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Old 02-04-2018, 04:35 AM
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Myka Myka is offline
Join Date: Mar 2004
Location: Saskatoon, SK.
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I found a thread on Reef2Reef discussing the new instructions, and Randy Homes-Farley explains why you won't see much difference:

Originally Posted by Randy Holmes-Farley
CA-1 is a dye the binds calcium. It is a different color when bound to calcium and when not. The amount is not critical except to provide enough color. It is a weaker binder of calcium than the reagent in CA-3. Less of it may actually give a sharper endpoint, but may be harder to detect visually.

Ca-2 solution is a hydroxide solution to precipitate magnesium hydroxide and prevent it from being detected. The amount of it is not important as long as there is enough to precipitate the magnesium.

The titrant (CA-3) is a strong calcium binder (e.g., EDTA, but I'm not certain what exactly they use). As it is added, it binds up calcium. Eventually, the only calcium left that is not already bound to the CA-3 reagent is bound to the dye. At that point more added CA-3 strips away the calcium from the dye, and so the color changes as the dye transitions from calcium bound to free dye.
Since Ca-2 precipitates Mg, then maybe 8 drops isn't enough for people with higher Mg levels in their tank??? Maybe that's why the change?
~ Mindy

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