Anyone know how to calculate this?

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Lodovico

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Hi All,

I just got updated water numbers from the city and they don't have a reading for Magnesium which I know can be pretty important. I'm wondering if I give you the rest of my numbers, including total hardness, if anyone can give a rough estimate based on having all the other info.

Maybe this isn't possible,but I would really appreciate ate it if someone knows how. Thanks!

Calcium- 88 ppm
Sodium- 18 ppm
Sulfate- 56 ppm
Chloride- 40 ppm
PH- 7.5
Hardness as CaCO3- 243
Alkalinity- CaC03- 200

What's the magnesium??
 
When a water authority doesn't report it that generally means that it isn't too significant.

All I can do is make the following assumptions
1. The 88 ppm is as Ca++ (not ppm as CaCO3)
2. The alkalinity titration was done to pH 4.3
3 There are no ions in the water except Ca++, Mg++, Cl-, Na+, HCO3-, CO3-. SO4--, H+ and (OH)-.

Based on that your magnesium is 13.4 mg/L.
 
they don't have a reading for Magnesium which I know can be pretty important.

I wouldn't categorize Magnesium as "pretty important". Trace amounts are all you need so single digit ppm are fine. The malt itself usually has enough Mg+ to take care of things.
 
Most regulatory testing has reportable levels, so when an analyte is below a reportable level, it generally won't be reported.
 
Not so. Many water authorities report ions below the MCL (or other limit). Besides which there is no MCL for magnesium other than indirectly through TDS/conductivity. Which is interesting as excessive Mg give lots of people the trots and makes the water taste bitter/sour.
 
I was referring to a reporting limit which is usually determined by the quantitation limits of a method. Usually when a level is so low that it is indistinguishable from a blank measurement, it is considered below reportable levels. Below a certain point ions cannot be quantified with any degree of precision unless you are using some sort of ICP or AA METHOD and even those methods have their limits.
 
Just went back and looked at the original post here. I learned
1. You have to read the post carefully
2. The report tells you what the magnesium level is:

Calcium- 88 ppm
Hardness as CaCO3- 243
What's the magnesium??

Calcium at 88 mg/L corresponds to calcium hardness of 50*88/20 = 220 ppm as CaCO3. Total hardness is 243 which means that the magnesium hardness is 243 - 220 = 23 less the hardness from iron, strontium, copper .... That makes the magnesium 12.15*23/50 = 5.6 mg/L. This is subject to error if there are other polyvalent cations in the water but should be a much more accurate estimate than the electroneutrality one I gave earlier.
 

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