322 . Prof. Adeney and Mr. Becker : Determination of Rate o] 



gases drawn over and measured at reduced pressure. The 

 absorption pipettes were of similar construction to the gas- 

 pipette, and were attached to the other capillary of the 

 eudiometer. 



A number of tubes of 40 mm. internal diameter and of 

 three different lengths were used to expose the water to be 

 tested. The lengths of the tubes were 12 cm., 22 cm., and 

 32 cm., while the columns of water experimented with were 

 about 2 cm. shorter in each case. 



The water used was freed from air and from mineral and 

 organic impurities by distillation in vacuo, the tap-water 

 being boiled at about 30° C. in a large glass flask, and the 

 distillate collected in a glass receiver of about 4 litres 

 capacity. In this way a large volume of purified water was 

 -obtained, with an average air-content of less than 1 c.c. of 

 total gases per litre. Each tube was rilled by siphoning the 

 water from the bottle into it, and allowing a fair quantity to 

 overflow 7 at the top. The tube was then quickly closed by 

 inserting a rubber stopper, provided with a glass stopcock, 

 without leaving any air-bubbles entrapped, and the tube was 

 placed in a thermostat until the contents attained the desired 

 temperature, before exposing the surface of the water to 

 the air. 



If, as is commonly assumed, the surface layer of the water 

 rapidly takes up as much of the gas as is possible under the 

 prevailing conditions, and the dissolved gases only diffuse 

 downwards through the mass of the water w r ith extreme 

 slowness, the air-content of the water in the shallow tubes 

 should have been nearly as great as that of the water in the 

 deep tubes, since the lower layers should receive but little 

 dissolved gas in the time during which experiments were 

 carried on. 



When a series of tubes were analysed, however, after 

 exposing them to the air for like periods of time, but too 

 short to ensure complete saturation, it was found that the 

 air-content of the water in them varied approximately in 

 proportion to the depth of the water-column employed. Thus 

 the tube containing 300 c.c. of water in each case contained 

 very nearly three times the amount of the dissolved gases 

 contained in the tubes holding 100 c.c. of water. Obviously, 

 if any concentration had taken place in the surface layers 

 of the columns of water, this should not have been 

 observed. 



The rate of absorption of air by the water in these tubes 

 proved, however, to be so very slow that it was not possible 



