Relating to or containing azo groups combined with sulphonic acid functional groups in a molecule.
From 'azo-' + 'sulphonic' (from 'sulphon-', relating to sulfonic acid, from Latin 'sulphur'), describing a class of dyes and reactive compounds developed in the late 1800s.
Azosulphonic compounds are the workhorses of modern acid dyes in textiles—the sulphonic acid part makes them dissolve beautifully in water while the azo part gives them color, which is why your colorfast jeans are probably dyed with something like this.
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