Re: polarizing microscope for the refractive index calculation

"brbandli" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> Hi Spiros, and group,
> 
> I'm sort of new to this group, but I must disagree with the following:
> 
> "George" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > It is not an easy subject to learn.  It is even more difficult to teach.
> 
> Granted, the subject of refractive index, as with any other abstract
> physical phenoma, is more difficult for some people to grasp than others.
> However, with the references listed, along with those of many others (Bloss
> being one of the more clearly written and illustrated), it is a very
> straight-forward process to make very acurate and precise refractive index
> measurements with a polarized light microscope and a little patience.  I may
> be biased in that I have done quite a bit of refractive index measurements
> on minerals and I had an expert in optical mineralogy instructing me, but if
> I can learn it, I believe anyone can.  Just remember, nothing is easy, some
> things are just less difficult.
> 
> That said, I haven't measured the refractive index of a polymer.  But,
> having some expierence with the process, I would be sure to test the
> solubility of your sample in the Cargille refractive index liquids if you
> are going to use the immersion method (as mentioned by Aaron).  If your
> sample is soluble, don't worry, there are other options.  Any transparent
> liquid will have a unique refractive index that can be measured with a
> refractometer.  Water, olive oil, expirement with a few if you have the
> time.  There are also lists in some references or try the web.  Also, the
> refractive index of a solution can be changed by changing the concentration.
> However, the refractive index of a material is highly dependent on
> temperature, if you use a refractometer to find the refractive index of some
> common liquid, be sure to take this into consideration.
> 
> Inducing strain at the edge of a sample when you section it is important to
> be aware of.  It might be reduced by freeze fracturing under liquid
> nitrogen.  Not sure if this is correct, but it's an idea.
> 
> Basically, don't be intimidated.  Consult a couple of the printed
> references.  If you have access to a university geology department, try
> contacting their mineralogist or petrologist.  They should at least have
> some experience with a polarized light microscope.  Shouldn't a polymer
> scientist know how to do this too?
> 
> Good luck, and let us know how everything turns out.
> 
> Bryan


This is a mail I've recieved from Steve Eckhardt  which explains
perfectly what I'm looking for:

""""""""Perhaps some terminology can help here.  Materials are
isotropic, uniaxial or biaxial.  In the first of these, there is only
one refractive index for the material, no matter which way you look at
it.  In the second case, there are two refractive indices, one in a
certain direction (the axis) and a second in any direction
perpendicular to the first.  Biaxial materials have three refractive
indices, Nx, Ny & Nz.

At 3M we make and measure uniaxial and biaxial polymer films, so I'm
sure
someone in the company knows how to measure them, but I'd have to find
them
and see what they're allowed to say about the subject.""""""""'  


(Bryan) I dont want to dilute my sample since its a stretched film
with specific chain conformation which I dont want to be lost. If I
dilute or melt it the sample wiil turn to an isotropic one but I'm
concerned about its optical properties as it is

I just want to know how these bizzare colored images coming out of a
polarized microscope can be translated to n???