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Topic: About the presence of magnesium and calcium in water  (Read 1857 times)

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Offline Student99

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About the presence of magnesium and calcium in water
« on: February 10, 2015, 08:21:03 AM »
How to determine the presence of magnesium and calcium in water?

Basically, I have 3 bottles:

1- Water with calcium
2- Water with Magnesium
3- Water with calcium and magnesium

I need to know how to identify them.

I have to identify them using a simple and convenient method. After, we'll need to develop a water treatment to precipitate the magnesium and calcium. Water softening is a good method, but firstly we need to identify the bottles.

Any idea?

Thanks in advance!

Offline Zyklonb

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Re: About the presence of magnesium and calcium in water
« Reply #1 on: February 10, 2015, 03:03:04 PM »
What anions are in solution? Calcium sulfate is sparingly soluble while magnesium sulfate is quite soluble, so if the solutions are concentrated enough, add a soluble sulfate salt. If a precipitate forms, it's calcium or calcium and magnesium. If a precipitate does not form, it's magnesium.

Offline kriggy

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Re: About the presence of magnesium and calcium in water
« Reply #2 on: February 10, 2015, 04:22:38 PM »
I suppose instrumental methods are out of qusetion? You could determine the one with magnesium by using flame test since magnesium doesnt color flame and calcium gives red flame. Then you could add murexide to the remaining two (it makes a complex with Ca but not with Mg) and that will tell you which one is calcium and which one is both of them.

Offline Hunter2

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Re: About the presence of magnesium and calcium in water
« Reply #3 on: February 12, 2015, 01:18:20 AM »
I suppose instrumental methods are out of qusetion? You could determine the one with magnesium by using flame test since magnesium doesnt color flame and calcium gives red flame. Then you could add murexide to the remaining two (it makes a complex with Ca but not with Mg) and that will tell you which one is calcium and which one is both of them.

But How you can figure out with this, what is what you have complexed Calcium and non complexed magnesium. And now?

Offline Borek

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Re: About the presence of magnesium and calcium in water
« Reply #4 on: February 12, 2015, 03:03:09 AM »
But How you can figure out with this, what is what you have complexed Calcium and non complexed magnesium. And now?

No, EDTA titration will determine the sum of both.

Not that it is necessary to mix methods, in pH high enough to precipitate Mg(OH)2 it is possible to determine Ca only.

I seem to remember determining both concentrations in one titration, titrating Ca at high pH first, then adding ammonia buffer and continuing till the second endpoint. But I can't remember what indicators we have used, and I do remember getting correct results was tricky.
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