Elementary inorganic chemistry Author:James Walker Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER V COMBUSTION There are a great many chemical reactions in which air plays a part. Atmospheric air consists of about one measure of oxygen and four me... more »asures of nitrogen. Although oxygen therefore occupies only one-fifth of the total volume of the air, it is nevertheless the active component of the mixture, the nitrogen merely serving to moderate the activity of the oxygen. Familiar instances of actions in which air takes part are to be found in the processes of combustion. For example, when fuel such as wood or coal burns in the air, the chief action is the union of the components of these substances with the oxygen in the air, the combustion taking place with such vigour that heat and light are developed. Similarly, the burning of a taper or coal-gas in air consists in the union of the materials of these substances with oxygen. The principal components of such ordinary fuels and illuminating agents are the elements carbon and hydrogen. On combustion the carbon unites with the oxygen to form carbon dioxide, and the hydrogen unites with oxygen to form water, according to the equations— C + O2 CO2 Carbon Oxygen Carbon dioxide 2H2 + O2 2H,O Hydrogen Oxygen Water That water is produced in the form of vapour may be easily shown by holding a cold bright object such as a polished piece of metal a little distance over a candle or gas flame. The cold metal cools the gases which rise from the flame, and the water-vapour condenses to minute drops of moisture on its surface, which in consequence immediately becomes dim. The presence of carbon dioxide in the gases produced by the combustion can also be simply shown as follows :—If a drop of lime water is taken up on the end of a glass rod, and held some distance over the flame, it will at once become milky, by the ...« less