CHAPTER XIII 



THE DECOMPOSITION OF THE ALKALIS 



A. THE COMPOSITION OF AMMONIA 



Alkalis regarded as elements. At the time when 

 Priestley succeeded in collecting " acid air " and " alkaline 

 air" over mercury as permanently-elastic gases, there was 

 no reason for supposing that either of these gases was other 

 than a simple substance. The fixed alkalis were also still 

 undecomposed and were generally thought to be simple, or 

 elementary, substances. 1 Thus Higgins, in a treatise, " On 

 Bleaching," published in 1799 (p. 18), writes : 



" Pure pot-ash, according to our present knowledge of 

 chemistry, is a simple elementary substance." 



The first alkali to be decomposed was the volatile alkali 

 which Priestley called "Alkaline air," and Bergman 

 " Ammonia." The decomposition was effected almost 

 simultaneously by Priestley himself and by Scheele, 

 Bergman's illustrious pupil. 2 



Priestley (1775) decomposes " alkaline air." Priestley, 

 in 1773, found that "alkaline air" was inflammable. In 



1 Lavoisier, however, suspected that they might be compound (see 

 below, p. 280). 



2 " It was well observed to me by a near relation of Bergman that 

 the greatest of Bergmarfs discoveries was the discovery of Scheele " 

 (Thomas Beddoes, 1786). 



