Starch indicator

[pkij]

The chemistry teacher has been doing iodine titration of vitamin c using starch indicator. I put out starch solution for the indicator but she says that using solid starch works better. I have not come across this before, just thought I would see if anyone else uses solid starch.
I did a search of my books and online and they all say starch solution so not sure about this one! would it matter using solid starch or solution.
(I did a test run myself and had no problems with the starch solution )

[nickyw]

No we use solution here made some up yesterday....i have never heard of using solid.

Let us know how it goes.

[smiley]

Tell her she's dreaming!

And I use those little starch packing beads. I will never use starch powder ever again! Experiment a little, but from memory it's between 5 packing beads per 100ml for a strong solution. I think I ended up at 10 beads per 500mL for last year's Vitamin C titrations.

Recipe is: 10 packing beads in a large beaker.
Add 300ml of very hot water.
Stir a lot - I use a magnetic stirrer
Add cold water to bring it up to 500mL
Filter if necessary to get the glunky bits out.

Too easy!

[pkij]

Thanks Smiley I will add that one to my recipes. I just threw out some of those starch packing beads, never again, I knew I should have kept them but I was in a cleaning frame of mind!
I am waiting for some confirmation about using starch solution before I talk to the teacher , then again I might not bother, its all too hard sometimes!

[mtg]

It only takes a second to make a paste with cold water and a couple of spatulas of starch and chuck in boiling water. Lovely indicator and then keep it in the fridge.

[lada]

I am with Smiley!!
Only drawback is, I asked everyone at school to keep the beads and now I need a special room just to keep them, he he he
They are very good for genetics in yr 10, they get a truckload of them and mark them as eggs or sperms and do predictions of sex of a baby, use them for testing food and everyday substances, just drop iodine straight on to one and it turns blue and offcouse use them for making starch

Lada