Use the data in the graph of colloid diameter
versus time as determined by dynamic light scattering to calculate the following
parameters. The graphs show the rates of aggregation of polystyrene latex
microspheres of d = 215 nm diameter. The concentration of latex
particles was N0 = 3.8x1014 m-3.
The experiments were conducted in water at 25°C.
(a) Calculate the aggregation rate coefficients (units of m3 s-1)
for the six ionic strengths shown in the graph. The electrolyte used to
control the ionic strength is sodium perchlorate. The ionic strengths are
0.075 M (∆), 0.2 M (filled squares), 0.25 M (open circles), 0.5 M (filled
upside-down triangles), 0.75 M (□), and 1.0 M (filled diamonds).
(b) Calculate the theoretical rate coefficients
for these latex particles.
(c) Calculate the stability ratios (W) and the collision efficiencies (a) for the six ionic strengths.
(d) What is the critical coagulation concentration for the latex?
Last updated on May 28, 2007 by Joe Ryan