naphthalenesulfonic acid
noun
naph·tha·lene·sul·fon·ic acid
variants:
or chiefly British naphthalenesulphonic acid \ -ˌsəl-ˌfän-ik-, -ˌfōn- 
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Medical Definition of naphthalenesulfonic acid
: either of two crystalline acids C10H8SO3 obtained by sulfonation of naphthalene and used in the synthesis of dyes and naphthols