Reef Chemistry Question of the Day #24 Calcium Concentration

Randy Holmes-Farley

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Reef Chemistry Question of the Day #24

Which of the following possible additives has the highest concentration of calcium in it?

A. RO/DI water saturated with calcium carbonate
B. RO/DI water saturated with calcium hydroxide
C. RO/DI water saturated with calcium oxide
D. RO/DI water with 10 grams/L of anhydrous calcium chloride added
E.
RO/DI water with 10 grams/L of calcium chloride dihydrate added
F. Natural seawater at 35 ppt salinity

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miamiangler

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I use NSW so I am going with F.
430ppm collected an hour before high tide .
 
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Randy Holmes-Farley

Randy Holmes-Farley

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This one turned out harder than I thought. :)

Here are the approximate values for calcium in each of those solutions:

A. RO/DI water saturated with calcium carbonate (10-20 ppm, depending on whether atmospheric CO2 is allowed to enter)
B. RO/DI water saturated with calcium hydroxide (~820 ppm)
C. RO/DI water saturated with calcium oxide (~820 ppm)
D. RO/DI water with 10 grams/L of anhydrous calcium chloride added (~3,600 ppm)
E.
RO/DI water with 10 grams/L of calcium chloride dihydrate added (~2,730 ppm)
F. Natural seawater at 35 ppt salinity (~420 ppm)

So the answer is:
D. RO/DI water with 10 grams/L of anhydrous calcium chloride
 
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Randy Holmes-Farley

Randy Holmes-Farley

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I would say B because calcium Hydroxide contains the most calcium by dry wight.

That's true, but calcium oxide and hydroxide are limited by fairly low solubility. That why folks using limewater/kalkwasser may not be able to use enough, even when replacing all evaporated water with limewater. :)
 

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