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- 

 posite sides, two pipes terminating in gallows screws, D D, 

 for the attachment of perforated brass knobs, soldered to 

 flexible leaden pipes communicating severally with leathern 

 bags, F F. The larger bag, is capable of holding about 

 fifty gallons, the smaller one, about fifteen gallons. 



The beak of the retort must be long enough to enter the 

 cylinder so that the gas in passing from the mouth of the 

 beak, may rise under, and be caught by the diaphragm. 

 This is so hollowed as to cause it to pass through the perfo- 

 rations already mentioned, which are all comprised within a 

 circle, less in diameter than the bell glass. The gas is, by 

 these means, made to enter the bell glass, and is, previously 

 to its entrance, sufficiently in contact with water, to be 

 cleansed from the acid vapor which usually accompanies it. 

 On account of this vapor, the employment of a small quan- 

 tity of water to wash the gas, is absolutely necessary ; and 

 for the same reason, it is requisite to have the beak of 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. 



The seams of 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- 



VoL. XVI.— No. 2. 1 1 



