The Tween family is a group of surfactants. All the major scientific dealers
who handle chemicals have it. Fisher Scientific, for one. If you can't find
a source, e-mail me directly and tell me where you are located and I can
probably look up a place near you. But it is a standard laboratory reagent.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net