146 VEGETABLE PRODUCTS. 



position by symbols: thus HO means that Hydrogen and 

 Oxygen combine one of each and form water ; but the weights 

 are 1 of Hydrogen and 8 of Oxygen. If 1 of Nitrogen unites 

 with 5 of Oxygen, we express it thus : N0 5 , which is Nitric 

 acid, which means that one atom of Nitrogen, which weighs 14, 

 is united with 5 atoms of Oxygen, which weighs 5 X 8 = 40. So 

 Starch is C, 2 , H 10 , Oj , meaning that 12 atoms of Carbon, united 

 with 10 each of Hydrogen and Oxygen, form Starch. 



280. Oxygen, Hydrogen, Carbon, and Nitrogen, are called 

 the organic elements, because they are essential to the constitu- 

 tion of every living being. The other elements are called in- 

 organic. Oxygen (0) is a gas or air, and forms one fifth of the 

 atmosphere |- of water. It supports combustion, and respira- 

 tion. No animal can live without it. 



Hydrogen (H) is a gas also, and forms one ninth of water. It is 

 the lightest body in nature and inflammable, and produces, by its 

 combustion, the highest heat known resulting from combustion. 



Nitrogen (N) is a gas, and forms four fifths of the atmosphere, 

 and is neither a supporter of combustion nor combustible. It 

 has no decided properties by itself. 



Carbon (C) is a solid, and is nearly pure in charcoal, and quite 

 so in the diamond. No organic substance exists without it. 

 Organic substances may want one or more of the other elements, 

 but never this. 



Phosphorus and Sulphur are well-known solids. Potassium 

 and Sodium are metals, and, when united with Oxygen, form 

 Potash, KO, and Soda, NaO. Silica, or sand, which enters in 

 large quantities in grains and grasses, is an acid, Si0 3 . When 

 oxygen unites with another element, and does not form an acid, 

 it is called an oxide. 



Carbonic Acid, C0 2 , is a gas, and is the principal food of 

 plants, and is yielded in great quantities from the respiration of 

 animals and combustion and decay of organic substances. 



Ammonia, NH 3 , is a pungent gas, and yields most of the 

 Nitrogen in plants. It is formed spontaneously in the decay of 

 organic substances. 



280. What are the organic elements ? Describe, oxygen. Hydrogen. 

 Nitrogen. Carbon. What element must all organic products have ? De- 

 scribe Potassium and Sodium. When do they form Potash and Soda 

 What is carbonic acid ? Ammonia ? 



