on the Vapour of Acids . 299 
weighed, it was I dw. 2 gr. In this procefs oz. of fixed 
air had been produced, and what remained of the air was of 
the ftandard of 0.94. Heating the brown powder to which 
the Pruffian blue was reduced in this experiment in inflamma- 
ble air, it imbibed 8f oz. m. of it, and became of a black 
colour ; but it was neither attracted by the magnet, nor was 
it foluble in oil of vitriol and water, as I had expedted it 
would have been. 
Again, I heated Pruffian blue in dephlogifticated air, of the 
ftandard of 0.2, without producing any fenfible increafe of 
its bulk, when I found three ounce meafures of it to be fixed 
air, and the ftandard of the refiduum, with two meafures of 
nitrous air, was 1.35. The fubftance had loft eleven grains, 
the greateft part of which was evidently water. 
To determine what quantity of fixed air Pruffian blue would 
yield by mere heat, I put half an ounce of it into an earthen 
tube, and got from it 56 oz. m. of air, of which i6oz. m» 
were fixed air, in the proportion of one- third in the firft por- 
tion, and one-fourth in the laft. The remainder was inflam- 
mable. There remained 5 dw. 20 gr. of a black powder, with 
a very little of it (probably the furface) brown. 
Comparing thefe experiments, it will appear, that the fixed 
air procured by means of Pruffian blue and dephlogifticated air 
r ~ 
muft have been formed by phlogifton from the Pruffian blue 
and the dephlogifticated air in the veflel : for if 240 gr. of 
this fubftance yield 16 oz. meafures of fixed air, ten grains of 
it (which is more than was ufed in the experiment) would have 
yielded only 0.6 oz. m. Nor is it poffible to account for the 
dilappearing of fo much dephlogifticated air, but upon the fup^ 
pofition of its being employed in forming this fixed air* 
