194 J. P. Cooke, Jr., on Lecture Experiments. 
tion of soda turned backward and forward through its entire 
length until the chforine is wholly absorbed. The end of the 
overflow tube is now opened under water colored blue with lit 
mus, which, as it rushes in, will be instantaneously bleached, 
indicating the presence of chlorine. The tube must now be 
immersed in the water until the level of the liquid is the same 
within and without, when it will be found that just one-half of 
the gas has been absorbed. We have now proved that one-half 
of the volume of gas evolved during the electrolysis of hydro- 
chloric acid consists of chlorine, and it only remains to show 
that the remaining half still left in the tube is hydrogen. For 
this purpose the delivery tube may be connected with a waler 
faucet and the gas’burnt as it is forced out through the overflow 
- 
is to be exposed for some time to bright diffused sun-light, and 
afterwards directly to the sun-beam until perfect combinati®? 
results. If the glass is quite thick, and the rubber stoppet® 
in very tight, the gases may even be exploded 2 the 
tube without danger, although this form of the experiment ® 
always attended with some risk. When the gases are in either 
way thoroughly combined, the end of the exit tube 18 is 
opened under mercury, in order to prove that no condensatio® 
has taken place, and afterwards under water colored blae | 
litmus, when a very rapid absorpti d 
; rption takes place, an 
mi? of the water will indicate that HCL has in fact bee? 
This tube we assume is graduated, or at least divided into st i 
parts of equal capacity. The tube full of gas is now slip] 
‘filled erie of a rubber cap, which bas been previous} 
illed with the see fig. 5 (left side of the wood cut) 
filled y gar ae F 
sunk in the mercury trough until the liquid is just level wi 4 
