Scm Corporation

Richard M Holsworth

Theodore Provder

Mark E Koehler

There is provided a new method for analysis of the size and/or distribution of particles emanating from a mother liquid by sedimentation in a rotating disc centrifuge, particularly a photosedimentometer. The method is characterized in that the spin fluid or medium is formed externally of the disc as distinct from being formed within the disc while it is rotating. The externally prepared spin medium is formed from at least two miscible liquids of different densities for example, methanol and water, in a manner such that they are substantially incompletely mixed whereby a density gradient is established in the spin medium. Thereafter the spin medium is injected into the disc while spinning at a given speed, and later the mother liquid is injected. Results are closely comparable to the buffered line start method described in U.S. Pat. No. 3,475,968.

Method for determining particle size and/or distribution

A method and apparatus for photogoniometric analysis of surfaces is disclosed. A photogoniometric instrument includes a light source (12) for providing a collimated beam of light illuminating a test surface (18). A light detector (20) is mounted for rotation about the point of intersection of the illuminating beam on the test surface. A motor (44) drives the detector through a range of reflectance angles, and a microcomputer (52) digitizes the detector output periodically, storing the digitized data words in its memory (68). These stored words define a photogoniometric curve (FIG. 2A) including a specular portion (FIG. 2D) and a nonspecular, or diffuse, portion (FIG. 2C). A host computer (62) receives the photogoniometric data from the microcomputer, deconvolutes the data into spectral and diffuse portions, and analyzes the two portions separately from one another. To accomplish this deconvolution, the host computer subtracts from the photogoniometric data the actual reflectance characteristic of a standard surface whose characteristic lacks the specular peak. This diffuse standard reflectance characteristic is stored in the host computer memory in the form of a mathematical equation which has been curve fitted to the actual reflectance characteristics of the diffused standard.

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Westlake, OH, United States of America

Richard M Holsworth