Extraction and Washing

Step 1. Extraction and separation of the acidic components. Shake 5-10 g. of the sohd mixture (or of the residue R obtained after the removal of the solvent on a water bath) with 50 ml. of pure ether. If there is a residue (this probably belongs to Solubihty Group II or it may be a polysaccharide), separate it by filtration, preferably through a sintered glass funnel, and wash it with a Uttle ether. Shake the resulting ethereal solution in a smaU separatory funnel with 15 ml. portions of 5 per cent, aqueous sodium hydroxide solution until all the acidic components have been removed. Three portions of alkaU are usuaUy sufficient. Set aside the residual ethereal solution (Fj) for Step 2. Combine the sodium hydroxide extracts and wash the resulting mixture with 15-20 ml. of ether place the ether in the ETHER RESIDUES bottle. Render the alkaline extract acid to litmus with dilute sulphuric acid and then add excess of sohd sodium bicarbonate. 

The complex is decomposed by stirring the reaction mixture into a solution prepared from 500 g of ammonium chloride in 2,000 ml of water to which 3 kg of crushed ice have been added. After extraction and washing, the ether is evaporated in vacuo at 40°C. The oily residue is taken up in 500 ml of petroleum ether and left to crystallize by cooling at -20°C. The yellowish crystals formed are dried (309 g) MPi< (Kofler block) 74°C yield 92%. 

Extraction is one of the more complex operations you ll do in the organic chemistry lab. For this reason, I ll go over it especially slowly and carefully. Another term you ll see used simultaneously with extraction is washing. That s because extraction and washing are really the same operation, but each leads to a different end. How else to put this ... 

Really soluble or miscible liquid pairs are no good for extraction and washing. When you mix them, they will not form two layers In fact, they ll mix in all proportions. A good example of this is acetone and water. What kinds of problems can this cause Well, for one, you cannot perform any extraction with two liquids that are miscible. 

So these terms, extraction and washing are related. Here are a few examples. 

EXCEPT for Class 4, steam distillation, two liquids that are to be separated must dissolve in each other. If they did not, they would form separable layers, which you could separate in a separatory funnel (see Chapter 11, Extraction and Washing ). 

Newer and more complex humus extractions have been developed. These typically involve more steps such as both physical separation on the basis of density and particle size (related to the size of soil inorganic components), and chemical separation based on extractions and washings with hydrofluoric acid (HF), hydrochloric acid (HC1), and sodium hydroxide (NaOH). The products of such separations are then subjected to spectroscopic analysis and interpretation [22,23],... 

The submitters have performed the extraction and washing in a countercurrent manner using three 2-1. separatory funnels. 

Solvents must be immiscible, hence there is a limited choice of extraction and washing solvents... 

The treatment costs for the GHEA Associates process depend on the soil matrix, properties, chemical composition of the contaminants, and other site-specific factors. The commercial-scale, integrated process, consists of the extraction and wash liquor purification steps. The estimated costs for the process range from 50 to 80 per ton of soil treated. Other separation processes have estimated treatment costs ranging from 90 to 200 per ton (D13377H, pp. 793, 799). 

The solvent extractions and washings should be done as rapidly as is possible since the crude methyl diformyl acetate is not stable to small amounts of acid or base over long periods. 

The extract and washings are returned to the distilling flask, and the alcohol is removed under reduced pressure. When practically all the alcohol has distilled, the temperature of the bath is raised to 1000 and the residue is heated for three hours under 30-mm. pressure (Note 4). 

Pool the n-hexane extracts and wash three times with 1 vol water. Dry over anhydrous sodium sulfate. 

Combine the epiphases from the two extractions and wash once or twice with a small amount (e.g., 1 or 2 ml) of half-saturated NaCl solution. 

Extract the mixture 3 times with 400 ml each of chloroform, pool the extracts, and wash the chloroform solution with water. Dry the chloroform solution with anhydrous sodium sulfate and filter. 

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