138 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



34 cubic inches of air which burns without detonating, 

 producing a very beautiful blue flame." 



" These two last experiments give an inflammable air of 

 quite a peculiar character ; for it does not make the 

 smallest explosion, nor the least noise when inflamed, 

 after mixing with common air or with dephlogisticated air ; l 

 from which it follows that there appear to. exist up to the 

 present two distinct kinds of inflammable gas ; one which 

 inflames rapidly with explosion and great noise when mixed 

 with common ^atmospheric air, and which detonates still 

 more strongly *when mixed with dephlogisticated, or pure 

 air ; and the second, which although mixed with the two 

 preceding gases, always burns quietly without noise." 

 (Mem.Acad. Sci., Paris, 1776, 90, 686-696 ; p. 691.) 



Priestley (1785) prepares an inflammable gas from 

 smithy scale. A few years later, in 1785, Priestley noticed 

 the production of a similar inflammable gas during the 

 reduction of SMITHY SCALE, or FINERY CINDER, the bluish- 

 black calx formed when iron is burnt in air. 



" Having made the scales of iron, and also the powder of 

 charcoal very hot, previous to the experiment, so that I was 

 satisfied that no air could be extracted from either of them 

 separately by any degree of heat, and having mixed them 

 together while they were hot, I put them into an earthen 

 retort, glazed within and without, which was quite impervious 

 to air. This I placed in a furnace, in which I could give it 

 a very strong heat ; and connected with its proper vessels to 

 condense and collect the water which I expected to receive 

 in the course of the process. But, to my great surprise, not 

 one particle of moisture came over, but a prodigious quantity 

 of air, and the rapidity of its production astonished me ; so 

 that I had no doubt but that the weight of the air would 

 have been equal to the loss of weight both in the scales and 

 in the charcoal; and when I examined the air, which I 

 repeatedly did, I found it to contain one-tenth of fixed air, 

 and the inflammable air, which remained when the fixed air 



1 i.e., oxygen. 



