EvergreenBuzzBuzz wrote:So for example, does that mean a TWW mix would have 5.25 grams of magnesium sulphate in 5 gallons (5x1050mg) vs the 1.14 for 70/30.
And the Potassium Bicarbonate would be only .75grams vs the 1.59 grams. How would one convert these amounts into the final hardness and alkalinity figures?
Yes. Compared to 70/30, TWW would have about half the bicarbonate and over 4x the Epsom (magnesium sulfate heptahydrate)
Taylor Minor has said that his magnesium sulfate is indeed ground epsom (the heptahydrate), and if we assume that his calcium citrate is the tetrahydrate the calculations give you:
magnesium hardness: 113 mg/L as CaCO3
calcium hardness: 42 mg/L as CaCO3
bicarbonate alkalinity: 20 mg/L as CaCO3
sulfate ion: 108 mg/L
And that would put it on that chart somewhere around 155 for total hardness and 20 for total carbonate/bicarbonate alkalinity. (I assume that any acid buffering from calcium citrate would have neglibile effect on total alkalinity.)
** Edit addition: After thinking and looking at the pKa values for citric acid, and considering what Taylor Miner has said about his alkalinity measures, I think the calcium citrate would affect a standard alkalinity test titration by about 14 mg/L as CaCO3. I base my estimate on 300 mg/gallon of the calcium citrate tetrahydrate (0.14 mmol/L) and figure about 2 protons per mole of the triprotic citric acid has reacted when the titration hits the pH 4.3 endpoint of a standard alkalinity titration. So you could place that TWW espresso water at 155 : 34 on the hardness vs. alkalinity chart. But if scaling is your concern, the alkalinity of 20 mg/L is the proper value to go by. When you start adding odd things like calcium citrate to a water all the usual assumptions about the predicted effects of an alkalinity measurement go awry.