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Last edited at 7:07PM on 3/15/2013
A very large class of dyes contain acidic groups, such as the sodium salts of sulfonic acids or phenolic groups. Acid dyes are more soluble and have less tinctorial value than basic dyes but they also have greater light fastness. They contain two groups of atoms-one acidic, such as a carboxylic group, and one colour-producing, such as an azo or nitro group. 2-Amino-4-nitrophenol(http://www.guidechem.com/cas-99/99-57-0.html) is the key intermediate of acid dye's synthesis.
The raw materials used in making acid dyes include hot tap water, acidic vinegar and food coloring. These ingredients are ideal for home made acid dyes. However, commercial ones are made using advanced ingredients.