The hydroyen ion concentration (pH) of the pigments, in aqueous suspension, were measured by the author, and it has become clear that they are closely related to the rust inhibitive properties of the pigments. All the acidic pigments, whose pH lying below 6, have shown to be rust stimulative, and none of them were rust inhibitive; vice ver'sa, all the basic pigments, whose pH being higher than 8, inhibited the rusting, and none stimulated the corrosion. The rust inhibitive properties of the pigments, whose pH lying between 6.2 and 7.8, have mostly shown to be indeterminate or somewhat inhibitive; while a few of them were strongly rust inhibitive or stimulative.
(I.) The socalled soluble drier “Soligen Trockner” were added in the form of turpentine solution (60 per cent) to two sets of varnishes of long oil and short oil types having Albertol and rosin as their resin-component and linseed oil and china wood oil as their oil-component in the ratio of 5 to 95. Then, the viscosities of the varnishes, drier solutions and the mixtures were measured at 30°C. From the data thus obtained, the deviations of the measured viscosites from those calculated by additive relation were calculated. (2) The deviations lie in minus side in the cases where the oil component was linseed oil and in the reverse direction when wood oil was used as oil component. These facts show that polymerized wood oil and drier behave in flocculating way and linseed oil and drier peptizes each other. (3) From the amounts of deviations in the cases where 5 per cent of drier solutions were added to the varnishes, corresponding deviations to the optimum additions were looked for by caluculation in which linear relation of viscosity change and drier content was assumed. It was shown by this procedure that the viscosity of the varnish is influenced very slightly in all casses, for the amounts of variation did not exceed 5 per cent.