Optical process and apparatus for determining particle size of colloidal solution

• US 4,274,740 A
• Filed: 07/19/1979
• Issued: 06/23/1981
• Est. Priority Date: 07/21/1978
• Status: Expired due to Term

• Current Assignee: Herrn H. Eidenschink, Marianne Eidenschink
• Original Assignee: Herrn H. Eidenschink, Marianne Eidenschink
• Inventors: Eidenschink, Marianne, Eidenschink, Herrn H.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Arnold, Bruce Y.
• Application Number:
  US06/059,081
• Time in Patent Office: 705 Days
• Field of Search: 356/335, 356/336, 250/222 PC, 250/574
• US Class Current: 356/336
• CPC Class Codes: G01N 15/0205 by optical means

Abstract

Method and apparatus for determining the colloid size of particles in a colloidal solution include the use of a wedge-shaped container for a sample of the colloidal solution. The container is moved in the direction of the wedge shape perpendicular to the path of a light beam to produce a measured sample thickness of the colloidal solution. Due to the Tyndall effect, the measured sample thickness is a function of the scattering of the light beam. A lens arranged between the sample holder and a dispersion prism directs the beam of light emerging from the sample holder to the prism for dispersion and impingement upon an image screen. The sample holder is moved until only red light appears on the image screen. The thickness of the light path through the sample is measured and the particle size is computed according to an equation.

Claims

1. A method for determining the particle size of a colloidal solution, especially a synthetic resin dispersion, the method including the steps of:

providing a colloidal solution sample with a thickness which varies in a given direction;

directing a light beam to propagate through the colloidal solution sample in the direction normal to said given direction;

causing the emerging light beam from the sample to undergo chromatic dispersion and to be incident onto an image screen;

establishing, by a relative displacement between the light beam and the varying thickness of the colloidal solution sample, a sample position which results in only the long-wave part of the visible spectrum to appear on the screen;

determining the thickness of the colloidal solution section which is traversed by the beam at said position; and

, determining the particle size of the colloidal solution in accordance with the formula;

##EQU5## where r=radius of the particle (μ

m),

c=concentration of the colloidal solution in volume %,

d=thickness of measured colloidal solution sample section (mm),

E.sub.(c) =concentration factor at concentration c, and

n=a constant.

2. The method according to claim 1 wherein said colloidal solution sample with a varying thickness is further defined to include a wedge-shaped sample of colloidal solution.

3. The method according to claim 2 wherein said step of establishing a measured colloidal solution sample section includes moving said wedge-shaped colloidal sample in the direction of the wedge and transversely to the direction at which said light beam is directed to propagate through the colloidal sample.

4. The method according to claim 1 wherein said long-wave part of the visible spectrum of dispersed light includes monochromatic red visible light.

5. The method according to claim 1 wherein said constant factor is further defined to equal 10⁶ /mm².

6. Apparatus for determining the particle size of a colloidal solution, especially a synthetic resin dispersion, said apparatus including the combination of:

a light source;

a condenser to direct light from said light source for producing a narrow light beam;

a wedge-shaped transparent sample holder for displacement in the direction of the wedge shape thereof within the path of the narrow light beam passed from said condenser, said sample holder being adapted to contain a sample of colloidal solution for the determination of the particle size thereof;

lens means arranged for propagating light passed through said sample holder;

means for dispersing light propagating from said lens means into the visible light spectrum; and

an image screen for impingement by the dispersed light propagated from the dispersion means.

7. The apparatus according to claim 6 wherein said condenser includes two plano-convex lenses.

8. The apparatus according to claim 7 further including a diaphragm having an aperture arranged in the light path between said two plano-convex lenses.

9. The apparatus according to claims 6, 7 or 8 further including a diaphragm having an aperture arranged in the light path between said condenser and said wedge-shaped transparent sample holder.

10. The apparatus according to claim 6 further including a parabolic reflector means having a focal point receiving said light source.