Journal of the Japan Society of Colour Material

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The apparent specific volumes (ASV) and liquid absorptions of pigments determined by different methods are known to have poor consistency. In spite of the similarity that should exist between these two values, there appears to be no interrelation.
A centrifugal method has been employed to determine the ASVs of pigments in air and in water. It was found that the reproducibility was excellent and there existed a definite interrelation between the two values. The ASV obtained by the centrifugal method was smaller than that obtained by the tapping method. As the density of the pigment became high, the ASV decreased sharply at first and then gradually. Pigment with a very small particle size (20-30μ) had a much larger ASV compared with its density. The porosity of most pigments was in the range between 65% and 85% with a mini-mum at the density of about 2.75.
The water absorption obtained by the centrifugal method was generally larger than that obtained by the beaker method. There seems to exist a linear relationship between the water absorption values obtained by these two methods. The ASVs in water and in air of silicate pigments such as talc and calcium silicate were nearly equal, but this was not the case with oxide pigments such as titanium dioxide and zinc oxide. In the latter case the value measured in water was smaller.
The ASVs of metallic soaps which are water repellent were also measured in 1% aqueous solution of polyoxyethylene (10) nonylphenylether (NP-10). Those were nearly equal to the ASVs obtained in air except the case of aluminum stearate. The ASVs of inorganic pigments in 1% NP-10 solution were also equal to those in water. The ASV of a pigment mixture in air was smaller than the algebraic sum of the ASVs of each pigment. Treatment of the pigment mixture with solid fatty acids caused to increase its ASV, but not when treated with other substances.

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