Calibration of light scattering photometers with Ludox

A simple and exact method is presented for the calibration of light scattering photometers in absolute turbidity units employing du Pont Ludox as the calibration medium. It is shown that previous attempts to employ Ludox as a standard took no cognizance of the relatively high scattering power of this substance in relating τ to I 90 , and hence results considerably in error were obtained. To check the validity of the calibration, molecular weights were run on the standard Cornell polystyrene in toluene and MEK, and on the I. U. C. sample III polymer in MEK at both 4358 and 5461 A. The results obtained show excellent internal consistency as well as agreement with published data.