Sxey.—Ovidation of Silver and Platinum. 333 
3. That silver thus modified by distilled water is brought back to the 
amalgamable state by contact for a short time with rain or 
spring water, also with acetic acid or ferrous sulphate, also by 
raising its temperature to about 500° F. 
4. That electric currents are generated by this metal in saline water 
free from chlorides, iodides, or bromides, also in water charged 
with any of these salts. 
5. That in dry air silver does not pass into this non-amalgamable state. 
6. That spongy silver immersed in an aqueous solution of sodic 
chloride (in an agate vessel) soon renders it very alkaline, 
These results, taken conjointly, signify, I think, undoubtedly that silver 
is a metal which oxidizes in a superficial way with far greater facility than 
we have heretofore considered possible. 
Thus, in experiment 1, I hold this metal is oxidized by atmospheric 
oxygen contained in the distilled water used, and the oxides of silver not 
being reducible or at least readily reducible by mercury, amalgamation is 
prevented or greatly retarded with water containing chlorides. In experi- 
ment 2, we must suppose the silver has also oxidized, but the oxide thus 
formed has been decomposed by the alkaline chlorides present, argentiferous 
chloride thus resulting as a secondary product, and this compound, being, 
as we know, readily decomposable by mercury, amalgamation proceeds with 
rapidity. However, in regard to silver thus acted upon by chlorides, I 
always noticed that amalgamation did not appear to proceed instantly 
when it was placed in contact with the mercury as clean silver does; there 
was, as it were, a momentary hesitation manifested by the mercury before 
amalgamation proceeded. 
The effect of acetic acid and of ferrous sulphate in experiment 8 is 
perhaps referable to a solution of argentiferous oxide in the one case, and 
to its reduction in the other. At the same time, however, we must con- 
sider that basic and insoluble silver salts may form here, and these, being 
readily decomposable by mercury, amalgamation is not retarded. The facts, 
Nos. 4, 5, 6, I think will be seen corroborative of the correctness of the 
conclusions I have above drawn. 
I may state in further support of this conclusion that I have observed 
silver, as precipitated from its nitrate, darken near the surface of the solu- 
tion, and itis only colourless and lustrous where distant therefrom, or when 
overhung by masses of silver. This darkening I attribute to a superficial 
oxidation of the silver by the atmospheric oxygen which has permeated the 
solution used. This metal also, contrary to general belief in regard to it, 
decomposes mercuric chloride. All these results were in the first place 
obtained from the metal electro-plated from its pure cyanide upon silver 
