Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Content or effect of a constituent of a liquid mixture
Patent
1994-04-05
1995-09-26
Williams, Hezron E.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Content or effect of a constituent of a liquid mixture
73 6165, 356335, 356336, G01N 1502, G01N 3300
Patent
active
054526027
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to photoelectric methods of sedimentation analysis of the degree of dispersion of powder materials of a homogeneous substance. This method may be employed to measure the granular composition of powders in physical chemistry, instrumentation, pharmacology, the food industry in the manufacture of starch, flour, dried milk, chocolate, coffee, cacao, in the manufacture of mineral fertilizers and plant protection substances, synthetic materials, metallic powders, cement, ceramics, quartz, clay, etc.
BACKGROUND OF THE INVENTION
A method for measuring powder distribution on the basis of the granular composition of particles by photoelectric scanning and a device for the implementation of that method are known (see British Patent No. 1069680, Aug. 21, 1964) in which particle size distribution in a powder sample being analyzed is directly measured. This method is carried out in a scanning mode wherewith a narrow beam of light is moved in the direction of the force of gravity. In the case of a homogeneous suspension of particles, the particle size distribution curve may be obtained by measuring the relationship between particle concentration and depth. It is assumed that the lateral thickness of the light beam is negligibly small and the sedimentation of the suspension particles takes place in a stationary Stoke's mode. The method provides a calculation algorithm within the limits of these assumptions.
A narrow beam of light having a negligible cross-sectional thickness is used in the aforementioned method. However, the citerion defining fulfillment of this condition is not determined quantitatively, and therefore, there is no exact assessment of the measurement error due to the existence of a finite cross sectional area in real light beams.
In the mode of continuous scanning in the direction of the force of gravity there will always be a loss of information on the quantity of small-size particles (r.sub.min), since they lag behind the scanning beam as they descent. Furthermore, measuring time increases when scanning is conducted in this direction.
In this method the moment at which sedimentation begins is taken as the starting point, following which after an arbitrary time period the source of light begins to move from the surface of the suspension downwards. Since the length of the pause after sedimentation begins is not fixed, the part of the powder consisting of larger particles with maximum radius is not fully registered.
A photoelectric method of sedimentation analysis of dispersion systems of a homogeneous substance is also known, wherein a beam of rays is passed through an unloaded cell and the initial value of the photocurrent created by a beam which is not scattered is measured. Then the cell is loaded with a suspension of uniformly dispersed particles of powder. The value of the photocurrent which is created by the non-scattered part of the beam is measured during the process of sedimentation. The relative optical density D(t) of the suspension of dispersed particles of powder is measured according to the equation through the unloaded cell, I.sub.t is the photocurrent at the current moment of time t. Then, using Stoke's equation .upsilon.=.alpha.r.sup.2, the values of the radii r of the particles descending in the suspension are determined, .upsilon. being the velocity of the descending particles (see, for example, P. A. Kouzov "Basics of Dispersion Analysis of Industrial Dust and Pulverized Materials," Leningrad, Khimaya, 1971, pp. 169-180).
Wherein, the relative optical density of the suspension is proportional to the total surface S.sub.o.sup.r of particles of the dispersive phase, the radius of which is between zero and r measuring system which do not depend on the process of sedimentation or on the properties of the photocurrent registering system, the surface S.sub.r.sup.r, of all particles whose radius is within the range of from r' to r is determined through S.sub.o.sup.r. Then, using the equation ##EQU1## the mass of the fractions whose particl
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Astakhov Alexandr V.
Bunin Alexandr V.
Khazov Stanislav P.
Aktsionernoe Obschestvo "Agrokhim-Biznes"
Wiggins J. David
Williams Hezron E.
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