text: in the process of the present invention , the perfluoroalkyl halide and also the co 2 or so 2 are introduced into a dispersion of zinc powder in a reaction solvent . zinc salts of the perfluorocarboxylic or perfluorosulphinic acids are thus obtained . these zinc perfluorocarboxylates can then be converted in known manner into perfluorocarboxylic acid , and the zinc perfluorosulphinates into either perfluorosulphinic acid or into perfluoroalkanesulphonyl chloride . the starting substances which are used in the process of the invention are perfluoroalkyl halides , particularly perfluoroalkyl iodides having the general formula c n f 2n + 1 i , wherein c n f 2n + 1 represents an unbranched or branched perfluoro radical containing from 2 to 12 carbon atoms . the reaction may be carried out in numerous types of solvent . the solvents usually employed for the reactions with organometallic derivatives are perfectly suitable provided that they are not reactive in relation to the perfluoroalkyl halides . it is thus , for example , possible to use aromatic hydrocarbons such as benzene or toluene , acetonitrile , dimethyl formamide , dimethyl sulphoxide , or hexamethyl phosphotriamide . dimethyl sulphoxide is particularly suitable and is preferred . the amounts of solvent which can be used are extremely variable and depend on the solubility of the perfluoroalkyl halides in the solvent used . the amounts used are generally between 100 and 500 ml . of solvent per mole of perfluoroalkyl halide . the process of the invention can be carried out within a wide temperature range . in order to facilitate the performance of the process , the operation is generally carried out under atmospheric pressure and at a temperature between ambient temperature and the boiling temperature of the reactional mixture , preferably between 30 ° and 100 ° c . it is possible to utilize substantial excesses of carbonic anhydride or sulphurous anhydride , but amounts close to the stoechiometrical amounts are sufficient . desirably , an excess of from about 5 to 20 % of these two reagents in relation to the fluorinated product is used . the molecular ratio between the zinc and the perfluoroalkyl halide is advantageously from 1 : 1 to 2 : 1 , and preferably from 1 . 2 : 1 to 1 . 5 : 1 . the zinc is generally used in powder form . commercial zinc powder can be used either untreated or treated . thus , it is possible for the zinc to be previously activated by surface treatment , such as the treatments described in the prior art literature ( houben - weyl 1973 xiii 2a -- p . 570 and 815 ). the zinc may be , for example , activated by treatments with acid agents , such as those having the structures ch 3 cooh , hcl , h 2 so 4 , or the like , or the formation of alloys with other metals . in the latter case , the alloys most frequently used are those based on copper which are known under the name &# 34 ; zinc - copper pair &# 34 ;. these surface treatments of the zinc , which make it possible to increase the reactivity of the zinc , are particularly advantageous in the case of the preparation of carboxylic acids , because in this case the utilization of an activated zinc results in a substantial improvement of the rate of conversion of the perfluoroalkyl halide . in the case of the reaction with so 2 , the activaton of the zinc is only of slight interest , because practically the same results are obtained with an untreated zinc as with an activated zinc . the following examples illustrate practice of the invention , and should not be deemed as limiting the instant invention . 500 ml . of dimethyl sulphoxide ( dmso ) and 98 g . of zinc powder are introduced into a stirred glass reactor . the mixture is heated to 40 ° c . and , while this temperature is maintained by external cooling , 346 g . of c 4 f 9 i are introduced over a period of three hours while bubbling so 2 into the reactional medium at a rate of flow of 8 . 5 liters per hour for three hours , which corresponds to about 1 . 06 mole of so 2 . at the end of the addition , the stirring of the mixture is maintained for three hours at 40 ° c ., and then about 400 g . of dmso is evaporated by vacuum . the residue is diluted with 500 ml . of water . a current of gaseous chlorine is introduced into this mixture at the rate of 20 liters per hour for 3 hours 45 minutes ( 3 . 1 moles ) while the temperature is kept at from 35 ° c . to 45 ° c . a bottom phase is formed , which is decanted ( 273 g .) and which contains : ______________________________________percentages by weight ingredient______________________________________86 % c . sub . 4 f . sub . 9 so . sub . 2 cl 4 % c . sub . 4 f . sub . 9 i5 . 3 % c . sub . 4 f . sub . 9 h______________________________________ the rate of conversion of c 4 f 9 i into c 4 f 9 so 2 cl is 73 . 7 %. by distillation of this organic phase , a colorless liquid was obtained which distills between 101 ° c . and 103 ° c . at atmospheric pressure and which is composed of practically pure c 4 f 9 so 2 cl . 123 g . of c 2 f 5 i and 0 . 6 mole of so 2 are introduced over a period of 2 hours into a reactor containing 150 ml . of dmso and 48 g . of zinc , while the temperature is maintained at 30 ° c . at the end of the introduction of the reactants , the mixture is kept at 30 ° c . for 2 hours , and then the dmso is evaporated by vacuum . the residue is treated with 200 ml . of water . by chlorination ( 2 hours at 15 liters per hour ), a dense liquid phase was obtained which on distillation ( boiling point 55 ° c .) furnished 68 g . of a colorless liquid containing 96 % of c 2 f 5 so 2 cl . the rate of conversion of c 2 f 5 i into c 2 f 5 so 2 cl was 59 . 7 %. 0 . 42 mole of c 6 f 13 i ( 187 . 3 g .) and 0 . 46 mole of so 2 are introduced over a period of two hours into a glass reactor containing a stirred mixture of 75 ml . of dmso and 39 g . of zinc powder heated to 80 ° c . throughout the reaction , the temperature is kept at 80 ° c . at the end of the introduction of the two reactants , heating at 80 ° c . is maintained for half an hour , and then 200 ml . of water are introduced . the mixture is cooled to 35 ° c . and chlorinated at that temperature for two and a half hours with a rate of flow of 8 liters per hour . by decantation , there are thus obtained 168 g . of lower phase containing : ______________________________________percentages by weight ingredient______________________________________2 . 2 % c . sub . 6 f . sub . 13 h7 . 6 % c . sub . 6 f . sub . 13 i90 % c . sub . 6 f . sub . 13 so . sub . 2 cl______________________________________ the rate of conversion of c 6 f 13 i was 93 . 2 % and the yield of c 6 f 13 so 2 cl in relation to c 6 f 13 i consumed was 92 . 3 %. by distillation of this product , it is possible to obtain c 6 f 13 so 2 cl with a purity higher than 99 . 5 %. the boiling point of this product was found to be equal to 58 ° c . at a pressure of 20 mm . mercury . by the same method of operation as that used for example 3 and with the same amounts of reactants , a series of tests were carried out at 40 ° c . with different solvents ( 75 ml .). the following results were obtained . ______________________________________ rate of yield of c . sub . 6 f . sub . 13 so . sub . 2 cl conversion in relation to c . sub . 6 f . sub . 13 iexample no . solvent of c . sub . 6 f . sub . 13 i consumed______________________________________4 dmso 95 % 87 % 5 dmf 95 % 77 % 6 ch . sub . 3 cn 38 % 73 % 7 hmpt 76 % 68 % 8 toluene 9 % 15 % ______________________________________ 546 g . of c 8 f 17 i ( 1 mole ) and 1 . 05 mole of so 2 are introduced with agitation over a period of 4 hours into a glass reactor containing 97 . 5 g . of zinc powder ( 1 . 5 mole ) and 200 ml . of dmso , while the temperature was maintained between 50 ° and 55 ° c . two hours after the end of the introduction , 400 ml . of water are added at 50 ° c . the mixture is cooled to ambient temperature , and the aqueous phase is eliminated by filtration . the solid product is taken up with 300 ml . of water and chlorinated for 4 hours at 50 ° c . with a rate of flow of chlorine of 24 liters per hour . by decantation in the hot state , 507 g . of liquid are obtained . this recovered liquid crystallizes in the cold state and contains : the rate of conversion of c 8 f 17 i into c 8 f 17 so 2 cl was 68 . 5 % and the yield was 82 %. in the same apparatus and by the same method as that used in example 1 , the following ingredients were reacted for two hours : ______________________________________ amount ingredient______________________________________ 0 . 2 mole c . sub . 12 f . sub . 25 i 0 . 22 mole so . sub . 2 19 g . zinc 100 ml . dmso______________________________________ after the addition of the two reactants , the mixture was diluted with 300 ml . of water , cooled to 40 ° c ., and chlorinated . 132 g . of a solid were received containing : ______________________________________percentage by weight ingredient______________________________________26 % mixture of c . sub . 12 f . sub . 25 h and c . sub . 12 f . sub . 2440 % c . sub . 12 f . sub . 25 i20 % c . sub . 12 f . sub . 25 so . sub . 2 cl______________________________________ the rate of conversion of c 12 f 25 i into c 12 f 25 so 2 cl was 18 %. 187 g . of c 6 f 13 i ( 0 . 42 mole ) and 0 . 46 mole of co 2 were introduced over a period of two hours into a reactor containing 40 g . of zinc powder and 75 ml . of dmso , while the temperature was kept for 4 hours at 30 ° c . the reactional mixture is then taken up with 200 ml . of water and acidified with 100 ml . of concentrated hydrochloric acid . by decantation 169 g . of a liquid containing 85 % of c 6 f 13 i and 6 % of c 6 f 13 cooh are thus obtained . the rate of conversion of c 6 f 13 i into c 6 f 13 cooh was 6 . 6 %. preparation of c 6 f 13 cooh with the aid of a zinc - copper pair 2 . 4 g . of copper acetate ( ch 3 coo ) 2 cu · h 2 o are dissolved in a mixture of 200 ml . of dimethyl sulphoxide ( dmso ) and 40 ml . of acetic acid kept at a temperature of from 45 ° c . to 50 ° c . after dissolving , 78 g . of zinc powder are introduced with agitation and in an atmosphere of nitrogen . the mixture is agitated for 30 minutes , and the zn / cu pair is then filtered and washed with 4 times 60 ml . of dmso . ( b ) reaction of c 6 f 13 i with co 2 in the presence of a zinc - copper pair co 2 is bubbled with a rate of flow of 6 . 5 liters per hour into a reactor containing 40 g . of the zn / cu pair dispersed in 600 ml . of dmso . 0 . 4 mole of c 6 f 13 i is then introduced over a period of three and a half hours while the temperature is maintained at 20 ° c . by external cooling . stirring of the reactional mixture is maintained for three additional hours . the reactional mixture is then filtered , the filtrate is freed of dmso by evaporation in vacuum , and the residue is treated with 500 ml . of 50 % hydrochloric acid . by decantation , an organic phase is obtained which is distilled . 91 . 7 g . of perfluoroheptanoic acid are thus obtained . this acid is identified by nmr and ir spectroscopy , and also by chemical analysis ( bp 50 mm 105 ° c .). the rate of conversion of c 6 f 13 i into c 6 f 13 cooh is 63 %. preparation of c 6 f 13 cooh with the aid of zinc powder activated with acetic acid the zinc powder is activated by the method described in example 12 for the preparation of the zn - cu pair , except that no copper acetate is introduced . 39 g . of this zinc are subjected to the same method of operation as that employed in example 11 . 138 g . of a liquid product containing 41 % of c 6 f 13 i and 35 % of c 6 f 13 co 2 h were obtained . the rate of conversion of c 6 f 13 i into c 6 f 13 cooh was 31 . 5 %. inasmuch as many changes and variations in detail are possible within the scope of the present invention , it is intended that the above description is presented for purposes of illustration and not by reason of limitation .