198 On Gems. 



That oxygen gas assists materially in the combustion of 

 the diamond, has been proved by some experiments made 

 by the London Philosophical Society *. These experiments 

 were suggested by Mr. Francillon, who supplied the stones 

 for that purpose from his cabinet. 



A diamond weighing ^^ths of a carat was exposed to the 

 action of a stream of oxygen gas upon ignited charcoal : in 

 one minute and fifty seconds it was found to have lost ^;^ths 

 of its original weight ; it had also lost its figure, transpa- 

 rency, and polish. The unconsumed portion was cut after 

 the experiment, and exhibited exactly the same lustre as 

 before. 



Several others were tried, with the same results : one, 

 which was accidentally thrown from the charcoal, was seen 

 distinctly burning during its passage through the air; the 

 flame was of a blueish pearl colour, and nearly 3-4lhs of an 

 inch in length. 



Guyton has proved, bv a series of experiments on the 

 diamond in oxygen gas, exposed to the action of the con- 

 centrated rays from the sun, that this substance is one of 

 the purest forms of carbon; aiid that the other known 

 classes of carbonaceous bodies are in intermediate states of 

 oxygenation, which to a certain degree increases their com- 

 bustibility, and power of decomposing the air. 



The difference between the degrees of temperature neces- 

 sary for the combustion of the diamond and charcoal are 

 as 188 to 2765 of a Wedgwood's scale. 



Charcoal set on fire in oxygen gas does itself maintain 

 the temperature necessary for its combustion ; but the com- 

 bustion of the diamond ceases as soon as it is no longer 

 maintained by the heat of the furnace, or the concentration 

 of the solar rays. 



The diamond requires for its complete combustion a 

 much greater quantity of oxygen than charcoal does, and 

 likewise produces more carbonic acid; for one part of char- 

 coal absorbs '■2^b'2^ of oxygen, and produces 3"575 of car- 

 bonic acid. But one part oF the diamond absorbs somewhat 

 more than four of oxygen, and really produces five of car- 

 bonic acid. 



The diamond is the pure state of carbon. Plumbago is 



its first stale of oxidation; charcoal its second; gaseous. 



oxide of carbon its third; and carbonic acid its completion. 



Guyton, to prove the carbonaceous property of the dia- 



xnondj converted soft iron into steel by cementation with 



* See Philosoj>Iiical Magazine, vol. viii. 



it. 



