15.1 Exercise 23

Public Health Service standards for drinking water set a maximum of 250 mg/L (2.60 $\times$ 10^–3 M) of $\text{SO}_{4} ^{\text{2}−}$ because of its cathartic action (it is a laxative). Does natural water that is saturated with CaSO₄ (“gyp” water) as a result or passing through soil containing gypsum, CaSO₄·2H₂O, meet these standards? What is the concentration of $\text{SO}_{4} ^{\text{2}−}$ in such water?