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The concentration analysis of liquid media is one of the most critical parameters for a proper process and quality control within the Chemical Industry.

By measuring the refractive index, concentration levels of many media consumed or created within the chemical and textile fiber industry, such as solvents, acids, caustics as well as other intermediate and end products, can accurately be monitored and a continuous quality control be assured.

The chemical design variant of the process refractometer PIOX R721 R is offered as a fully stainless steel design variant with all wetted materials made out of grade 316 Ti / 1.4571 steel.

When dealing with highly corrosive media, such as hydrochloric, strong sulfuric or hydroflouric acid, the PIOX R inline refractometer is also available as a special carbon reinforced PTFE design variant offering an unrivalled corrosion resistance, long term stability and reliability in such harsh environments.

Both designs are highly durable against any corrosive and toxic media due to their internal FFKM gaskets, the media and scratch resistant sapphire optics as well as the complete separation of the sensorhead from the electronics compartment.

Being ATEX Zone 0/1 certified and available with long and short sensorheads that can be integrated into the process via DIN / ANSI flange or the proprietary FLEXIM flow cell, chemical refractometer PIOX R721 is the ideal process analytical technology for a wide array of liquid media within the chemical industry.


  • Patented transmitted light measurement principle - offering completely drift free, precise and long term stable measurements
  • Highly accurate optical process technology making costly laboratory tests obsolete
  • No flow velocity needed - as known from conventional technologies
  • Independent in regard to gas bubbles and turbidity as well as the media‘s viscosity
  • Internal self diagnostic tools for predictive and low maintenance efforts
  • Ready for Advanced Meter Verification


Industry Applications

Technical Facts

Measuring quantities
Refractive index and refractive index at standard temperature, fluid temperature, concentration g/l, mass and vol.%, density and density at standard temperature, scale values for example °Brix and °API, additional quantities programmable
Measurement range
nD: 1.3 ...1.7, °Brix: 0 ...100
Measurement accuracy
nD: 0.0002 (corresponds to: 0.1 °Brix, 0.1 w%)
nD: 0.00002 (corresponds to: 0.01 °Brix, 0.01 w%)
Diagnostic values
- 20 °C ... (+ 130 °C) + 150 °C
Media temperature
150 psi; on request 300 psi
(depending on process connections)
Fluid pressure
Sensor: IP67, FM Class I Div. 2
Transmitter: IP65, FM Class I Div. 2
Degree of protection
Sensor R500: IP67, ATEX (IECEx) zone 0,/1
Transmitter R721: aluminum or stainless-steel enclosure, IP66, ATEX (IECEx) zone 2
Wetted parts, materials
Stainless steel 316Ti (1.4571)
Housing Material
Stainless steel 304 (1.4301)
Process connection
DIN/ANSI flange, sight glass fitting, proprietary FLEXIM flow cell
Cleaning systems
PTFE Chemical Design variant: Wetted parts, materials: PTFE carbon-fiber reinforced bulk material
Advanced Meter Verification (AMV)