White pigments refractive indices

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). 

Table 7. Refractive Indexes and Reflectivities of White Pigments...

The oxide titania, Ti02, because of its high refractive index, is used in high-grade white pigments of great opacity and covering power. The... 

In passing, we note that reaction 17.39 is also used in the conversion of natural rutile ore, which is usually red-brown because of its iron(III) content, to pure Ti02, which is used as a filler for paper, as a white pigment in paints, and as a photocatalyst (Sections 10.4 and 14.4.2). The high optical refractive index gives Ti02 the best available covering power in... 

With a refractive index close to 1.5, similar to that of paint and plastics media, ultramarine gives a transparent blue in gloss paints and clear plastics. Opacity is obtained by adding a small quantity of a white pigment. Increasing quantities of white give paler shades, and a trace of ultramarine added to a white enhances the whiteness and acceptability. 

Zinc Sulfule. Whereas zuic sulfide is important mainly as a component of the composite white pigment lithopone. it also has a limited use as a single pigment After titanium white, it has the second highest refractive index of all the while pigments. However, its chemical and thermal resistances are inferior to those of TlO. ... 

Extender pigments are low-cost, generally colorless or white pigments with a refractive index less than 1.7. Sometimes diese pigments are also referred to as fillers. Many extenders are derived from natural sources and display many diverse properties. They are added to various formulations to improve technical and application properties and to reduce costs, Like pigments, extenders are dispersed in media in which they do not dissolve, but compared to pigments they do not have any significant coloristic properties. 

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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