Check your calcium levels in your homemade 2-part!

[Fraggle Rock2]

Ok, so I followed your calculations using the data I got to obtain the following:


CaCl

195g/CUP

Assume 95.5% CaCl by weight

Ca comprises 36% of CaCl by weight

Each cup contains – 195 X 0.955 X 0.36 = 67g of Ca

2 Cups (390g) of CaCl per gallon = 134 g of calcium per gallon (gallon = 3.789L) or 35,366 g/L = 0.884 molar (134 g / 40 g per mol / 3.789 L per gallon)

Alkalinity

To match calcium = 2 X 0.884 molar = 1.768 molar Na2CO3 equivalents

Na2CO3 weighs 208 grams per measuring cup

Molecular weight of Na2CO3 is 106 g/mol

Thus, according to your calculation = 1.768 mol/L X 106 g/mol = 187.4 g/L OR 710 grams per gallon = 3.4 Cups.

However, given that you said you would use less Na2CO3 so I am confused by the results I obtained.

Of course, given that the molecular weight of Na2CO3 is higher than NaHCO3 wouldn't you expect to use more? Or is the molar ratio of Calcium to Na2CO3 less than 2?

[Randy Holmes-Farley]

Carbonate is not intended to exactly match calcium, but it is reasonably close. It is intended to not match because magnesium and other ions take some of the calcium sites. So calcium is a bit less than matching.

However, you added an extra factor of 2. Calcium is close to matching 2 moles of baking soda (bicarbonate) or one mole of sodium carbonate.

[Fraggle Rock2]

Ok thanks again Randy!! Wasn't sure about what I did. I tried to go through some of your articles to get an idea if the molar ratio was < 2. Not sure I understand why, maybe you can point me to something that would help me understand that. [nevermind, figured it out - 1 mole of Na2CO3 (in the presence of H2O and CO2) produces 2 moles of NaHCO3 ].

Ok, so the corrected calculation for alk is:

Alkalinity

To match calcium = 1 X 0.884 molar = 0.884 molar Na2CO3 equivalents

Na2CO3 weighs 208 grams per measuring cup

Molecular weight of Na2CO3 is 106 g/mol

Thus, according to your calculation = 0.884mol/L X 106 g/mol = 93.7 g/L OR 355 grams per gallon = 1.7 Cups.

So, the twopart recipe suggests 2C of Na2CO3. Thus, I assume your original thought (alk too high) is correct and responsible for the dropping Calcium?

Cheers!

[Fraggle Rock2]

I forgot to ask, kinda an off topic question, but what was the gram weight of 1 CUP of MAG flake? I couldn't find that in your article.

Cheers!

[Randy Holmes-Farley]

Wasn't sure about what I did. I tried to go through some of your articles to get an idea if the molar ratio was < 2. Not sure I understand why, maybe you can point me to something that would help me understand that.

Calcium combines 1:1 with carbonate to form pure claicum carboante CaCO3.

But it takes two bicarboane to make one carbonate:

2HCO3- ---> H2O + CO3--

[Randy Holmes-Farley]

I forgot to ask, kinda an off topic question, but what was the gram weight of 1 CUP of MAG flake? I couldn't find that in your article.

The published bulk density of MAG flake is 0.8-0.9 g/ml.

http://www.meltsnow.com/msds-mag-flakes.htm

You tested MAG pellets, which I note in my article likely has a different density, but that I did not know what it was. You got a value just above the range I quote for MAG flake.

[Randy Holmes-Farley]

So, the twopart recipe suggests 2C of Na2CO3. Thus, I assume your original thought (alk too high) is correct and responsible for the dropping Calcium?

No. The bulk densities for washing soda (sodium carbonate) fall into two ranges. One is a very low bulk density, and the other is higher. Two Part Solutions uses a very low density one so that folks can mix equal quantities of the sodium carbonate and the Dowflake. So their ratio looks fine to me (although you may personally get a slightly different value when measuring weight and volume), I'm not sure how to interpret that).

FWIW, I've gotten a couple of emails from them explaining what they use.

[Fraggle Rock2]

Thanks again Randy. You've been most helpful!

[Randy Holmes-Farley]

You're welcome.