Calcium from Calcium Hydroxide, Ca(OH)2, Slaked Lime, Pickling Lime?

[Silver_Is_Money]

My calcium chloride prills dropped out a white precipitate after I liquefied them in distilled water. I've since heard this is rather common. It indicates that some percentage of CaCl2 is actually CaCO3 contamination. And it also indicates low quality control.

In rethinking this, the precipitate I noticed was only seen days to weeks later. The CaCl2 contaminant is therefore more likely to be Ca(OH)2, which with use and exposure to CO2 drops out as CaCO3. If CaCl2 prills are mixed with water and the pH of the water rises then this is indeed the case. And to think that people add CaCl2 to lower pH. This might be just another reason why it's so hard to get mash pH prediction software to hit things right.

Ca(OH)2 + 2HCl = CaCl2 +2H2O (or alternately, CaCl2.2H2O, which is the dihydrate state of CaCl2)

My guess is that the above balanced chemical formula is representative of how CaCL2 is commercially produced. And if the mix is a bit off and there is more Ca(OH)2 in the reaction vessel than need be, then the remaining Ca(OH)2 stays behind as a contaminant when the mix is evaporated to dryness to form prills.

 

[dmtaylor]

In rethinking this, the precipitate I noticed was only seen days to weeks later. The CaCl2 contaminant is therefore more likely to be Ca(OH)2, which with use and exposure to CO2 drops out as CaCO3. If CaCl2 prills are mixed with water and the pH of the water rises then this is indeed the case. And to think that people add CaCl2 to lower pH. This might be just another reason why it's so hard to get mash pH prediction software to hit things right.

But CaCl2 will still lower pH in the mash. The wee bit of Ca(OH)2 or CaCO3 that may form in the water while it heats up shouldn't make much difference unless it's really bad quality CaCl2. When used for the mash, the remaining dissociated Ca++ (probably like >95% of it) will immediately be available to react with phosphates and whatever else in the mash to effectively lower pH. Close enough for me, maybe not for you but at this point I question whether you're just overthinking all this. We're not really dealing with plain water here, we're ultimately always dealing with a mash.

EDIT: And hopefully, if CaCl2 contains impurities for one of us, hopefully it's all of a consistent enough quality for all of us that it doesn't affect a pH model too terribly for any of us. As long as we're consistent in our inconsistency or whatever.