We have hard water from our well. It is filtered twice before boiling it: by the water filter and with a manual on-the-counter filter. When boiled in a clean kettle a white substance floats in the water, and it isn't calcium which is hard and sinks at the bottom. Then we filter that hot water through a coffee paper filter and a white creamy substance remains. I called water related companies but no one knows. Anyone have a answer to this one?

  • $\begingroup$ You could always separate the white creamy substance and test it... $\endgroup$ – Eashaan Godbole Nov 7 '16 at 2:53
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    $\begingroup$ It may be an organic matter - proteins that is. Try drying it and burning it - if it turns black then it is organic. $\endgroup$ – vapid Nov 7 '16 at 8:50
  • $\begingroup$ Thank you. I'll do the drying and burning part for certain. $\endgroup$ – Pierre H. Nov 7 '16 at 18:00
  • $\begingroup$ did you try to burn the precipitate and if so what was the result? I have observed something similar with a white colloidal suspension forming after boiling water which eventually precipitates to the bottom of the kettle. This is totally different in appearance and behaviour to normal kettle scale that I've seen previously in the same kettle. I’ve tested the precipitate with indicator, it’s around pH10 BUT a flame test does not give any red/orange flame expected of calcium ions. We have a scale inhibitor cartridge treating our water supply so wonder if this has stopped working and/or is now le $\endgroup$ – Tee Jul 15 '19 at 14:46

I assure you it is calcium carbonate.

The particles are so small they do not just sink to the bottom like a stone. Instead, they aggregate at the nearest phase boundary. All small impurities do that, unless they have a very low interfacial tension with water. It's energetically much more favourable than sinking.

Over time, this creamy substance aggregates further, up to a point where the aggregates are large and dense enough to dissociate from the surface, and sink to the bottom.

  • $\begingroup$ Thank you Karl. This week I'll be installing a bigger water filter (adding salt to it or either potassium I'm told), hoping that it will get rid of that "calcium" as you say. If it is calcium carbonate in very small particles, then such calcium is unharmful to the body I presume. Small amount of natural calcium (126 mg/l from the analysis) can only be healthy. I really appreciate you feed back. Thank you. $\endgroup$ – Pierre H. Nov 7 '16 at 17:58
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    $\begingroup$ "adding salt to it or either potassium I'm told" What? Do you mean you have an ion exchanger like in a washing machine? That's not a filter, and I've never heard of using a Ca-Na exchanger for drinking water. $\endgroup$ – Karl Nov 7 '16 at 19:05
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    $\begingroup$ This is what they call a water softener. (Autotrol) And yes they add salt... unfortunately. $\endgroup$ – Pierre H. Nov 8 '16 at 0:12

Hard water often contains magnesium as well as calcium. A ppt of Mg(OH)2 or Mg2CO3(OH)2 would give a pH ~10 (Tee's result).

The ppt could be a function of the pH of the water; temporary hard water contains bicarbonates which are more soluble than the carbonates. When the water is heated, it drives off CO2, which could drive nano particles to the surface until they grow and fall.

Try dissolving the creamy ppt with acid (vinegar or HCl). That would give some indication of metallic nature. To be complete, you could try adding household ammonia (no soap in it) to see if you get dissolution (clarification of the liquid).

You could also take the twice-filtered, but cool, water and add sodium bicarbonate to see if you get a ppt. Then take the supernatant and boil it - there should be no more ppting. And likewise, to be complete, try adding a little vinegar to get a pH ~ 4-5; this would likely keep Ca and Mg in solution.

Magnesium gives no color in a flame test. https://en.wikipedia.org/wiki/Flame_test


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