Sentence:  Sets of reaction <WSD>tubes</WSD> containing 0.2 of an atmosphere of added oxygen in one case and added moisture in another , both gave reaction rates in the range of 0.1 to 0.4 of the chlorine exchanged per hour . 
Meaning of the word marked with <WSD> tags:  conduit consisting of a long hollow object (usually cylindrical) used to hold and conduct objects or liquids or gases