Zeta-meter

There are a number of complications in the experimental measurement of the electrophoretic mobility of colloidal particles and its interpretation see Section V-6F. TTie experiment itself may involve a moving boundary type of apparatus, direct microscopic observation of the velocity of a particle in an applied field (the zeta-meter), or measurement of the conductivity of a colloidal suspension. 

Several devices are available commercially to measure mobihty. One of these (Zeta-Meter Inc., New York) allows direct microscopic measurement of individual particles. Another allows measurement in more concentrated suspensions (Numinco Instrument Corp., Monroeville, Pa.). The state of the charge can also be measured by a streaming-current detecdor (Waters Associates, Inc., Framingham, Mass.). For macromolecules, more elaborate devices such as the Tisehus moving-boundaiy apparatus are used. 

Electrokinetic Measurements. Electrophoretic mobilities were measured with a flat-cell apparatus manufactured by Rank Brothers, Cambridge, England. In addition, several mobility values were checked for accuracy with a Zeta Meter, New York. Mobilities were determined with a small volume of the suspension (approximately 25 cc) that had been prepared for the adsorption experiments. The pH of the solution was measured prior to determining the electrophoretic mobilities, which involved measuring the velocities of five to ten particles in each direction. An average value of the mobilities was recorded. Samples containing the flocculated particles were dipped into an ultrasonic bath for approximately one second prior to making the pH and mobility measurements. 

In this experiment a zeta-meter is used to determine the variation in the zeta potential of silica at constant pH (5.7) over a range of concentrations of a cationic surfactant CTAB, which should adsorb on the ionized silanol groups on the silica particle surface. 

Electrophoretic mobilities of the quartz particles in cobalt (II) perchlorate solutions were determined with a calibrated Zeta-Meter apparatus. Coagulation sedimentation behavior was followed using a stop-flow type apparatus. The dispersion is pumped in a closed loop from an equilibration vessel through an optical cell located in the sample compartment of a recording spectrophotometer. From the optical densitytime curve obtained from the time the pump is switched off, the turbidity index (in arbitrary units) is obtained as the slope of the curve at zero time. 

Electrophoretic mobilities of the alumina particles were determined for the same conditions as were used to obtain the adsorption isotherms. For this purpose, a sample of the alumina suspension was transferred to the electrophoresis cell for measurement of the electrophoretic mobilities. A Zeta-Meter was used for this part of the program. 

Figure 4.2 Illustration of the diffuse electric double layer showing the distributions of counter- and co-ions. Courtesy L.A. Ravina, Zeta-Meter, Inc., Staunton, Va.

Figure 5.9 Illustration of the effect of electrolyte on colloid stability. The photomicrographs A through D show how 1.1 tm size silica particles are progressively coagulated by increasing additions of alum (0, 10, 30, 40 ppm, respectively). The corresponding zeta potentials are -30 mV (A), -14 mV (B), -6 mV (C), and -0 mV (D). From Zeta-Meter [544], Courtesy L.A. Ravina, Zeta-Meter, Inc., Staunton, Va.

Hunter, R.J. Coll. Surf. A, 2001, 395, 205-214. Riddick, T.M. Control of Stability Through Zeta Potential, Zeta Meter Inc. New York, 1968. Okada, K. Akagi, Y. J. Chem. Eng. Japan 1987, 20,11-15. 

Zeta-Meter Applications Brochures, Zeta-Meter Inc., New York, 1982. 

Zeta potential can be measured by the use of a zeta meter, which is commonly employed in municipal water-treatment facilities to evaluate the flocculation potential of suspended biosolids. 

Measurements were carried out using three methods (a) A Zeta meter (Zeta Meter, Inc., New York) was used for determining electrophoretic mobilities. The gelatin was first coated on glass beads or AgBr grains, and the mobility of these particles was measured as a function of pH according to established procedures (6). 

Figure 12. Simplified illustrations of the electrical double layer around a negatively charged colloidal emulsion droplet. The left view shows the change in charge density around the droplet. The right view shows the distribution of ions around the charged droplet. (Courtesy of L. A. Ravina, Zeta-Meter, Inc., Long Island City, NY.)...

Riddick, T. M. Control of Stability Through Zeta Potential Zeta Meter New York, 1968. 

Nash and Haeger have described the applications of the Zeta-Meter, a device which conveniently measures the electrophoretic mobility of suspension particles. The instrument appears to be useful in suspension and emulsion formulation work and in basic studies related to dispersed systems. 

From Zeta-Meter (ZM, Z-Meter, Riddick) Zeta-Meter (there is a photograph and description of a model without a number in [104]) models 2.0, 3.0, 3.0-1- (illustrated in [256-258]), 77, and 80... 

---