weighed 33'82 grains, and that the same measure of carbonic acid
gas weighed 47-26 grains.
In the first experiment which they made upon the combustion of charcoal, four grains of box-wood charcoal were employed. and it was found that only firth of a grain remained of a white ash. The volume of gas employed appeared unaltered after the heat had sub- sided; but the combustion of 3'98 grains of charcoal had produced 29-13 inches of carbonic acid gas, or 13'76 grains; so that according to the experiment, 100 grains carbonic acid gas contains 28'92 char- coal. But by a computation founded on the quantity of oxygen con- sumed, it would appear that the quantity of charcoal is only 28-77 per cent.
In their next experiment 2'49 grains of diamond, in small frag— ments, were consumed. In this case, as in the former, the combus- tion caused no apparent increase or diminution of the quantity of gas; but there were found to be 18'20 inches of carbonic acid gas, in which the diamond would appear to be contained in the proportion of 2895 per cent. But again, by estimation from the weight of 18'20 inches of oxygen consumed, the proportion of diamond was slightly difi‘erent, being 28-81 per cent.
In this experiment, the authors could perceive no appearance of moisture or dullness on the surface of the quicksilver, or sides of the glasses; and they observed that the diamond had left no discoloura- tion of the tray, and no residual ash.
In a second experiment eleven small diamonds, weighing 4'01 grains, were consumed; and they produced 13'91 grains of carbonic acid gas, in the proportion of 2882 parts diamond for each 100 of
By a similar experiment upon stone-coal from Wales, such as is _employed by maltsters, the quantity of carbonic acid gas produced was found to contain 2820 per cent. of coal; but in this case the proportion deduced from the quantity of oxygen consumed, rather exceeded the estimate formed from the carbonic acid, instead of being less, as in former; experiments.
Carbonic acid formed in the same manner from the combustion of plumbago, contained 28-46 of carbonaceous matter, whether esti- mated from the gas produced, or from the oxygen gas consumed.
From the average result of these five experiments, the authors con- clude that 100 parts of carbonic acid contain 2813 of carbon, 9. quan- tity rather greater than appeared to Mr. Tennant, who did not find it more than 27'8: but this difference may easily be accounted for, by the different modes of operating.
The authors conclude, that the estimate given by Lavoisier at 28, which is between that of Mr. Tennant and their own, is very near the truth.
2ndly. That the diamond is pure carbon.
3rdly. That well burned charcoal contains no hydrogen, but soon absorbs moisture from the air. which would occasion fallacious results.
