Chemical Instruments and Operations, 



295 



Another process suggested. 



1 will take this opportunity of 

 suggesting, that the comparative 

 graviues of the gases might be 

 found, by means of tv>^o bodies, 

 counterpoised, as represented in 

 the accompanying cut, by ascer- 

 taining the rarefaction or conden- 

 sation of each gas, which would 

 make the bodies equiponderate 

 in it, as if it were atmospheric 

 air. In that case, the smaller 

 body should be of platina, which 

 of all bodies is the heaviest in 

 proportion to its bulk ; and the 

 larger should be of glass, as thin 

 as would be competent to sustain 

 the requisite changes of pressure; 

 since I know of no body, equally 

 firm, and impervious, which would 

 be as light in proportion to its 

 bulk. The changes of density ,^^^ 

 being effected by the air-pump or ^^^^^^== 

 condenser, might be measured by 

 means of a barometer gage. 



Protoxide of nitrogen or nitroics oxide. 



This substance does not exist in nature. When artificial- 

 ly obtained, it is gaseous ; yet the experiments of Mr. Fara- 

 day have taught us that under great pressure, it may be con- 

 verted into a liquid. 



Means of obtaining nitrons oxide. 



It may be obtained by the action of dilute nitric acid upon 

 zinc : by exposing nitric oxide gas to iron filings, sulphites, 

 or other substances, attractive of oxygen. It is best procur- 

 ed by exposing nitrate of ammonia to heat, and receiving the 

 product in an apparatus described in the following article. 



