premise: Following observation of the fact that the reaction rates of supposedly identical reaction mixtures prepared on the same filling manifold and exposed under identical <mask> often differed by several hundred per cent , a systematic series of experiments was undertaken to see whether the difficulty could be ascribed to the method of preparing the chlorine , to the effects of oxygen or moisture or to the effect of surface to volume ratio in the reaction tubes .
hypothesis: the proper context for <mask> here should be a state at a particular time