Critical coagulation concentration measurements

The principle of this method is that the initial slope (time = zero) of the optical density-time curve is proportional to the rate of flocculation. This initial slope increases with increasing electrolyte concentration until it reaches a limiting value. The stability ratio W is defined as reciprocal ratio of the limiting initial slope to the initial slope measured at lower electrolyte concentration. A log W-log electrolyte concentration plot shows a sharp inflection at the critical coagulation concentration (W = 1), which is a measure of the stability to added electrolyte. Reerink and Overbeek (12) have shown that the value of W is determined mainly by the height of the primary repulsion maximum in the potential energy-distance curve. 

The definitions of the term critical coagulation concentration (a) in relation to experimental measurements and (b) as a means for... 

An approximate measure of the influence of an electrolyte on the flocculation of a lyophobic sol is the critical coagulation concentration (c.c.c.), which is the minimum concentration of that electrolyte leading to rapid coagulation under specified conditions of concentration of sol, rate of addition of electrolyte, etc. 

The authors acknowledge gratefully the contributions of J. G. Cobler and Miss C. Kleeman for the ultracentrifuge particle size measurements, E. B. Bradford for the electron microscope particle size measurements. Miss D. L. Dickens, A. S. Teot, and N. Sarkar for the critical coagulation concentration experiments, R. D. Van Dell for the SDS adsorption experiments, the East Main Analytical Laboratory for the osmometric molecular weight and nitrogen adsorption measurements, the Chemical Physics Laboratory for the X-ray fluorescence measurements, and J. B. Shaffer in the preparation of the latexes. 

Figure 3. Critical coagulation concentration versus surface concentration of potential determining species, N the solid curves are for N from adsorption data, the dashed curves are for N from mobility measurements, curves 1 and 3 are for Na and 2 and are for Mg as the coagulating species ...

For a water dispersion of positively charged AI2O3 particles, the following values of the critical coagulation concentration (CCC) have been measured ... 

The stability of PEG-coated nanosphere suspensions was determined by measuring the critical coagulation/flocculation concentration as a ftmc-tion of electrolyte concentration (Stolnik et al, 1995). In the presence of... 

The intrinsic viscosity [t]] of the coagulant protein was measured for protein concentration, c, in the range 0.02—0.15 g/mL in 0.1 M NaCl. Solution environment such as presence of surfactants can affect protein conformation. To study interactions SDS and SDBS with the cor ulant protein, capillary viscosities of the surfactant/protein solutions were measured using a capillary viscometer. The protein concentration (% w/v) was kept constant at 0.05% whereas the surfactant concentration was varied up to concentrations higher than the critical micelle concentration (CMC). The protein solution was used as the reference standard for surfactant dissolved in 0.05% protein. The SDS (99% purity) was supplied by Sigma-Aldrich whereas SDBS was supplied by Fluka, and both surfactants were used without further purification. The measurements of surface tension, fluorescence, and circular dichroism spectral correlation coefficients of SDS solutions in the presence of protein were done in similar manner, and the details are described elsewhere [15-18]. 

The surface tension of the continuous phase of a polymer emulsion may be used as a measure of the free onulsifier concentration. ITie term free onulsifier is used here to denote surfactant which is dissolved in the aqueous phase rather than being adsorbed on to polymer particles or monomer droplets, or aggregated into micelles. The free emulsifier concentration is widely considered to be a critical variable in the phenomenon of steady-state oscillation in a CSTR and in preventing coagulation during polymoization. 

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