Boyle's Law

in physics, a principle relating to the elasticity of gases. Every boy who has a popgun knows that air can be compressed;--that the harder he pushes, the smaller the space into which the air is crowded. The smaller the space into which the air is compressed, the greater its expansive force, and the farther it will throw the pellet. About 1662 Robert Boyle, a member of the Royal Society of London for Improving Natural Knowledge, reduced these observations to a principle known as Boyle's Law. It may be stated in two ways. Both come to the same thing:

The temperature remaining the same, the volume of a given body of gas varies inversely as the pressure upon it. Or, At constant temperature, the product of the pressure and the volume of a given mass of gas is a constant.

Boyle means by this that if twice the pressure be exerted on a given mass of air, it will occupy half as much space, and that if four times the pressure be exerted, the gas will be crowded into onefourth the space.

This statement seems exceedingly elementary at the present day, when every high school boy is expected to be familiar with it; but it should be remembered that in Boyle's day philosophers were not through yet with the search for some method of converting the baser metals into gold.

The same principle was discovered about 1676 by a Frenchman named Mariotte; hence in French school books the principle is called Mariotte's Law. It should be stated that Boyle's and Mariotte's Law does not hold good for quite all cases; nor does it hold good at high pressures. Stated popularly, one hundred times the pressure does not reduce gas to one one-hundredth of its former volume. Boyle's Law holds good, however, for all ordinary purposes.