late
the volume which a gas will occupy under standard conditions from the
volume which it occupies under any other conditions. This may be done in
accordance with the following laws.

~Law of Charles.~ This law expresses the effect which a change in the
temperature of a gas has upon its volume. It may be stated as follows:
_For every degree the temperature of a gas rises above zero the volume
of the gas is increased by 1/273 of the volume which it occupies at
zero; likewise for every degree the temperature of the gas falls below
zero the volume of the gas is decreased by 1/273 of the volume which it
occupies at zero, provided in both cases that the pressure to which the
gas is subjected remains constant._

If V represents the volume of gas at 0 deg., then the volume at 1 deg. will be
V + 1/273 V; at 2 deg. it will be V + 2/273 V; or, in general, the
volume v, at the temperature t, will be expressed by the formula

(1) v = V + t/273 V,

or (2) v = V(1 + (t/273)).

Since 1/273 = 0.00366, the formula may be written

(3) v = V(1 + 0.00366t).

Since the value of V (volume under standard conditions) is the one
usually sought, it is convenient to transpose the equation to the
following form:

(4) V = v/(1 + 0.00366t).

The following problem will serve as an illustration of the application
of this equation.

The volume of a gas at 20 deg. is 750 cc.; find the volume it will occupy at
0 deg., the pressure remaining constant.

In this case, v = 750 cc. and t = 20. By substituting these values,
equation (4) becomes

V = 750/(1 + 0.00366 x 20) = 698.9 cc.

~Law of Boyle.~ This law expresses the relation between the volume
occupied by a gas and the pressure to which it is subjected. It may be
stated as follows: _The volume of a gas is inversely proportional to the
pressure under which it is measured, provided the temperature of the gas
remains constant._

If V represents the volume when subjected to a pressure P and v
represents its volume when the pressure is changed to p, then, in
accordance with the above law, V : v :: p : P, or VP = vp.
In other words, for a given weight of a gas the product of the numbers
representing its volume and the pressure to which it is subjected is a
constant.

Since the pressure of the atmosphere at any point is indicated by the
barometric reading, it is convenient in the solution of the problems to
substitute the latter for the pressure measured in grams per s