CHEMISTRY AND INDUSTRY 523l'ortlriiitl ceiiitwt is ~)rotlucetl by n clinkering process in \vliicli sonic %lo/, to 30% of tlic mix bcconios liquid at tlic clinkcriiig temperature. T t has I)ccn slio\vii~ tlint if coiiiplctc cqiiilil~riuni is to 1)c innintriirictl in t Iic ccinciit clinker, ns tlic llogiir cnlcirlntion I )~C S I~~) I ) C I S C~~, sonic rcrictioii hct.\vc!cn this liquid nncl t.lii. rsistiiig solid mist in nitilly cilscs occur tliiring cooliiig of tlic clinkcr. I t scciiis t h n t irndcr the coiitIitioiis of ccincnt protlrictioii no such rc:iction occiirs diiriiig cooliug owing to t,lic short tinit: tiviiil-;il)lt! over t Iic tcrnpcriitirrc riingc wliich is in\-olvcd. Tlie coiicc*pt ion thnt l'ort,liiiitl cciiiciit clinker is to Iic rt!piirclt~tl ;is i i iiiritcriril whicli closcly npi)ronclies ~qiiilil~riiiiii :it. thc clinkering tcniprriitiire, but in \vliicli tlic cqiiilil)riiiin is " frozcii " on cooling, hiis t Iitwftirc gniiicd much support. On t,liis concept ion. ~sliich hi: been discussctl by t.he writer clsewhwe,2 tlic cunipoiintl content. of ceiiicnts miiy diiTcr sonic-