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Titrating by Spectrophotometry

A project log for PoolButler

Determine the chemical properties of your swimming pool automatically, while keeping you in the loop

DigiGramDigiGram 08/19/2014 at 06:090 Comments

Titration, for those non-chemists out there, is the process of adding a chemical to a solution until an equilibrium is achieved. The important parts here is to measure the amount of chemical you add accurately, and noticing the end point (or equilibrium point) correctly. In my career it is easy to measure the amount you add accurately, but our end points is measured either at a certain pH, or with a very slight colour change.

Fortunately the colour change in swimming pool liquid testing kits are much more evident. The process I'm contemplating so far involves as red laser diode shining through the optic cell towards the photo-diode. The photo-diode will measure the basic obscurance at 635 nm. I expect the obscurance to change slightly during titrant addition, but once a colour change occurs, I expect a much more significant change.

If it does not work as expected, I will try ultra-violet laser beams, as we have used that in the lab for a similiar application. Allthough I'm sure this will not be accurate enough for lab quality titrations, this should be more than enough to get as accurate result as pool testing kits allow.

I can't wait to go home and test this theory, but sadly you all will have to wait another 3 weeks before I can go home. Will keep you updated though.

Happy Waiting

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