I used my water kettle (metal ones, not the plastic ones) to boil my water. Usually, if I did not consume all the water in the kettle and the water was cold, I usually topup extra water to the kettle and turn it on to boil.

So, after many weeks of boiling in this way, I notice that there are white powder outside the kettle. (I notice that when the water is boil, some water was splashed to the outside of the kettle and I left those water splashed out to dry as time goes)

Is the white powder actually called fluoride? How do I tested it to verify if the white powder chemical is safe or not?

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    $\begingroup$ I've never seen a kettle where that hasn't happened :) If you're concerned, clean it off. But take notice that it's actually coming out of the water. So drinking the water pure will mean you're getting more of it than you are when you've boiled it. $\endgroup$
    – user1160
    Feb 7, 2013 at 14:19
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    $\begingroup$ As BBftw's answer says, the white powder is probably largely calcium carbonate. Chalk is calcium carbonate. So the white powder is probably no more harmful than chalk. $\endgroup$ Feb 12, 2013 at 10:55
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    $\begingroup$ You can clean out the kettle by boiling with some white vinegar. // By boiling the water you're boiling out carbon dioxide which makes the solution more basic. This makes mainly calcium carbonate precipitate. $$\ce{Ca(HCO3)_{2(aq)} -> CaCO3_{(ppt)} + CO2_{(gas)} + H2O}$$ $\endgroup$
    – MaxW
    Nov 9, 2015 at 3:34

2 Answers 2


It's likely that your home is supplied with "hard" water (that is, water with a high mineral content). These dissolved minerals typically include calcium or magnesium ions (from dissolved calcium bicarbonate and magnesium bicarbonate, respectively). Heating or boiling your "hard" water in a kettle will soften it by precipitating the calcium carbonate as its solubility decreases with increasing temperature.

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This (calcium carbonate) could be the white powder you have observed after evaporation. Hard water should not pose any health risks, and in fact can add some extra calcium and magnesium to your diet. If it's still concerning to you, there are hundreds of products available that can soften your water before you use it, just google "water softener" and you'll be overwhelmed.



I live a place where the water is extremely hard, and I regularly remove calcium carbonate from my electric heater. The method is quite simple: fill the kettle with water, add citric acid (as solid) and heat. You will notice a lot of gas which is carbondioxide (CaCO3 + 2H+ -> Ca2+ + H2O + CO2). You can use any acid but citric acid is cheap.

  • $\begingroup$ You can also boil a bit of white vinegar, should dissolve it as well. $\endgroup$
    – kenorb
    Jan 20, 2018 at 14:05

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