Chemically Talking, this molecule is "midway" amongst Sorbitan Oleate and Sorbitan Trioleate, that means that it's also an attachment of sorbitan (a dehydrated sorbitol (sugar) molecule) with the unsaturated fatty acid Oleic Acid, but in a ratio of two:three hence the "Sesqui" aspect from the molecule's identify. The emollient plant oil coming thr