[alt-photo] Re: The Gum Arabic Report (was: Re: Re: evaporation of gum mixture)

[Alberto Novo]

Katharine,
thanks for your report.
With two Polaroid filters and a led one can build an home-made polarimeter, 
so the qualitative analysis of the various brands would be possible. 

> ... In 1990,  a sentence  was added 
> to the definition that specified that the the solution must  fall within a 
> specific optical rotation range,  that effectively  excluded A. seyal.  
> (A. senegal is levorotary; A. seyal and some  other A. species are 
> dextrorotary).
 

Alberto
www.grupponamias.com
www.alternativephotography.com/articles/art102.html