on the Nature of certain Bodies. 73 
black, inflames spontaneously, and burns with a deep red 
light in the atmosphere.* 
The non-conducting nature of the diamond and its infusi- 
bility, rendered it impossible to act upon it by Voltaic elec- 
tricity ; and the only new agents which seemed to offer any 
means of decomposing it, were the metals of the alkalies. 
When a diamond is heated in a green glass tube with po- 
tassium, there is no elastic fluid given out, and no intensity of 
action ; but the diamond soon blackens, and scales seem to 
detach themselves from it, and these scales, when examined 
in the magnifier, are gray externally, and of the colour of 
plumbago internally, as if they consisted of plumbago covered 
by the gray oxide of potassium. 
In heating together three grains of diamonds in powder, 
and two grains of potassium, for an hour in a small retort of 
plate glass filled with hydrogene, and making the compara- 
tive trial with two grains of potassium heated in a similar ap- 
paratus, without any diamonds, I found that the potassium 
which had been heated with the diamonds, produced, by its 
action upon water, one cubical inch and of inflammable 
air, and that which had been exposed to heat alone, all other 
circumstances being similar, evolved nearly one cubical inch 
and T 7 -, both of which were pure hydrogene. 
In another experiment of a similar kind, in which fragments 
of diamonds were used in the quantity of four grains, the 
potassium became extremely black from its action upon them 
during an exposure to heat for three hours, and the diamonds 
• In the Bakerian Lecture for 1807, I have mentioned the decomposition of car- 
bonic acid by potassium, which takes place with inflammation. If the potassium is 
in excess in this experiment, the same pyrophorus as that described above is formed. 
MDCCCIX. L 
