The csiict. ilclitiit-ion of ~iiirticlc size i i t d sliapc is rL firctor of iinlmrt:iticc in inriiiy rcsciirclics conncctctl with IJuilditig inirt~criiils, fillers, niid iii tlic preparation of otlicr powdcrctl tiiitieriils. Thc! object of this pirpci: is to describe tlic various tiictliotls of dcfiniiig tltcsc propcrtics :ind to give t h e rcsults of sonic nicnsiiretiicitts tiliide 011 tniitcriiils iisetl for roiitl constriict,ioti. Tliis piper is rcstrictctl to the proI)lciii of dcfining t l ~c size iititl s h p c of n sit& particle of irrcgihr shapc, or of tlic iivcriige V~IIIICS for IL gr0111) of 1)ilrticlcS of :~pproxitiiiitcly the S ~I I I I C size, i i i i d is not, coiiccrticd witli tlic tlctcriiiiiitition of tlic tiiciiti sizc of ii systciii of pnrticlcs estcntling over required to discuss fiilly tlic liittcr problem.
Tltc iiictliotls of tlcfiiiitig tlie tiiciiii diiinictcr of' t i n irrcgdiirly shaped piirticle iiiiiy be dividcd iitto two grotlps, ttii1lidy, tliosc biiscd oil tllc size of tlic projected iiiiiigc of tlic pitrt.iclc d i c n pliiccd in t h e most stable position iilld tiietJhotls IJtiScti 011 t,ltc volu~iic of tlic piirticlc. Alciisureiiicnts I.iiisetl 011 tlic projcctctl iiniigc of tlic purticlc i i i tlic iirost stiiblc positioii igtiorc tlic: t,hickness of t.lic piirt,iclc, hit. :in iil10~v:iiicc ciiii I)c tiiiitlc for this factor, ;IS is sho\ti iit, !t I i i t ~r s t : i p i i i thc pi11)cr. Tliis inctltotl of iiic:isitr(!inctit is piirttciiliirly iipplictiblc to fiiic po\vdcrs tliiit (!:in oiily be csiitniiictl with tlic iiitl ol' tlic tiiicroscopc. A inure iicciiriitc iivc!riigc of tlic t Iircc diiiiciisions of the p r t iclc is obt.iiiiiet1 froin tlic tticiisiirctliciit of t.ho vol~~tne, \ J u t t,liis procedure presetits liriicticiil tlilliciilt.ics wit.11 sitiiill piirticlcs. u wide riLiigc of sizes. A sCI)iiriitC 11ii1)er ~011ld be DIAMETERS BASED ON THE PROJECTED IMAGE OF THE PARTICLE