Refractive index titanium dioxide pigments

The refractive index of these pigments is about 1.5, which means that they give a transparent blue when used in paints and clear plastics. Opacity can be increased by adding small amounts of titanium dioxide. The principal failing of ultramarine is its lack of resistance to acid, which can even decompose the pigment if there is sufficient available. Coated grades are made with substantially improved acid resistance. 

The refractive index of a pigment at each wavelength is determined by its crystal structure. Titanium dioxide pigments (rutile and anatase) differ from each other and from other white pigments or crystalline substances, like silicon dioxide, in the proportion of radiant energy that is transmitted, absorbed, or re-... 

Despite its low refractive index (1.94), basic lead carbonate pigment was used in paint compositions for many years, but it is no longer used in the modern coating industry due to the toxicity of lead and the availability of more efficient titanium dioxide pigment with almost ten times more hiding power. 

White pigments, some of rather variable composition, that have been used in the past include white lead (Cl Pigment White 1), refractive index 1.9 zinc oxide (Cl Pigment White 4), r.i. 1.9 lithopone (Cl Pigment White 5), r.i. 1.84 zinc sulphide (Cl Pigment White 7), r.i. 2.3 antimony oxide (Cl Pigment White 11), r.i. 2.2. All have been eclipsed by titanium dioxide (Cl Pigment White 6). 

Titanium dioxide is found in nature in three crystal forms anastase, brooldte, and rutile. Its extreme whiteness and brightness and its high index of refraction are responsible for its widespread use as a white pigment in paints, lacquers, paper, floor covering, plastics, rubbers, textiles, ceramics, and cosmetics, see also Aluminum Catalysis and Catalysts Copper Fertilizer Haber, Fritz Iron Steel. 

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