218 On the Quantity of Carton in Carhonic Acidj 



receiver R, equal to two inches: the communication with 

 the gasometer was then closed, and the column was support- 

 ed without alteration. This was always tried previous to, and 

 after every experiment. As the joints would bear this degree 

 of exhaustion, we were confident they would resist a much 

 greater pressure than we had any occasion to employ. The 

 glass tubes GG, which connected the platina tube with the 

 gasometers, enabled us to observe any flash arising from the 

 combustion of hydrogen which might be contained in the 

 substances subjected to experiment. In order to avoid prolix- 

 ity, we shall generally state the method which was invariably 

 followed. 



We soon found that oxygen gas, even when secured in 

 bottles with ground glass stoppers, was not always to be de- 

 pended upon, but was sensibly deteriorated by keeping ; and 

 therefore in all our experiments we made the gas within an 

 hour or two of the time of using it, and always from the 

 hypcroxygenised muriate of potash. Its degree of purity 

 ■was constantly ascertained by the eudiometer before every 

 experiment, and was generally determined in about 10 

 minutes. The solution employed was that recommended by 

 professor Davy; namely, the solution of green sulphate of 

 iron saturated with nitrous gas *j and whenever (he dimi- 

 nution had arrived at its maximum, and the gas began to 

 increase in volume, we substituted a simple solution of the 

 green sulphate of iron for that saturated with nitrous gas, 

 and always had the most satisfactory results : for the simple 

 sulphate absorbs any nitrous gas which may have escaped 

 from the saturated solution, and the residuum in this case 

 enables us to ascertain exactly the quantity of oxygen con- 

 tained in the gas. 



\\re determuied to make our first experiment with char- 

 coal, and as Morozzo and Rouppe had ascertained the absorb- 

 ing properties of this substance, and as our results must 

 obviously be influenced by it, our attention was directed to 

 this point. — ^The fallowing quantities of diflTerent kinds of 

 wood, sawed into slips -^ of an inch were weighed : — 



* This solution ibsorbs oxygen much more rapidly in warm weather than 

 in cold. 



White 



