Fish hook in classifier efficiency curves: An update

• Optical parameters influence sizing of sub sieve particles by laser techniques.
• Fish hook effect is a consequence of erroneous particle size analyses.
• Theoretical models to explain fish hook adequately are not available.
• Fish hook is a scientifically insignificant placebo.

Fish hook in classifier efficiency curves has been receiving attention in the last three decades, more so with the advent of laser diffractometry. In the first part of this paper, we analyse two occurrences of fish hook reported recently in Separation and Purification Technology. It is shown that in both the cases, inaccuracies in measured particle size distributions could be the likely cause of the observed fish hook. In the second part, we re-examine the present state of knowledge on fish hook including the limitations of experimental observations reported so far and the drawbacks of theoretical explanations. Finally, we provide a basis on why it is to be considered nothing more than a scientifically insignificant placebo.

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