Note 399 — Chapter XI · THE COPPER AND SILVER GROUPS. PRECIPITATION WITH HYDROGEN SULPHIDE
Reading edition
We can obtain the relation, directly, from H2S ⇄ 2 H+ + S2− and [H+]2 × [S2−] / [H2S] = K = 1.1E−22. For a given pressure of the hydrogen sulphide, [H2S], expressing its solubility (about 0.1 molar at 25°), is constant, and therefore [H+]2 × [S2−] = a constant, as given in equation (IV). Putting [H2S] = 0.1, we have [H+]2 × [S2−] = 0.1 × 1.1E−22 = 1.1E−23.