TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method : The organic solvent capable of coordination-bonding to a metallic ion, comprises a non-protonic organic polar solvent which is an ether, sulforan, hexamethyphosphoric triamide, acetonitrile, dimethylformamide, dimethylsulfoxide, ethylacetate and/or tetramethyl urea. The ether solvent is grime-solvents, diethylether, diiospropyl ether, tetrahydrofuran, dioxane, anisole, and/or a crown ether. The grime solvent is dimethoxy ethane, diethoxy ethane, monoethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethyleneglycolmonomethyl ether and/or diethylene glycol monoethyl ether. The non-protonic organic polar solvent is a grime solvent and contains 250 ppm or less of water. The non-protonic organic polar solvent is preferably diethylene glycol dimethyl ether which contains 250 ppm or less of water. The organic solvent (B) has a dielectric constant of 4 - 10. The organic solvent (B) is a halogen-containing hydrocarbon and/or ether, and is chloroform, dichloromethane dichloropentafluoropropane (Freon R225) or dichloromonofluoroethane (Freon R141b). Another method for purifying a water-soluble fluorinated vinyl ether comprises mixing a mixture comprising the water-soluble fluorinated vinyl ether and an inorganic salt with an organic solvent (C) and removing the inorganic salt. The organic solvent (C) does not dissolve the inorganic salt but does dissolve the water- soluble fluorinated vinyl ether. The mixture, comprising the water-soluble fluorinated vinyl ether and the inorganic salt, is dried before it is used in this method. In the process, the mixture obtained by removing the inorganic salt is subjected to drying at 25 - 300 degreesC. The inorganic salt is NaF, KF and/or CsF. Preferred Definitions:    Z = COOM1, -OSO3M1, -SO3M1, -O2PM1, -OP(OM1)2, -O2P(OM1), - OPO(OM1)2, -PO2(OM1), -PO(OM1)2, -COOM21/2, - OSO3M21/2, -SO3M21/2, -O2PM21/2, -OP(OM21/2)2, - OPO(OM21/2)2, -PO2(OM21/2), -PO(OM21/2)2 or a substituted amonio group which forms a salt with the conjugated base group of a mineral acid or fatty acid.    M1 = alkali metal, quaternary N atom or H atom ;    M2 = alkali earth metal    In (I), n is 0, Y2 is F atom, m is 2 and Z is -SO3M1 or - SO3M21/)-SO3M21/2.    WIDER DISCLOSURE - A purified water-soluble fluorinated vinyl ether is obtained by the invented method.    EXAMPLE - A compound (X) was obtained by reacting tetrafluoroethylene with SO3 at 40 - 60 degreesC, reacting the resulting tetrafluoroethane beta-sulton with ethylene glycol dimethyl ether in the presence of KF, reacting the resulting FSO2CF2COF with hexafluoropropylene oxide at 20 - 40 degreesC, neutralizing the resulting FSO2CF2CF2OCF(CF3)COF with a 20 % NaOH solution, filtering and drying at 120 degreesC for 12 hours. The compound (X) (6 kg) and diethylene glycol dimethyl ether (5.5 liter) were reacted at 140 degreesC for 2 hours. Diethylene glycol dimethyl ether was removed from the reaction solution. The resulting solution was dissolved in water, and then chloroform was added to the aqueous solution. Chloroform was added to the aqueous solution and the mixture was vigorously shaken so as to separate the two phases. The chloroform phase was collected. This chloroform abstraction was repeated 7 times. The resulting solution was dried at 80 degreesC for 12 hours so as to obtain powdery pure CF2=CFOCF2CF2SO3Na.