Zeiss Pulfrich nephelometer

In the early methods used to estimate haze, samples, viewed at 45 to the incident light, were compared visually with a suitable standard such as Fuller s earth or barium sulphate [175]. It was usually necessary to transfer the sample to a suitable cell so that only one measurement could be made. More precise measurements are made using either the Zeiss Pulfrich nephelometer [162, 176] or the Radiometer hazemeter [162, 169]. Measurements are made in the former 45° to the incident light but at 90° in the latter. In both, the sample is held in a cell which is immersed in distilled water in a cylindrical chamber in the instrument to eliminate irregularities in the cell s construction. Accordingly the cell can be replaced by standard... 

Using the Zeiss Pulfrich nephelometer with a green filter, the following relationships were found [177] ... 

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