Addition of methanol, ethanol, and n-propanol to aqueous dispersions of Namontmorillonite (2% w/w) reduces the apparent viscosity and the yield value. In the presence of NaCl the flow parameters increase to a maximum at medium alcohol concentration. Thus, the gel strength of Nabentonite dispersions can greatly change with the alcohol content of the dispersion. This is probably caused by the transition of dispersed clay mineral particles (individual silicate layers or lamellae of a few of these layers) to band-type networks with optical homogeneity and weakly attractive particle-particle interaction. When attraction between the particles becomes too strong at high alcohol concentrations, the bands are condensed to short fragments and, eventually, freely moving particles, reducing the viscosity and the yield value.
The interparticle interaction energy is calculated for the constant charge model by van Olphen's (1977) method. Agreement with the experimental results is only obtained when the Stern layer adsorption is governed by a specific adsorption energy μ, which increases with decreasing dielectric constant.