CS239205B1 - A method for treating a sample suspension layer when measuring particle size on a disk centrifuge - Google Patents

Abstract

Method of treating the suspension layer during particle size measurement on a disk centrifuge in such a way that the suspension layer in which the particle size measurement is carried out is underlaid with a continuous, preferably 0.2 to 2 mm thick layer of immiscible liquid, which wets the suspended particles and has a density greater than the maximum average density of the suspension. A chlorinated hydrocarbon-based liquid is preferably used. In the case of volatilization of some suspension residues, the layering is carried out with a continuous, preferably 0.2 to 10 mm thick layer of immiscible liquid, with a lower density than the minimum average density of the suspension, preferably a higher alkane or a mixture thereof

Description

The present invention relates to a multi-layer technique applied to the treatment of a sample suspension layer for particle size measurement in a disk centrifuge, which eliminates the effect of entrainment of already deposited particles back into the measured particle suspension and the effect of evaporation of volatile fractions of the suspension.

Particle size measurements are performed on a disk centrifuge by a homogeneous or bilayer technique, or an improved bilayer technique using a buffer layer. These techniques differ in particular from the nature of the radial distribution of the particle concentration at the beginning and during the measurement. A common feature of these techniques is the frequent distortion of results due to entrainment of already deposited particles back into the suspension and in centrifuges whose disc is not closed during measurement due to evaporation of the volatile fractions of the suspension. The extent of distortion of the measurement results by the mentioned influences is greater for slowly sedimenting suspensions.

These drawbacks are overcome by a method of adjusting the sample suspension in the particle size measurement of a disc centrifuge according to the present invention using a multilayered technique, wherein the liquid layer in which the particle size measurement / measurement particle suspension / sublayer is continuous is preferably 0.2 to 2 mm thick. a non-miscible liquid layer which wets the suspended particles well and has a density greater than the mean density of the suspension, preferably a halogenated hydrocarbon-based liquid, and in the case of volatilization of any component of the measured suspension, overlaps with a continuous, preferably 0.2-10 mm a thick layer of a non-miscible liquid of a lower density than the minimum mean density of the suspension, preferably a higher alkane or mixtures thereof. The suspension underlayer with the liquid properties listed above serves to trap particles that have undergone sedimentation during sedimentation

239 205

- The presence of the superimposed liquid prevents the volatile components of the measured suspension from evaporating. · The basic requirement is that the two auxiliary liquid layers are continuous. The actual thickness of both layers is related to the character of the measured suspension and to other experimental conditions.

Taking already sedimented particles back into the measured suspension is an effect that increases the concentration of particles in the suspension over the expected course · Further increases the concentration of particles in the suspension and evaporation of solvents / which is the most common volatile component of the suspension in evaluating bias in favor of finer particles · Using the measurement technique of the present invention, these undesirable effects are suppressed and more accurate analysis results are obtained ·

The following examples illustrate the measurement technique:

Example 1

1.5 ml of trichlorethylene, 20 ml of a suspension of zinc oxide in a 1% aqueous solution of an ethoxylated castor oil-based nonionic dispersant, and 5 ml of a mixture of alkanes with the average number of carbon atoms is 12. At the selected rotation frequency, a photosedimentometer measurement is performed and an evaluation corresponding to the measurement conditions is performed using a homogeneous suspension.

Example 2

1.5 ml of trichlorethylene and 20 ml of a suspension of beta modification of copper phthalocyanine in polypropylene oil having an average molecular weight of 300 are injected sequentially into a disc centrifuge. The further procedure is identical to that of Example 1.

Claims (1)

REFLECT THE INVENTION 239 205 A method of treating a sample suspension layer in a particle size measurement on a disk centrifuge, characterized in that the suspension layer in which the particle measurement is carried out is layered continuously, Preferably a 0.2 to 2 mm thick, non-miscible liquid layer which wets the suspended particles and has a density greater than or equal to the maximum mean density of the suspension, preferably a halogenated hydrocarbon-based fluid, and preferably a 0.2 to 10 mm thick, non-miscible liquid layer of lower density than the minimum average suspension density, preferably a higher alkane or mixtures thereof.