Determination of size of small particles by light scattering. experiments on ludox colloidal silica
Laboratory of Physical Chemistry, Faculty of Science, University of Zagreb, Zagreb, Croatia (Yugoslavia)Colloid and Polymer Science (Impact Factor: 1.87). 11/1960; 173(1):38-48. DOI: 10.1007/BF01513625
Four samples of Ludox colloidal silica were studied by the light transmission and angular scattering method and the size of particles determined. It was found essential for light scattering work to centrifuge the original Ludox solution in order to remove the aggregated material. After this treatment each Ludox sample regardless of age could be used successfully for calibration purposes. The apparent particle sizes in aqueous solutions of Ludox were smaller than those in 0.05 M NaCl solutions, the latter being in very good agreement with electron microscopic values. The refractive index increments of Ludox in water and 0.05 M NaCl were determined at three wavelengths. The influence of cell length and blackening of the cells in transmission measurements were also studied. Dissymmetries and depolarizations were small. All results indicated that particles of Ludox behave practically as Rayleigh scatterers. The usefulness of these results for the calibration of light scattering photometers is discussed.
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ABSTRACT: An extensive and more complete study of light scattering of three BASF and eight Dow polystyrene latexes was undertaken. The measurements were performed at four wavelengths of the mercury are, and theoretical functions, published in a foregoing paper, were applied. Five different methods of determination of particle size by light scattering were used: transmission, scattering at 90°, dissymmetry, polarization ratio, and positions of maxima and minima in angular distribution. The results are in good agreement with earlier data obtained on some of the latexes investigated in this work. It was found that the particle sizes are generally smaller than those obtained by electron microscopy. Any definitive explanation of this behavior could not be found.
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ABSTRACT: A survey of the literature on the calibration of light scattering instruments has been made, including an extensive bibliography. The values of the Rayleigh ratio R90 and depolarization ρμ for benzene, toluene, carbon tetrachloride, and carbon disulfide and the excess turbidity of Cornell polystyrene and D.C./P.J.3 polystyrene (0.5% solutions in toluene) were tabulated for two wavelengths (4358 and 5461 A.). Examination of these results showed a larger variation in reported values than is generally assumed acceptable (only so-called “high” values have been considered). No correlation was found with the various standards used for the original calibration. Some aspects of the most usual methods of calibration are discussed and arguments are considered which would favor those values of R90 (or excess turbidity) that are at the lower limits of the range reported (but still in the region of “high” values). The difficulty of using Einstein's equation in determining the exact values of R90 is pointed out.
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