title: Inhibition of bubble coalescence by electrolytes in binary mixtures of dimethyl sulfoxide and propylene carbonate.
abstract: We have investigated the effect of solvent composition on inhibition of bubble coalescence by electrolytes in binary mixtures of dimethyl sulfoxide (DMSO) and propylene carbonate (PC). Unlike most mixtures, combinations of DMSO and PC exhibit minimal foaming over all compositions (with the strongest effect being at 25% PC by volume); thus, the influence of electrolytes can be investigated. Both LiBr and KSCN at moderate concentrations inhibit bubble coalescence at all solvent compositions. However, the concentration of electrolyte required to inhibit coalescence was in both cases a minimum at the PC(v/v) of 25%. The surface tension of electrolyte solutions in the mixed solvents indicates that the gradient in surface tension is not correlated with coalescence inhibition and therefore inhibition cannot be attributed to surface elasticity. We have also studied the inhibition of bubble coalescence by HCl at different solvent compositions. HCl is strongly inhibitory in DMSO but only weakly so in PC. We have found that HCl exhibits strong inhibition behavior at all mixtures studied. All electrolytes studied were most effective at inhibiting bubble coalescence at the PC(v/v) of 25%, indicating that the interactions between solvent molecules strongly determine the influence of electrolyte on coalescence inhibition. We propose that the formation of solvent complexes between DMSO and PC results in an increase in surface viscosity and the presence of electrolytes further amplifies this effect.
authors.affiliation: Department of Applied Mathematics, Research School of Physical Sciences and Engineering, The Australian National University, Canberra ACT 0200, Australia.
authors.forename: Guangming
authors.initials: G
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Hou
authors.forename: Guangzhao
authors.initials: G
authors.lastname: Zhang
authors.forename: Vincent S J
authors.initials: VS
authors.lastname: Craig