the several Gases in the At ynosphere . 35f 



In ail these cases the oxygen enters into combination and 

 loses its elasticity ; and if the several processes be conducted 

 skilfully, the results are precisely the same from all. In 

 all parts of the earth, and at every season of the vear, the 

 bulk of any given quantity of atmospheric air appears to be 

 reduced nearly 21 per cent, by abstracting: its oxygen. This 

 fact, indeed, has not been generally admitted till lately ; 

 some chemists having found, as they apprehended, a great 

 difference in the quantity of oxygen in the air at different 

 times and places; on some occasions GO per cent, and on 

 others 30 and more, of oxyeen are said to have been found. 

 This I have no doubt was owing to their not understand- 

 ing the nature of the operation, and of the circumstances 

 iutluencing it. Indeed, it is difKcult to see, on any hypo- 

 thesis, how a disproportion of these two elements should 

 .ever subsist in the atmosphere. 



As the first of the processes above mentioned has been 

 much discredited by late authors, and as it appears from 

 my experience to be not only the most elegant and expedi- 

 tious of all the methods hitherto used, but also as correct 

 as any of them when properly conducted^ I shall, on this 

 occasion, animadvert upon it. 



1. Nurous gas may be obtained pure by nitric acid di- 

 luted with an equal bulk of water poured upon copper or 

 mercury ; little or no artificial heat should be applied. — 

 'J'iie last product of gas this way obtained does riot contain 

 any sensible portion of azotic gas ; at least, it mav easily be 

 got with less than 2 or 3 per cent, of that gas. It is pro- 

 bably nearly free from nitroui oxide also, when thus ob- 

 tained. 



2. If 100 measures of common air be put to 36 of pure 

 nitrous gas in a tube 3- lOths of an inch wide and 5 inches 

 long, after a few minutes the whole will be reduced to 7!) 

 or 80 measures, and exhibit no signs of either oxygenous 

 or nitrous gas. 



3. If 100 measures of common air be admitted to 72 of 

 nitrous gas in a wide vessel over water, such as to form a 

 thin stratum of air, and an immediate momentary agitation 

 be used, there will, as before, be found 79 or 80 measures 

 of pure azotic gas for a residuum. 



4. If, in the last experiment, less than 72 measures of 

 nitrous gas be used, there will be a residuum containing 

 oxygenous gas ; if more, then some residuary nitrous gas 

 will be found. 



These facts ckarly point out the theory of the process : 

 the elements of oxygen may combine with a certain portion 



of 



