From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: sci.chem
Subject: Re: Electrolysis - NaOH
Date: Sat, 15 Aug 1998 15:46:14 GMT

On Sat, 15 Aug 1998 10:57:20 +0000, andymcfar-x-@netmatters.co.uk
(Andy McFarlane) wrote:

>Matthew Steinbroner <msteinbroner@electrosynthesis.com> wrote:
>
>> You're forgetting the extra hydrogen...the outcome of this is the
>> chloralkali industry.
>> Take brine:produce caustic and hydrochloric
>>
>HUM..... I don't think so. You seem to be forgetting your
>electrochemistry. The outcome of elecrolysis of brine is the production
>of chlorine (and some oxygen apparently) at the anode and production of
>hydrogen at the cathode.


HUM again.... Not necessarily. The electrochemistry that I still
remember tells me that it depends on the cathode used. When the
cathode is mercury then sodium metal is indeed deposited at the
cathode instead of hydrogen (due to the overvoltage of hydrogen on Hg)
and the sodium amalgam reacts with water in a second chamber to
produce sodium hydroxide and hydrogen.

This was common practice and the careless containment of mercury (or
lack of containment) led to some serious mercury contamination which
hit the industry (1974) like the proverbial waste product hits the
fan.

Notable examples were in Michigan, the Niagara River, and several
locations in Canada. All hell broke loose for the chloralkali
business.

>So that's what happens to the extra hydrogen.
>Of course what's left in the aqueous solution is sodium hydroxide. The
>real chloralkali industry. Note the name, if you were right wouldn't it
>be the hydrochloralkali industry?
>
>Andy McFarlane
>
>Nipa Labs