Re: polarizing microscope for the refractive index calculation

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