FLUORINE. — PHOSPHORUS. 25 
and muriate of magnesia and muriate of lime, both 
of which exist in the waters of the ocean, contain 
a considerable quantity. One remarkable property 
of chlorine is, that it discharges all vegetable col- 
ours ; hence it is extensively employed for bleach- 
ing. 
Fluorine does not exist to any great extent. In 
combination with hydrogen it forms fluoric acid, 
which is most often met with in fluor spar or fluate 
of lime, a very interesting mineral, not only on ac- 
count of its beautifully variegated colours, but also 
on account of the varied form of its crystals. Fluo- 
rine exists in small quantity also in mica, hornblende, 
feldspar, greenstone, &c. 
Phosphorus abounds in nature to a limited extent, 
and is, for the most part, met with in the bones 
of animals. Human bones contain about 5) per 
cent, of phosphate of lime, and the enamel of the 
teeth 78 per cent, of the same substance. It has 
been ascertained by Dr. Turner, that the fossil bones 
of animals contain phosphorus ; and he obtained 
from the rib and tooth of an ichthyosaurus 50 per 
cent, of phosphate of lime. This substance, when 
pure, inflames when exposed to the atmospheric air. 
The metallic bases of the alkalies and earths are of 
considerable importance in geology. Of these* 
silicium is by far the most abundant on the surface 
of our planet, as it enters largely into the composi- 
tion both of the chemical and mechanical rocks. 
Silica is contained in the rocks enumerated beneath 
in the following proportions : 
* It is now maintained by some that silicium is not a metal. 
Thomson ranks it with boron and carbon, and calls it silicon. 
It wants the metallic lustre, and is a non-conductor of electrici 
ty, properties incompatible with its being a metal. The ques- 
tion may, however, as yet, be considered as unsettled. 
C 
