P H 0 
PHQ 
V H O 
33 phosphat of ammonia 
• 33 phosphat of magnesia 
33 water 
99. 
Phosphoric acid and silica, when mixed to- 
gether and exposed to a strong heat, melt into 
a beautiful transparent glass, which Is not de- 
composed either by the action of acids or of 
alkalies. Fourcroy has given this compound 
the name of phosphat of silica ; but it is essen- 
tially different from salts, and ought therefore 
rather to be ranked among some other class of 
bodies. 
PHOSPHITES, salts formed with the 
phosphorous acid united to the earths, alka- 
lies, and metallic oxides. These salts may 
be distinguished by the following properties : 
1. When heated, they emit a phosphorescent 
flame. 2. When distilled in a strong heat, 
they give out a little phosphorus, and are 
converted into phosphats. 3. They detonate 
when heated with nitrat or oxymuriat of po- 
tass, and are converted into phosphats. 4. 
They may be converted into phosphats by 
nitric and oxy muriatic acid. 5. They are 
fusible in a violent heat into glass. 
The phosphites at present known amount 
to eight : 
1. Phosphitp of lime. This salt maybe 
formed by dissolving lime in phosphorous 
acid. When the saturation is complete, the 
salt precipitates in the state of a white 
powder. It is tasteless and insoluble in wa- 
ter; but it dissolves in an excess of acid, and 
forms a superphosphite. This last salt may 
be obtained in prismatic crystals by evaporat- 
ing the solution. It is not altered by expo- 
sure to the air. When heated, it phospho- 
resces and emits a little phosphorus. In a 
violent heat, it melts into a transparent glo- 
bule. 
It is composed of 34 acid 
51 lime 
15 water 
100 . 
2. Phosphite of barytes may be formed by 
• pouring phosphorous acid into barytes water, 
orthis last water into a solution of phosphite 
of soda. In either case phosphite of barytes 
precipitates in the form of a white powder. 
It is tasteless, and but very sparingly soluble 
in water, unless there is an excess of acid. 
It is not altered by exposure to the air. Re- 
fore the blowpipe it melts, and is surrounded 
with a light so brilliant that the eye can 
scarcely bear it. The globule which it forms 
becomes opaque as it cools. 
It is composed of 41.7 acid 
51.3 barytes 
7.0 water. 
100.0 
3. Phosphite of magnesia is best formed by 
mixing together aqueous solutions of phos- 
phite tif potass or soda and sulphat of magne- 
sia; the phosphite of magnesia gradually 
precipitates in beautiful white flakes. It has 
no sensible taste. It is soluble in 400 parts 
■ok water at the temperature of 60°, and 
scarcely more soluble in boiling water. When 
its solution is evaporated slowly, a transpa- 
rent pellicle forms on its surface, flakes are 
deposited, and towards the end of the nro- 
VOL. II. 
cess small tetrahedral crystals are precipi- 
tated. When exposed to the air it effloresces. 
When heated it phosphoresces and melts into 
a glass, which becomes opaque on cooling. 
It is composed of 44 acid 
20 magnesia 
36 water 
100 . 
4. Phosphite of potass. This salt is formed 
by dissolving carbonat of potass in phospho- 
rous acid, ana evaporating the solution slowly 
till it deposits crystals of phosphite of potass. 
It crystallizes in four -sided rectangular 
prisms, terminated by dihedral summits. Its 
taste is sharp and saline. It is soluble in three 
parts of cold water, and still more soluble in 
boiling water. It is not altered by exposure 
to the air. When heated, it decrepitates, 
and then melts into a transparent globule, 
which becomes opaque on cooling. It does 
not phosphoresce so evidently as the other 
phosphites, perhaps because it contains an 
excess of potass, which saturates the phos- 
phoric acid as it forms. 
It is composed of 39-5 acid 
49.5 potass 
110 water. 
100.0 
5. Phosphat of soda may be prepared ex- 
actly in the same way as phosphite of potass. 
Its crystals are irregular four-sided prisms or 
elongated rhomboids. Sometimes it assumes 
the form of square plates, or of plumose 
crystals. Its taste is cooling and agreeable. 
It is soluble in two parts of cold water, and 
scarcely more soluble in boiling water. When 
exposed to the air it eflloresces. Before the 
blowpipe it emits a beautiful yellow flame, 
and melts into a globule, which becomes 
opaque on cooling. 
It is composed of 16.3 acid 
23.7 soda 
60.0 water. 
100.0 
6. Phosphite of ammonia may be prepared 
! by the same processes as the two last-de- 
! scribed phosphites. It crystallizes sometimes 
in long transparent needles, and sometimes 
in four-sided prisms terminated by four- 
sided pyramids. It has a very sharp saline 
taste. It is soluble in two parts of water at 
the temperature of 60°, and -till more soluble 
in boiling water. When exposed to the air, 
it attracts moisture, and becomes slightly de- 
liquescent. When distilled in a retort, the 
ammonia is disengaged partly liquid and 
partly in the state of gas, holding phosphorus 
in solution, which becomes luminous when 
mixed with oxygen gas. Before the blow- 
pipe on charcoal, it boils, and loses its water 
of crystallization; it becomes surrounded 
with a phosphorescent light ; and bubbles of 
phosphureted hydrogen gas are emitted, 
which burn in the air with a lively flame, and 
form a fine coronet of phosphoric acid va- 
pour. This gas is emitted also when the salt 
is heated in a small glass bulb, the tube be- 
longing to which is plunged under mercury. 
This salt is composed of 26 acid 
51 ammonia 
23 water 
100 . 
3 G 
4 \? 
7 . Phosphite of ammonia and magnesia. 
This salt ni3y be formed by mixing together 
the aqueous solutions of its two component 
parts. It is sparingly soluble in water, and 
may be obtained in crystals; but its proper- 
ties have not been examined with precision. 
8. Phosphite of alumina may be prepared 
by saturating phosphorous acid with alumina, 
and then evaporating the solution to a pro- 
per consistence, it does not crystallize,' but 
forms a glutinous mass, which dries gradu- 
ally, and does not afterwards attract moisture 
from the air. Its taste is astringent. It is 
very soluble in water. When heated, it froths 
and gives out phosphorus, but it does not 
readily melt into a globule of glass. 
PHOSPHORIC ACID. phosphorus 
forms an acid with two different proportions 
of oxygen : combined with the largest por- 
tion of oxygen, it constitutes phosphoric acid, 
and with the smaller it constitutes phospho- 
rous acid. 
1. It may be formed by setting fire to a 
quantity of phosphorus contained in a v essel 
filled with oxygen gas. The phosphorus 
burns with great rapidity, and a great number 
of white flakes are deposited, which are phos- 
phoric acid ,in a state of purity. ' It may be 
obtained too by heating phosphorus under 
water till it melts, and then causing a stream 
of oxygen gas to pass through it by means of 
a tube. In this case the acid as it forms com- 
bines with the water; but the liquid may be 
evaporated off by the application of heat, and 
then the acid remains behind in a state of 
purity. But the usual method of procuring 
it is, to throw phosphorus in small pieces at a 
time into hot nitric acid. A violent effer- 
vescence takes place, the phosphorus com- 
bines with oxygen, and nitrous gas is emit- 
ted. Alter the whole of the phosphorus is 
acidified, the liquid is to be evaporated to 
dryness, in order to drive off the remains 
ot nitric acid which may not have been 
decomposed. 1 his process was first put in 
practice by Lavoisier. Care must be taken 
not to apply too much heat, nor to add too 
much phosphorus at once, and not to have 
the nitric acid too strong; otherwise th@ 
phosphorus takes lire, and usually breaks the 
vessels in pieces. 
2. The acid, thus prepared, may be put 
into a platinum crucible, and heated to red- 
ness to drive off all the water. It is then in 
a state ot purity. It is solid, colourless, and 
transparent, and not unlike glass r n appear- 
ance. It reddens vegetable blues ; it has jio 
smell: its taste is very acid, but it does not 
destroy the texture of organic bodies. • 
\\ hen exposed to the open air, it soon at- 
tracts moisture, and deliquesces into a thick 
oily-like liquid, in which state it is usually 
kept by chemists. When exposed to the fire 
in a platinum crucible, its water gradually 
evaporates, and leaves it in the state of a 
transparent jelly. If the heat is increased it 
boils and bubbles up, owing to the separation 
of the remainder of its water accompanied 
•with a small portion of acid. At a red heat 
it remains in the form of a transparent liquid, 
and when cooled assumes the form ofdhe 
purest crystal. In this state it is known hv 
the name of phosphoric glass. This glass ss 
merely phosphoric acid totally deprived of 
water; It has an acid taste, is Voluble m 
water, and deliquesces when exposed to tire 
air. 
I 
f- 
