*20 



Gain by a 

 week's expo- 

 sure to air. 



This probably 

 by absorption 

 of water. 



"Experiment 

 with willow 

 charcoal. 



ON THE QUANTIFY OF CARBOtflN CARBONIC ACID. 



These being exposed to the air during one week, increased 

 in weight thus : 



Fir 13 per cent. 



Lignum Vita • • 0/6 



Box 14 



Beech l6*3 



Oak 16-5 



Mahogany .... 18 



Certain quantities being confined in common air increased 

 very little in weight, and all in the same proportion ; we are 

 therefore much inclined to think, that this increase is owing 

 to an absorption of water from the air ; and we repeatedly 

 found, that the greatest increase of weight took place in the 

 first hour or two after exposure, and arrived at its maximum 

 in less than 24 hours, as the following experiment, selected 

 from several others, will prove. 



Forty grains of charcoal from willow wood, which had 

 been put into a bottle with a ground glass stopper immedi*- 

 ateltf after they were removed from the fire, were exposed in 

 the scale of a delicate balance, in a room where the thermo- 

 meter was 62° Fahrenheit, barometer 30*26. 



Grains. Total Increase. Time. 



6 o'clock P. M. 40 



\ past 407 + *7 



7 41*3 + •<> = 1*3 1 hour. 



I past 41*6 + '3 ~ V6 If hour. 



8 41*8 + -2 = 1*8 2 hours. 



The pieces were now spread out on paper after every weigh- 

 ing, to expose them more completely. 



£ past 8 42-5 -f 7 = 25 2f hours. 



9 42*8 + "3 n 2*8 3 hours. 



§ past • 43.1 + '3 ' — 3-1 3j hours. 



10 43-3 -f -2 c 3*3 4 hours. 



\ past 43*4 + -1 SE 3-4 4| hours. 



Here it was left all night. 



10 A. M. 45 +1*6 =: 5 lG hours. 



4 P.M. 45 



6 P.M. 



