dach pt aquo 2 ii sulfate complex is placed in a 20 l polypropylene tank thereafter 32 4 g of oxalic acid dihydrate h 2 c 2 o 4 u00d7 2 h 2 o 0 26 mol and 81 6 g barium hydroxide octahydrate ba oh 2 u00d7 8 h 2 o 0 26 mol are added under stirring the reaction mixture is stirred for 20 hours at room temperature the ph of the suspension is maintained at about ph 6 then the filtration of the precipitated baso 4 is conducted through a filter unit step c u2032 before start of filtration a suspension of activated carbon is applied over the filter paper the filter cake is washed with 1 5 l of deionized water and collected for pt recovery the resulting solution is evaporated in a rotavapor at 40 u00b0 c to almost dryness whereby the oxaliplatin precipitates the resulting precipitate is washed with 0 2 0 3 l of cold highly purified water free of bacteria and then with acetone to protect the product against light these operations are conducted under low intensity light finally the product is dried under vacuum for 2 hours the total yield of pure product is 65 the product is thereafter analyzed for impurities typically the ag content as detected by atomic absorption spectroscopy aas is lt 5 ppm preferably lt 3 5 ppm if necessary a recrystallisation step in purified water is added in this example the nitrate content is lt 1 ppm as detected by ion chromatography this example is conducted according to example 1 however barium oxalate bac 2 o 4 is used instead of barium hydroxide and oxalic acid i e step c is employed barium oxalate is prepared separately by reacting equimolar portions of oxalic.