As. Dukhin et al., MODIFIED LOG-NORMAL PARTICLE-SIZE DISTRIBUTION IN ACOUSTIC SPECTROSCOPY, Colloids and surfaces. A, Physicochemical and engineering aspects, 138(1), 1998, pp. 1-9
The modified log-normal distribution is a smooth continuous distributi
on depending on four parameters: median size, standard deviation, mini
mum size and maximum size, This distribution introduced by Kottler [J.
Franklin Inst. 250 (1950) 339] and Irani [J. Phys. Chem, 63 (1959) 16
03] gives an opportunity to restrict the particle size range. This dis
tribution is asymmetrical on the logarithmic scale of particle sizes.
The modified log-normal distribution is especially useful for acoustic
spectroscopy because sound attenuation is very sensitive to the prese
nce of large particles. Particles with size above 3 mu m cause signifi
cant scattering losses. As a result, sound attenuation spectra show a
sharp growth within a sound frequency range 10-100 MHz when large part
icles are present. The high sensitivity to large particles is a very u
seful feature of acoustic spectroscopy allowing one to detect these pa
rticles. This feature requires a special approach allowing the charact
erization of large particles with a high accuracy. Regular log-normal
distribution tends to overestimate the fraction of large particles and
underestimate the median size. Experimental tests have been performed
with silicon particles dispersed in water. The particle size distribu
tion has been measured independently by X-ray sedimentation and by an
acoustic spectrometer. This test shows that the lognormal distribution
provided by the acoustic spectrometer deviates from the sedimentation
data. Implementation of the modified log-normal distribution resolves
this discrepancy. (C) 1998 Elsevier Science B.V.