Re: ATM [OT] Corn oil.

["PETER JOHN SMITH" <pjifl@bigpond.com>]

> >Corn oil has almost the same refractive index as high silica glass.

Most easily obtained natural organic oils fall in the range 1.465 - 1.475
Corn, cotton, safflower, soya, grape are some.

Slightly higher - 1.475 - 1.485
castor, linseed, sunflower.

A few are unusually high - eg. tung oil 1.52

Since some of these harden on exposure to air (especially tung and linseed)
they could only be used for quick testing. They are of little practical
use. The figures vary as composition and purity is not fixed.

Others are :-

Glycerine - 1.473.

Kerosene - 1.45

The real problem is to obtain a liquid with high refractive index. Some do
exist up to 1.8. Scientific or Jewellers supplies will be able to sell you
special high index liquids essential for use in refractometers. Even in
very small quantities the price will probably blow you away.

A moderately high index product (1.567) which is very useful is 'Refractol'
from Lapidary supplies. It is cheap enough to be useable in slightly larger
amounts.

A useful selection would be castor oil, medicinal parafin (under 1.5 but
pleasant to use), refractol, and if needed special refractometer fluid.

It is also possible to 'blend' producing exactly the refractive index
required.

Does anyone know of the refractive index of Silicone oils ??????


Peter Smith, INNISFAIL, AUSTRALIA. pjifl@bigpond.com.au
For eyepiece stuff try http://www.users.bigpond.com/pjifl