When combined with DI, my 98% calcium hydroxide resulted in a pink solution. I am trying to make limewater for a class demonstration and have only ever seen limewater as a colourless solution. Anyone else had this issue?


  • 3
    $\begingroup$ Why organic-chemistry tag? Is there an organic substance or indicator present in the solution? DI usually stands for "deionized". Deionized what, water? How clean was the glassware? Could you upload a photo and specify lighting conditions to eliminate possible light scattering effects? $\endgroup$
    – andselisk
    Feb 9, 2022 at 11:32
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    $\begingroup$ Try different water ( even tap one ) and different glassware/vessel. Still pink ? If still pink then my educated guess says there must be a pink dye in the calcium hydroxide lot. If not there may be dye contamination of the vessel, possibly some phenolphthaleinum from prior activities. $\endgroup$
    – Poutnik
    Feb 9, 2022 at 11:48
  • $\begingroup$ Thank you for your responses, it seems a phenolphthaleinum contamination was the issue and subsequent attempt to make limewater have resulted in a clear solution. Thanks! $\endgroup$ Feb 9, 2022 at 11:53
  • $\begingroup$ It's almost as if there were phenolphthalein in the solution. $\endgroup$ Feb 9, 2022 at 14:41


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