6 Mr . Milner on the Production of 
and by a little perfeverance I was enabled to colled confidera- 
ble quantities of air, which on trial proved highly nitrous. 
I have fince frequently repeated this experiment, and have 
always in forne degree fucceeded. Much depends on the kind 
of manganefe employed, much on the heat of the furnace, 
and much on the patience of the operator ; as thefe are va- 
ried, there will be great variations of the products. A minute 
detail of all the particulars of my experiments feems unne- 
eeffary ; but it may be proper to give a general account of the 
principal fads, and of the methods which were ufed to avoid 
erroneous conclufions. 
ii. In general I made ufe of clean gun-barrels with which 
no previous experiments had been made. The manganefe 
was ufed in rough powder ; for when it is too finely pow- 
dered, the tube is choaked, and the air cannot pafs. 
In fome experiments I applied the vapour of the volatile 
alkali diredly to the hot manganefe. In others I fuffered 
the manganefe to remain a confiderable time in a red heat 
before I made the volatile alkali, contained in the retort at the 
end of the tube, to boil; and by this means I informed my- 
felf of the nature of the airs which the manganefe yielded 
per fe. 
In neither cafe could I ever perceive the leaft appearance of 
? 
nitrous acid or nitrous air till the volatile alkali was ufed. 
Manganefe, per fe , gives airs of different kinds (but chiefly 
fixed and dephlogifticated airs) as foon as ever it is fubjefted 
to a confiderable heat ; but nothing nitrous comes from it, 
either on the firft application of heat, or after it has been con- 
tinued a long time ; and I examined this point with great dili- 
gence. But foon after the volatile alkali begins to be applied, 
the jars in which the air is received will frequently turn 
flightly 
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