aeration atmospheric pressure baia mare ball-and-stick model calcium hydroxide carbon in pulp carl wilhelm scheele chemical reaction comminution controversy cyanide electrowinning froth flotation glasgow gold gold extraction hydrogen cyanide hydrogen peroxide john stewart macarthur kumtor gold mine lake cowal leaching merrill-crowe process metallurgy michael faraday montana ore oxygen oxygen saturation ph pascua lama peter bagrationi poison potassium cyanide proton reagent room temperature scotland sodium sodium cyanide sodium hydroxide sodium metabisulfite stoichiometry sulfur summitville mine thiocyanate