^94 Dr. Priestley’s 'Experiments 
formed ; whereas, in the other cafe, it was communicated to 
the water in the worm- tub. 
In one of the proceffes with boiling fpirit of fait, in a glafs 
tube, hermetically fealed, I had the fame white vapour danc- 
ing in the middle of the tube as in the experiment with the 
oil of vitriol ; but this tube burfl, and I never had the fame 
appearance again, though I repeated the experiment feveral 
times for the fake of it. 
The vapour of dephlogifticated marine acid, which M. 
Berthollet difcovered, and with which water may be im- 
pregnated as with fixed air, being made to pafs through the 
hot earthen tube, became dephlogifticated air as in the follow- 
ing experiment. 
Having poured a quantity of fpirit of fait upon fome man- 
ganefe in a glafs retort, I heated it as in the preceding experi- 
ments with a proper apparatus both for receiving the diftilled 
liquor, and the air. I found feven-tenths of the air was fixed 
air, and the remainder very pure dephlogifticated. The quan- 
tity I could not meafure on account of one of the junctures in 
the apparatus giving way ; but I do not imagine that quite fo 
much pure air could be got in this method as from the manga- 
nefe itfelf in a direct procefs. The liquor received in this dis- 
tillation refeinbled ftrong fpirit of fait in which manganefe had 
been put. 
This procefs immediately fucceeding that in which the glafs 
tube, joining the earthen tube and worm-tub, was left full of 
black matter by the diflillation of the alkaline liquor (which 
will be mentioned hereafter), the blacknefs prefently vanifhed, 
and the tube became tranfparent as before. On this account, 
however, it is poffible that I might receive lefs pure air than I 
fhould otherwife have done* 
Diftilled 
