ISO 21493:2019 pdf – Petroleum products – Determination of turbidity point and aniline point equivalent.
1 Scope This document specifies a method to determine the turbidity poi nt of p et roleum products based on di st illates from crude o il. This docum ent also specifies how to convert the turb idity point to an aniline point equivalent. This document describes a procedure using automated or automatic apparatus suitable for transparent samples with an initial boiling point above ambi ent temperature. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the l atest edition of the referenced document (including any amendments) applies. – Single-volume pipettes liquids – Manual sampling Petroleum liquids -A utomatic pipeline ling 3 Terms and definitions For the purposes of this document, the following terms and definitions ISO and I EC maintain terminological databases for use in standardiza tion at the following addresses:
Reduce the viscosity of viscous or waxy samples by warming to a temperature below that which would cause the loss of light ends or the dehydration of the drying agent. If suspended water is visibly present, centrifuge the sample to remove the water before carrying out the final drying with drying agent. Remove any suspended drying agent by centrifuge or filtration. Heat samples containing separated wax until they are homogenous and keep heated during the centrifuging or filtration operations. 9 Procedure ‘9.1 Clean and dry the apparatus. ‘9.2 Pipette 10 ml± 0,02 ml of p-anisaldehyde and 10 ml± 0,02 ml of the sample into the test tube. lf the material is too viscous for pipetting, weigh to the nearest 0,01 g, a quantity of the sample corresponding to 10 ml at room temperature. ‘9.3 Prepare the apparatus in accordance with the manufacturer ’ s instructions. Use the expected temperature for the sample as guidance for setting up the apparatus. If the sample is unknown, perform an exploratory scan on the sample to determine the approximate turbidity point, and use that temperature for the immediate repeat analysis of the same material. ‘9.4 Stir the p-anisaldehyde-sample mixture the inclusion of air bubbles and, if necessary, heating at a rate of to until complete obtained by applying heat directly to the jacket tube. lf the p-anisaldehyde-sample mixture is completely miscible at room temperature, substitute a non- aqueous cooling bath for the heat source.
9.5 Allow the mixture to cool slowly at a rate of between to during continuous stirring, to a temperature to below the temperature at which appears according · 9.6 Record as the turbidity point the temperature, to the nearest which the mixture suddenly becomes cloudy throughout. NOTE 1 This temperature, and not the temperature of the separation of small amounts of material, is the minimum equilibrium solution temperature. NOTE 2 The true turbidity point is characterized by a turbidity which increases sharply as the temperature is lowered. ·9.7 Repeat the observation of the three times by heating and cooling of the same sample. 10 Evaluation and expression of results If the range of the three successive determinations does not exceed and report the average of the three determinations as the turbidity point, to the nearest 0,1 °C. If the range of the three successive determinations do exceed the equipment, reagent, an d overall execution of the test method. Repeat the test after investigations.