Quality Control by Refractometry of Mineral Oils and By-Products

15 Aug 2008
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The characterisation of the purity of oils, waxes, fats and other by-products of the raffination process of mineral oils is easily done with an ABBE-refractometer. This historic instrument standard is easy to use in the laboratory but has some difficulties when it comes to emulsions or darker samples.

Nowadays the standard instrument should be an automatic refractometer with a minimum resolution of 0.0001 nD. The measurement according to ASTM D 1218, ASTM D 5006, DIN51521 and DIN51423-2 can be better and more effectively performed with an automatic instrument.

The Automatic Alternative

Using the KRÜSS refractometer model DR6300-T the temperature is controlled through a built-in peltier-thermostate which controls in the range 10 - 80°C with an accuracy of 0.1°C.

The temperature stability is 0.05°C. This temperature control allows a resolution of the refractive index of 0.00001. For an example measurement of the temperature related refractive index change of Paraffin oil, the accuracy still is 0.00004.

All KRÜSS refractometers of the DR model range are compliant to ASTM D1218 and can be used with the small external Peltier thermostate PT31 or in the T-version have a built-in Peltier thermostate. Due to these thermostatisation possibilities the KRÜSS refractometers can be used not only for standard temperatures but also for applications with samples that are only fluid at higher temperatures like fats, wax, paraffins and other by-products.

All instruments can be calibrated with a 1-, 2- or 3-point calibration. The measuring time is about 4 sec. The stainless steel sample compartment and the sapphire prism are easy to clean and are IP65 protected. All models are equipped with a serial interface, a printer connection and an USB-port.

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A.KRÜSS Optronic GmbH