R salt
R salt, or disodium 2-naphthol-3,6-disulfonate (CAS 135-51-3), is a water-soluble naphthalene derivative that carries a phenolic hydroxyl group flanked by two sodium sulfonate groups and is also known as 3-hydroxy-2,7-naphthalenedisulfonic acid disodium salt or R acid disodium salt. The commercial product is usually a pale grey to beige powder with an assay around 85 to 90 percent, freely soluble in water and only slightly soluble in alcohols and other organic solvents. The hydroxyl group is strongly activated towards electrophilic substitution and diazo coupling, while the two sulfonate groups confer high aqueous solubility and produce intense colour once the ring is incorporated into a larger conjugated chromophore. It is a classical, large-volume dye intermediate manufactured from naphthalene by sulfonation, alkali fusion and neutralisation.
1. Dye intermediate: the main commercial use is as a coupling component for azo dyes, particularly acid, direct and reactive dyes in red, scarlet, carmine and magenta shades for textiles, paper, leather and inks, where the two sulfonate groups improve water solubility and substantivity.
2. Chromogenic and analytical chemistry: employed to prepare azo dyes and reagents used in analytical studies for detecting organic explosives and propellants by fast liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and other trace-detection techniques.
3. Precursor chemistry: a starting material for further sulfonated naphthols used in organic pigments, pH indicators, photographic colour couplers and metal-complexing structures, and a versatile building block in organic synthesis research.
4. Handling and storage: hygroscopic and light sensitive; keep containers sealed and dry away from strong oxidisers and direct sunlight, avoid dust generation during weighing and charging, and follow standard industrial hygiene practice with appropriate eye and respiratory protection.
Product Name: R salt
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