VIII 



THE BURNING OF INFLAMMABLE GASES 



149 



this, Dumas and Stas 

 carried out in 1841 an 

 elaborate investigation of 

 the weight of carbonic 

 anhydride produced by the 

 combustion of different 

 forms of carbon (Ann. de 

 Chiniie, 1841, 1, 5 in ; 

 Stas's Works, I. 235 287). 

 For their combustion 

 they used (i) Natural 

 graphite, freed from mineral 

 matter by igniting with 

 potash, extracting with 

 acids, and finally heating 

 to a white heat in a current 

 of chlorine gas (Chap. XI) 

 during twelve to fifteen 

 hours. (2) Arti ficial 

 graphite separated from 

 cast iron and purified in 

 the same way. (3) Dia- 

 monds, of which 10 to 12 

 grams were burnt ; these 

 were used mainly because 

 the purified graphite had 

 become so porous that it 

 was difficult to weigh it free 

 from condensed air and 

 moisture. 1 



1 The property, which char- 

 coal possesses in a remarkable 

 degree, of condensing gases in 

 its pores, was discovered by 

 Fontana in 1777 and has been 

 used largely in recent work. 



a 2 



