Re: NaOH Solution

lew wrote:

Any reason I shouldn't add it to a slush of crushed ice and cool water?

You can try to add a small amount to ice, but the NaOH will melt the ice and it will heat up markedly. It's safer to add a small amount (10% or so) to the water, let it dissolve, and permit the solution to cool before the next addition.

As I said:

> "If you intend to use it in that manner, care must be used
> when dissolving the sodium hydroxide. While dissolving,
> the solution temperature can easily exceed that of boiling
> water, and common containers made of plastic will melt,
> and glass will crack. The solution is very caustic, and
> can cause immediate damage to skin (deep ulcers) or blindness.

BTW, the 50% solution is inconvenient to use. Since it is a W/W
mixture (50 g NaOH + 50 g (ml) H2O), the amount of 50% solution required must be weighed before use. It isn't measured by volume. The advantage over dry NaOH is that the weight is more accurate since carbonates and water alter the composition of the crystals.

If you want a solution that is convenient to use, make up a 10% W/V
solution by adding 10g NaOH to 80 ml water, and after it dissolves, bring the volume to 100 ml. Then if you need 0.5 g, pour out 5 ml. That approach is more than accurate enough for photographic processing.
.

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