The Student Room Group

How sensitive is the Iodine Starch Test?

Has anybody done this practical? Honestly, I'm not bad at scientific experiments and write-ups etc - but I had an awful teacher when we did this practical a few days ago. He rambled on; only really telling me what the objective was towards the end when I forced him to.

I literally struggled through the experiment which I didn't really know anything about or why I was doing it. Apparently it is to test the sensitivy of the Iodine-Starch test. I ended up with a value and I don't even know what it represents! I am literally at a loss. I used instruments I have never before used, and I'm not even sure what all the names are!

I have to write-up this experiment as homework; but the teacher I did it with (not permanent thank god!) was quite honestly hopeless.

Can anybody help me out? Anybody done this before?


(This is a Biology practical by the way!)
Reply 1
You might have several starch solutions with different molarities (I.e. 0.1M 0.2M) and found out which was the lowest molarity which gave a positive Iodine-Starch test result.

The figure you have could be the lowest molarity. It might help us to identify what you did if you gave us the figure.
when you say "instruments" I am assuming that you used a colourimeter?

You tested the absorbance of light of a specific wavelength?

You applied the Beer-Lambert law?

give us a clue!
Reply 3
No, it wasn't anything to do with light I'm afraid. It was indeed testing the 'sensitivity' of the test ie. how little starch the iodine can detect. The final value was a percentage though; apparently the Iodine-Starch test can detect as little as 0.004% starch in a solution. That's what it was about - I asked a different teacher! Simple when it's explained properly! Thanks anyway guys (Aired - it was very similar to what you are talking about!)