Anton Paar’s density sensor L-Dens 7400 and sound velocity sensor L-Sonic 5100 are suitable wherever an H2SO4 measurement is required. Together with the L-Com 5500 a continuous and accurate monitoring of H2SO4 and oleum, even in the transition range 90 – 110%, is possible.

Concentration measurement of H2SO4 solutions and oleum

Sulfuric acid (H2SO4) is a colour- and odourless oily liquid that is soluble in water in any ratio, in a reaction that is highly exothermic.

It is a central substance in the chemical industry and is used in different concentrations for the production of fertilizers, oil refining, wastewater processing and chemical synthesis as well as for a wide range of end applications, e.g. as electrolyte in lead-acid batteries.

Anton Paar sensors are suitable wherever H2SO4 measurement is required and cover the entire concentration range of H2SO4 (0 – 100 %) as well as in the oleum range (0 – 45 % free SO3).

Wetted parts are built of highly resistant materials such as Tantalum or Hastelloy.

To guarantee highest accurate H2SO4 concentration measurement in the process, the physical property which shows the biggest change upon change in acid concentration should be employed.

Depending on the measuring range, different measuring methods are available to achieve highly accurate measurement results.

The large product portfolio of Anton Paar ensures the best process measuring solution for every concentration range.

Measurement Setups

The acidic nature and the specific behaviour of H2SO4 at different concentrations require special materials and instruments. Depending on the application Anton Paar offers different setups for the online concentration measurement of H2SO4 solutions and oleum:

All sensors can be equipped with the transmitter Pico 3000. This transmitter can be integrated into the electronics housing of the sensor or into a remote control housing.

Different interfaces are offered for direct communication with your plant. An HMI is also available as an option.

H2SO4 concentration monitoring 0 – 90%

Anton Paar’s highly accurate density sensor L-Dens 7400 Version TAN with the wetted parts made of Tantalum is the perfect solution for H2SO4 concentration measurement from 0 – 90 % w/w.

Density has a steep and almost linear dependence and ensures continuous and highly accurate monitoring of the H2SO4 concentration. The modular design of the L-Dens 7400 allows different possibilities for an easy installation into the process.

The sensor can be installed inline or in a bypass system.

H2SO4 concentration monitoring 90 – 100%

The L-Sonic 5100 Version HAS sound velocity sensor was specially designed to measure sulfuric acid from 90 – to 100 % w/w with very high accuracy as the sound velocity is strongly influenced by a concentration change.

Using Hastelloy® BC1®, the newest generation of corrosion resistance material, no plastic coating is required which would negatively influence the concentration measurement.

Continuous H2SO4 monitoring from 90 – 110%

The L-Com 5500 Version HAS, the combined density and sound velocity sensor, masters the challenge of measuring in the transition zone between sulfuric acid and oleum. Only Anton Paar is able to measure continuously from 90 to 110% w/w H2SO4with just one sensor.

A specially developed concentration formula combines both measuring values to a continuous measurement. Using only one measurand it can not be determined secured whether the concentration is below or above 100% H2SO4.

The installation of the L-Com 5500 is equal to the L-Dens 7400 installation.

Oleum monitoring 0 – 45%

The concentration of oleum (H2S2O7) is expressed as the amount of “free SO3” in 100 % sulfuric acid. Thus 45% oleum contains 45 % of free SO3 in 100 % sulfuric acid and corresponds to a concentration of 110 % H2SO4.

In the oleum range of 0 to 45% free SO3, the density sensor L-Dens 7400 Version HAS is best suited. Sound velocity would also be possible in a reduced range (0 – 30 % oleum) and with a lower accuracy.


  • Measurement of the entire H2SO4and oleum concentration range
  • Continuous monitoring from 90 to 110% H2SO4
  • No plastic coating of sensor material

– Fast reaction even under rapid temperature changes

– Highly accurate measurement results

  • Easy integration and operation
  • Automatic temperature compensation

H2SO4 applications

  • Production of H2SO4 and oleum
  • H2SO4 dilution
  • Fertilizer production
  • Lead–acid battery production
  • Pickling bath monitoring
  • Anodizing of aluminium


Wiaan Goosen
Anton Paar Southern Africa
Tel. +27 82 651 2308

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