142 Scientifie Intelligence. 
The product ae ape gia s method—the fifth above given— 
when dried at 250° till the weight is constant, approaches very 
near to the Sopeices of chromium dioxide. It is a fine deep 
w has conducted a series of experiments on the 
denporaiion i volatile reeds especially ether. Such experi- 
ments have hitherto led t results expressible in the form of 
laws ne conditions nae Iyhie they were made were not 
simple enough ; yet they were sufficiently varied. The science of 
evapoeation, especially of the diffusion of vapors, remained an 
beer ae ed field. 
e following experiments, to avoid the i ie lowering of the 
tem ree: at the surface, narrow tubes were chosen for evapo- 
rating vessels, instead of the wide vessels hithert rto used. 
(1.) The veloc city of the evaporation of a liquid from a tube is 
inversely proportional to the distance of the level of the liquid 
from the open end of the tube. This law holds with —. 
exactness when the distance of the level a little exceeds 1 
(2.) The velocity of the evaporation is independent of ‘i diame- 
ter of the tube, This result was obtained from experiments with 
tubes the diameter of which varied from 0°3"™ to 
(3.) The velocity of the evaporation increases with the tempera- 
ture, so far as with this the vapor-pressure of the liquid _ 
p be the maximum of elasticity of the vapor correspondin e 
temperature of the observation, P the atmospheric presi 
under which the liquid evaporates, the velocity of the evapora- 
the numerator and P-p the denominator. If the pressure of the 
vapor becomes equal to that of the air, this logarithm becomes 
infinitely great, and signifies 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 silee: 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. 
f the immersed tube contains hydrogen instead of air, the same 
number of bubbles form in one-fourth of the time. Evaporat ion 
a liquid can be evaporated in an open tube in various gases 
consists of a T-shaped glass tube, through the horizontal cross 
