1824.] the Vapour of Water. 47 



7. Of the other solutions whose colour is changed bv deoxi- 

 dation, I examined acetate of silver, which became discoloured, 

 like the nitrate, but more feebly ; and muriate of platinum, 

 which underwent no alteration. 



8. Sea-water and solutions of common muriate of soda and of 

 muriate of magnesia, when boiled, and when the disengaged 

 vapour is passed through a solution of nitrate of silver, occasion 

 appearances of a more complicated nature. In this case, the 

 metallic solutionis decomposed, not merely by aqueous vapour, 

 but by the muriatic acid which is disengaged from the boiling- 

 liquid; and a quantity of chloride of silver is formed, which the 

 action of the aqueous vapour subsequently renders violet- 

 coloured, provided it at the same time raises the temperature of 

 the solution of nitrate of silver to the boiling point. Should any 

 portion of the nitrate of silver be left undecomposed, it is deoxi- 

 dized by the vapour of water, and a yellow or brown colour is 

 developed, which mixes with the violet, and imparts to it 

 various modifications of shade. My original opinion, therefore, 

 that the change of colour is caused by the muriatic acid which 

 distils over along with the water, is confirmed, but at the same 

 time restricted, by this experiment. Muriatic acid is also dis- 

 engaged from a boiling solution of the common muriate of soda, 

 although in much smaller quantity, than from a solution of 

 muriate of magnesia. "Whether in the case of muriate of soda, 

 the acid proceeds from a small residue of muriate of magnesia, 

 or muriate of iron, I do not venture to determine. Neither of 

 the bases (soda, magnesia) appears to pass over : at least, the 

 distilled water leaves no residue when evaporated. 



9. This yellow, reddish-brown, or dark-brown coloured solu- 

 tion of nitrate of silver, produced in so remarkable a manner by 

 the deoxidizing action of aqueous vapour, retains its colour for a 

 long time unaltered, but it at last deposits a dark-brown oxide 

 of silver. 



10. If previously to the introduction of aqueous vapour the 

 solution of nitrate of silver be raised to the boiling point bv the 

 immediate application of heat, it does not completely retain its 

 transparency utter having been exposed as usual to a current of 

 the vapour, but the discoloration which it sustains is greatly 

 inferior. 



v The deoxidizing property of aqueous vapour, demonstrated 

 beyond a doubt by the foregoing experiments, deserves to be 

 still further investigated, and would, perhaps, already admit of 

 some practical applications. It is my intention to continue my 

 experiments on the subject. Before concluding, I may observe, 

 that the vapour of water does not appear to produce any change 

 upon a solution of corrosive sublimate, or upon solutions of the 

 protoxide or peroxide of mercury in nitric acid. 



