Question

For measuring oxygen dissolved in water, a polarographic cell with

silver anode, gold cathodes and KCl electrolyte can be used; in this

the current is related to the oxygen reaching the cathode via a

membrane. Why is it necessary to renew the electrolyte and the

anode? How can this problem be alleviated together with reducing

the effects of fouling of the membrane?

Answer 1

system

polarographic cell contain silver anode and gold cathode with KCl as a electrolyte in reaction chamber which is separated by the membrane.

Working Principle

DC voltage is applied to the system.O2 will diffuse because of partial pressure differance and reduced at gold cathode. there is electrochemical reaction so according to faradys Law material consumption or deposition will occor.

so here gold will be consumed and on silver silver bromide will be deposited. so after some time it create voltage drop. so we have to change the both after sometime.

To alleviate the fouling of the membrane,we can use referance electrode which can help to maintain proper voltage.

to reduce fouling, use of proper membrane and we can use gaurd mambrane.

NOTE-To get knowledge of animated working principle, you can watch video from youtube. u will get proper solution. search dissolved oxygen measurement.