On the Decomposition of Water ly Charcoal. 305 



oflf water from the potash, and a gas began to be set free, 

 which issued incessantly during parts of the operation. This 

 gas was insoluble in water; it had a feeble empyreumatic 

 smell ; it did not disturb lime water, and it was inflam- 

 mable, burning like a mixture of hydrogen gas and carbu- 

 retted hydrogen gas : it made lime water turbid after its 

 combustion; when mixed with oxygen in Volta's eudio- 

 meter, it detonated by the electric spark. 



The disengagement was kept up a long time at a weak 

 heat ; nevertheless I increased the fire until the bottom of 

 the retort was red hot : I always obtained the same product, 

 only the hydrogen became purer. 



After some lime the disengagement of gas slackened. I 

 increased the fire : and when the retort was very red it be- 

 gan again; but the gas which I obtained this time was en- 

 tirely absorbed by the water, and by the lime water which it 

 rendered turbid. It was no longer inflammable, and proved 

 to be pure carbonic acid. At the end of the operation, how- 

 ever, it left a combustible residue, when it was shaken with 

 lime water: this residue was probably gazeous oxide of car- 

 bon. The potash had become almost white, and the re- 

 tort was attacked. 



It appears to me that we may explain this operation in, 

 the following manner : The water in presence of the char- 

 coal and of the potash, acts in the same way as when it is 

 in contact with an alkaline sulphuret or phosphuret. Car- 

 bonic acid and a carbonate are formed; since the potash 

 purified by lime may contain at this temperature a greater 

 quantity of carbonic acid than that which it contains al- 

 ready ; and if when the retort is red hot it is extricated from 

 this acid, this perhaps is merely owing to the combination 

 of the potash with the earths of the retort, a combination 

 which does not admit of the presence of carbonic acid. 

 Lastly, the gaseous oxide of carbon certainly proceeds from 

 the decomposition of a little acid by a residuum of charcoal. 



I confirmed this experiment on potash very much charred 

 and carbonated, obtained in the following manner : — I eva- 

 porated to dryness alcohol containing a great quantity of 

 potash in solution; not effervescing with the acids, but 

 very high coloured, although transparent. The evapora- 

 tion was effected in a silver vessel in order to obtain pure 

 potash : in proportion as the operation advanced, the potash 

 became very black ; and towards the end it swelled up, giv- 

 ing out an inflammable gas: filially, it became dry and 

 spongy. It was treated with water, and evaporated to dry- 

 ness without filtering ; it was black like charcoal, and ef- 



Vol. 36. No. 150. Oct. 1810. U 'fervesced 



