274 



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 T Vth 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 28*95 per cent. But again, by estimation from the weight of 

 18*20 inches of oxygen consumed, the proportion of diamond was 

 slightly different, 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 28*82 parts diamond for each 100 of 

 gas. 



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 28*20 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 28*6 of carbon, a 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 re- 

 sults. 



