Manual of chemistry for dispensers / War Office.

Date:
1931
Catalogue details

Licence: Public Domain Mark

Credit: Manual of chemistry for dispensers / War Office. Source: Wellcome Collection.

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    CHAPTER 12 COMPOUNDS—ACIDS AND BASES AND THEIR PROPERTIES Chemical Compounds WHENEVER two or more elements combine together they form a chemical compound, and these compounds in turn may combine producing other substances. There are therefore existing in nature an immense number of different compounds, and the chemical action which occurs in producing these may be one of three distinct types. The Union of Two Elements.—The simplest form of chemical reaction is where one element acts on another. It is obvious the compound resulting from this action can only contain two elements. The form it takes may be solid, liquid, or gaseous ; for example, when most metallic elements are exposed to the air, or heated in the presence of air, compounds which are called oxides are formed with the element oxygen. Iron “rusts ’? when it is exposed to the air—that is, its surface is covered with a compound of iron and oxygen known as ivon oxide. 2Fe + 30.= Fe,O, Copper when heated in the presence of air takes up oxygen and forms a compound, copper oxide. Cu + O = CuO If the element carbon is burnt in oxygen, a gaseous compound is formed called carbon dioxide gas. If the gases hydrogen and oxygen are mixed together and ignited by an electric spark, they combine together to form a liquid, water. Ho. =-. O-==O The Union of an Element and a Compound.—Secondly, there is the action where one element combines with a com- pound. If the element sodium is placed in the compound water, a new compound, sodium hydroxide, is formed, hydrogen being set free at the same time. 2Na + 2H,O = 2NaOH + H, Most metals if mixed with dilute acids form compounds with the liberation of hydrogen gas. FForexample, the metallic