by filtration and the subsequent addition of hydrochloric acid to reduce the ph to a value of about 3 5 so as to precipitate the zwitterionic product formyl and dichloroacetyl protecting groups may then be removed by means of aqueous base e g aqueous sodium bicarbonate solution which when z is a hydrogen atom produces the sodium salt of the corresponding cephalosporin the free acid may then be obtained by means of acidification in a typical procedure the hydroxyl protected cephalosporin is dispersed in aqueous sodium bicarbonate solution and the resulting solution is overlayered with a suitable water immiscible organic solvent e g ethyl acetate after acidification of the aqueous phase to a ph value of about 2 0 the organic phase is then separated dried and subsequently evaporated in vacuo to leave an oil which can then be triturated with dry diethyl ether to yield the free acid form of the desired u03b1 hydroxy cephalosporin in a typical procedure involving the reaction of a mixed anhydride v with the compound ii the latter compound is first dissolved if necessary with the aid of a base such as triethylamine in a suitable solvent e g aqueous tetrahydrofuran and then mixed with a solution of the anhydride in for example tetrahydrofuran after mixing for a period of about an hour preferably at a temperature of 10 u00b0 c to 0 u00b0 c the coolant is then removed and the solution allowed.