Page 1 of 1

INDUSTRIAL OILS AND DERIVATIVES

AOCS Official Method Td 3a-64Replaces L 15a-58 • Reapproved 1997

Color after HeatingDEFINITIONThis method measures the color stability of fatty acids after heating under the specified conditions ofthe test.SCOPEApplicable to all normal fatty acids.

APPARATUS1. Oil bath—5000-mL stainless steel beaker equipped

with a mechanical stirrer and containing any light-col-ored alkali-refined oil. Hydrogenated cottonseed oil issuitable for this purpose.

2. Heat source—Tirrill burners (3) are satisfactory, butelectric immersion heaters with suitable thermostaticcontrol may be used.

3. Thermometer—partial immersion, 95–255°C, AOCSSpecification H 11-58.

4. Tubes—2.5 × 24 cm with ground-glass joint (see Fig.1). Available from Kontes, Vineland, NJ USA, or anyother manufacturer of special glassware (see Notes, 1).

5. Test tube holder—see Figure 2.6. Timer—interval timer capable of measuring intervals

of time up to and including 120 min.7. Filter paper—fine porosity such as Eaton and Dikeman

no. 512, Whatman no. 12, Reeve–Angel no. 871, S andS no. 596, or any equivalent filter paper.

8. Nitrogen—source of nitrogen capable of being regulat-ed to 1–2 psi pressure.

PROCEDURE1. Bring the bath to a temperature of 205 ± 2°C and

maintain the temperature within the specified range.

2. If the sample to be tested is not liquid at room tempera-ture, liquefy by heating on a water bath to a tempera-ture not more than 10°C above the titer of the sample.

3. Fill a clean, dry tube to a depth of 12.7 cm with thesample, and place in the oil bath.

4. Adjust the level of the oil in the bath to 14 cm from thebottom of the tube(s). When placing several tubes in thebath, the bath temperature should not drop more than5°C below the minimum bath temperature, and therecovery time to reach 205°C should not exceed 5 min.

5. Adjust the flow of nitrogen so that the surface of thesample is blanketed by inert gas at all times.

6. Set the timer for 60 min if the sample has an iodinevalue >15, or for 120 min if the sample has an iodinevalue of ≤15.

7. Remove the tube(s) from the bath and read the colorimmediately using AOCS Official Method Td 1a-64and Gardner color standards.

NOTES1. Glassware cleanliness is of utmost importance. The

suggested method is washing with detergent and rins-ing with reagent-grade acetone or alcohol. Dichromatesolutions should not be used.

/

9 / ′′

1 / ′′ 1 / ′′

/

2 / ′′

/ ′′

1 / ′′2′′

4 / ′′

Ts

Ts

Figure 1. Details of color stability tube.

8 / ′′

7′′

4′′

1′′

6 holes 1 / ′′ diaon 4 / ′′ dia boltcircle

6 holes / ′′ diaon 4 / ′′ dia boltcircle

7 holes / ′′ diaon 2′′ dia boltcircle

3 holes / ′′ diaon 6′′ dia boltcircle

12 holes / ′′ diaon 4 / ′′ dia boltcircle

Top plate 5 / ′′ dia/ ′′ thick

Bottom platesame as aboveexcept as noted

3 rods / ′′ dia5 / ′′ long threaded1 / ′′ on each end,6– / ′′ hex. H.D. nutshold plates

Tube holder for heatstability test aluminumor stainless steelScale: / ′′ = 1′′

5-L Stainlesssteel beaker

Figure 2. Details of tube holder for heat stability test.