Binary copper(I)-acetylene and ternary copper(I)acetylene-chloride complexes in aqueous solution

The complexation equilibria were studied at 25 degrees C in 3 M NaClO4 medium by potentiometric methods using a Cu+/Cu-Hg half-cell. The test solutions, saturated with acetylene gas at partial pressures ranging from 2 to 99.5 kPa, were prepared to contain concentrations of metal and chloride ions, respectively, in the intervals 10(-4) to 2x10(-2) M and 0 to 1 M. The potentiometric data, combined with the solubility constant for C2H2(g) reversible arrow C2H2(aq) K-P = (2.50 +/- 0.05)X10(-4) M/kPa, were explained by assuming: Cu+ + C2H2(aq) reversible arrow CuC2H2+, log beta(10) = 5.14 +/- 0.01 Cu+ + C2H2(aq) + Cl- reversible arrow CuC2H2Cl(aq), log beta(11) = 6.56 +/- 0.04 Cu+ + C2H2(aq) + 2Cl(-) reversible arrow CuC2H2Cl2-, log beta(12) = 7.18 +/- 0.022 2Cu(+) + C2H2(aq) reversible arrow Cu2C2(s,am) + 2H(+), log *K-S = 14.7 +/- 0.2 in addition to binary complexes CuCl(aq), CuCl2-, CuCl32- and CuCl43- known from a separate source. Effects of medium changes and extrapolation to zero ionic strength were evaluated by the specific interaction theory.