Which of the following is NOT a Dye Lake dye?

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

Answer: (D)

Dye lakes are insoluble pigment forms produced by precipitating a dye with a metal salt, making the color stable in solid and solid-phase reagents. Titan Yellow, Clayton Yellow, and Thiazole Yellow are dyes that are encountered as dye lake pigments, formed to give a stable, non-dissolving color in test tablets and strips. Calmagite, however, is a soluble dye used as a metallochromic indicator that forms colored complexes in solution to detect calcium and magnesium; it is not used as a lake pigment. Because it remains soluble and changes color through complex formation rather than existing as an insoluble lake pigment, it is not a Dye Lake dye.