i44 Dr. Priestley’s Experiments on the 
till it became of a deep orange colour ; and when it was opened 
under water, there came out of it 2.83 oz. m. of air exceedingly 
turbid, of the ftandard of 0.66, with two equal quantities of 
nitrous air, when that of the common air, with one equal 
quantity of nitrous air, was 1.07. Computing in the manner 
above mentioned, there was in the tube before the procefs 
0.7477 oz< m * phiogifticated air, and after the procefs 
0.8792 oz. m. But the dephlogifticated air, amounting to 
1.7 oz. m. being of the ftandard of 0.66, will be found to 
contain 0.374 oz. m. of phiogifticated air, which being de- 
duced from 0.8792, there will remain only 0.5052 oz. mu 
which is confiderably lefs than 0.7477 oz. m. 
That the nitrous acid can become coloured, without imbibing 
any thing from phiogifticated air, is evident not only from its 
becoming fo when heated in vacuo , as defcribed above, but 
alfo, when it was in contact with any other kind of air, as free 
from phiogifticated air as I could make it. But from the man- 
ner in which thefe experiments were neceffarily made, it was 
impoffible intirely to exclude phiogifticated air, either as part 
of the atmofpheric air, or as contained in the impurities of the 
air that I made ufe of ; for I firft filled the tube with fpirit of 
nitre, then plunging the orifice of it in a veffel of the fame, I 
introduced a quantity of the air which I wiflied to expofe to it* 
After this, putting my finger upon the orifice, I turned it up- 
fid e down, and applying to it the clofed end of a glafs tube, of 
about the fame diameter, I fealed it hermetically with a blow- 
pipe as expeditioufly as I could. This is a neceffary imper- 
fection in the experiment; but I know not howto remedy it, 
if any of the acid is to be left in the tube. However, the 
phiogifticated air introduced in this manner from the atmo- 
fphere muft have borne a very fmall proportion to the air in 
7 ' the 
