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Author: Subject: Cleaning the cooling jacket of a condenser
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[*] posted on 14-2-2024 at 23:54
Cleaning the cooling jacket of a condenser

This is just to report on something interesting I noticed, maybe it's of use to others if they find themselves in a similar situation.

I had acquired a jacketed coil condenser with some really nasty stains in the cooling mantle. The coil was full of brown stains, and there were some thick white deposits in the outer cooling jacket, all over, so it looked like cooling water had evporated several times in the condenser.

First I soaked the condenser in ~500 g/L citric acid solution overnight (I used a syringe to inject it into the mantle until it was full), which cleaned up the brown stains quite nicely and left me with a neon green solution (probably iron?). The white deposits were still very visible however. A mixed cleaner containing citric, tartaric and malic acid fared similarly.

So it was suggested to me to try soaking in strong sodium carbonate solution, since sulfates would probably be converted into the carbonates, which then should be much more susceptible to acid. I filled the condensers cooling jacket with a strong solution of Na2CO3 and let it sit. Curiously, after a few hours already I could see the stains dissolve, which was not what I was expecting. After sitting overnight, pretty much all the thick white deposits are now gone. (Then I rinsed with another portion of citric acid and then clean water several times.)

It was suggested to me it might've be a silicatic stain, but other people said old dried silicates are probably not that much easier to dissolve than the glass itself - and the stain really did dissolve and not just crumble off like in a base bath.

Either way, this managed to clean the condenser really well off the water stains. Maybe it helps someone who faces something similar.

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[*] posted on 15-2-2024 at 04:53

Nice to know, thanks.

Is there a treatment for the inner surface of the cooling jacket that will minimise the formation or retention of bubbles?

(a wastefully high water flow rate helps remove bubbles,
I've read that a West condenser addresses this problem, but,
if efficiency is necessary then I use my Dimroth
For 10/14 I only have short fat Leibigs so a treatment would be good,)

CAUTION : Hobby Chemist, not Professional or even Amateur
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[*] posted on 15-2-2024 at 07:19

I've found sodium carbonate and percarbonate to be very effective cleaners, no matter what the stain is.

“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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[*] posted on 15-2-2024 at 23:27

Reddish brown stains are iron, so a hydrochloric acid soak generally does the trick.
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[*] posted on 16-2-2024 at 05:11

In my lab red stains are from microbial contamination/films. They are stubbornly resistant to most things other than mechanical manipulation with small brushes which on some condensers is out of the question. A concentrated ABF solution though makes short work of them. I've also one one occasion used a small piece of pipe cleaner and pushed it through with water pressure.

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[*] posted on 27-2-2024 at 18:32

I often clean condensers in HCl, sodium dithionate also is good to remove iron stains. Of course the base bath often will remove enough glass to take off any stains. I use one daily at work for various goo and gunk to remove.
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[*] posted on 28-2-2024 at 15:23

Yep I'd try strong sodium carbonate solution as suggested, H2O2 (30%+), HCl, or sulphuric acid. My last line of defence is piranha fluid, which I'm currently using to clean a flask of unknown nastiness.
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