iodine colour numberiodine testionion exchangeion exchange charomatographyion exchangerionicionic bondionic micelleionisingionizationionizing radiationirce type 6iridescenceiridexiridyeirisiron liquoriron proffingironbuffironingirraditionirregular satten weaveirregularityirresolvableirreversibleirreversible processisoisochromaticisochromicisocyanate resinisocyclic ringisodisperesisoelectricisoelectric pointisoelectric point precipitationisoelectric regionisoionicisolanisolated motifisomerisomerisationisotacticisothermisothermalisotonicisotonic solutionisotropicisotropyisovyl