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Author: Subject: polypropylene caps for conc. H2SO4/HNO3
ahill
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[*] posted on 29-11-2016 at 18:43
polypropylene caps for conc. H2SO4/HNO3


I keep a bit of conc. H2SO4 and HNO3 around - I am not super happy with my acid bottles (ground glass stoppers wound with PTFE tape), and thought I'd buy some proper ones.

Westlab, who I have had good experience with in the past, recommended these and these when I asked - the 500/1000ml versions look like just the thing, and the price is OK - but I am a bit concerned about the caps - are these polypropylene/polystop caps suitable for storing 98% H2SO4 and 68% HNO3 ?
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Chlorine
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[*] posted on 29-11-2016 at 18:55


Polypropylene won't hold up against nitric acid or sulfuric acid. I'd suggest looking for an amber glass bottle with teflon stopper caps.
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Deathunter88
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[*] posted on 29-11-2016 at 20:14


Quote: Originally posted by Chlorine  
Polypropylene won't hold up against nitric acid or sulfuric acid. I'd suggest looking for an amber glass bottle with teflon stopper caps.


Because sulfuric acid isn't volatile and it isn't in direct contact with the cap, it is fine to store it with a polypropylene cap (or basically any cap for that matter). Nitric acid will eat through basically any cap except teflon caps. But it takes 5-10 years for this to happen so I wouldn't worry about it too much. Just change caps every 5 years and you should be fine.
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PeterC
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[*] posted on 11-12-2016 at 10:29


If you want a secure bottle with a GL45 cap (like the ones in the first Westlab link) all you really need to do is buy a PTFE lined GL45 cap (commonly red or blue with a red element). http://www.duran-group.com/en/products-solutions/laboratory-...
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ahill
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[*] posted on 11-12-2016 at 22:32


Thanks for the link Peter - these look like just the thing.

Now I have just got to find someone to sell me some.

I actually bought the clear westlab bottles I linked to. (after they assured me that they would be up to it) - and they _are_ lovely. I left a couple of drops of 98% H2SO4 on one cap for a few days with no visible effect, and so have pressed them into service - but wouldnt mind replacing / upgrading them to PTFE lined anyway.

How did you know the caps were GL45 ?
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PeterC
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[*] posted on 11-12-2016 at 23:39


GL45 is the stereotypical thread found on lab media bottles and if you check the manufacturers catalog (http://helmaus.com.au/wp-content/uploads/2014/10/28tgi_labor...) you'll see that all their bottles have a GL45 thread.
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