The word "iothion" is spelled /aɪˈoʊθiən/. The first syllable "io" is pronounced as "eye-oh" and is followed by "thion" pronounced as "thee-uhn". This spelling is derived from the chemical compound "iodothion", which is commonly used as a fungicide. The word might be difficult to spell since the pronunciation of the first syllable does not follow the typical English pronunciation of "i-o-d" but instead is a combination of two vowel sounds.
Diiodohydroxypropane, a thick, yellowish, oily liquid obtained by the action of potassium iodide on dichlorhydrin; employed as a substitute for the iodides, applied by inunction in a 25-50 per cent. ointment with lanolin and petrolatum.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.