Preliminary Solvent Extraction of Gross Additives from Aqueous and Alcoholic Extractants

1 Preliminary Solvent Extraction of Gross Additives from Aqueous and Alcoholic Extractants 

In addition to using diethyl ether as the extraction solvent, depending on the partition coefficient of the additives between the extraction liquid and the solvent, other low boiling solvents might be suitable in certain instances, e.g., petroleum ether, methylene dichloride and benzene. The ether used for extraction can be purified by shaking 2 litres of ether with 300 ml of 30% aqneous sodium hydroxide in a separating funnel. The lower phase is rejected and the ether phase washed with water. Finally the ether is distilled from 20 g solid sodium hydroxide and stored in an amber bottle. 

1 Extraction Test (Assuming the Extraction Test is Carried Out on 700/800 mi Scaie) 

To the contents of the extractor (700/800 ml) add 100 g solid sodium chloride and stir to dissolve. Charge with ether and extract for 10-15 hours. To the ether extract add 3 g of anhydrous sodium sulfate. Shake, filter off the ether and wash the sodium sulfate with fresh ether into the receiving flask. Remove ether on a warm water bath, working the residue in stages into a 10 ml beaker with appropriate ether washings at each stage to avoid losses of residue. Finally, quantitatively transfer the residue to a 2 ml volumetric flask. 

This procedure was used to check the recoveries of dilauryl thiodipropionate (DLTDP) by ether extraction. The method was checked at the 15 and 75 ppm DLTDP level from 700 ml of the aqueous and alcoholic extraction liquids. DLTDP was determined in the extracts by infrared spectroscopy and by elemental analysis for sulfur as discussed in Chapter 4). Table 12.1 shows that the recoveries are in excess of 80%. 

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