X6<2 COMBUSTION OF CHARCOAL AND OF HIDROGEN. 



previously heated red hot in the fire; for these two sub- 

 stances gave the same results. They assert, that dry char- 

 coal produces no water in burning, and contains no hidro- 

 gen : but the details of their processes show, that their re- 

 sults can be considered only as approximations sufficiently 

 doubtful, 

 burned char- In each of their experiments these gentlemen burned 



coa in too on ].. f our g ra i ns f charcoal, and it is impossible to obtain 

 small quantity. J 5 . ' . " 



accurate results with such small quantities. J hey esti- 

 mated the density of the oxigen gas and the acid gas by 

 weighing merely 21 cubic inches of these gasses, and de- 

 terminations of this kind should be made from much 

 larger quantities. We cannot justly give these results a 

 preference over those which Lavoisier, Fourcroy, Vauque- 

 lin, Seguin, and JBiot obtained with fifteen and even forty 

 Qitantity more times the quantity, and very sensible balances; though in- 



lmportantthan^ | ^ sensibility of a balance is a very inadequate 



accuracy of J . ' , 



weighing. compensation for a defect of quantity in the substance 



weighed. 



The experiments of Messrs. Allen and Pepys do not prove, 

 that charcoal previously heated red hot furnishes no hidro- 

 gen gas in burning: for they did not seek for this gas in the 

 air remaining after the combustion, and it is well known,, 

 that hidrogen gas will not inflame when it exists but in very 

 small proportion in oxigen gas. 



These considerations have induced me to make known my 

 researches on the same subjects, the diamond excepted, 

 which I could not burn; and they have led me to some im- 

 portant conclusions on the most usual eudiometrical pro- 

 cesses. 



Weight of oxigen gas and carbonic acid gas. 



VvVi»h»s of One of the most important points in the analysis is to de* 



©xi«ei> gas ami t ermme ^ ne exact weight of oxigen gas and carbonic acid. 



carbon. c acid + • 4 7 • 



examined. In a process so delicate I judged it proper, not to rely on 



my own experiments alone, but to take the mean of the re-» 



suits, that appeared to me most deserving confidence. The 



balance I used in the following experiments was made by 



Fortin. When loaded with the globe employed for weigh* 



ing the gashes it is sensible to a milligramme [0-01544 of a 



