# Compute the pH (acidity) of a solution based
# on the activity of hydrogen ions
#
# https://en.wikipedia.org/wiki/PH

fn pH_acidity(activity_hplus: Molarity) -> Scalar =
    - log10(activity_hplus / (mol / L))

print(pH_acidity(5e-6 mol / L))
assert_eq(pH_acidity(5e-6 mol / L), 5.3, 0.1)