Borek you mean coprecipitation as in :
Pb2+ + 2 I- ---> PbI2
Cu2+ + 2 I- ----> CuI + 1/2 I2
I titrated with thiosulfate the iodine released from the 2nd reaction.
Arkcon ,
Yes I precpitated the lead with sulfate , filtrated the solution and then titrated it against thiosulfate ( after adding KI , starch ... )
For the 1st method the volume was 20.4 ml ( C = 0.1632 M ) , for the 2nd 20.8 ml ( C = 0.1648 M ).