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 51 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 



