Although both Becke line (BL) and dispersion staining (DS) can be used to determine refractive index (RI) of a solid immersed in an immersion oil, DS has several advantages complementary to the BL method that make it a versatile aternative technique for refractive index determination using immersion method:

• - it is very easy to estimate the RI difference between a solid in a mismatched oil using DS and quickly find the next oil to be used using the chart below;
• - only DS is capable of determining 2 or 3 principal RI’s for a low-birefringence solid using a single oil;
• - only DS is capable of estimating the percentage of particles having a specific RI mixed with other particles with significantly different RI’s;
• - only DS is capable of image analysis applications to amorphous or isotropic transparent particles.

This presentation illustrates the above points with several practical application examples.

Su（2005）による『Dispersion staining - A versatile complement to Becke line method for refractive index determination』から