Water Alkalinity measurements after boiling

[mabrungard]

As many know, boiling a water with high Temporary Hardness can be used to reduce hardness and alkalinity. The reported practical lower limit for alkalinity is somewhere between 50 and 65 ppm (as CaCO3). I was wondering if any brewers have performed alkalinity testing of their post-boiled water and they can confirm or negate those reported limits?

Thanks!

[john luc]

As far as I can find out,the solubility of calcium carbonate is 47 ppm, so the maximum calcium carbonate in the boiled wort would be around that number (Note the wort acidity of around pH 5 does not affect the solubility !)

[mabrungard]

47 ppm CaCO3 is the solubility under 1 atmosphere (with its partial pressure of CO2) and also at standard temperature (20 to 25 C). When you boil, you drive off all the dissolved CO2 and CaCO3 will precipitate. Under that condition, the solubility of CaCO3 is much reduced. But that is not the alkalinity value that I mention above. That is "alkalinity as CaCO3", not the solubility of CaCO3.

There was a response on this same inquiry on the UK Homebrewers Forum. Values down to 45 ppm alkalinity were measured in post-boiled water.