Dana on Nitrous Gas. 339 



ble difference in tiie quantity of oxygene contained in the 

 air in different places, even in situations most favorable for 

 producing decided differences, provided no uneasiness is 

 produced by the respiration of such air. The experiments 

 of Cavendish are characterized by great accuracy, yet even 

 in his hands, nitrous gas seems to have been capricious in 

 its effects, producing at one time a diminution in a mixture 

 of 125 nitrous gas and 100 of air of 115 parts, at other 

 times of 121.2 parts. 



Chymists seem to have bestovi^ed peculiar attention on 

 this subject; both to ascertain the causes of variation in 

 the effects produced by nitrous gas in eudiometry, and to 

 discover some method of using it with unerring accuracy 

 in the analysis of the air ; yet there are other methods 

 which appear more eligible. Davy proposed to use this 

 gas condensed by absorption in a solution of muriate of 

 iron ; Dalton affirms that, if dilute oxygene gas and dilute 

 nitrous gas are mixed together in very narrow tubes over 

 wa'er, an uniform diminution of bulk occurs, and conse- 

 quently the proportion of oxygene can be deduced ; Dr. 

 Henry denies that any reliance can be placed on the indi- 

 cations of nitrous gas employed in Dalton's method, when 

 the air submitted to the examination, contains much more 

 or much less oxygene than 21 per cent. It is unnecessary 

 to refer to any other method of using this gas in eudiome- 

 try than that proposed by Gay Lussac ; a method which is 

 preferable to any other, since it affords uniform results. It 

 is almost unnecessary to say, that the method consists in 

 introducing a portion of air previously measured in a grad- 

 uated tube, into a wide vessel, like a tumbler, over water, 

 and afterwards adding an equal portion of nitrous gas ; red 

 vapours are produced ; the mixture is suffered to stand one 

 minute and then transfered to the graduated tube, and the 

 diminution in volume noted ; this divided by 4 gives the 

 quantity of oxygene. The diminution, if 100 parts of air 

 and of nitrous gas be used, will be nearly 84 parts ; and 

 84-^-4=21. In my own trials of this method, there has 

 been a close correspondence between the results, and those 

 afforded by Hydrogene and the electric spark. 



The true theory of the effect, thus produced by nitrous 

 gas, has never yet been explained in any chymical book ; 

 authors uniformly ascribe it to the formation and ahsorp- 



