ISO 10370 Petroleum products - Determination of carbon residue - Micro method
5 Reagents and materials
5.1 Nitrogen, low oxygen content, i.e. 99.998 % (V/V) or better, with appropriate regulation to provide a delivery pressure of 0 kPa to 200 kPa.
NOTE The practical minimum delivery pressure is 140 kPa.
6 Apparatus
6.1 Glass sample vials, of 2 ml capacity, 12 mm outside diameter, approximately 35 mm high.
A vial of 4 ml capacity, 12 mm outside diameter, approximately 72 mm high may be used with samples of very low carbon residue content, i.e. below approximately 0.20 % (m/m), but no precision data has been obtained for them.
NOTE 1 An interlaboratory study has been carried out by the Energy Institute on the 10 % volume distillation residue procedure for middle distillates using 4 ml vials and automatic distillation units and the precision is given in Clause 12.
NOTE 2 A glass sample vial of approximately 20 ml capacity (20.5 mm to 21 mm outside diameter by (70 +/- 1) mm high) for samples that are expected to yield residues < 0.10 % (m/m) may also be used, so that a more appreciable mass difference may be determined. In this case, a 5 g sample size is suggested. No precision has been determined for this technique, but it may be found suitable for very low 10 % residue samples.
6.2 Eyedropper or small rod, suitable for sample transfer.
6.3 Coking oven, comprising a circular heating chamber approximately 85 mm diameter by 100 mm deep for top-loading, capable of heating to 500 °C at a rate of between 10 °C and 40 °C per min, with exhaust port of 13 mm inside diameter for nitrogen purge of oven chamber (inlet near top, exhaust at bottom centre), with thermocouple sensor located in oven chamber next to but not touching sample vials, and with lid capable of sealing out air.
The condensate outlet leads into a short vertical section where most of the vapour condenses and falls into a removable trap located directly below the oven. A schematic diagram is given in Figure 1.
6.4 Sample vial holder, comprising a cylindrical aluminium block approximately 76 mm diameter by 17 mm thick with 12 evenly spaced holes (for vials) each 13 mm diameter by 13 mm deep.
The holes shall be arranged in a circular pattern approximately 3 mm from the perimeter. The holder shall have legs 6 mm long with guides to centre in the oven chamber, and an index mark on the side to use as position reference. A typical holder is shown in Figure 2.
6.5 Thermocouple, iron-constantan, with exterior read-out and a range including 450 °C to 550 °C.
6.6 Analytical balance, of 0.1 mg sensitivity.
6.7 Cooling vessel, desiccator or similar tightly closed vessel, without desiccant.
