484 Intelligence and Miscellaneous Articles. 



In the experiments whose results are here given, the more vola- 

 tile liquids, and in the first place ether, were employed. In order 

 to avoid the great lowering of the temperature at the surface, nar- 

 row tubes were chosen for evaporating-vessels, instead of the wide 

 vessels hitherto usual. 



1. The velocity of the evaporation of a liquid from a tube is inversely 

 poportional to the distance of the level of the liquid from the open end 

 of the tube. This law holds with rigorous exactness when the dis- 

 tance of the level a little exceeds 10 millims. 



2. The velocity of the evaporation is independent of the diameter of 

 the tube. This result was obtained from experiments with tubes 

 the diameter of which varied from 0*3 to 8 millims. 



3. The velocity of the evaporation increases with the temperature, 

 so far as with this the vapour-pressure of the liquid rises. If p be 

 the maximum of elasticity of the vapour corresponding to the tem- 

 perature of the observation, P the atmospheric pressure under 

 which the liquid evaporates, the velocity of the evaporation is propor- 

 tional to the logarithm of a fraction of which P is the numerator, and 

 P— p the denominator. If the pressure of the vapour becomes equal 

 to that of the air, this logarithm becomes infinitely great, and sig- 

 nifies that under this condition the liquid boils. 



Experiments were also made on evaporation in closed tubes. 



If the open end of a tube, the other end of which is closed, be 

 dipped in ether, bubbles form and issue continually from the tube, 

 and, at first, the times in which successively equal numbers of bubbles 

 form are proportional to the odd numbers. 



If the immersed tube contains hydrogen instead of air, the same 

 number of bubbles form in one fourth of the time. Evaporation 

 proceeds in hydrogen four times as rapidly as in air. 



The same result was also furnished by an experiment in apparatus 

 in which a liquid can be brought to evaporation in an open tube in 

 various gases. It consists of a T-shaped glass tube ; into its ver- 

 tical arm enters the tube containing the liquid to be evaporated ; 

 through the horizontal cross-piece a continual current of the gas is 

 conducted. 



If a tube provided with a cock be dipped with the cock open in 

 ether, the level of the liquid within the tube will sink below that 

 outside ; and, at first, the depths to which the interior level sinks below 

 the exterior in definite times are as the square-roots of those times. — 

 Sitzung der math.-naturw . Classe der Kaiserl. AJcad. d. Wissensch. in 

 Wien, Oct. 23, 1873. 



