418 
PHO 
V H O 
P H O 
The specific gravity of this acid, in a state 
of dryness, is 2.687; in the state of glass 2.85; 
in the state of deliquescence 14. 
3. This acid is very soluble in water. 
When in the state of white flakes, it dissolves 
with a hissing noise similar to that made by 
red-hot iron plunged into water. When in 
the state of glass it dissolves, much more 
slowly. The heat evolved during the com- 
bination of this acid and water, is much infe- 
rior to that evolved when sulphuric acid en- 
ters into a similar combination. Phosphoric- 
acid obtained by deliquescence, when mixed 
with an equal quantity of distilled water, ac- 
quired so little heat as to raise the thermo- 
meter only one degree, as Mr. Sage observ- 
ed. Mr. Lavoisier raised the thermometer 
from 50° to 63°, by mixing phosphoric acid 
boiled to the consistence of a syrup with an 
equal quantity of water; and from 50° to 
104° when the acid was as thick as turpen- 
tine. 
4. Oxygen gas has no action on phos- 
phoric acid, whatever is the temperature. 
Neither is it decomposed or altered by any 
of the simple combustibles, if we except char- 
coal ; which, though it has no action on it 
while cold, at a red heat decomposes it com- 
pletely; carbonic acid is formed, and phos- 
phorus sublimed. This is the common pro- 
cess for obtaining phosphorus. 
5. Neither of the simple incombustibles 
lias any particular action on it. 
6. This acid, when in a liquid state, is ca- 
pable of oxidizing some of the metals, espe- 
cially when assisted by heat; at the same 
time hydrogen gas is emitted. Hence we 
see that the oxidizement is owing to the de- 
composition of water. In this manner it ox- 
idizes iron, tin, lead, zinc, antimony, bis- 
muth, manganese; but on some of these it 
acts very slowly. When fused with several 
of these metals, as tin, iron, and zinc, it is 
converted into phosphorus; a proof that 
they have a stronger affinity for oxygen. 
It does not act upon gold, platinum, silver, 
copper, mercury, arsenic, cobalt, nickel. It 
appears, however, to have some action on 
gold in the dry way, as it is called; for when 
fused with gold-leaf it assumes a purple co- 
lour, a proof that the gold has been oxidized. 
7. Phosphoric acid combines with alkalies, 
earths, and metallic oxides, and forms with 
them salts known by the name of phosphats. 
S. Its affinities are as follow : 
Barytes, 
Strontian, 
Lime, 
Potass, 
Soda, 
Ammonia, 
Magnesia, 
Glucina, 
Alumina, 
Zirconia, 
Metallic oxides, 
Silica. 
9. The component parts of this acid have 
been ascertained in a more satisfactory man- 
ner than almost any other chemical com- 
pound. Mr. Lavoisier proved, that 45 parts 
of phosphorus, when burnt in oxygen, ab- 
sorbed about 69.375 parts of that gas, and 
produced about 1 14 parts of phosphoric acid 
Hence it follows that this acid is composed 
of about 60 oxygen 
40 phosphorus 
100 , 
or 3 parts oxygen to 2 parts of phosphorus. 
This acid is too expensive to be brought 
into common use. If it could be procured 
at a cheap rate, it might be employed with 
advantage, not only in several important 
chemical manufactures, but also in medicine, 
and perhaps even in domestic economy. 
PHOSPHO ROUS ACID: the acid obtain- 
ed by the burning of phosphorus differs ac- 
cording to the rapidity of the combustion ; 
or, which is the same thing, according to the 
temperature in which the process is con- 
ducted. When heated to 14 1° it burns ra- 
pidly, and the product is phosphoric acid : 
when allowed to burn gradually, at the 
common temperature of the air, the pro- 
duct is phosphorous acid, which contains 
a smaller proportion of oxygen. The differ- 
ence between these two acids had been re- 
marked by Sage, by Proust, and by Mor- 
veau; but it was Lavoisier who first, in 1777, 
demonstrated that they form different com- 
pounds with other bodies, and that the dif- 
ference between them is owing to the differ- 
ent proportions of oxygen which they contain. 
1. Phosphorous acid is prepared by expos- 
ing phosphorus during some weeks to the 
ordinary temperature of the atmosphere. 
Even in winter the phosphorus undergoes a 
slow combustion, and is gradually changed 
into a liquid acid. For this purpose, it is 
usual to put small pieces of phosphorus on 
the inclined side of a glass funnel, through 
which the liquor which is formed drops into 
the bottle placed to receive it. From one 
ounce of phosphorus about three ounces of 
acid liquid may be thus prepared. 
2. Phosphorous acid, thus prepared, is a 
viscid liquid, of different degrees Of con- 
sistence, adhering like oil to the sides of the 
glass vessel in which it is contained. It emits 
the smell of garlic, especially when heated. 
Its taste is acid, like that of phosphoric acid, 
and it produces the same effect upon vege- 
table colours. Its specific gravity has not 
been determined. 
3. It combines with water in every propor- 
tion ; but it cannot, like phosphoric acid, be 
obtained in a concrete state. 
When heated, part of the water which it 
contains is at first evaporated. When large 
bubbles of air rise to the surface, there they 
break, and emit a dense white smoke, or even 
take fire if the experiment is performed in 
an open vessel. The emission of these bub- 
bles of phosphureted hydrogen gas continues 
for a long time. When the process is finish- 
ed, the acid which remains is no longer phos- 
phorous, but phosphoric acid. These phe- 
nomena would lead one to suspect that phos- 
phorous acid is not, as has been hitherto 
supposed, a compound of phosphorus and 
oxygen; but that it is phosphoric acid satu- 
rated with phosphureted hydrogen gas. 
4. This acid is converted into phosphoric 
acid by exposure to air or oxygen gas. The 
process is exceedingly slow, and the conver- 
sion is never complete. It succeeds better 
when the acid is diluted with a great propor- 
tion ot water. 
9 . Phosphorous acid is not acted upon by 
any ot the simple combustibles except char- 
coal, and perhaps also hydrogen. Charcoal 
decomposes it at a red heat as well as phos- 
phoric acid. The products are carbonic 
acid and phosphorus. It does not act on the 
simple incombustibles. 
6. Its action on metals is exactly similar to 
that of phosphoric acid, excepting only that 
the hydrogen gas evolved during the oxy- 
disement of the metals has a fetid smell, and 
holds phosphorus in solution. 
7. It combines with alkalies, earths, and 
metallic oxides, and forms compounds distin- 
guished by the name of phosphites. 
8. Sulphuric acid produces no change 
upon it while cold ; but at a boiling heat it 
parts with some of its oxygen, and the phos- 
phorous acid is converted into phosphoric. 
Nitric acid also, when assisted by heat, con- 
verts it readily into phosphoric acid. This 
furnishes us with by far the best process for 
obtaining phosphoric acid at present known. 
9. The affinities of phosphorous acid, as 
ascertained by Bergman, Fourcroy, and 
Yauquelin, observe the following order : 
Lime, 
Barytes, 
Strontian, 
Potass, 
Soda, 
Ammonia, 
Glucina, 
Alumina, 
Zirconia. 
This acid has not hitherto been put to any 
use. The history of its preparation is suffi- 
cient to convince us, that it is composed of 
the same constituents as phosphoric acid : 
but the exact proportion of these constituents 
has not hitherto been ascertained. 
PHOSPHOROUS, in chemistry, a combus- 
tible substance remarkable for its strong at- 
traction for oxygen, and which consequently 
spontaneously inflames in the open air at a 
moderate temperature. 
History of its discovery. It was acciden- 
tally discovered by Brandt, a chemist of 
Hamburgh, in the year 1669, as he was at- 
tempting to extract from human urine a liquid 
capable of converting silver into gold. He 
showed a specimen ot it to Kunkel, a Ger- 
man chemist of considerable eminence, who 
mentioned the fact as a piece of news to one 
Kraft, a friend of his at Dresden. Kraft im- 
mediately repaired . to Hamburgh, and pur- 
chased the secret from Brandt for 200 dol- 
lars, exacting from him at the same time a 
promise not to reveal it to any otlier person. 
Soon after he exhibited his phosphorus pub- 
licly in Britain and France, expecting doubt- 
less that it would make his fortune. Kunkel, 
\\ ho had mentioned to Kraft his intention of 
getting possession of the process, being vexed 
at the treacherous conduct of his friend, at- 
tempted to discover it himself; and about 
the year 1674 he succeeded, though he only 
knew from Brandt that urine was the sub- 
stance from which phosphorus had been pro- 
cured. Accordingly he is alway s reckoned, 
and deservedly too, as one of the discoverers 
of phosphorus. 
Boyle likewise discovered phosphorus, and 
revealed the process to Godfrey Hankwitz, a 
London apothecary, who continued for many 
years to supply all Europe with phosphorus. 
Hence it was known to chemists by the 
name of English phosphorus. 
'Phosphorus may be procured by the fol- 
