Direct Yellow 4 is a chemical compound with the formula . This is a direct dis-azo dye, a diamine derivative with separated azo groups. Due to its properties, value and strength, it is considered one of the most important dyes based on

stilbene Stilbene may refer to one of the two stereoisomers of 1,2-diphenylethene: * (''E'')-Stilbene (''trans'' isomer) * (''Z'')-Stilbene (''cis'' isomer) See also * Stilbenoid Stilbenoids are hydroxylated derivatives of stilbene. They have a C6–C ...

. It can be used as an acid-base indicator. In an alkaline environment, the yellow color of the dye deepens through orange to red at a pH of 6.4 → 8.0.

Synthesis

The compound can be obtained by coupling tetrazotized diaminostil-benesulfonic acid twice to

phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...

Physical properties

The compound forms orange powder. It is water-soluble, producing a golden brown color, and moderately soluble in

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

, also yielding a golden brown shade. It is slightly soluble in

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

and soluble in fiber materials. When treated with concentrated

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, it turns red to light purple; diluted sulfuric acid produces a purple color with blackish light purple precipitate. In

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

solution, it shows a dark brown color (not in all solutions).{{cite web , title=Direct Yellow 4 , url=https://www.worlddyevariety.com/direct-dyes/direct-yellow-4.html , publisher=worlddyevariety.com , access-date=19 April 2025 Adding concentrated

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

to the dye solution results in a dark purple color with precipitation. When thick

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...

solution is added, it turns pale light orange; with 10% sodium hydroxide solution, it becomes bright red.

Uses

This dye is primarily used for coloring cellulose and polyamide fibers but is also suitable for dyeing leather and paper. It is known for its excellent dyeing properties and outstanding discharge fastness. Direct Yellow 4 is also used as an

acid-base indicator A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence, ...

References

PH indicators Complexometric indicators Aromatic compounds Azo dyes Sulfonates Nitrobenzene derivatives