Experimental measurements that describe the dispersive behavior of production samples of optical glasses are fit with models of minimum complexity for the purpose of in terpolation and extrapolation. Software to perform this procedure on a regular basis is presented, and shown to dis tinguish between models of inappropriate complexity. Two degrees of freedom usually provide a statistically optimum fit to the data contrary to the widespread practice of fit ting a general, six term model to such measurements. Using specially developed analysis tools, it is concluded that annealing does not significantly change the partial dispersion of the sample. Partial dispersion is established at the time the ingredients are combined in a melt and is in variant from one annealing to another. This is an important result to consider when planning the fabrication of optical systems whose prescription changes with changes in material characteristics
