Common old buddy and tell them what the real name is! Some folks might just
want to be more accurate in their use of the name.<g>
Dick Sullivan
At 01:16 PM 11/12/97 -0500, you wrote:
>So much has been bandied about regarding this surfactant, that (for those
>of you who wish to be confused further) thought I might provide some details.
>
>First of all, Tween (the numbers show the degree of polymerization) belongs
>to the polyethylene ester group of surfactants (detergents to the
>uninitiated). It is also known as Polysorbate, but Tween is specifically
>purified for medicinal purposes, and is used as an emulsifier in
>medications for human internal use. Chemically, it is an oleate ester of
>sorbitan, which makes it a bit more complex than the other surfactants in
>the group. Use-wise, it should behave just like any other non-ionic wetting
>agent. (OK, there are three types: negative-ionic, positive-ionic, and
>non-ionic; for photographic purposes we normally use only the non-ionic as
>they do not react with alkalinic or acidic materials. Most household
>detergents are ionic, which is why they don't do well in photography; ionic
>is cheaper.)
>
>So Tween, Polysorbate - they're identical and you can use what you can get.
>For our purposes, the molecular polymerization number is almost meaningless
>(the most common is 80, but I note 20 is marketed; these are not
>concentrations, but merely how many molecules are in each polymer). And,
>remember, this is stuff that is used in medicinal products, so ingestion is
>harmless (cheaper surfactants are used as emulsifiers in most food
>products). Good to know in these days of chemical scare tactics!
>
>Any questions?
>
>Sil Horwitz, FPSA
>Technical Editor, PSA Journal
>silh@iag.net
>
>
>
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