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I made $\ce{CoCl2}$ crystals by making a concentrated solution. After the crystals formed I took them out of the solution for drying. After a time I noticed that they were still wet so I dried off the water with a cloth and left them. Again they got wet and it seemed that the crystals just melted enough to get wet. No matter how many times I wipe them they again get wet. Currently I am keeping them in an airtight container inside refrigerator.

So why does it happen and is there a way to preserve $\ce{CoCl2}$ crystals?


My explanation: I think that it is possible that $\ce{CoCl2}$ crystals that I made exist as $\ce{CoCl2.2H2O}$ (which is purple, as are my crystals) and it reacts with humidity to form $\ce{CoCl2.6H2O}$ (pink in color, as was the wet melted crystal) Though I may be wrong.

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  • $\begingroup$ What color was your product initially and afterwards? You likely isolated crystals of a hexahydrate which is highly deliquescent. $\endgroup$
    – andselisk
    Nov 29, 2019 at 13:35
  • $\begingroup$ I have added in the question, anyway the salt was dark purple-pink, the crystals are very dark purple and the melted crystal is dark pink. So how do I preserve deliquescent crystals ? $\endgroup$ Nov 29, 2019 at 13:41
  • $\begingroup$ Well, your explanation makes sense, the salt is hygroscopic and forms higher crystallohydrates gradually which are all deliquescent. There is no melting to speak of, the salt is getting dissolved in water vapors from the air, that's all. Are you asking why this is happening in this particular case or how to prevent it? $\endgroup$
    – andselisk
    Nov 29, 2019 at 13:48
  • $\begingroup$ Did you flush the airtight container with dry N2 before sealing it? That's a good way to keep things dry. Also put something in the container that will absorb any remaining moisture. $\endgroup$
    – Andrew
    Nov 29, 2019 at 13:52
  • $\begingroup$ @andselisk I was asking why this was happening and how to prevent it. I guess keeping in airtight container and removing moisture is the only way? Can I try coating the crystals with something like transparent nail polish ? $\endgroup$ Nov 29, 2019 at 14:13

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