S A M P L I NG NG A N D A NA NA L YS YS I S O F C O M M ER ER C I A L F AT AT S A N D
AOCS Official Method Ca 3a-46 Replacing Ca 3 - 25 and Ca 3-46
Reapproved 1997
Insoluble Insoluble impurities impuritie s
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DEFINITION This method determines determin es dirt, dirt, meal meal and other foreign for eign substances substance s insoluble insolubl e in kerosene and petroleum ether. SCOPE Applicable to all normal fats and oils.
APPARATUS Gooch crucible--prepared with a glass-fiber filter without organic filler (Reeve Angel 934 AH or Wash the filter with and Dry to constant weight at I Cool in a desicca tor to room temperature and weigh. 2. Filter flask of convenient size Gooch crucible v adapter. REAGENTS (see Notes, Caution) Petroleum Petrol eum ether ether AOCS Specification H 2-41. 2. Kerosene refined petroleum distillate with a flash point not below 23°C (75°F). as determined by the American Society for Testing and Materials Standard Method using the tag closed tester. The kerosene should be filtered through a Gooch crucible, prepared as in Apparatus, I , before using.
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PREPARATION O F SAMPLE Samples must be mixed thoroughly. thorou ghly. If If necessary, soften with gentle heat (do not melt) and mix thoroughly with an efficient mixer.
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PROCEDURE Use the residue from the moisture and volatile matter determination (AOCS Official Methods Ca 2b-38 or Ca or a sample prepared in the same manner (see Notes, I). of kerosene to the heat in a 2. Add 50 water bath to dissolve the fat.
3. Filter through the prepared Gooch crucible cru cible with the aid of a vacuum. Wash with five portions of hot kerosene, allowing each portion to drain before adding the next. 4. Wash thoroughly with petroleum ether to remove all of the kerosene. Dry the crucible and contents to a constant weight at cool to room temperature in a desiccator and weigh. CALCULATIONS Insoluble impurities, = gain in mass.of mass.of crucible mass of sample taken for
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NOTES Caution
Petroleum ether and kerosene are flammable solvents. A fume hood should be used at all times when working with these solvents. NUMBERED NOTES certain feed stocks) with a higher than . I . Samples usual percentage of insoluble inso luble impurities impuri ties may may be difficult, if not impossible, to filter. A study among five laboratories indicated that, for such samples, a 2 -g subsample (rather than a 5-g subsample as specified in AOCS Methods Ca 2b-38 and 2d-25) can be used without greatly affecting the precision of the method.
