“…However, azo dye classes such as sulfur azo dyes (organic compounds containing sulfur or sodium sulfide) and vats (chemically complex, and water-insoluble; among the oldest dyes employed) in fibrous textiles based on cotton and wool, exhibit poor performance, thereby motivating further research and development. Though ample works have been published on azo dyes on the basis of spectroscopic (Bielska et al, 2009;Cegarra and Riva, 1988;Fazeli et al, 2012;Gokturk and Tuncay, 2003;Karukstis et al, 1998;Karukstis et al, 2010;Mahbub et al, 2019e), potentiometric (Ghoreishi et al, 2007;Hosseinzadeh et al, 2007;Sharma et al, 2016;Simončič and Špan, 1998), and tensiometric (Khamis et al, 2005;Sachina et al, 2019) approaches, there is a dearth of conductometric study on the azo dye-surfactant ion pair. The association behavior of anionic azo dye with anionic, cationic, as well as nonionic surfactants in H 2 O has been reported in the literature (Nora, 2012).…”