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Old Dec 17th 2017, 09:01 AM   #1
guineaman
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KNO3 solidification under increased pressure?

I used a blender to mill the potassium nitrate granules into finer powder, which worked just fine except that some of the KNO3 got between the rotating knife and the container's pivot. (See picture https://www.google.rs/url?sa=i&rct=j...13618772565000
) Anyway KNO3 is moderately soluble in water, so washing it was not a problem, except for that part between the rotor and the pivot. White solid coating is now permanently attached to the plastic and is not going away.
I tried scrubbing hard with water, no use.
Tried the same with acetic acid, no use. Tried to leave it immersed in acetic acid over night, nothing.
I even tried to use chlorine (bleach), it still won't go away.
I am assuming the KNO3 in that area was exposed to increased pressure and temperature, although I doubt that either of those was anything grand.
I kept the blender going for a full minute, so temperature could have gotten maybe to 50-60 Celsius (122-140F) at most.

My question is, what kind of reaction happened here?
Is the white solid coating still KNO3 or is it something else?
How can I dissolve the white solid coating?
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Old Dec 17th 2017, 09:14 PM   #2
oz93666
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I can't imagine any chemical change has occurred or any reaction with the plastic or metal .

This has to be potassium nitrate , just strongly impacted ,and hence slow to dissolve. I've observed the same thing in the ball mill I use to powder nitrate .. a ball mill will produce a finer powder than a blender.

It is soluble in water , no need to look for another solvent ... I would leave it soaking in water for as long as it takes to dissolve. (weeks)

If it won't dissolve , just ignore it (assuming you use this blender for food preparation ) ... it's a totally non toxic chemical, sometimes used in the food industry.

There is a remote possibility that if high temperatures were achieved (150 C) the powder mixed in with the softening/melting plastic .

Last edited by oz93666; Dec 17th 2017 at 09:34 PM.
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Old Dec 22nd 2017, 11:13 AM   #3
guineaman
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Thank you for your reply, I think you might be right about the softening of plastic and KNO3 getting mixed in. When I examine the surface of the plastic pivot, it seems that KNO3 is at the same level as the plastic itself. Never would have imagined such a high temeperature was achieved.
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