I should point out first that I'm not a chemist, but I'm currently doing a little bit of chemistry; this should clarify that I don't have formal training in a chemistry lab (other than some basic chem classes in my BS).

So the question is this: what is standard practice for keeping salts moisture free if you can't afford a nitrogen generator system (or afford to swap nitrogen tanks out continuously with a desiccator chamber)?

I currently use iridium tetrachloride and I find that a few months after receipt, I have sludge (it's highly hygroscopic). I've tried storing in a tightly sealed bag with desiccant packs (the sealed kind) to no avail. I tried storing in a vacuum chamber but I can't hold vacuum for more than a few hours unless I have it on vacuum continuously (or hook it back up regularly).

I've been told by a local chemist that a simple vacuum desiccator chamber with a bunch of consumable silica gel at the bottom is about the best I can do, I just have to regularly pull vacuum again and swap the silica gel as soon as I see color change.


  • $\begingroup$ You didn't say what your "tightly-sealed bag is made of, but if it's plastic, those are generally permeable to small gas molecules like water vapor. What you need is a container made from metal or glass that can be hermetically sealed. I wonder if a mason jar would work. You also want a dessicant that attracts water more strongly than your hydgroscopic salt. It would also be helpful to drive off the moisture by heating prior to sealing—IrCl4 decomposes at 763 C, giving off toxic HCl(g), but I assume heating to ~100 C wouldn't be a problem. But check this first w/ the manufacturer. $\endgroup$
    – theorist
    Jan 9, 2021 at 6:09
  • $\begingroup$ Yup, it seems to be some weight of polyethylene, good call. Do you mean heat the whole chamber or just the salt container? $\endgroup$
    – PoGaMi
    Jan 9, 2021 at 15:38
  • $\begingroup$ My suggestion was about the container holding the salt. Put the salt and the dessicants in something like a mason jar, heat it to drive off the moisture from the salt and the dessicants (check to make sure this works for the dessicants you are using), and seal it. But before doing any of the above, check with the chemical company that supplies the salt for their guidance. They may even be able to supply appropriate dessicants and/or a container. $\endgroup$
    – theorist
    Jan 9, 2021 at 19:48


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