Patents by Inventor David F. Tunstall

David F. Tunstall has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4279512
    Abstract: A method of measuring mean particle size and/or standard deviation of particles involves illuminating a suspension of the particles with three beams of radiation of wavelengths R.sub.1, R.sub.2 and R.sub.3 and measuring the beam intensities passing through the suspension. The results are compared with those of the liquid medium free of particles and attenuation ratios of the beams at wavelengths R.sub.1 and R.sub.3 and at R.sub.2 and R.sub.3 are compared with previously calculated values for these ratios.This comparison enables the desired parameters to be obtained easily; preferably by using a spectrophotometer in which two or more optical densities at two or more wavelengths are compared simultaneously.The method is of particular use for aqueous suspensions of titanium dioxide pigment using wavelengths R.sub.1, R.sub.2 and R.sub.3 of 480 to 520 nanometers, R.sub.2 of 600 to 800 nanometers and R.sub.3 of 400 to 480 nanometers and not greater than (R.sub.1 -40) nanometers.
    Type: Grant
    Filed: February 25, 1980
    Date of Patent: July 21, 1981
    Assignee: Tioxide Group Limited
    Inventor: David F. Tunstall