Date:         Thu, 20 Apr 1995 22:15:55 -0600 (MDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Jack Reed <jackr@fortnet.org>
Subject:      Re: Speaking of batteries...



On Thu, 20 Apr 1995, Alistair Bell wrote:

> 
> 
> On Wed, 19 Apr 1995, Jack Reed wrote:
> 
> > I have several pounds of EDTA kicking around my office that I'd like to 
> > get rid of.  When used according to directions, EDTA will reduce and/or 
> > prevent sulfation of battery plates, the number one killer of young 
> > batteries.
> > 
> 
> Jack, whats the principle behind this? I use EDTA
> (ethylamine-diamine-tetra-acetic acid) at work in some buffer recipes. It
> functions, in my applications, as a divalent cation chelator. In other
> words, it binds ions like Ca+2, Mg+2. Its this property that is used in

Exactly the same action occurs in a lead-acid battery.  Not being a 
chemist, I can't specify the exact reactions for you.  My understanding 
of it thought is that the EDTA binds to the sulfate ion in a weak bond.  
Both ions then sink to the bottom of the tank, where the sulfate ion 
remains in a non-conductive state.  The EDTA ion then is free once again 
in solution to bond with other sulfate ions.

As I said, strictly layman's terms, but I can hunt up the aforementioned 
papers and send them to you for a more technical explanation.  Btw, EDTA 
is also used in Orange Crush to remove the aluminum ion from that 
solution.  Also to remove heavy metals poisoning, such as lead, from 
those too young to know better.  It's extremely benign, even in high 
concentrations, as I'm sure you're aware.

> the somewhat controversial arteriosclerosis treatment. The EDTA is
> supposed to bind and solubilize the Ca+2 (calcium ions) in plaques.
> The electrochemistry of the lead acid battery is well known, but not by me
> right now! I forget what the valence state(s) of the sulfur/sulphate are.
> 
> 
> Alistair, who is going to get the right textbook  
> 

Let me know what you find.

Jack