140 Self-regulating Reservoir, for Gases. 
Self-regulating Reservoir, for Hydrogen and other Gases, 
= 
as used in the Chemical Laboratory of the University of 
Pennsylvania. 
ul 
The preceding figure, represents a self-regulating reser= 
voir for hydrogen gas, (whether pure or sulphuretted 3) or for 
Nitric oxide, or carbonic acid gas. 
is very icuous engraving, requires but little to be 
said in explanation of it. Suppose the glass jar without, to 
re-enters the cavity of the bell, and the evo- 
lation of hydrogen is yenewed, and continued until again ar- 
rested, as in the first Instance, by reventing its escape, and 
consequently causing it to displace the acid from the interior 
of the bell, within which the zinc is sus 
