Wool Fast Pink

Reagent C - 0.2% Wool Fast Pink RL in 10% acetic acid solution... 

The mechanisms involved in the binding of Wool Fast Pink RL (Figure 1) to the protein molecule is as well not fully understood but probably involves a combination of ionic interactions between the charged groups on the dye and protein molescules, and hydrophobic interactions between the dye and protein molecules. 

Figure 1. Suggested structural formula for Wool Fast Pink RL...

Perspiration tests similarly indicated the presence of two dyestuffs. In the alkali solution, the yellow color seemed to be removed almost completely, leaving a pink-colored fabric. In the acidic solution, the yellow dye migrated to the wool, silk, and nylon sections of the multifiber test strips, staining these fibers a bright yellow shade. The pink color seemed to bleed minimally a small amount of color was transferred in the alkali solution tests, but generally this pink color remained comparatively very fast. 

In many applications ultramarine blue is stable to around 400 °C, violet to 280 °C and pink to 220 °C. All have excellent light fastness with a 7-8 rating (full and reduced shades) on the International Blue Wool Scale. Color fade attributed to light exposure or moderate heat is almost always caused by acid attack. Ultramarines react with all acids, and if there is sufficient acid, the pigment is completely decomposed, losing all color, to form silica, sodium and aluminum salts, sulfur, and hydrogen sulfide. Evolution of hydrogen sulfide with acids is a useful test for ultramarine. 

---