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Old 11th January 2009, 06:22 PM
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Default PMK - Part B very milky

Just mixed some PMK for the first time in ages. Part B is very milky. I used purified water, whatever that means, so I don't think that's a problem.
Do you rekon it will clear over the next 24 hours ?
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Old 11th January 2009, 06:43 PM
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Its also a long time since I mixed PMK. However I seem to recall that the Sodium Metaborate in part B was difficult to dissolve. I expect it will clear overnight?
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Old 11th January 2009, 07:33 PM
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I warmed it up and it has cleared completely.
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Old 12th January 2009, 09:10 AM
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Part B is generaylly highly saturated solution so when the temperature falls it will start to go cloudy or begin to precipitate out.
You can zap it in the microwave if in a hurry
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Old 12th January 2009, 05:53 PM
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Cloudy doesn't matter; when you add it to the water it effectively becomes less saturated and all dissolves.
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Old 12th January 2009, 06:38 PM
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Quote:
Originally Posted by Peter Hogan View Post
Cloudy doesn't matter; when you add it to the water it effectively becomes less saturated and all dissolves.
But presumably it does have to be completely dissolved?
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Old 12th January 2009, 07:09 PM
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What had happened is that the chemical was not completely dissolved as some of it was in suspension which is why it was milky. Having left it for around an hour, the chemical in suspension sank to the bottom and the remaining solution was almost clear. Warming it by placing the bottle in some hot water allowed that last bit to dissolve completely which is when it cleared completely.
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Old 12th January 2009, 08:10 PM
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It's called a super-saturated solution. It's an exo-thermic reaction, which means that as the chemical is dissilved it gives off heat. This warms the water. Warmer water can hold more of the chemical in solution. As the water cools some of the chemical precipitates out to form the solid again. Hence the cloudy liquid. Adding the cloudy liquid to water dilutes the mixture, allowing the excess chemicals to go back into solution - with a stir, of course. Sometimes the excess chemicals, if it gets pretty cold, will crystallize and form a solid layer on the bottom of the container. This is when you need to heat the liquid to dissolve the crystals. Using the B solution without dissolving the crystals will result in underdeveloped negs.
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