K-PG325(M) by Sumita

$$n(\lambda) = \sqrt{2.23851 - 0.00701582\,\lambda^2 + 0.00956921\,\lambda^{-2} + 0.000186066\,\lambda^{-4} - 8.42855 \times 10^{-6}\,\lambda^{-6} + 5.31744 \times 10^{-7}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.86 \times 10^{-5} + 2(-3.2 \times 10^{-9})\,\Delta T + 3(-2.53 \times 10^{-11})\,\Delta T^2 + \frac{4.98 \times 10^{-7} + 2(8.02 \times 10^{-10})\,\Delta T}{\lambda - 0.172}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$