--- [EMAIL PROTECTED] wrote:
 
> The blue-->brown with bleach issue has me wondering
> if your blue is actually
> indigo, which (I believe, unless I have things
> backwards) turns yellow in basic
> solutions and blue again in acids.  That might also
> explain why it's so very
> hard to remove.  Try dipping your brown swatch in
> vinegar to return it to blue?
>  If it works, you know you've got indigo (or a
> synthetic version of the same
> chemical) and could do research from there.
> 
> Emma

Indigotin is not an indicator.

The indigo dye bath is basic, and is yellow, but
that's from the reduced form of indigo, indoxyl, where
blue is the oxidized form.

I'm not sure what's going on with the brown, except
further chemical reactions--there are several
chemicals with common names of [color] indigo, per an
old CRC Handbook via my faulty memory.  i.e., red
indigo, brown indigo, and blue indigo.

While looking up some indigo chemistry to supplement
said faulty memory, I came across an interesting page
<http://www.indigopage.com/chemistry.htm>, which show
the Tyrian purple molecule as found in the Murex
species--it is 6,6'-Dibromoindigo.
Only two bromines away from indigo!

But nothing to supplement the [color] indigo list in
my immediate search.

Ann in CT


      
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