18^0.] On two new Compounds of Chlorine and Carbon. 33 



of changing it out of daylight ; nor have I been able, even in 

 the sunshine of this month, to make hydrogen act on chloride 

 of silver in several hours. 



Still, however, hydrogen may be allowed in certain circum- 

 stances to have the power of decomposing chloride of silver, 

 but the circumstances are not such as were, I believe, gene- 

 rally supposed to have place in the experiment first referred 

 to. When zinc, iron, tin, &c. are thrown into moist chloride 

 of silver, the first decomposition is occasioned by the action of 

 the zinc on the chloride, afterwards a voltaic circle is formed 

 by the zinc, the reduced silver and the water; water is de- 

 composed, the zinc takes oxygen, the hydrogen liberated at 

 the surface of the silver takes the chlorine from the chloride 

 in its immediate neighbourhood, and thus the reduction will 

 go on to the distance of an inch or more from the piece of 

 zinc, and the consequent products are silver and solution of 

 muriate of zinc. But as this is a case of decomposition entirely 

 different to the supposed one of the reduction of chloride of 

 silver by hydrogen, any denial of the latter is not at all invali- 

 dated by the truth of the former. 



On two new Compounds of Chlorine and Carbon, and on a new 



Compound of Iodine, Carbon, and Hydrogen*. 



[Read Dec. 21, 1820.] 



ONE of the first circumstances that induced Sir H. Davy to 

 doubt the compound nature of what was formerly called oxy- 

 muriatic acid gas, was the want of action of heated charcoal 

 upon it ; and considerable use of the same agent, and of the 

 phenomena exhibited by it in different circumstances with 

 chlorine, was afterwards made in establishing the simple nature 

 of that body. 



The true nature of chlorine being ascertained, it became of 

 importance to form all the possible compounds of it with other 

 elementary substances, and to examine them in the new view 

 had of their nature. This investigation has been pursued with 

 such success at different times, that very few elements remain 

 uncombined with it ; but with respect to carbon, the very cir- 



* Phil. Trans. 1821, p. 47, and Phil. Mag. lix. p. 337. 



D 



