I have a case with two liquids: Water and another chemical which is miscible in water. The chemical has a density of 800 g/l so it's 20% less dense than water.

Initially the chemical was mixed with the water but now it has been sitting stagnant for 20 years.

Since such a long time has passed what could I expect to see in terms of the mixing of the liquids? Will the different densities have caused the two liquids to separate? Will there still be a trace of the chemical dissolved in the water?

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    $\begingroup$ Vodka is pretty much a binary mix of ethanol $(ρ = \pu{789 g L-1})$ and water. I have a 1970s bottle of Stoli from my grandfather and it's still a homogeneous ready-to-drink solution. So no, unless there were some chemical reactions involved resulting in building up of a residue of third component, there is likely no reason for a mix of miscible liquids to split. $\endgroup$ – andselisk Jun 12 '19 at 18:16
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    $\begingroup$ If the liquids are miscible, I would expect no separation at all. $\endgroup$ – electronpusher Jun 12 '19 at 18:16
  • $\begingroup$ If they were gasses then gravity will have an effect, but a column of gas kilometres high will be needed. Density will vary as $\rho=\rho_0 \exp(-Mg\Delta H/(RT))$ with $g$ acceleration due to gravity, $M$ molar mass (kg/mole) and $\Delta H$ elevation ( metres). You could increase the force used to separate by using a centrifuge. $\endgroup$ – porphyrin Jun 13 '19 at 11:37

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