Becker — Apparatus for Ohserving Reaction hettoeen Gases, etc. 339 



of ferrous hydrate, and, consequently, the oxygen is absorbed at a constant 

 rate, as shown by the fact that the graph at this portion is practically a 

 straight line. In the second stage, when all the ferrous hydrate has been 

 oxidized, the absorption falls off gradually, so that the graph becomes a 

 logarithmic curve. During this stage the water becomes completely 

 re-aerated. In the figure, the second graph shows a more gradual approach 

 to saturation than the first ; this is due to the fact that during this experi- 

 ment the speed of the motor driving the stirrer varied suddenly owing to 

 variation in the voltage of the supply. This observation indicated the 

 advisability of determining the time necessary to attain equilibrium under 

 certain conditions. As this was intimately connected with some work which 

 had been done previously on the rate of solution of gases by water, it was 

 considered worth while to examine it more fully. 



Fig. 4. 



v.— Experiments on the Effect of Stikking on the Eate of Solution 



OF Oxygen in Water. 

 The method consisted in introducing into the apparatus known amounts 

 of a solution of ferrous sulphate and precipitating the hydrate by means of 

 a solution of caustic potash ; the stirrer was then driven at certain definite 

 speeds by means of a small alternating-current motor (which could be relied 

 upon not to vary in speed to any large extent), and the rate at which the 

 oxygen was absorbed noted by observing the manometer. 



