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Re: CuC12 in a SW bucket cap??



Original poster: "Mike Hollingsworth by way of Terry Fritz <twftesla-at-qwest-dot-net>" <megavolts61-at-yahoo-dot-com>

Hi All,
   There are a couple of things to consider in
comparing electrolytes and conductivity.  First, you
must compare the total number of ions that are in the
salt.  Copper chloride has three ions in the formula,
whereas copper sulfate has two.  But, you also have to
consider the solubilities of the electrolyte as well. 
I, unfortunately, am not at home, so I cannot look at
the data to make a comparison at this moment.
  One last thing to consider, that comes to mind that
relates to long-term stability of the cap:  the
corrosivity of the electrolyte.  Inevitably, a certain
amount of gases are evolved during operation.  Likely,
there is a small amount of acid formed when oxygen gas
is formed.  Comined with chloride, it would make a bit
of a corrosive electrolyte which would lead to etching
the electrodes, which over time could degrade
performance of the cap bank.  Sulfate is almost inert
by comparison and is used by industry in electrolytic
refinement of copper.  It does form a very weakly
acidic ion called bisulfate which acts as a buffer, so
it is not as corrosive as hydrochloric which is strong
acid.
   Terry found out that for good conductivity in
copper plating that a bit of sulfuric acid actually
had to be added for better conductivity in the
plating.  I don't know how that will relate to cap
operation, but maybe someone has already used copper
sulfate in SW caps and can tell us.  Seems that for
availability and corrosivity, the sulfate wins(of
these two salt anyway). 
  Cheers,
Mike