PllO 
remove the cork, and push the phosphorus 
from the mould with a piece of wood. Tims 
prepared, it must be preserved in close ves- 
sels, containing pure water. When phospho- 
rus is perfectly p\ire, it is semi-transparent, 
and has the consistence, of wax. It is so soft, 
that it may be cut with a knife. Its specific 
gravity is from 1.77 to 2.03. p has an 
acrid and disagreeable taste, and a peculiar 
smell, somewhat resembling garlic. 
When a stick of phosphorus is broken, it 
exhibits some appearance of crystallization. 
The crystals are needle-shaped, or long oc- 
tahedrons ; but to obtain them in- their most 
perfect state, the surfiice of the phosphorus, 
just when it becomes solid, should be pierc- 
ed, that the internal liquid phosphorus may 
flow out, and leave a cavity for their forma- 
tion. When phosphorus is exposed to the 
light it becomes of a reddish colour, which 
appears to be an incipient combustion. It 
is therefore necessary to preserve it in a 
dark place. At the temperature of 99° it 
becomes liquid, and if air be entirely ex- 
cluded, it evaporates at 219°, and boils at 
554°. At the temperature of 43° or 44°, it 
gives out a white smoke, and is luminous in 
the dark. This is a slow combustion of the 
phosphorus,which becomes more rapid as the 
temperature is raised. When phosphorus 
is heated to the temperature of 148° it takes 
fire, burns with a bright flame, and gives 
out a great quantity of white smoke. Phos- 
phorus enters into combination with oxygen, 
azote, hydrogen, and carbon. Phosphorus 
is soluble in oils, and when thus dissolved 
forms what has been called liquid phos- 
phorus, which may be rubbed on the face 
and hands without injury. It dissolves too 
in ether, and a very beautiful experiment 
consists in pouring this phosphoric ether in 
small portions, and in a dark place, on the 
surface of hot water. The phosphorie 
matches consist of phosphorus extremely 
dry, minutely divided, and perhaps a little 
oxygenized. The simplest mode of making 
them is to put a little phosphorus, dried by 
blotting paper, into a small phial ; heat the 
phial, and when the phosphorus is melted 
turn it round, so that the phosphorus may 
adhere to the sides. Cork the phial Closely, 
and it is prepared. On putting a common 
sulphur match into the bottle, and stirring 
it about, the phosphorus will adhere to the 
match, and will take fire when brought out 
into the air. 
PHOSPHURETS, in chemistry, are sub- 
stances formed by an union with phospho- 
rus ; thus we have the phosphuret of car- 
PLO 
bon, which is a compound of carbon with 
phosphorus : we have also the phosphuret of 
lime, hydrogen, &c. 
PHOSPHURETTED hydrogen, phos- 
phorus dissolved in hydrogen gas; which 
may be done by introducing phosphorus 
into a glass jar of hydrogen gas standing 
over mercury, and then melting it by means 
of a burning glass ; the gas dissolves a large 
proportion of it. The compound has a very 
fetid odour, something like that from putrid 
fish. Wlien it comes into contact with 
common air, it burns with great rapidity, 
and if mixed with that air it detonates vio- 
lently. Oxygen gas produces a still more 
rapid and briHiant combustion than common 
air. When bubbles of it are made to pass 
up through water, they explode in succes- 
sion as they reach tlie surface of the liquid ; 
a beautiful column of white smoke is form- 
ed. This gas is the most combustible sub- 
stance known. Its combustion is the com- 
bination of its phosphorus and hydrogen 
with the oxygen of the atmosphere, and 
the products are phosphoric acid and water. 
These substances, fnixed or combined, con- 
stitute the white smoke. 
PHOTOMETER, an instrument intend- 
ed to indicate the different quantities of 
light, as in a cloudy or bright day, or be- 
tween bodies illuminated in difl'erent de- 
grees. The ratio of the intensities of two 
luminous objects has been attempted to be 
measured by placing them at different dis- 
tances from a given object, until that ob- 
ject cast two shadows of equal darkness; 
or by observing when two equal objects 
appeared to be equally illuminated each 
by one of the luminous objects ; for then 
by a well known and established law, the 
proportion of the intensities of their light 
was supposed to be as the squares of the 
distances. Thus if two equal objects 
appear to be equally illuminated, when one 
of them is tliree feet from a tallow candle, 
and when the other is nine feet from a 
wax candle, then it is inferred that the in- 
tensity of the light of the former candle is 
to that of the latter as nine to eighty-one. 
Mr. Leslie has more recently invented an 
instrument of this kind, the essential part 
of which consists of a glass tube like a re- 
versed syphon, whose two branches should 
be equal in height, and terminated by balla 
of equal diameter ; one of the balls is of 
black enamel, and the other of common 
glass, into which is put some liquid. 
The motions of the liquor, which is sul- 
phuric acid tinged red with carmine, ate 
