Oleum

Oleum (CAS 8014-95-7), also sold as fuming sulfuric acid or Nordhausen acid, is a solution of sulfur trioxide in concentrated sulfuric acid available in a range of free SO₃ concentrations.

It functions as a sulfonating and acidifying agent in large-scale chemical manufacturing, delivering higher reactivity than standard sulfuric acid where process chemistry demands it.

In detergent and surfactant manufacturing, it sulfonates alkylbenzenes and fatty alcohols to produce the anionic surfactant intermediates used in household and industrial cleaning formulations.

Dye and pigment producers rely on it to introduce sulfonic acid groups into aromatic compounds, a step critical to solubility and fixation in textile dyeing processes.

Petroleum refiners use the chemical in alkylation and sulfonation reactions during lubricant and specialty chemical production to ensure high efficiency and yield.

In mining and metals processing, it serves as a leaching and digestion acid where elevated reactivity is required to dissolve refractory ores or process intermediates.

The product is supplied as a fuming liquid, with free SO₃ content typically ranging from 20% to 65%, with 20%, 30%, and 65% grades the most commonly traded.

It is handled and shipped in dedicated acid-resistant tankers or drums under strict transport classifications. Technical grade is the standard commercial specification.