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I'm finally getting around to beginning to test this deep eutectic electrolyte. I mixed choline chloride with urea in a 1:2 mole ratio in a glass container. It formed a sludge. I sealed the container and then came back two days later to begin electrolysis and the mixture had formed a hard solid!

The whole time the mixture was at room temperature, and except for the mixing stage it was sealed.

So what am I missing? Is this a sign my reagents are bad? Or do these eutectics have a limited mixed life?

Update: Following Beerhunter's suggestion I ran the reagents in a blender until they formed a very liquid (low viscosity), homogenous mixture. But one day later the DES is crystallizing again at room temperature:

enter image description here

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You have to keep mixing the components until the liquid forms. If you have a sludge, you will have mixed something, but not everything intimately, so you won't have the correct component ratio. The DES is not going to form spontaneously, so leaving it will not have helped. We have had DES's remain as liquids for 6 months and counting.

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  • $\begingroup$ Are there any good indicators that it is properly mixed? Like do you know what sort of viscosity should be attained with these particular eutectics? Can water or some other solvent, and/or heat, be introduced to improve the mixing? $\endgroup$
    – feetwet
    Jan 23, 2016 at 14:26
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    $\begingroup$ We haven't measured the viscosity, but if you tip it at 45 degrees, it takes over a second to level itself. If it's mixed properly, it will become a liquid. We use automation, but old school is mortar and pestle. The literature frequently makes reference to using water to dissolve the solids, then evaporating the water (under vacuum may be better?) to leave the DES. DES properties can still be exhibited with small amounts of water, but obviously this composition change alters the properties vs the pure DES $\endgroup$
    – Beerhunter
    Jan 25, 2016 at 18:10

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