Rudolph Refractometer Calibration Standards

** Please contact us for pricing & details. Online orders will not be accepted.


Refractometer Calibration standards are:

  • Supplied in 28ml bottles
  • Supplied with a calibration certificate traceable to the National Institute of Standards and Technology (NIST)
  • Shelf life of unopened bottle is 5years
  • Shelf life of opened bottle is 2.5 years
  • Fluids calibrate at temperatures between 20°C and 40°C are accurate to 0.0001 Refractive index
  • Fluids calibrate at temperatures above 40°C are accurate to 0.0005 Refractive index
  • Some fluids available with calculated Brix values
  • Some fluids available with calculated Urine Specific gravity numbers


Choosing a Refractometer Calibration Fluid

Rudolph Research Analytical offers two types of refractometer calibration fluids:

  • NIST traceable refractive index fluids
  • Brix standards made from sugar and water


This article is designed to serve as a guide as to which fluid will suit the application best.


Technical Considerations


Refractive Index Fluids

Brix Fluids


Description of Fluids

Refractive index fluids are made from chemical compounds such as methylene iodide, silicon oil and alpha bromonapthalene. These chemicals are chosen as they are non toxic though some of the fluids do have an unpleasant odor (alpha bromonapthalene = mothballs).

Brix fluids are a mixture of sucrose and water.

Brix fluids
They are so safe you could drink them. They are just sugar and water.

Traceability of Fluids

Refractive index fluids are provided with a certificate showing traceability to a national standards body – NIST.

Brix fluids are made using the method specified in ICUMSA and are provided with a non-traceable certificate of analysis.

Refractive Index fluids
NIST traceability is the ultimate US standard.

Shelf Life

Refractive index fluids have a rated life of 5 years unopened, 2.5 years opened. Care should be taken that they are not frozen, but otherwise they can be stored at room temperature.

Brix fluids have a life of 30 days and must be kept refrigerated.

Refractive Index fluids
Stored at room temperature for 2 years.

Clean Up

After calibration with the refractive index fluids the refractometer must be cleaned with an organic solvent such as acetone.

After calibration with the Brix fluids the refractometer can be cleaned with water.

Brix fluids
No toxic solvents needed


Refractive index fluids are available over the full range from 1.30 – 1.70 Refractive Index and 0 – 95 Brix.

Brix fluids are available over the range 0 – 67.5 Brix.

Refractive Index fluids Wider range of calibration options

Temperature Dependency

All fluids are temperature dependent. The refractive index fluids have a different temperature dependency than the temperature compensation setting on a refractometer and so can only be used on a temperature CONTROLLED refractometer.

Brix fluids have the same dependency as a temperature compensated refractometer and so can be used on any instrument.

Brix fluids
They can be used to calibrate hand refractometers as well as bench models.