I have created a solution that should contain hydroxide ions. Therefore, the pH > 7, but is there any way to roughly estimate the pH in absence of any indicator? Maybe using current, or checking whether it dissolves certain chemicals?

Please mind that I am limited in equipment and so complex science is not feasible for me.

  • $\begingroup$ You could make your own red cabbage indicator $\endgroup$
    – alemi
    Commented Jul 13, 2014 at 16:12
  • $\begingroup$ I cannot make that,... I am not allowed to by the household ;p so in that respect I am restricted $\endgroup$
    – user209347
    Commented Jul 13, 2014 at 16:25
  • $\begingroup$ Basic solutions are slippery (like soap). $\endgroup$
    – LDC3
    Commented Jul 13, 2014 at 16:34
  • $\begingroup$ How accurate do you need to be, and what kinds of materials are realistically available to you? Is there any particular reason why you can't purchase some inexpensive litmus paper or a universal indicator? If you expect the solution to be highly basic, then you may be able to get a very rough qualitative sense of its basicity by reacting it with an acid and measuring temperature change. Another possibility is reacting it with soluble salts of common metals (e.g., calcium or magnesium) and looking for a precipitate of the insoluble hydroxide. Use a control sample of plain water for comparison. $\endgroup$
    – Greg E.
    Commented Jul 13, 2014 at 16:40
  • 5
    $\begingroup$ If the household don't allow you to use red cabbage indicator I really don't know what else more easy and safety to do you can use :-) $\endgroup$
    – G M
    Commented Jul 13, 2014 at 17:05

1 Answer 1


Have you tried with red or black tea? It turns lighter in acidic media and turns dark in basic media. I tried once adding the pulp juice of one lemon to a cup of tea and it lighted up (mainly for acetic acid), then I added NaOH-based salt and turned very black and opaque.

Maybe that suits for your solution.

  • 1
    $\begingroup$ The ideal solution for me! Thank you! Maybe you have a chemical explanation? That would be very nice. $\endgroup$
    – user209347
    Commented Jul 23, 2014 at 14:57
  • $\begingroup$ Good and not a simple question, I believe oxidation - reduction of polyphenols play that role. You can look at this for approach: www.worldoftea.org $\endgroup$
    – Orr22
    Commented Aug 1, 2014 at 14:00
  • 1
    $\begingroup$ I just tested it with earl grey and it works! $\endgroup$ Commented Sep 1, 2014 at 16:21

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