[Determination of the dispersity of suspensions using photoelectric colorimeters of different makes].

Different conditions of measuring the suspension dispersity of photoelectric colorimeters of two brands,KFK-2 and FEK-56, result in distorted data: the dispersity index (DI) measured by KFK according to the method developed for FEK is inaccurate. The presence of 2 photoreceptors in the KFK apparatus, in contrast to the FEK one, results in elevated values of optic density (D) when the apparatus sensitivity is changed, starting from 590 nm wavelength (this fact is mentioned in the operation instructions) and eventually breaks the inversely proportional relationships between the D value and wavelength. DI estimation is based on the proportional relationships between wavelengths and D values obtained with a selected light filter pair. The wavelength selection mode had to be changed in the procedure of DI measurement by KFK-2 (or by KFK-MP) so that the light filter pair was placed in the same sensitivity zone; the distance between the cuvette and photo element was also changed (the cuvette with the sample was placed not in the cuvette holder but at a maximum distance from the photo element, closer to the source of light). Such modifications helped obtain compatible results of optic density measurements and DI values with photoelectric colorimeters of various brands. This is true only for suspensions rather than for transparent solutions, which fact is explained by the theory of light dispersion by suspension particles.