392 Dr. Turner's Chemical Examination of the Fire Damp, 



quite satisfactory. To myself, they do not leave the shadow of a doubt on 

 the question. Those who are not familiar with such researches, may be 

 warned that, in repeating my experiments, they will certainly fail of wit- 

 nessing the same phenomena, unless they are very scrupulous in having 

 pure gases, and in employing platinum balls with their full energy. The 

 influence of platinum on gases is modified by such very slight circumstan- 

 ces, that a small matter will cause a ball to be wholly inert which would 

 otherwise have acted with effect. 



In applying nitrous gas to determine the quantity of oxygen in fire- 

 damp, I employed the method of Dr. Dalton, as described in Dr. Henry's 

 Elements of Chemistry. A measured quantity of fire-damp was added to 

 the nitrous gas contained in a graduated tube half an inch wide, and the 

 gases were allowed to act on each other over water, without agitation. The 

 diminution of volume had attained its maximum in five or six minutes, 

 and in general much sooner. Of the total loss, ^yths. were taken as oxy- 

 gen. This method is not in all cases rigidly correct, but its indications 

 were sufficiently exact for my purpose, controuled as they were by the 

 action of platinum, by the analysis of the gas by detonation with oxygen, 

 and by the specific gravity of the gases. Before relying at all on this 

 method, however, I applied it in the analysis of gaseous mixtures, contain- 

 ing known quantities of oxygen gas. On applying it to the analysis of at- 

 mospheric air it indicated 204 per cent, of oxygen. On agitating the air 

 and nitrous gas, just after admitting them into the same tube, the diminu- 

 tion in volume was excessive. In a specimen of nitrogen gas, to which so 

 much air was admitted that the whole mixture contained 3 per cent, of 

 oxygen, nitrous gas indicated 3'3 per cent, of oxygen in one experiment, 

 and 3"2 in a second. With nitrogen, which contained 3'6 per cent, of 

 oxygen, nitrous gas indicated 4"4 in one trial, and in a second 4*1 per cent_ 

 of oxygen. In nitrogen gas, with 4 - 7 per cent, of oxygen, nitrous gas indi- 

 cated 4 - 7 per cent, in one trial, and 5 - 2 in a second. In nitrogen, contain- 

 ing 7"3 per cent, of oxygen gas, nitrous gas indicated 7*4 in the first expe- 

 riment, and 8 - 4 in the second. In the last case a large excess of nitrous 

 gas was employed. In nitrogen gas in one experiment, and 11 "5 in a se- 

 cond. In this last case, also, nitrous gas was used in large excess. 



