Size Measurement Methods Quiz

Size Measurement Methods

• Methods and instruments for size measurement are categorized into six groups for simplicity.
• Visual methods: Optical, electron, and scanning electron microscopy, image analysis.
• Separation methods: Sieving, classification, impaction, electrostatic differential mobility.
• Stream scanning methods: Electrical resistance zone, optical sensing zone measurements.
• Field scanning methods: Laser diffraction, acoustic attenuation, photon correlation spectroscopy.
• Sedimentation and Surface methods: Permeability and adsorption.

Visual Methods: Microscopy

• Microscopy is used alongside other size analysis methods to determine the size range and degree of dispersion.
• It's the only method that allows visualization of individual particles.
• Common measurement ranges include:
  • 3-1000 µm for optical microscopy
  • 2 nm to 1 µm for Transmission Electron Microscopy (TEM)
  • 20 nm to 1000 µm for Scanning Electron Microscopy (SEM)

Equivalent Diameter

• Defining the size of irregularly shaped particles is done by comparison with standard shapes, usually spheres.
• Volume diameter (d_v): The diameter of a sphere having the same volume as the irregular particle. Formula: d_v = (6V_p/π)^1/3 = 1.241V_p^1/3
• Surface diameter (d_s): The diameter of a sphere having the same surface area as the irregular particle. Formula: d_s= (4A_p/π)^1/2= 0.564A_p^1/2
• Stokes' diameter: The diameter of a sphere having the same settling velocity as the particle under Stokesian conditions.
• Newton's diameter: The diameter of a sphere having the same settling velocity as the particle under Newtonian conditions.

Separation Methods: Sieving

• Test sieves are circular brass shells used to separate particles based on size.
• Sieve cloth made of wire with uniform square openings for separation.
• Aperture (or Opening): Distance between parallel wires.
• Mesh number: Number of apertures per linear inch.
• Mesh size: Distance between wires. Mesh number and mesh size are inversely related. (Higher mesh number, smaller mesh size)
• Sieve analysis: A mineral processing method where particles are separated based on size.
• Procedure:
  • Arrange sieves into a nest (coarsest to finest).
  • Place the material to be tested on the topmost sieve.
  • Shake the sieves to allow particles to pass through.
  • Weigh the material retained on each sieve.
  • Calculate the percentage of material retained on each sieve to produce the differential analysis.

Particle Size Distribution Data

• Particle sizes are often measured and reported in tabular format (e.g., Table 1).
• Weight percentages of retained material on each sieve are calculated for differential analysis.
• Cumulative weight percentages are obtained by sequentially adding the individual weight percentages from either top or bottom of the table.
• Mean particle sizes for each fraction are calculated (e.g., Table 2). Formula for calculating average size: Average size = 100/Σ (w_id_i), where w_i is the weight percent of the material retained by the sieve, and d_i is the mean size of the material retained by the same sieve.

Test your knowledge on various size measurement methods including visual, separation, stream scanning, and field scanning techniques. This quiz covers essential instruments used for size analysis, with a focus on microscopy and its applications. Challenge yourself to understand the methods and their respective measurement ranges.