I know the difference between Span and Tween, I know the first number is describing the length of the fatty acid, the second is the number of fatty acids (0 meaning one, 1 meaning only PEG-4 in Tweens, 5 meaning 3 fatty acids) but what is Span 83? It is described as sesquioleate. The structures you can find are quite strange (even as fatty acid-sorbitol mix, though it should be an ester). Is it a mix of mono- and di-oleated sorbitan?