firft with a very flight fire, but 
it becomes gradually dry in proportion as its water of 
cryftailization. is dillipated. With a greater beat it har¬ 
dens, and the ammoniac is partly difengaged ; and, if 
the heat be kept up, it is fubiimed in vapours in the 
dome of the retort as acid fulphat of ammoniac; this 
arifes from the operation of the double affinity, particu¬ 
larly that of the caloric for the ammoniac. This decom- 
pofition fliews that fulphat of ammoniac can become an 
acid fulphat, as well as fulphat of potafh. 
The acidulated fulphat of ammoniac is not deconi - 
pofable by water; it cryftallizes well, and reddens tinc¬ 
ture of turnfole. But the rednefs of the tincture mu ft 
not be depended on as a certain fign that the ammonia- 
cal fait is in the acidulated ftate, for the neutral ammo- 
niacal falts get red with heat. As tin&ure of turnfole 
is only a red tindiure blued with foda, the ammoniac at¬ 
tracts the foda, and the turnfole appears in its primitive 
ftate. The perfeCt neutrality of tbefe falts may be known 
by trying them with a folution of carbonat of magnefia : 
if an acid is prefent, an effervefcence takes place. 
Sulphat of ammoniac abforbs the moifture of the air 
in winter, but fcarcely at all in fummer. It cannot be 
decompofed by combuftion, like the other lulphats, for 
only the exteffive portion of the oxygen in the fulphuric 
acid is diftipated, the acid remaining in the ftate of ful- 
phureous acid ; now this fulphuric acid cannot retain 
all the ammoniac; a great part flies off in vapour. In 
this experiment the charcoal takes away the excels of 
oxygen; fulphureous acid and a fulpMt remain; but, as 
the fulphit volatilizes very eafiiy. it fublimes ; and by 
this means- charcoal efcapes in the decompofition, and 
ammoniac and carbonic acid pais over. Sometimes in 
this operation there is formed a prufiic acid, proceeding 
from the carbon and the ammoniac. 
It is very foluble in water; two parts of cold, or one 
of hot, water, being fufficient to hold it in folution. It 
cryftallizes by cooling; but the cryftals are by no means 
S T R Y. 231 
regular or fine. By diflblution in water it produces cold, 
and this cold is much more fenfible than what is produc¬ 
ed from other falts, becaufe it diflolves quicker. It like- 
wife unites with ice, which it melts, producing an ex- 
ceflive degree of cold. 
Nitric and muriatic acid do not decompofe this fait en¬ 
tirely; barytes, however, decompofes it, forming an in- 
foluble fulphat of barytes. Potafh and foda form foluble. 
falts with this, the ammoniac being difengaged in the 
gafeous ftate. Strontian works the fame effedt as barytes. 
Quicklime decompofes it alio ; the mixture heats, and 
the ammoniac is difengaged : if the, operation be perform¬ 
ed in a retort, the ammoniac may be extradited. This 
fait is decompofed by phofphat of lime in the following 
manner : Bones calcined to whitenefs; pulverifed, and 
well walhed in acetous acid, to diflblve the lime, or car¬ 
bonat of lime, which may exift in the bones, are put into 
a folution of fulphat of ammoniac. After filtering the 
liquor, the prefence of phofphork acid may be Ihown by 
adding fome lime-water, which produces a copious pre¬ 
cipitate of the phofphat of lime. It holds alfo a fmall 
portion of the fulphat of lime in folution, as may be 
leen, by pouring into it a folution of oxalat of potafh. But 
the greater part of the fulphat of lime remains on the 
filter with the undecoinpofed bone. This refidue, when 
dried, is found to weigh o 52 parts more than the phof¬ 
phat of lime originally employed. 
The effefts of heat oil fulphat of ammoniac have been 
very accurately obferved by Mr. Hatchet of London. In 
dillillmg this fait -by itfelf, he remarked, that a confider- 
able quantity of alkaline gas was difengaged. A white 
cloud of minute giiftering cryftals was. formed, which 
quickly difappeared, and was followed by a great quan¬ 
tity of fulphureous acid gas and water. In this experi¬ 
ment, the fait was not only decompofed, but alfo a part 
of the ammoniac refolved into its conftituent- principles. 
A portion of the undecompofed fait was fubiimed into 
the neck of the retort. The fulphureous acid gas, unit¬ 
ing with the alkaline gas in the receiver, formed the ful¬ 
phit of ammoniac, which appeared in the form of the 
minute giiftering cryftals. The gas which remained after 
this combination feemed to poffefs all the properties of 
azotic gas. .When fulphat of ammoniac was diltilled 
with yellow oxyd of iron, pure ammoniac came firft over, 
and afterwards fome fulphureous acid. The iron was 
converted to the ftate of a red oxyd, and mixed with 
fome fulphat of iron. With oxyd of zink, the refidue 
was the fulphat of that metal. Minium triturated with 
fulphat of ammoniac, immediately decompofed it iikelime 
or .alkalis, and, when diltilled together, the retort contain¬ 
ed fulphat of lead. When native green oxyd of copper 
was diltilled with fulphat of ammoniac, the refidue con- 
fifted partly of red oxyd, and fome fulphat of the lame 
metal. The ammoniac in this experiment came over in a 
concrete ftate, by reafon of the carbonic acid contained 
in the green copper. Pbilof. Tranf. for 1796. Sulphat 
of ammoniac is but of little ufe, though Glauber recom¬ 
mends it ftrongly for metallurgic operations. 
Sulphat of Magnesia.— This is known in phar¬ 
macy under the name of Epfom-falt, from the name of a 
Ipring near that town, where it was firft obtained. It 
exifts in lea-water, and in the mother-water whence fea- 
falt has been extradited ; alio in the waters, of Egra, Sed- 
litz, and Seydfchutz; and in the well-water of Paris ; 
likewife in the martial pyrites, in the compofition of 
alum, &c. 
Sulphat of magnefia is purified for fale by diffolving 
it in water, and leaving it to cryftallize." It may be pre¬ 
pared alfo by fatur-ating pure magnefia with lulphuric 
acid. The cryftailization is in Ifnall needles, but very 
confufed. But, by diffolving it in coid water, and ex- 
poling it in the air to a lpontaneous evaporation, it is 
obtained in fine quadrangular priiins, terminated by 
quadrangular pyramids, all the furfaces being fimooih 
and without furrows 5 its cryftals in general,are Ihorter 
and 
