«20 On the Quantity of Carbon in Carbonic Acid, 



Grains. 



6 o'clock P. M. 40 Total increase. Time. 



4- past - 407 + *7 



7 - - 4I-3 + -6 = 1,3 1 hour. 

 •J-past - 41-6 f '3 = 1,6 \\ hours, 



8 - - 4rS-f-'2 = 1,8 2 hours. 

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

 ing, to expose them n)orc conjplctcly. 



i past 8 - 42-5 + -7 = 2-5 2^ hours. 



9 - - 42-8 {-'3 = 2-8 3 hours, 

 •^past - 43-1 -f -3 = 3-1 3^ hours. 



10 - - 43-34-'2, = 3-3 4 hours, 



■ipast - 43-4 + -1 * = 3-4 44: hours. 

 Here it was left all night. 



10 A. M. - 45 +1-6 — o 16 hours. 



4 P. M. - 4.5 . 

 6 . - 44-5— -5 = 



9 - - 44-4— -1 = 



Next day. 

 •i-pastS A. M.44-94- -3 = 

 -.i-past 1 P. M. 44- 7— -2 = 

 10 - - 44-5— -2 = 



Hence charcoal seems to act as an hygrometer : its greatest 

 increase was 5 grains on 40, or 12-l per cent. And in order 

 to ascertain to what the increase of weight was owing, we 

 put 27'25 grains of charcoal, which had been thus exposed, 

 into a small bottle and tube connected with a receiver stand- 

 ing in the mercury bath, the whole of the vessels being also 

 filled with mercury in order to exclude common air. Heat 

 applied by an Argand'slamp produced gas equal to about half 

 the bulk of the charcoal ; but as soon as the temperature of 

 the mercury rose to 214" Fahrenheit, elastic fluid streamed 

 from every piece of charcoal, which quickly condensed, and 

 4-inch of the tube was occupied with water. 'Ibis proved 

 that our suspicion of the increase of weight being piiacipally 

 attributable to water, was well founded. 



The result of these, a|id other experiments, plainly point- 

 ed out the precautions which were aecesoary in order to ob- 

 tain an accurate result with charcoal ; for if we had weighed 



4 orair.s 



