i III.MK'AI. I'KKI.IMINARIES 



tions, as graphite, diamond, charcoal. It occurs in combina- 

 tion to a wide extent in nature ; chalk and limestone, which 

 form mountain ranges, consist very largely of carbon united 

 with oxygen and lime. It occurs in all animal and vegetable 

 substances. 



Sulphur (S) is a solid element which exists in the free 

 state near volcanoes, having been deposited from the volcanic 

 gases. It is also found in large quantities in combination with 

 other elements. Sulphur is present in combination in many 

 animal and vegetable substances. 



Phosphorus (F) is a solid, easily inflammable element, 

 which is chiefly known in two varieties, one yellow and semi- 

 transparent, and the other red. It does not exist free in 

 natural substances. It occurs in combination in bones, and 

 is obtained chiefly from bone ash. 



Chlorine (Cl) is a greenish -yellow gas not found in 

 nature in the free state, but occurring abundantly in combina- 

 tion. Common salt, present in large amount in sea water, is 

 the most plentiful of its compounds. Much common salt is 

 found in the body. 



Air is a mixture of gases consisting of about four-fifths 

 nitrogen and one-fifth oxygen, and a very small amount of car- 

 bonic acid gas. There is also present a varying amount of 

 aqueous vapour, that is, water in the condition of a gas. The 

 atmosphere exerts a pressure on everything it has access to. 

 This pressure is equal to about I 5 pounds on every square 

 inch of surface. 



The following are the chief metallic elements or metals, 

 compounds of which arc found in, and are necessary to, the 

 animal body. 



Sodium (Na) is a soft white metal existing in nature in 

 large quantities in combination as rock salt, and (Glauber's salt. 



Potassium (K) is a soft metal like sodium, and like it 

 exists in nature only in combination. Saltpetre and potash 

 are compounds of potassium. 



Calcium ((.'a) is a metal occurring in combination in 

 enormous masses in nature. Chalk, mountain limestone, 

 marble, and planter of Paris arc compounds of calcium. 



Magnesium (Mg) < s -'i metal like calcium in many 

 respects, occurring also abundantly in earthy compounds. 



