Which of the following is NOT a Dye Lake dye?

• A. Titan Yellow
• B. Clayton Yellow
• C. Thiazole Yellow
• D. Formazan

Answer: (D)

Dye lakes are insoluble pigments made when a water-soluble dye is precipitated with a metal salt, such as aluminum or calcium, to form a stable metal-dye complex. This insolubility in water is what defines a lake pigment and makes it useful as a pigment in foods, cosmetics, and printing.

The yellow dyes listed are known to form lake pigments when treated with suitable mordants, so they fit the idea of Dye Lake dyes.

Formazan, however, refers to a class of dyes used mainly in biochemical assays and cell biology. These dyes are typically water-soluble or used in contexts where they do not form the insoluble metal-dye lake pigments. Because it does not create an insoluble metal complex like the lakes do, it is not considered a Dye Lake dye.