1818.] Combustion of the Diamond. 11 



Combustion of the Diamond*. 



SIR H. DAVY was the first to show that the diamond was 

 capable of supporting its own combustion in oxygen without 

 the continued application of extraneous heat, and he thus 

 obviated one of the anomalies exhibited by this body when 

 compared with charcoal. This phenomenon, though rarely 

 observed, is easily exhibited. If the diamond, supported in the 

 perforated cup, be fixed at the end of a jet, so that a stream 

 of hydrogen can be thrown on to it, it is easy, by inflaming the 

 jet, to heat the gem, and whilst in that state to introduce it 

 into a globe or flask containing oxygen. On turning off the 

 hydrogen the diamond enters into combustion, and will remain 

 burning until nearly consumed. The loss of weight in the 

 diamond, the formation of carbonic acid, and the actual com- 

 bustion are thus very easily shown. 



Description of a New Apparatus for the Combustion of the 



Diamond-\. 



IN the course of the experiments which Sir Humphry Davy 

 made at Florence on the combustion of the diamond, he dis- 

 covered that when the gem began to burn in an atmosphere of 

 pure oxygen, having free access to it on all sides, it would 

 continue burning, though the original source of heat were 

 removed, until the particles were rendered so small as to be 

 too readily cooled by the little platinum tray which supported 

 them. (Philosophical Transactions, 1814, p. 557.) In conse- 

 quence of this observation, an idea arose, that if the diamond 

 were well heated, and then introduced into oxygen, it would 

 go on burning, and afford an easy method of exhibiting- its 

 combustibility. Upon trial this was found to be the case, and 

 a notice to that effect put in this Journal (see above). Since 

 then, an apparatus of this kind has been perfected, and is now 

 represented in Plate I. fig. 1. 



It consists of a glass globe, of the capacity of about 140 

 cubic inches, furnished with a cap, having a large aperture ; 

 the stopcock, which screws into this cap, has a jet A rising 



* Quarterly Journal of Science, iv. 155. t Ibid. ix. 264. 



