Boron, phosphorus, arsenic, antimony and other impurities are at least partially removed from a mixture containing at least one chlorosilane and/or organochlorosilane by a) contacting the liquid mixture with a carrier material functionalized with an amidoxime of the general structural formula (I), ##STR00001##
where CAR=carrier material and R.sup.1, R.sup.2 are independently of one another H, alkyl, alkenyl, aryl, alkylaryl; and b) optionally removing the functionalized carrier material.