![]() ![]() We can obtain information about the size of a particle using the angle and intensity of scattered light. Refraction occurs as light changes angle traveling throught the particle. This gives the weight of particles of a particular size in the entire sample.Diffraction is also known as "edge diffraction" as that is where it occurs. The weight of the sediment layer is measured.These different layers are taken as particles of a particular size only present in the sediment layer.Hence different layers of sediment are formed.The rate of sedimentation varies based on particle size.Here the particles are suspended in a liquid medium and allowed to sediment or settle down in a cylindrical tube.There are different methods to carry out this procedure like the Anderson pipette method, balance method, and hydrometer method.This represents the diameter of an equivalent sphere that has the same rate of sedimentation.The size of particles here is expressed as stokes diameter d st.Similarly smaller ones settle slower and lie at the top of the sediment. So large particles settle fast and at the bottom of the sediment.Since in a given powder, all the particles are of the same density, they settle only based on size.This principle is used in particle size determination.The smaller and lighter settles slowly.The bigger and denser ones settle fast.We notice that when a particle falls into a liquid, it slowly settles down.This method can be used for particle size measurements in the range of 1μm to 200μm.Sedimentation method of particle size determination Since the sieves are shaken, the particles collide with each other and there are chances of further size reduction which can lead to errors.If the is wet, the pores of the sieves can get clogged with particles and sieving would be improper.The lower limit is 50μm so that small particles can be measured.It is less expensive as the sieves are reusable.The standard sieves with different mesh numbers as per U.S.P are available commercially.Sieves of different pore sizes are used to sieve the powder.This is a rough and fast method and one can obtain the weight distribution of particle sizes.The size of particles is expressed as d seive which is the diameter of the sphere that passes through the sieve aperture.Particles with a size range of 50 to 1500μm are measured by this method.Sieving method of particle size determination So particle dimension is taken in 2 sides and not in all three sides. Only length and breadth are measured, but depth is avoided. ![]() During the measurement, the particle is not in motion and at rest which gives a precise measurement.Agglomerates of particles can be seen and avoided while counting.It is simple and the particle shape can be directly seen.This microscopy method is used for particle size analysis in suspensions, aerosols, and emulsions. Are used to note the size of particles in microscopy. Around 625 particles are to be measured to get the data.ĭuring particle size measurement, dimensions likeĪ) Martin diameter: Length of the line that bisects the particle (irregular) image.ī) Ferrets diameteris also called an end-to-end measurement.A large number of counting are needed to obtain statistically valid data.After taking a fixed number of particle drawings on graph paper, the size is estimated by formulas.The shape of each particle is drawn with a pencil.Then using the micrometer, a reflection of particle shape is created on graph paper placed beside the microscope.This slide is covered with another glass slit to prevent the movement of particles.A fixed quantity of powder is mixed with oil and suspended on a slide.Here the particle dimensions are directly measured by observing into the microscope or by projecting onto a screen for ease.Particles in the size range of 0.2 μm to 100μm can be measured using this method.One can observe the particles directly for their shape and size through the microscope.Here the compound microscope parts, i.e., the eyepiece is fitted with a micrometer.This can be done by the use of a compound microscope.Conductivity or Coulter counter method.Direct microscopy or Optical microscopy.Hence their size measurement is checked to decide the properties like shape, the size distribution of entire matter, their nature like crystalline or amorphous type, the inter-particle space, etc. The particle size largely influences the proprieties of the material like their solubility, disintegration, stability, etc. ![]()
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