Chemical Instruments and Operations. 297 
Apparatus for evolving and preserving nitrous oxide gas. 
A, represents a copper vessel of about eighteen inches in 
height, and nine inches in diameter, which is represented as 
being divided longitudinally in order to show the inside. 
The pipe, B, proceeds from it obliquely, as nearly from the 
bottom as possible. 
Above that part of the cylinder from which the pipe pro- 
ceeds, there is a diaphragm of copper, perforated like a cul- 
lender. A bell glass is surmounted by a brass cock, C, sup- 
porting a tube and hollow ball, from which proceed on op- 
ags, F F. 
fifty gallons, the smaller one, about fifteen gallons. 
The beak of the retort must be long enough to enter the 
retort so long, as to convey the gas into the water, without 
touching the metal; otherwise, the acid vapor will soon cor- 
rode the copper of the pipe, B, so as to enable the gas to 
escape. But while a small quantity of water is necessary, 
a large quantity is productive of waste, as it absorbs its own 
bulk of the gas. On this account, I contrived this appara- 
tus, in preference to using gasometers or air holders, which 
require larger quantities of water. E 
f the bags are closed by means of rivets, 
agreeably to the plan of Messrs. Sellers & Pennock for fire 
hose. The furnace is so contrived, that the coals, being 
situated in a drawer, G, may be partially, or wholly removed, 
in an instant. Hence the operator is enabled, without diffi- 
culty, to regulate the duration or the degree of the heat. 
This control over the fire, is especially desirable in decom- 
Vor. O.. 2. 11 
