Pyro
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does anybody have an idea as to what happened?
hi,
today I took my dry K2CrO4 out of my evaporation dish (I made it from K2Cr2O7 and KOH) and when i washed the dish I got a big surprise!
the entire bottom of the dish was frosted! Could the KOH I used have caused this? i never heated it over 140*C. wouldn't it take a lot longer to do
this?
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Hexavalent
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What's with the magical '140*C'?
Concentrated solutions of alkali metal hydroxides will eat glass anyway, how long was the KOH solution in contact with the glass for?
I've seen this happen a few times and have a got a few beakers in this kinda state.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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Pyro
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3 days. whenever I was there I heated it. but when I was heating it i saw the temp. on my hotplate and it was mostly between 95-120* because
temperature has to do with how fast an alkali attacks glass.
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Hexavalent
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Naturally, as it is a chemical reaction between the KOH and the SiO2 in the glass to make potassium silicate.
Even at these temperatures you mention, a fair amount of dissolving would have taken place, particularly if the solution was concentrated.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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woelen
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Yes, Hexavalent is right. Even at room temperature, strong alkalies can attack glass. I once had a glass jar, which held a saturated solution of NaOH.
I kept it in the jar for a week or so and after that week I could clearly see to what level the liquid was stored.
Never keep strongly alkaline solutions in glass for more than a few hours at room temperature and not more than a few minutes at higher temperature
around 100 C.
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