# calculating aluminum dissoluted for voltage regulated dc supply

#### mallikarjund

Joined Jun 23, 2008
1
i am basically a chemical engg. my project is based on electrocoagulation. i have made an electrochemical cell recently...its construction and working is similar to that of an electrolytic cell. I am using a 24 volts,5 Amps DC voltage regulator to conduct my experiments. The conductivity of the electrolyte (load resistance in other words) changes with time in my experiment. This in turn changes the current value from 0.22 to 0.12 Amps when a voltage of 10 V is applied.

i have to calculate the amount of aluminum dissoluted to form aluminum hydroxide for a specific time(say 90 minutes). The dissolution can be calculated using fardays laws... the relation is given as

aluminum dissoluted (m)= itM/ZF...

Faradays law is used to relate the current flow (I for time t ) to the amounts (m) of aluminum and hydroxide ions generated within the reactor. Z is the number of electrons transferred in the reaction at the electrode, M is the molecular weight (g /mol) and F is Faradays constant (96 486 C /mol).

But in my case as current value is changing with time what modification do i have to bring in the expression to calculate the the amount of Aluminum dissoluted? will simple integration or the arthematic average of the current values suffice the purpose? plzz help me out ...

#### John Luciani

Joined Apr 3, 2007
477
It would be easy to keep the current constant using an opamp and MOSFET.
There is a schematic of a current sink at
http://www.luciani.org/geda/util/matrix/index.html
(near the bottom of the page).

Also check the application notes for linear regulators and the TL431. There
are a variety of simple constant-current circuits.

(* jcl *)