Enhanced safety for the determination of sulfuric acid and oleum concentration with DSA 5000 M

Sulfuric acid, H₂SO₄, is a colourless and odourless oily liquid that is highly hygroscopic. Dissolving sulfur trioxide, SO₃, in concentrated sulfuric acid results in a fuming solution called oleum (or fuming sulfuric acid). Sulfuric acid is widely used in the organic-chemical industry, such as the plastics industry and petrochemistry, in the production of phosphoric acid and fertilizers, and also in other industries, e.g. with metallic mordants or accumulators.

The production of sulfuric acid proceeds in several steps starting from sulfur dioxide SO2. Concentration determination for quality control and subsequently adjustment of process parameters is important in the production stage when concentrated sulfuric acid containing dissolved sulfur trioxide is diluted with water to the desired concentration.

A standard method for concentration determination is to titrate sulfuric acid or oleum with a base, commonly sodium hydroxide, NaOH. The acid sample has to be diluted prior to titration – a time-consuming and hazardous operation. The accuracy of the results is influenced by several factors, such as the skill of the operator, the quality of the standard base solution, the precision of the burettes, the quality of the indicator used, etc. In routine analysis accuracies of 0.1 to 0.5 % w/w H₂SO4 can be attained.

The Anton Paar DSA 5000 M Density and Sound Velocity Meter uses an efficient method for concentration determination of sulfuric acid and oleum by combining two physical properties, namely density and sound velocity.