258 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



1775 ne discovered further that it was decomposed by 

 electric sparks, increasing largely in volume, and was thus 

 converted into an inflammable gas which was insoluble in 

 water. 



" I dipped a lighted candle into a tall cylindrical vessel, 

 filled with alkaline air, when it went out three or four times 

 successively ; but at each time the flame was considerably 

 enlarged, by the addition of another flame, of a pale yellow 

 colour ; and at the last time this light flame descended 

 from the top of the vessel to the bottom. At another time, 

 upon presenting a lighted candle to the mouth of the same 

 vessel, filled with the same kind of air, the yellowish flame 

 ascended two inches higher than the flame of the candle. 

 The electric spark taken in alkaline air is red, as it is in 

 common inflammable air " (Priestley, Experiments on Air, 



I. 175). 



" I took the electric explosion in a small quantity of 

 alkaline air, in the same manner as in the two preceding 

 experiments, and observed that every stroke added consid- 

 erably to the quantity of air ; and when water was admitted 

 to it, just as much remained unabsorbed as had been added 

 by the explosions. I then took about an hundred explosions 

 of the same jar, in a larger quantity of alkaline air ; after 

 which, so much of it remained unabsorbed by water, that I 

 could examine it with the greatest certainty. It neither 

 affected common air, nor was affected by nitrous air, and 

 was as strongly inflammable as any air that I had ever 

 produced " (Experiments on Air, II. 239-240). 



Scheele (1774) oxidises ammonia by means of "man- 

 ganese." The inflammable nature of ammonia was also 

 recognised by Scheele in his essay " On Manganese "(17 74). 

 It has been shown in a preceding chapter (p. 210) that this 

 mineral dissolves in dilute acids only in presence of reducing 

 or deoxidising agents, substances "rich in phlogiston," as 

 Scheele described them. Amongst these substances was. 

 the volatile alkali ammonia, the salts of which were able to 

 dissolve the mineral when acids alone failed to act upon it. 



