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1820.] 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 circumstances to have the power of decomposing chloride of silver, but the circumstances are not such as were, I believe, generally 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 decomposed, 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 invalidated 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.]

of the first circumstances that induced Sir H. Davy to doubt the compound nature of what was formerly called oxymuriatic 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