# Help on how to find and calculate Na concentrations from NaCl and convert NaCl in ppt to Na in milli-equivalents per litre

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I have a LAQUAtwin Salt 11 which has a NaCl mode and ranges from 0ppt to 100ppt (or 0% to 10.00%). I am wanting to work out the Na concentrations from the NaCl and I want to convert the Na component to Milli-equivalents per litre. I can't seem to find any information on the net to help me. Could anyone please help educate me with a worked example please? I would really really appreciate it. Thanks for looking  and my kindest regards to all.

newbie Chris

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Posted (edited)

1 ppt = 1 ng/ kg

NaCl molar weight is 58,5 g/ mol,

Na  molar weight 23 g/ mol

The ratio is 1 g NaCl is equal to 0,39 g Na

So 1 ppt NaCl is 0,39 ppt Na = 0,39 ng/kg Na

100 ppt correspond to 39 ng/kg

For the volume you need specific gravity of the solution.

Probably with this low concentratian it's 1 g/ml

Edited by chenbeier
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thanks heaps chenbeier 😀 that clears the first part up.  So how do convert the Na measurement to cmol/L.  for example:

Let say from a 50ml water solution with NaCl dissolved into it, I get a 100 ppt NaCl of which 0.39 ng/kg is Na as kindly demonstrated above.  (molecular WT being 23 g/mol)

How do I convert the Na measurement into cmol/L?

😅

thanks again Chris

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Posted (edited)

As I wrote to make it accurate you need specific gravity of the solution.

If you have this then you can convert ng/kg to ng/l

Roughly 1 kg ~ 1 l

The mass you can convert to mol  with n = m/M

In this case for 100 ppt it is  39 * 10^-9 g/ 23 g/ mol = 1,69 * 10^-9  mol

This amount is in 1 l, so the concentration is 1,69*10^-9 mol/l.

Edited by chenbeier

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