Which of the following is a common white pigment ?

Options

A. `Cr_(2)O_(3)`
B. `PbCrO_(4)`
C. `TiO_(2)`
D. `CrO_(3)`

Answer

C

Explanation

Prior to the use of `TiO_(2)` in paints, the common white pigment was ''white lead'' , `Pb_(3)` `(CO_(3))_(2)` `(OH)_(2)` . Apart form its toxicity, it discoloured in industrial city atmopspheres to give black lead sulphide (PbS). `TiO_(2)`, which is stable to discoloration in polluted air, has now replaced white lead completely. Not only is `TiO_(2)` of very low toxicity, it has the highest refractive index of any white or colourless inorganic substance (even higher than diamond). As a result of this high light-scattering ability, it covers and hides provious pains, it os also added to colored paints to make the colors paler and mask previous colors beter. Just as lead (II) chromate (Chrome yellow) is an important yellow pigment, so chromium (III) oxide is common green pigment.