If your phenolphthalein alkalinity is 2.5 mg/l and total alkalinity is 10 mg/l, what is your bicarbonate alkalinity?

To determine bicarbonate alkalinity, we use the relationship between phenolphthalein alkalinity, total alkalinity, and bicarbonate alkalinity. The phenolphthalein alkalinity measures primarily the hydroxide and carbonate ions present in the water, while total alkalinity accounts for all alkaline species, including bicarbonate, carbonate, and hydroxide.

In this case, the phenolphthalein alkalinity is given as 2.5 mg/L, indicating the amount of hydroxide and carbonate ions. The total alkalinity is provided as 10 mg/L, representing the sum of all alkaline species. To find the bicarbonate alkalinity, we subtract the phenolphthalein alkalinity from the total alkalinity.

The calculation is as follows:

Total Alkalinity (10 mg/L) - Phenolphthalein Alkalinity (2.5 mg/L) equals Bicarbonate Alkalinity.

So, 10 mg/L - 2.5 mg/L = 7.5 mg/L.

Thus, the bicarbonate alkalinity in this scenario is 7.5 mg/L. This demonstrates that the remaining alkalinity, after accounting for phenolphthalein alkalinity, is due to bicarbonate ions