Phosphoric Acid and Calcium

[dstar26t]

Is there an easy way to calculate how many ppm Ca is removed per mL of phosphoric acid (assume a concentration of 100%) added to the mash? Would this reaction be the same if added to sparge water as it would be if added to the mash?

Thanks!

Nate

[ajdelange]

Is there an easy way to calculate how many ppm Ca is removed per mL of phosphoric acid (assume a concentration of 100%) added to the mash?

Guess that depends on your definition of "easy". It depends on how much calcium is in the mash (from the water, from the grain and from any additions) and how much phosphate is in the mash (from grains and added phosphoric acid) and on the pH produced by the particular addition. Given the pH and some assumptions about how much phosphate is in the malt one could wag the amount left but the math involved is a little hairy. It involves solution of a set of equations which can be done on a spreadsheet but unless you are familiar with this flavor of chemistry you probably wouldn't consider it easy.

Would this reaction be the same if added to sparge water as it would be if added to the mash?

The reactions are the same

6H3PO4 + 10Ca++ + 2H2O --> 6H+ + 6H2PO4- + 10Ca++ + 2H2O --> 12H+ + 6HPO4-- + 10Ca + 2H2O --> Ca10(PO4)6(OH)2 + 18H+

but the conditions are different because a lot of the phosphate (and calcium) will have already been precipitated in the mash.

[dstar26t]

I guess I'll stick with lactic then, haha
I was hoping I could stick a cell in my spreadsheet that would tell me x ppm extra Ca needed per mL of acid added but I'm not that good at chemistry.

Thanks