Principles of cryometric impurity determination as applied to samples of small sizes

Abstract

A co nsideration of the faclo rs that tend to prevent attainmen t of t hermal a nd t hermod.vna mic1equ ilibrium d ur ing t hermometri c m etl;ods of purity an alysis s uggests t lmt t he p r o~1 ems. la rgely o n glll ate from sp onta neously. llltr oclucecl inequali ties i n com p os it ion . D un ng eit her a fr eeZin g or m el tlllg cycle, t he soh d phase settl es in t he liqu id. T his r eslil ls i n a greater a \'er age puri ty i n the boLlo m t han in t he upper part of t he \" esse!. TIle effecls would be par ticul a rly s trong duri ng a melling sequence \\ 'here the liquid released by melting of t he solid " -ould prov ide t he co mpositio n al en vironm ent for t he establis hment of fin a l temperature. This hyp ot hesis has been tested by t he des ign of a new cell f or s mall samples. The dcsig n inco rp orates use of s mall go ld p a ns to hold solid and liqui d in close contact. T he resul ts are co mpar able i n precision Lo t hose from conventional t i me-temperature curves witll muc h la rger samples, a co nd iLion not ordinarily p os ible wit h small samples.