With allotropic
silver the case is very different, the particles dry in optical
contact with each other, the surfaces are brilliant, and the material
evidently continuous. That this should be brittle indicates a totally
different state of molecular constitution from that of normal silver.
_Specific Gravities._--The allotropic forms of silver show a lower
specific gravity than that of normal silver.
In determining the specific gravities it was found essential to keep
the sp. gr. bottle after placing the material in it for some hours
under the bell of an air pump. Films of air attach themselves
obstinately to the surfaces, and escape but slowly even in vacuo.
Taken with this precaution, the blue substance, B, gave specific
gravity 9.58, and the yellow substance, C, specific gravity 8.51. The
specific gravity of normal silver, after melting, was found by G. Rose
to be 10.5. That of finely divided silver obtained by precipitation is
stated to be 10.62.[1]
[Footnote 1: Watts' Dict., orig. ed., v. 277.]
I believe these determinations to be exact for the specimens employed.
But the condition of aggregation may not improbably vary somewhat in
different specimens. It seems, however, clear that these forms of
silver have a lower specific gravity than the normal, and this is what
would be expected.
Chestnut Hill, Philadelphia, May, 1889.
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