A double ion chamber can be used to measure absolute intensities of UV light, and the absorptivity and photoionization yield of gases. New methods have been developed and tested which make double ion chambers simpler to build and use. These methods allow for collection regions of unequal length and for a body of absorbing gas in front of the chamber. Such methods make it possible to mount the chamber away from the source of ionizing UV light without displacing other experiments. The methods described use the relationship between the outputs of a chamber of nominal dimensions, over a range of gas pressures, to obtain information about the light and the gas in the chamber and the effective dimensions of the chamber. Some errors due to pressure fluctuations and uncertainties in the construction of the chamber are avoided by these methods.