It may be noted here
that increasing the size of the cells does not necessarily increase the
intensity of the current.
In two determinations on pure electrotype copper the following results
were obtained:--
Copper Taken. Copper Found.
0.8988 gram 0.8985 gram
0.8305 " 0.8303 "
The presence of salts of ammonia, &c., somewhat retards the deposition,
but has no other ill effect.
The organic matter generally present in copper ores interferes more
especially in the colorimetric determination of the residual copper. It
can be detected on dissolving the ore as a light black residue insoluble
in nitric acid. It is filtered off at once, or, if only present in small
amount, it is carried on in the ordinary process of the assay and
separated in the last filtration before electrolysis.
The following experiments were made to test the effect of the presence
of salts of foreign metals in the solution during the precipitation of
copper by electrolysis:--
--------------+----------------------------------------+---------------
Copper Taken. | Other Metal Added. | Copper Found.
--------------+----------------------------------------+---------------
0.1000 gram | 0.1000 gram of silver | 0.1800
0.1050 " | 0.1000 " " | 0.
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