88 Prof. Adenej and Mr. Becker on the Rate of Solution 



hence under these conditions the formula already deduced 

 would apply. However, these conditions do not ordinarily 

 occur. 



The conditions stated under section (2) are those which 

 are commonly assumed to obtain, although there seems to be 

 very little justification for such an assumption in practice. 

 Obviously if there be no mixing of the water, the only 

 process by which the air can penetrate into the mass of the 

 water is by diffusion of the dissolved gas molecules ; hence 

 the ordinary law for the diffusion of solutes would hold 

 under these conditions. But there is no experimental 

 evidence to show that such conditions ever occur under 

 natural conditions ; and it is doubtful if they have ever been 

 produced artificially even in the laboratory. On the other 

 hand, there is evidence to show that it is not possible to 

 expose a mass of water to the air and still keep the exposed 

 and unexposed portions of the water unmixed. Thus, when 

 Huefner was determining the velocity of diffusion of dissolved 

 gases in water, he found it necessary to expose the columns 

 of water to the gas at the lower surface through the medium 

 of a porous plate of hydrophane, in order to avoid the 

 mixing that he found to occur when the upper surface of 

 the columns of water was exposed to the gas. A considerable 

 number of experiments made by one of the authors also 

 points to the fact that the dissolved gases do not accumulate 

 in the upper layers of a column of water exposed to the air, 

 as they would tend to do if there were no mixing. Hence 

 calculations based on the law of diffusion cannot be of any 

 practical value. 



The third set of conditions postulated, namely, solution 

 at the surface with slow mixing, seems to be that which 

 would occur most frequently in practice. Under these 

 conditions the rate of solution will be dependent on the rate 

 of mixing. 



The formula applicable in this case might be expected to 

 be of the same form as that already derived from the experi- 

 ments with thin films, where the mixing was extremely 

 rapid, but the constants will alter according to the rate of 

 mixing. It will be shown that the results of the experi- 

 ments quoted here can be approximately represented by an 

 equation of the required form, and that the constants vary 

 with (1) the humidity of the air in contact with the water, 

 and (2) the salinity of the water. 



The method of experimenting consisted in filling a number 

 of tubes of about 30 cm. length and 4 cm. diameter with 

 de-aerated tap-water, and inserting rubber stoppers in such 



