4 5 
fire, if in contact with the air, and burns with a 
pale blue flame. In this process it dissolves in the 
oxygene of the air, and produces a peculiar acid 
elastic fluid. The number representing it is 30. 
10. Phosphorus is a solid of a pale red colour, of 
specific gravity 1770. It fuses at 90°, and boils at 
550°. It is luminous in the air at common tem- 
peratures, and burns with great violence at 150°, 
so that it must be handled with great caution. 
The number representing it is 222. It is procured 
by digesting together bone-ashes and oil of vitriol, 
and strongly heating the fluid substance so pro- 
duced with powdered charcoal. 
11. Boron is a solid of a dark olive colour, in- 
fusible at any known temperature. It is a sub- 
stance very lately discovered, and procured from 
boracic acid. It burns with brilliant sparks, when 
heated in oxygene, but not in chlorine. Its spe- 
cific gravity, and the number representing it, are 
not yet accurately known. 
12. Silicon is procured from silica, or the earth of 
flints, by the action of potassium : it appears as a 
dark, fawn-coloured powder, which is inflammable, 
and which produces silica by combustion. It de- 
composes water and acids; and detonates when 
heated with alkaline carbonates. It is more analo- 
gous to boron in its properties and chemical habi- 
tudes than to any other substance. 32 is an ap- 
proximation to the number representing silicon. 
13. Selenion , or, as M. Berzelius, the discoverer, 
names it, selenium, is a substance which forms a 
sort of intermediate link between the inflammable 
solids and the metals. It is semitransparent, of a 
