PH value
The refractive index, represented by the letter n, of a material describes how light propagates through and is bent by, that material. The magnitude of the refractive index, depending upon the electronic structure of the molecules, governs to what extent the path of light changes, when entering or leaving a material.
Particles in a matrix, like pigment particles surrounded by the binder system in a coating, ink or plastic, can change the propagation direction of light when the particles and the matrix have a different refractive index. This phenomenon, called scattering, results in both white color (provided that the particles do not absorb visible light) and the hiding power of the coating.
Available studies in humans and postmortem analysis of tissues suggested that the oral bioavailability of titanium dioxide in humans is very low. JECFA noted that there are currently no epidemiological studies that allow any conclusions to be drawn with respect to an association between dietary exposure titanium dioxide and human health effects.