NH4Ac-Miniprep becomes bad - why?

Keith Leppard Keith.Leppard at warwick.ac.uk
Fri Aug 30 06:32:25 EST 1996

jose.mejia at well.ox.ac.uk (Jose E. Mejia) wrote:
> > Just a guess... Do you store your Amm.Acetate soution at room 
> > Temperature? In that case, you do not have much of it left in soln. after 
> > a month.
> 1. What's happening to the ammonium acetate solution stored at room
> temperature? Is there a known explanation?
This is digging back a bit in my on-board computer but here goes:

Ammonium acetate is a salt of a weak acid and a weak base and as such
will exist in equilibrium with ammonium hydroxide and acetic acid. The 
ammonium hydroxide is itself in eqm with ammonia and H20. Both ammonia 
and acetic acid are volatile and so their solutions will be in eqm with
the vapour phase which diffuses out of the bottle. Hence, as time goes
by, the ammonium acetate ends up as gaseous acetic acid and ammonia. 
Low temp will slow down the loss from solution.

Keith Leppard

> 2. The lysis solution is unstable, because atmospheric CO2 dissolves into
> the alkaline solution very readily and neutralizes NaOH. A fine
> precipitate of sodium carbonate may be visible.
> Jose
> -- 
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> Windmill Road, Oxford OX3 7BN, UK
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> Email: jose.mejia at well.ox.ac.uk

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