Microtrac Particle Analyzer Maxwell postulated a demon that could sort m1l particles 1111 the basis of s p e d We might postdate a demon that muld count susl)ended particles and sort them out on the basis ofsire. T h e interesting thing is that the functions olsuch a demon are being performed hy an existing instrument. When W.('. Wiley assumed his dutiesas Vice-President.Technology a t I.eedsnnd Northrup he sought tu adapt certain wtexploiled (er.hnckrpies to process cmtrrd. Discussion with lalmrntor.~personnel and a consultant in optics reached the conrlusim that it shmld he pussilrlu t o measure the total volume of particles in a smoke hy the use (rf light scattering techniques. Another consultant, Profesxrr W. L. Wilcox of the University of North W a l a was given the assignment of determining if this conclusion were really valid. His analysis of the scattering of light by small particlesshowed that the total diffracted flux is proportional 10 the sewnd power of the radius of the particles, whereas the diffracted flux in only a small central region 01 the scattering pattern is pnrpurtional to the frwrth power of the particle radius. lly employment ofwitahle rotating fillers or masks (discs with slots ofsuital~legeometry rut in theml the scattering is pmportionnl t o the third puwer (volume) of the three t \ . l x s d scatterineoln laser beam can h e c ~ n v e r t e dinto themdius. Hv mennsofan at~~rc~nriatedetectiondeviee.
from t h a t which motivated the original study Business Week. July 11.1977. p. 8
WCF
Volume 58
Number 10
O c t o b e r 1981
765
