Chloride process. This process requires a high titanium feedstock. Rutile is reacted with hydrochloric acid to produce titanium tetrachloride, which can be hydrolyzed with steam or oxidized with air to render the dioxide. A rutile form of titanium dioxide is obtained.

When used as a base or colorant in a product, titanium dioxide becomes handy in formulas meant to offer a lot of brightness and opacity. Titanium dioxide is so pigmented, in fact, that it’s used not only in white and pastel-colored products but also in darker shades, as well.

Although barium sulfate is almost completely inert, zinc sulfide degrades upon exposure to UV light, leading to darkening of the pigment. The severity of this UV reaction is dependent on a combination of two factors; how much zinc sulfide makes up the pigments formulation, and its total accumulated UV exposure. Depending on these factors Lithopone B301, Lithopone B311 powder itself may vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant might be used, like small amount of cobalt salts, which would be added to the formulation. This process creates cobalt-doped zinc sulfide. The cobalt salts help to stabilize zinc sulfide so it will not have as severe a reaction to UV exposure.

Prof. Maged Younes, Chair of EFSA’s expert Panel on Food Additives and Flavourings (FAF), wrote of the decision: “Taking into account all available scientific studies and data, the Panel concluded that titanium dioxide can no longer be considered safe as a food additive. A critical element in reaching this conclusion is that we could not exclude genotoxicity concerns after consumption of titanium dioxide particles. After oral ingestion, the absorption of titanium dioxide particles is low, however they can accumulate in the body.”

What titanium dioxide is really emblematic of ... is the failure of FDA to look back at these old decisions and ask whether its decisions that were made in this case ... 56 years ago (in the 1966 approval) still hold up, he said.

Applications:

Lithopone, an alternative to titanium dioxide