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Back Extractions of Sulfuric Acid-Rich Solvents in Con› tinuous Column-Sulfuric acid-rich extracts comprising sul› furic acid, TEHA, 2-ethylhexanoic acid, and heptane derived from the forward extraction of hydrocarboxylation effluents were fed to the continuous Karr column at a temperature of 70° C. as described above and contacted with an aqueous formaldehyde extraction solvent ( continuous phase). The sul› furic acid-rich extracts were introduced to the Karr column at location F5 and the aqueous formaldehyde solvent was intro› duced at location Fl. Feed and solvent compositions, and flow rates of the forward extraction experiments are summa- rized in Table 20. In each experiment, the column reached steady state within an hour and was run continuously for six to eight hours, with sampling occurring every one to two hours. Averaged recoveries of TEHA, 2-ethylhexanoic acid, and heptane to the raffinate product, and glycolic acid and sulfuric acid to the formaldehyde extract product over the time of steady state operation are given in Table 21. 

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## Examples 43-48 

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Extraction of Sulfuric Acid from Aqueous Glycolic Acid› Sulfuric acid was added to a 85 wt% glycolic acid-15 wt% water mixture to produce a solution comprising 3 wt% sul› furic acid. Extraction solvents were prepared by mixing an amine and diluents(s) as specified in Table 22. Five grams of each amine solvent solution was mixed with five grams of the sulfuric acid-aqueous glycolic acid mixture and allowed equilibrate at the temperature specified in Table 22. If two phases resulted, samples of each phase were analyzed by x-ray for sulfur content and converted into a sulfuric acid concentration in each phase (grams of sulfuric acid per gram of amine phase and grams of sulfuric acid per gram of aque› ous glycolic acid phase). 

## Example 49 

