the system through line 10 and recovered water can be recycled through line 11 to line 2 at point 12 for reuse sufficient oxalic acid is continuously added to line 2 to continue the separation process as described the organic acids subjected to the separation process of this invention are derived from the oxidation of their corresponding aldehydes using catalytic amounts of a mixture of soluble manganese and copper catalyst such as manganous acetate and cupric acetate which are soluble in the acid product and will contain from 6 to 9 carbon atoms these acids include hexanoic heptanoic octanoic and nonanoic acids and are substantially insoluble in water the unique separation process of the present invention is particularly useful in purifying heptanoic and nonanoic acids which in turn are useful in the preparation of various esters used as additives in lubricating oils as previously stated when an aqueous solution of oxalic acid is mixed with organic acid containing soluble manganese and copper compounds insoluble manganous oxalate and cupric oxalate are precipitated from the organic acid phase into the aqueous phase and subsequently settle to the bottom of the aqueous phase the time required for the organic and aqueous phase to form decreases as the organic acid to water volume ratio decreases the volume ratio of the organic acid to water can range from about 0 5 to about 5 0 to 1 preferably 1 1 to 2 5 to 1 more preferably 1 1 to 1 7 to 1 at 25 u00b0 c under these conditions the phasing time can range from about 2 minutes to 30 minutes with shorter times being preferable at volume ratios of organic acid to water in excess of.