Why must care be taken not to substitute cedar wood oil with another when making microscopic observation?

Question

Why must care be taken not to substitute cedar wood oil with another when making microscopic observation?

Answer 1

Cedarwood oil is a classic medium to use with immersion oil lenses because the oil has a refractive index similar to that of the glass coverslip.  The refractive index of Cedarwood oil is 1.515.

There are other suitable media that can be used depending upon the exact microscope and slides used, but they should never be mixed.