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Author: Subject: GL45 bottles: blue cap versus red cap

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[*] posted on 29-11-2020 at 14:06
GL45 bottles: blue cap versus red cap

The GL45 reagent bottles commonly have blue caps (polypropylene), which I think are good for most situations. Also available are more expensive red cap versions; these have a PTFE liner. When would you prefer the more expensive red cap over the blue one?
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[*] posted on 29-11-2020 at 14:08

Looking at the compatibility charts, when you have to store something that could react with PP at any circumstances.

I have one bottle that leaks a little, no matter how tight I screw it. Also, toluene seems to react with the gasket band around the neck, it swells to larger diameter so it just falls off. Makes pouring more difficult as the ring has a rim that helps pouring.
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[*] posted on 30-11-2020 at 02:20

The red caps are much more durable in certain cases. I use these red caps for storing Br2, conc. HCl and certain organics. The blue caps are good for many chemicals, they are good for storing chemicals, which themselves not not very corrosive, but which need protection against air and moisture. I store Ca-metal and Li-metal in small Schott-Duran bottles with blue cap and this works great. When I take out some metal, I immediately after taking out some of the metal spray some butane gas from a cigarette lighter refill canister in the bottle and recap it, while there still are a few liquid drops of butane at the bottom. My Ca-metal still is shiny, after years of storage!

For storage of the truly agressive things, even the red caps do not work for more than half a year or so. My NbCl5, SO2Cl2 and PCl5 make the caps blister and dirty brown oil gets from below the PTFE-liner. The only thing, which works for long-term storage is glass ampoules with these chemicals. The red caps, however, do withstand 30% reagent grade HCl, Br2, CCl4, SO2(OH)Cl, oleum. The red caps withstand acyl chlorides, but only if they are not oxidizing. Eg. PCl5 and SO2Cl2 are in equilibrium with PCl3+Cl2 and SO2+Cl2, and the combination of this, with the acyl chloride, is REALLY corrosive. Even a red cap will be eaten away in months. Non-oxidizing acyl chlorides can be kept much better, e.g. benzoyl chloride, cyanuric chloride (as free flowing powder), acetyl chloride. PCl3, POCl3 and SOCl2 can be kept much better than SO2Cl2 and PCl5, but in the long run, the red caps also are destroyed by these reagents. It does take a few years instead of a few months with these chemicals.

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[*] posted on 30-11-2020 at 16:12

The red caps are more stable to high temperatures. The PP blue/orange ones can take short temps exposures of about 140C. The red caps can handle up to 200 C and have a taflon liner. 140 is enough to allow for autoclaving for sterilization, but just enough.

I have used the red caps on 100 ml media bottles to allow me to heat them up to about 150 C to run reactions in them (in a secondary heating container, behind a shield, in case of pressure buildup). They are very hard and quite industructable.

There are also other types of caps, I have some white ones with PTFE linings that are chemical resistant, but don't appear to be able to handle high temps, but not sure.
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[*] posted on 30-11-2020 at 17:58

HydrogenSulphate, I've got some teflon disks for cap liners that I can send you if needed. See
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