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I believe that electrolysis of salt water creates lye ($\ce{NaOH}$ - sodium hydroxide). In salt water, there's $\ce{Na+}$, $\ce{Cl-}$, $\ce{H+}$ and $\ce{OH-}$ as of ionts.

So at cathode, you get $\ce{Na2}$ and that should react with water into $\ce{NaOH}$.

I want to test, if this is true - how do I do it with household items? The solution didn't react with aluminium.

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  • $\begingroup$ I found more general question asking about measuring pH using household items. $\endgroup$ – Tomáš Zato Aug 31 '14 at 22:52
  • $\begingroup$ The aluminium probably did not react because of its highly shielding oxide layer. $\endgroup$ – tschoppi Aug 31 '14 at 23:04
  • $\begingroup$ I scratched it. I think the solution is not concentrated at all. I've left a drop on my skin and nothing happened. $\endgroup$ – Tomáš Zato Aug 31 '14 at 23:06
  • $\begingroup$ A will filter out the copper chloride and procceed with electrolysis. $\endgroup$ – Tomáš Zato Aug 31 '14 at 23:06
  • $\begingroup$ Where did you make copper chloride now? This is starting to confuse me... $\endgroup$ – tschoppi Aug 31 '14 at 23:14
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The easiest way to measure the pH of a solution is to use an acid-base indicator. Limited to household supplies only, I would suggest a solution made from red cabbage, which should turn blue-greenish in the alkaline region.

The ions you actually get from your reaction is a higher concentration of $\ce{Na+}$ and $\ce{OH-}$, due to the fact that you are removing $\ce{H2}$ and $\ce{Cl2}$ (from $\ce{H+}$ and $\ce{Cl-}$ ions respectively) via the performed electrolysis. Under no circumstances would you generate a $\ce{Na2}$ species, you would rather write it as $\ce{2Na}$. Also, in aqueous solutions the $\ce{NaOH}$ most certainly dissociates. So speaking of the formation of solid $\ce{NaOH}$ from $\ce{Na}$ in water is quite a stretch.

Bottom line: Since the salt is already dissolved when you start the electrolysis, all you get is a change in concentration of the ions involved. The thereby induced change in pH can be measured observed using an acid-base indicator such as the juice of the red cabbage.

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  • $\begingroup$ So what happens to $\ce{Na+}$ ionts when I dry the water? I don't think I'm gonna get pure sodium... $\endgroup$ – Tomáš Zato Aug 31 '14 at 22:46
  • $\begingroup$ If you evaporate all the water, you will be left with a mixture of NaCl and NaOH. They need water to exist in their ionic form. $\endgroup$ – tschoppi Aug 31 '14 at 22:51
  • $\begingroup$ How does the sodium come in contact with chlor? I never meant to think that solid NaOH will appear in water by the way. But since that's what I get after drying the water, it's just about the same. $\endgroup$ – Tomáš Zato Aug 31 '14 at 22:54
  • $\begingroup$ Electrostatic interactions. And it comes in contact with chloride, not chlorine. (Chloride is the anion of chlorine.) $\endgroup$ – tschoppi Aug 31 '14 at 22:56
  • $\begingroup$ It is easy and cheap to buy pH testing strips from an aquarium store or from Amazon. I bought SEOH brand strips from Amazon.com and have been happy with them. I'm sure many others are just as good. $\endgroup$ – Curt F. Apr 10 '15 at 19:20

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