THOSPHATS. 
416 
from the atmosphere, and is converted into 
a viscid liquid. When heated, it first under- 
goes the watery fusion ; then allows its water 
ot crystallization to evaporate, and is reduced 
to dryness. In a high temperature it melts 
into a transparent glass, which deliquesces 
again when exposed to the air. 
It is completely decomposed by the sul- 
phuric, nitric, and muriatic acids; and by 
barytes, strontian, and lime. 
2. Phosphat of potass. This salt may be 
formed by mixing together superphosphat of 
potass and pure potass, and exposing them to 
a strong heat in a platinum crucible. A 
.white-coloured substance is obtained, which 
is the phosphat in question. This salt is 
tasteless and insoluble in cold water, but so- 
luble in hot water, and it precipitates as the 
solution cools in a gritty brilliant powder. It 
is extremely fusible; melting before the blow- 
pipe into a transparent bead, which becomes 
opaque on cooling. It is soluble in nitric, 
muriatic, and phosphoric acids: the solutions 
.are thick, glutinous, and adhesive. When 
sufficiently diluted, the alkalies occasion no 
.precipitate in these solutions ; but when they 
are concentrated, a precipitate appears. 
Phosphat of soda. This salt exists ready- 
formed in urine, and was the first known of 
all the phosphats. It occupied a good deal 
.of the attention of chemists; and the diffi- 
cult y of analysing it gave occasion to various 
hypotheses concerning its nature, Iicllot 
remarked it in urine; and described it in 
! 737, as a salt different from those that had 
usually been observed. Iiaupt described it 
in 1.740 under the name of sal mirabile per- 
latum, or “ wonderful perlated salt.” It was 
called perlated from the grey, opaque, pearl- 
like colour, which it assumed when melted 
by the blowpipe. Margraff examined it in 
1745, and found it would not yield phospho- 
rus when treated with charcoal, as the other 
salts of urine did. 
Or. Pearson afterwards introduced it with 
great advantage into medicine as a purga- 
tive. He gives the following process for 
preparing it: Dissolve, in a long-necked ma- 
trass, 1400 grains of crystallized carbonat of 
soda, in 2100 grains of water at the tempe- 
rature of d‘50°. Add gradually 500 grains of 
phosphoric acid of the specific gravity 1.85. 
Boil the liquor for some minutes ; and while 
it is boiling-hot, filtrate it, and pour it into 
a shallow vessel. Let it remain in a cool 
place, and crystals will continue to form for 
several days. From the above quantities of 
materials he has obtained from 1450 to 1550 
grains of crystals. 
Its crystals are rhomboidal prisms, of 
which the acute angles are 60°, and the ob- 
tuse angles 120°, terminated by a three-sided 
pyramid. Its specific gravity is 1.333. Its 
taste is alniost the same with that of common 
salt. It is soluble at the temperature of 60° 
in about four parts of water, and in two parts 
of boiling water. This solution crystallizes 
on cooling; but in order to obtain the salt 
properly crystallized, the solution should 
contain a slight excess of alkali. When ex- 
posed to the air, this salt very soon effloresces 
on the surface. When heated, it undergoes 
the watery fusion. At a red heat it melts 
into a white enamel. Before the blowpipe 
it melts into a transparent globule, which be- 
comes opaque on cooling, and its surface 
acquires a polyhedral figure. It is not altered 
by combustibles nor metals. With metallic 
oxides it enters into fusion, and forms a co- 
loured globule of glass. Sulphuric, nitric, 
and muriatic acids, decompose it partially, 
and convert it into superphosphat of soda. 
In this state it is more soluble in water, and 
not so easily crystallized ; but may be obtain- 
ed, by proper evaporation, in the state of thin 
scales, not unlike boraoic acid. 
The greater number of earths may be 
fused along with this salt, and converted into 
glass.. 
This salt has been applied to various uses. 
It has been introduced into medicine as a 
purgative, and on account of its pleasant 
taste has of late been much used. It is usu- 
ally taken in broth, which it is employed to 
season instead of common salt. It may be 
substituted for borax to promote the solder- 
ing of inetals. Mineralogists employ it very 
much as a flux when they examine the ac- 
tion of heat .on minerals by means of the 
blowpipe. 
Phosphat of ammonia. It exists .also in 
urine, and seems to have been lirst accu- 
rately distinguished by Reuelle. It .is usu- 
ally prepared by saturating with ammonia 
the superphosphat of lime obtained from 
bones, and evaporating the solution to such 
a consistency, that when allowed to cool, the 
phosphat of ammonia is obtained in crystals. 
It crystallizes in four-sided prisms, termi- 
nated by equal-sided pyramids. Its taste is 
cooling, salt, and ammoniacal. Its specific 
gravity is 1.80. It is soluble in four parts of 
water at the temperature of 60°, and in ra- 
ther a smaller proportion of boiling water. 
It is by spontaneous evaporation that it is 
obtained in, the state of regular crystals. It 
is not altered by exposure to the air. When 
heated, it undergoes the watery fusion ; it 
then dries; but if the heat is continued, it 
swells up, Iosi s its alkaline base, and the acid 
melts into a transparent glass. It is the only i 
one ot the earthy and alkaline phosphats 
which can be decomposed by heat. Hence 
the reason that it yields phosphorus when 
distilled along with charcoal. 
It is decomposed bv the sulphuric, nitric, 
and muriatic acids, and by the fixed alkalies 
and alkaline earths. It is capable of com- 
bining with an additional dose of acid, and of 
passing into the state of a superphosphat. 
This salt is much employed as a flux in 
experiments with the blowpipe. It enters 
also as an ingredient in those coloured glasses 
called pastes, which are made in imitation of 
precious stones. 
Phosphat of magnesia. It is usually pre- 
pared by dissolving carbonat of magnesia in 
phosphoric acid, and evaporating the solu- 
tion gradually till the salt crystallizes; but it 
may Ire obtained in large regular crystals by 
a much easier process. Mix together equal 
parts of the aqueous solutions of phosphat of 
soda and sulphat of magnesia. No apparent 
change takes place at lirst ; but in a few hours 
large transparent crystals of phosphat of 
magnesia make their appearance in the solu- 
tion. 
Its crystals are six-sided prisms, the sides 
of which are unequal. It has very little taste; 
however, it leaves a cooling and sweetish im- 
pression upon the tongue. Its specific gra- 
vity is 1.55. It requires about 15 parts of 
cold water to dissolve it. It is more soluble 
in boiling water, but it crystallizes in part: 
as the solution cools. When exposed to the 
air it loses its water of crystallization, and 
falls down in powder. When heated mode- 
rately, it is also reduced to a dry powder. In 
aiiigii temperature it melts into" a transparent 
glass. 
Phosphat ofglucina. It isobtained by pour- 
ing phosphat of soda into the solution of °!u- 
cina in sulphuric, nitric, or muriatic acids. 
The phosphat of glucina is precipitated in 
the state of a white powd. r. It does not ervs- 
tallize. It is tasteless, insoluble in water 
unless it contains an excess of acid, and not 
liable to be altered by exposure to the air. 
When heated strongly’ it melts into a trans- 
parent glass. 
Phosphat of yttria. When the solution of 
phosphat of soda is mixed with the sulphat, 
nitrat, or muriat of yttria, phosphat of yttria 
precipitates in gelatinous flakes. 
Phosphat of alumina. It may be formed by 
saturating phosphoric acid with alumina. It, 
is a tasteless powder, insoluble in water. 
Dissolved in phosphoric acid it yields a gritty 
powder, and a gummy solution, which by 
heat is converted into a transparent glass. 
Phosphat of soda and ammonia, known to 
chemists by the names of microcosmic salt, 
and fusible salt of urine, was extracted from 
urine, and examined, much sooner than any 
of the other phosphats: it was long before 
philosophers were able to form precise no- 
tions concerning its nature, or even to obtain 
it in a state of purity. This indeed could 
not be expected till the phosphats of soda 
and of ammonia had been accurately exa- 
mined, and their composition ascertained. 
Fourcroy was the first who gave a precise 
account of the proportion of its component 
parts. According to him, it is composed of 
32 acid 
24 soda 
19 ammonia 
25 water 
100 . 
The properties of this salt are nearly those 
of the phosphat of soda and phosphat of am- 
monia joined together. It answers better than 
the first of them as a flux ; because the heat 
soon drives off the ammonia, and leaves an 
excess of acid. Its specific gravity is 1.5. 
When exposed to the air, this salt effloresces, 
and gradually loses its ammonia. 
Phosphat of ammonia and magnesia was 
first discovered by Fourcroy, whofouncl it in 
a calculous concretion formed in the colon of 
a horse. Since this discovery Fourcroy and 
Vauquelin have observed it also in human 
urine. 
It might be prepared by mixing together 
solutions of the phosphats of ammonia and of 
magnesia in water ; the triple salt immedi- 
ately precipitates in the state of a white 
powder. When urine is allowed to remain 
a considerable time in close vessels, it often 
deposits this salt in regular crystals on the 
sides and bottom of the vessel. ’ These crys- 
tals are small four-sided prisms, terminated 
by irregular four-sided pyramids. This salt 
is tasteless, scarcely soluble in water., and net 
liable to be altered by exposure to the aF, 
When heated it falls to powder, gives out its 
ammonia, and in a high temperature melts 
into a transparent globule. It is composed of 
