Flocculation of veegum suspension by electrolytes

The effect on the apparent viscosity of 2 wt. % Veegum suspensions of different types of electrolytes and of different electrolyte concentrations was studied. Measurements were made with a Bookfield Synchro-Lectric viscometer, using a No. 3 spindle at 30 R.P.M. at 24?C. As electrolyte concentration increased, the apparent viscosity was observed to increase to a maximum and then decrease. Changes in viscosity were in general agreement with predicted results based on the Hofmeister sequence and the Schulze-Hardy rule. Three flow phenomena were noticed which were dependent upon the concentration of electrolyte when the viscosity measurements were plotted against time; namely, a thixotropic flow at high electrolyte concentration, a Newtonian flow at intermediate electrolyte concentration, and a dilatant flow when low concentrations of electrolyte added to the Veegum system. The observed wlectrolyte effect on the apparent viscosity was discussed in terms of the Verwey-Overbeek theoroy. Typical stress-relaxations curves of the thixotropic flow were analyzed by a derived equation for stress-relaxation. :Card-Stack" model of flow unites was postulated to interpret the three electrolyte. An approximate formula of Veegum was computed from chemical analysis applying the Marshall approach.