434 Some Experiments on the Comluslion of the Diamond. 



the results were such as to show that both substances afforded 

 the same quantities of ehistic fluid. 



I heated some ol" the carl)ouate from the diamond in a tube 

 which contained potassium, anci passed the potassium through 

 it in vapour : tliere was ignition, and a substance cf a dense 

 black colour was formed ; this substance was acted on bv dilute 

 nmriatic acid, wlien it left a fine black powder which, burnt like 

 lamp black, and ^\-hen thrown into fused nitre >cintillated and 

 disappeaied in the same manner as powdered charcoal. 



The gas that remained in the second experiment, after the 

 absorption of the carbonic acid gas, vividly supported combus- 

 tion, and diminished with nitrous gas ; but as the degree of 

 purity of the oxygen gas with which the globe vyas filled had 

 not been determined before the experiment, it was impossible 

 to ascertain with precision, that no elastic matter had been 

 emitted during the process. To determine this ])oint, I made a 

 third experiment. A thin diamond weighing -93 of a grain 

 was introduced into the platinum capsule, whicli was placed in 

 a globe filled with water and inverted in water; some oxygen gas, 

 the last portion from the decomposition of hyper-oxymuriate of 

 potassa, was thrown into the globe, so as to displace the water 

 below the level of the capsule. The focus of the great lens was 

 thrown upon the capsule, which with the diamond was instantly 

 rendered dry by it, and the diamond soon entered into combus- 

 tion and burnt as usual. After the process was finished, the 

 carbonic acid was al)sorbed by lime-water, and the remaining 

 gas, v,-hich equalled about one-third of the quantity of oxygen 

 originally used, was compared analytically in several experiment* 

 with a portion of the same oxvgen as that introduced into the. 

 globe, two measures of nitrous gas being added to a measure of 

 each of the gases ; the diminution was less by from -5-^ to -^-g- 

 parts in the cases in which the gas that had been exposed to 

 the action of the diamond was used; but this minute difference 

 is what might have been expected, and which indeed could not 

 fail to exist, when it is considered that, during the absorption 

 of carbonic acid gas by water and lime water, a small quantity 

 of common air is always expelled from the water. 



In this last experiment ;i small fraguient of diamond remained 

 imconsumed, which was similar in appearance to tliat mentioned 

 in the second experiment, and its colour, which was originally 

 yellow, was rendered rather darker. In no one of the three experi- 

 ments was there any distinct appearance of carbonization, when 

 the process was stopped in consecjuence of the impurity of the 

 gas ; though the diamonds were of various colouis and different 

 lustres. 



A piece of plumbago from Borrowdale in Cumberland, weigh- 



