Panache
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On the practical use of piranha solution
So how do you piranha a larger vessel? All the seemingly obvious answers to that question are rather unacceptable, either on the basis of cost (both
monetarily and environmentally), or safety.
Has anyone ever made up 5l of piranha, does the temperature ramp past boiling? That would be horrible, I’ve had it spew over due to metal ions
catalysing it’s breakdown too quickly but it wasn’t boiling and it wasn’t 5l, still ate a hole in my nicely finished timber bench.
I know analytical heads often use piranha on glassware, so there must be a way better than swirling.
Does remind me of that old chemistry adage ‘only the inside of the flask needs to be clean...’
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Sulaiman
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For a 5l rbf, a H2O2 + HCl solution will clean most stains,
no need for 5l of solution - just stopper all but one hole and swirl occasionally,
quicker/more active if heated but often not required.
Cheaper is a moderately concentrated KOH solution.
I've not tried an alcohol base bath but they seem to be highly recommended.
I think that the best is to know what you are trying to dissolve and use a suitable solvent.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Texium
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Yeah, they're great! Glass comes
out shiny and brand-new looking every time, and the problems with etching are over-exaggerated. As long as you don't soak it for a week or more you
won't have issues, and even the enameled labels on the glass (as long as it's a reputable brand that uses a durable enamel) will not come off under
those conditions, in my experience.
If you use your glassware regularly, and you can afford to, buy a drum of anhydrous isopropanol and a couple kg of KOH. Get a 5 gallon bucket with a
lid from the hardware store, and dissolve about 500 grams of KOH per 4 liters of isopropanol. Keep the lid on at all times to prevent evaporation and
fumes. Avoid putting wet glassware in, to prevent dilution of the bath with water, and it will last you a really long time before you need to change
it out.
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Panache
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Quote: Originally posted by Texium (zts16)  | Yeah, they're great! Glass comes
out shiny and brand-new looking every time, and the problems with etching are over-exaggerated. As long as you don't soak it for a week or more you
won't have issues, and even the enameled labels on the glass (as long as it's a reputable brand that uses a durable enamel) will not come off under
those conditions, in my experience.
If you use your glassware regularly, and you can afford to, buy a drum of anhydrous isopropanol and a couple kg of KOH. Get a 5 gallon bucket with a
lid from the hardware store, and dissolve about 500 grams of KOH per 4 liters of isopropanol. Keep the lid on at all times to prevent evaporation and
fumes. Avoid putting wet glassware in, to prevent dilution of the bath with water, and it will last you a really long time before you need to change
it out. |
This is an excellent idea and I actually have a spare 20l of ipa, is it essential that’s its Koh or is naoh to all intents and purpose identical.
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Texium
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I believe that KOH is preferred because it is more soluble in isopropanol than NaOH. NaOH may still work well enough, but I haven’t tried it before.
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clearly_not_atara
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^on the contrary, I think KOH is preferred because it is less corrosive to glassware.
http://www.sciencemadness.org/talk/viewthread.php?tid=15633#...
http://doi.org/10.1007/BF00911336
Sodium hydroxide corrodes silicate glasses of all compositions to a greater extent than all the other hydroxides. It is proposed to call this
phenomenon the “sodium anomaly.”
[Edited on 04-20-1969 by clearly_not_atara]
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Bmoore55
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I am currently using a piranha solution to clean some alumina crucibles right now. But when it comes to glassware I have always used a KOH base bath
to remove organics. And Texium is right, the etching problem is usually very exaggerated.
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Texium
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Interesting! I had no
idea
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draculic acid69
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I also thought Koh would be just as damaging as naoh.
Nurdrage dried lioh in a flask and no noticeable damage
was observed.guess it is just sodium
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