Sodium Beta-Naphthalenesulphonate: Naphthalene Sulphonated at 170 °C

The salt that caustic soda turns into beta-naphthol, a dye component. Gattermann (1914): heat naphthalene with sulphuric acid at 170 to 180 °C, which favours the beta acid three to one; take the acid up as its calcium salt, let the less soluble beta salt crystallise, and swap calcium for sodium with soda. 50 g of naphthalene give 60 to 70 g. Hot strong acid: goggles and gloves. The picture: our own drawing.