Sodium Hydroxide: solution shelf-life?

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Does anyone know what the expected shelf-life of should be? I'm talking about a solution in the 10% range. Also, any idea on how long is might last when filled vs. repeatedly open and partially filled, as would be the case with a solution used for daily use. I'm assuming, of course, a tightly capped amber bottle.

Any ideas on extending the working life of the solution--an additive that might prevent it from combining with carbon dioxide when exposed to air, but would not alter its characteristics?

-- Ted Kaufman (writercrmp@aol.com), July 27, 2001

Answers

A 10% solution of Sodium Hydroxide will keep indefinitely. I'm not being funny; indefinitely is the scientific term for 'until the cows come home'.

-- Pete Andrews (p.l.andrews@bham.ac.uk), July 27, 2001.

Thanks, Pete. Does that include a bottle that is repeatedly opened and closed and not filled completely?

-- Ted Kaufman (writercrmp@aol.com), July 27, 2001.

Ted:

Indefinitely - as many times as you open and shut the bottles. The only difference will be a miniscule difference in concentration if the humidity is different each time you open it-the difference being in parts per million.

If you took a bottle of 10% NaOH (Sodium Hydroxide) and placed it beside a standard silver print, the print would fade (100 yrs) before the NaOH would change. It may dissolve a bit of the glass bottle, but it would not deteriorate. Of all the photochemicals used, it is most likley the least affected by time or oxygen.

Yours chemically.

Richard

-- RICHARD ILOMAKI (richardjx@hotmail.com), July 27, 2001.


Ted, do you, by any chance, have a freezer full of Ektaflex materials, just waiting silently to be awakened by a kiss of Sodium Hydroxide?

-- Bill Mitchell (bmitch@home.com), July 27, 2001.

Suggestion: review freshman chem.

Even though sodium ion and hydroxide ion are stable, I wouldn't make too much solution especially if frequent bottle opening is expected, concentration is rather low, or stable pH is required.

There are some CO2 available in air, which is easy to dissolve in alkaline solutions. The result will be in loss of OH ions because CO2(g) + water produces protone and this protone and OH- form water. Thus H+ is removed from one side of CO2 equation and therefore CO2 is extremely readily soluble into hydroxide solution. Sodium hydroxide is a strong base, near 100% dissociation and pH is not buffered at all.

-- Ryuji Suzuki (rsuzuki@rs.cncdsl.com), July 28, 2001.



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