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); Department of Applied Biochemistry, “Andrija Štampar” School of Public Health, Faculty of Medicine, University of Zagreb, Zagreb, Croatia (Yugoslavia); Division of Applied Biology, National Research Council, Ottawa, Canada
Colloid and Polymer Science (Impact Factor: 2.16). 01/1960; 173(1):38-48. DOI: 10.1007/BF01513625

ABSTRACT 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 asRayleigh scatterers. The usefulness of these results for the calibration of light scattering photometers is discussed.
Die Teilchengröße von vier Proben von Ludox (kolloides Siliciumdioxyd) wurde mit Hilfe der Lichtdurchlässigkeits- und Winkelstreuungsmethode
bestimmt. Für das Arbeiten mit Lichtstreuungsmethoden wurde die Beseitigung von aggregierten Teilchen durch Zentrifugieren
als wesentlich gefunden. Nach solcher Behandlung kann man alle Ludox-Proben, ohne Rücksicht auf ihr Alter, für Kalibrierungszwecke
verwenden. Die scheinbaren Teilchendurchmesser von Ludox verdünnt in Wasser waren kleiner als diejenigen von Ludox in 0,05
M NaCl-Lösungen, welche mit den elektronenmikroskopisch gewonnenen Werten sehr gut übereinstimmten. Die Brechungsindex-Inkremente
von Ludox in Wasser und in 0,05 M NaCl wurden für drei Wellenlängen bestimmt. Auch wurde der Einfluß von der Küvettenlänge
und vom Schwärzen der Küvetten auf die Lichtdurchlässigkeitsmessungen untersucht. Die Unsymmetrien und Depolarisationsgrade
waren klein. Die gewonnenen Resultate weisen darauf hin, daß die Lichtstreuung von Ludox-Teilchen sehr nahe an derRayleigh- Streuung liegt. Die praktischen Konsequenzen von vorliegenden Ergebnissen für die Kalibrierung von Lichtstreuungsphotometem
werden diskutiert.

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