326 Prof. Adeney and Mr. Becker : Determination of Rate of 



allowing the water to come into contact with air. The small 

 bubble left, at the top was removed by taking out the rubber 

 stopper, and quickly filling up the space with air-free water 

 from a pipette, and allowing it to overflow. The cork was 

 then replaced, and the tap closed, thus leaving the tube 

 completely filled with water. 



The tube was then clamped vertically, and the lower 

 stopcock connected with a standard burette by means of 

 pressure tubing full of water. The level of the burette 

 having been read, both stopcocks of the tube were opened, 

 and the water was allowed to flow from the tube into the 

 burette until the correct volume of water (15 c.c. in most 

 cases) had flowed out. All the taps were then closed, and 

 the pressure in the bubble adjusted to that of atmospheric by 

 repeatedly turning the two-way tap so as to connect the 

 bubble alternately with the atmosphere and the manometer. 



The tube was then swung steadily round a central axis, so as 

 to invert it, and allow the bubble to form without splashing ; 

 when the bubble reached the inverted end of the tube, the 

 latter was returned to its first position, and on the bubble 

 reaching the top, the pressure in it was measured by opening 

 connexion with the manometer. The time taken by the bubble 

 to traverse the tube was measured in every case, and found to be 

 practically constant, at eighteen seconds for a double journey. 



The air in the bubble was renewed after each observation 

 by taking out the stopper and inserting a tube connected with 

 a filter-pump, which drew a current of air through the space. 

 The stopper was marked, so that it could be always inserted 

 in the same position. 



As the water approached saturation and the readings of the 

 manometer got smaller, the number of inversions between 

 each reading was increased gradually from two up to ten. The 

 readings were continued until after ten inversions the mano- 

 meter showe J no distinct movement ; and the w r ater in the tube 

 was then drawn into the pump and analysed for dissolved gases. 



Considerable difficulty was at first experienced in getting 

 an experiment done at an absolutely constant temperature, 

 owing to the fact that the temperature of the laboratory 

 varied considerably, and, when the tap-water was tested, it 

 was also found to be subject to rapid and relatively large 

 variations in temperature. 



The difficulty was overcome by making the manometric 

 observations in a room the temperature of which was not 

 subject to serious fluctuations. A supply of water at steady 

 temperature was secured by setting up in this room a large 

 thick- walled wooden vat capable of holding about sixty 

 gallons, and filling this with tap-water, the day before it was 

 required for use, thus allowing it to attain a steady temperature 



