Hi all,

I looked into the catalogue of a local dealer selling all sorts of
devices for chemical laboratories.

A refractometer is a device for measuring the refractive index of a
liquid. This is done by sending a light beam through the liquid and a
second beam through a prism. The angle between both beams is compared
and directly says which refractive index the liquid has.

For the Brix there is some calculation done with the refractive index
which I couldn't find out. But the Brix is in principle the same as the
refractive index.

So this all means:
- you have to have a liquid. A solid medium won't do
- the liquid has to be transparent - milk won't work
- the liquid shouldn't be too dark else it is impossible to send a light
  beam through it. Good refractometers have a very strong light bulb to
  measure even dark liquids.

The prices in my catalogue range from 500 DM to 18,000 DM and I think
the dollar is around 1.80 DM, so calculate yourself...

While the full scale seems to be 0..90 Brix, most refractometers can
measure only one third of that. The catalogue lists refractometers
for 0..32 Brix, 33..58 Brix etc.
One refractometer (price 1000 DM) was a full range one.

Concerning measuring the quality of foods a bunch of questions arise:

- obviously the food must be juiced before measuring and the juice must
  be filtered to make it transparent. How to measure coconut flesh and
  other seeds/nuts then? Does one have to make oil of them? (Complica-
  ted - needs an oil mill)

- why should "more Brix" equal "better quality"? Just the fact, that
  there are more molecules present in the juice which give a higher re-
  fractive index, doesn't say if they are "good" molecules. Couldn't an
  artificial fertilizer give the same result?

- what about denatured molecules which yield a high Brix? This food
  would have a high Brix then but would be (partially) denatured

- if the Brix originally was for grapes, I would understand it. The
  vinters are hunting for more sugar contents and more sugar gives a
  higher Brix. But can one generalize this to other foods?

- much much more questions. I will save them for later.

Best refractive regards,

Stefan
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