English
The electrochemical behavior of the tungsten electrode to
copper(Ⅱ)and the elimination of interferences from tita-nium and chromium in
aluminium determi-nation are studied. It is found that the tungsten electrode has a characteristic response to
copper(Ⅱ)with high selectivi-ty. The response time is short and the potential
can be recovered easily by rins-ing with water. The potentiometric
deter-mination of aluminium is permitted in the presence of a large amount of
tita-nium and chromium. Interferences from titanium and chro-mium are eliminated
by the addition of masking agent amygdalic acid or tartaric acid. The amount of
tartaric acid must be controlled, because it can also forms complex with
aluminium. If tartaric acid in excess is added too much, low results will be
obtained. Moreover, the reaction be tween chromium(Ⅲ)and CDTA can be facilitated
by increasing temperature and prolonged by standing of the test solu- tion.
Therefore in the determination of aluminium in the presence of chromium(Ⅲ), the
solution should not be heated to a temperature higher than 50℃ after the
addition of masking agent and CDTA, and, should be back-titrated immediately by
copper(Ⅱ)after the solution is cooled. The method has been successfully used in
the determination of aluminium in glass(～l0% TiO_2), coating (5-90%TiO_2),
chromium oxide(～95%C_2pO_3,～5%AI_2O_3). etc. with satisfactory results. Hence
this method is recommended as a simple and accurate method for the determination
of aluminium in the presence of a large amount of titanium and chromium.
