[bytheway]

Hello,

I need to make a solution that is 400mg/L of MgCl2 (anhydrous) and 55mg/L of NaHCO3.

I have the following ingredients:
-Magnesium Chloride Hexahydrate: MgCl2.6H20
-Bicarbonate soda
-Distilled water in 600ml bottles

How can I make stock solutions of the MgCl2 and NaHCO3 that I could use kitchen scales to measure the quantities ie whole grams diluted in 600ml of water, and then what quantity of these stock solutions would I add (using a syringe) to another 600ml bottle of water to get the desired solution (ie 400mg/L of MgCl2 (anhydrous equivalent) and 55mg/L of NaHCO3?

Also, is it as simple as adding the salts to the water and shaking in order to make the stock solutions?

Many thanks, Ben

[Hunter2]

Yes it is possible. First you have to convert from anhydrous to water containing product. This you can do with the molecular weight.  It is 95,21 g/mol and 203,1 g/mol. For 400 mg you need then   854 mg/l calculate with the volume 0,6 l = 512 mg. The Hydrogen carbonate is the 55 mg/l *0,6 l = 33 mg.

Now you can decide make stronger concentrates to get your end concentration by dilution.

[bytheway]

Thanks! Also, is it as simple as adding the salts to the water and shaking in order to make the stock solutions?

[Hunter2]

yes I think so.

[billnotgatez]

@bytheway
 

I could use kitchen scales to measure the quantities ie whole grams

 

Does your scales display in whole grams only or does it display to tenths of grams or hundredths?

[bytheway]

My current kitchen scales only display whole grams, but I will be getting a set that do tenths of a gram.  That's why I want to make the concentrated stock solutions and then dilute to reduce the effect of the imprecise scales

[bytheway]

Is this correct?

MgCl2: target concentration is 400mg/L
512mg of MgCl2.6H20 in 600ml water
51.2g of MgCl2.6H20 in 600ml water is 100x concentrated
Add 6ml of this to 600ml for correct concentration

NaHCO3: target concentration is 55mg/L
33mg of bicarbonate soda in 600ml water
9.9g of bicarbonate soda in 600ml water is 300x concentrated
Add 2ml of this to 600ml for correct concentration

[sjb]

Is this correct?

MgCl₂: target concentration is 400mg/L
512mg of MgCl₂.6H₂0 in 600ml water
51.2g of MgCl₂.6H₂0 in 600ml water is 100x concentrated
Add 6ml of this to 600ml for correct concentration

NaHCO₃: target concentration is 55mg/L
33mg of bicarbonate soda in 600ml water
9.9g of bicarbonate soda in 600ml water is 300x concentrated
Add 2ml of this to 600ml for correct concentration

Not quite, although depending on your application this may be good enough. You need to take your 6 ml (and 2 ml) sample and make it up to 600 ml. Also, it's not clear but should your final solution contain both magnesium chloride and sodium bicarbonate

[bytheway]

Ah yes...make it up to 600ml.  The solution contains both MgCl2 and NaHCO3.  I think this will be good enough because it is actually a recipe for water to brew coffee with that extracts the flavour from the beans well!

[bytheway]

Hi all, just wondering how I work out what the concentration of Mg2+and HCO3- ions is in mg/L or ppm in this solution? (ie  400mg/L of MgCl2 (anhydrous) and 55mg/L of NaHCO3) Thanks!

[bytheway]

Hi all, just wondering how I work out what the concentration of Mg²⁺ and HCO₃^- ions is in mg/L or ppm in a solution containing only 400mg/L of MgCl₂ (anhydrous) and 55mg/L of NaHCO₃. Thanks!

[Borek]

Hint: you need molar masses for that. There is one mole of Mg per one mole of MgCl₂.

[bytheway]

Thanks Borek, I think I know what you mean, will have a go when I get time and check my calculations with you.