While editing the first issues of Particle Characterization it has been recognized by the editors that the papers submitted differ widely in the representation of data and in the nomenclature chosen to characterize such common variables as particle size, different equivalent particle diameters, average particle sizes, cumulative and density values of a distribution etc. In oder to make papers published in this Journal more readily assimilable and graphs representing particle size analysis data instantly recognizable by using agreed upon standardized nomenclature the following paper has been submitted by one of the editors. It was first presented at the Harold Heywood Memorial Symposium, September 1974, at the University of Technology, Loughborough, U. K.

For several years the size distributions of particulate matter have increasingly been determined by using diffraction pattern analysis. In order to evaluate particle size distributions from the far field intensity distribution of light diffracted by a distribution of particles, a linear set of equations must be solved. Since, in many cases of application, conventional methods for solving linear sets of equations become unstable, the calculated particle size distribution may also be grossly in error. By applying special, known mathematical methods we succeeded in obtaining a parameterfree solution of the above problem.After a brief description of the mathematical method used, a diffraction pattern analyser will be presented as well as some experimental results obtained with it. The results obtained with aerosols and suspensions come from experiments performed with narrow-sized latexes and mono-and bimodal particle size distributions of limestone and quartz. 0 VCH Verlagsgesellschaft mbH, D-6940 Weinheim 1985 0176-2265/85/0105-ooM $02.50/0

In der Windsichtung kommen zu der durch Strömung und Anfangsbedingungen determinierten Bewegung isolierter Einzelteilchen eine Reihe von Wechselwirkungen zwischen Wand, Strömungsmittel und Teilchen hinzu, die sowohl das determinierte Bewegungsverhalten verändern als auch eine stochastische Bewegungskomponente überlagern. Dabei ergeben sich für die verschiedenen möglichen Sichtanordnungen und für die absatzweise und stetige Sichtung unterschiedliche Prinzipien des Zusammenwirkens dieser Phänomene. Für einige charakteristische Erscheinungen werden Berechnungsansätze und Ergebnisse angegeben. Andere Phänomene, wie Desagglomeration und Vermeidung von Gutansatz, werden nicht näher behandelt. Die Untersuchungsergebnisse an zwei neuentwickelten Analysensichtern und einem Querstromsichter werden mitgeteilt, wovon der letzere für technische Sichtungen geeignet sein könnte.

The investigations of single and combined properties of particles or of particulate matter still belongs to the most important areas of present research and practical applications of Particle Characterization. Methods to measure single particle properties, as for instance particle size, shape, composition and velocity, are of much higher sophistication than before and they still aim at improved accuracy and higher resolution. There still is a considerable lack of understanding, and lack of theoretical interpretation and of experimental evidence of the differences seen in the correlation of different equivalent diameters, obtained when analysing the same irregularly shaped particle, or a distribution of particles, using different physical principles. Furthermore, there still is a lack of understanding of the influence of shape on the results obtained with optical methods using diffraction, light scattering etc., thus asking for more information with respect to the transferability of results from one physical principle to another. The measurement of combined particle properties comprises the simultaneous measurement of, for instance, size, velocity and concentration, which is of particular importance in the comprehensive description of multiphase flow systems. Those instruments which are in working order are highly complicated, not easy to use and to handle and they are in most cases special adaptations for a limited range of the variables to be analysed. There is also growing interest in the evaluation of socalled property functions. Particle Characterization will remain for quite a number of years just as exciting as it has been in the past. If industrial demand enforces the use of on-line inskumentation it might even become more interesting.QVCH Verlagsgesellschaft mbH, D-6940 Weinheim, 1986

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