[pure-silver] Re: baking soda as wash aid
- From: "John Black" <jblack@xxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 18 Feb 2005 17:29:40 -0500
>
> I disagree. Bicarbonate is a base form of carbonic acid. Carbonate is
> another base form of carbonic acid. Carbonic acid will lower the pH of
> either solution. Review of the freshman chem textbook is in order.
>
Sodium bicarbonate is used as the dissolved component in most, but not all,
tissue culture media so as to mimic the buffering system in the blood.
Bicarbonate freshly put in solution is acid. The solution, though, rapidly
becomes quite alkaline as the solution gives up CO2 into the air. If the CO2
concentration in the air is increased to about 5%, the solution pH is driven
down again towards neutrality. Bicarbonate only acts as a buffer in the
presence of excess CO2. One cannot talk about the pH of bicarbonate
solutions without regard to CO2 concentrations. At ambient air CO2
concentrations, the pH of baking soda solutions rises and becomes
substantially alkaline in fairly short order.
JB
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