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Re: More on ammonia

> Date: Thu, 23 Mar 2000 08:20:51 EST
> From: SCraig9087 at aol_com
> Subject: More on Ammonia
> Hi,
> Ammonia which is lethal can be converted to ammonium which is not lethal by
> reducing PH below 7.0.  Many "cheap" aquarium products use large amounts of
> sodium thiosulphate to reduce PH thereby converting ammonia to ammonium.
> Unfortunately, if your PH goes up the resident ammonium converts back to its
> lethal form.  Tropical Science makes a product (Complete Care) which breaks
> the chloramine bond and then converts the released ammonia into ammonium
> di-basic which is not sensitive to changes in PH.  I don't know about other
> products, but using straight sodium thiosulphate can be a problem.

Hi, no offense, but this message seems a bit muddled to me.  The first reason
is picky I know, but ammonia is not all converted to ammonium at pH below
7.0.  The relationship is logarithmic since it is directly related to pH.  In other
words an ammonia/water solution with pH of 7.0 has 10 times as much
ammonia present in the ammonium form as the same solution at pH of 8.0.
Second, sodium thiosulfate in solution with water has a neutral to alkaline pH
according to information in the MSD sheets eg.   http://siri.uvm.edu/msds/
So even if you added enough to have any influence on the pH, I don't think it
would lower it.  Certainly 1-2drops/gallon (normal dosage to neutralize
chlorine) of the already diluted solution (something like 4oz Na2S2O3/gallon),
does not have _any_ effect on the pH.

The problem with using only sodium thiosulfate with chloramine is indeed the
fact that it has NO effect on the ammonia released into solution.  It breaks
the bond with ammonia and chlorine and neutralizes the chlorine leaving the
ammonia in solution.  Yes, that ammonia will be mostly represented by
ammonium at lower pH, but the pH has nothing to do with the sodium
thiosulfate.  Unless I am completely off base, but I don't think so.
On the plus side you can use it as an antidote for cyanide poisoning, if
you ever find yourself in such a predicament ;-)