The units typically used in static light scattering (SLS) measurements are given in the table below.
| Parameter | Symbol | Units |
|---|---|---|
| Wavelength | λ | cm |
| Avogadro's number | NA | mol-1 |
| RI increment | dñ/dC | cm3g-1 |
| Rayleigh Ratio | Rθ | cm-1 |
| Concentration | C | g cm3 |
| Molecular weight | M | g mol-1 |
| 2nd Virial coefficient | A2 | cm3 molg-2 |
Dimensional analysis is a simple method for showing the need for unit consistency when performing an SLS molecular weight measurement. When the Rayleigh equation is written in the standard form shown below, it is easily seen that the collection of units on the left hand side of the equation must ultimately reduce to units of inverse molecular weight, i.e. mol/g.
