Reef Chemistry Question of the Day #110 Dolomite

[Randy Holmes-Farley]

[h=3][/h]Reef Chemistry Question of the Day #110

When added to a calcium carbonate/carbon dioxide reactor, dolomite can be a suitable way to maintain existing magnesium levels. It is not, however, a suitable way to raise low magnesium levels. Which of the following is the primary reason it is not suitable for substantially raising magnesium?


A. Because it is too slow to dissolve
B. Because it adds to much sulfate to the water
C. Because it adds too much alkalinity to the water
D. Because it is too fast to dissolve

Good luck!




































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[beaslbob]

C
(adding characters to get more than 3 for post)

 

[fuzzone99]

Guessing...C

 

[Randy Holmes-Farley]

And the answer is...C. Because it adds too much alkalinity to the water

If you use dolomite to boost magnesium, it is basically dissolving magnesium carbonate (and some calcium carbonate, but we can ignore that for purposes of this question).

When magnesium carbonate dissolves, it releases one magnesium for one carbonate ion.

MgCO₃ → Mg²⁺ + CO₃^2-

That means that for a 100 ppm rise in magnesium, alkalinity will necessarily rise by 23 dKH (8.2 meq/L)

This has more:

http://www.advancedaquarist.com/issues/oct2003/chem.htm

 

[Jmcdaniel0]

Randy, i really enjoy your posts. Having a BS in Organic Chemistry, I really enjoy reading through your articles. You give just enough detail in the science to make it interesting, but it's not overwhelming for the laymen.

Just thought ide toss that out there

 

[Randy Holmes-Farley]

Thanks very much!

Happy Reefing.

 

[beaslbob]

even a broke clock tells the time correctly twice a day

 

[Randy Holmes-Farley]

Yes, but you knew the answer!