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July 3, 2015

Homework Help: Chemistry

Posted by annie on Wednesday, October 6, 2010 at 6:23pm.

I found the following procedure to prepare starch indicator solution on a website:-

To prepare starch indicator solution, add 1 gram of starch (either corn or potato) into 10 mL of distilled water, shake well, and pour into 100 mL of boiling, distilled water. Stir thoroughly and boil for a 1 minute. Leave to cool down. If the precipitate forms, decant the supernatant and use as the indicator solution. To make solution long lasting add a pinch of mercury iodide or salicylic acid, otherwise it can spoil after a few days.

If I add salicylic acid to my starch solution, what would you recommend to be the expiry date of my solution? I would put it at 3 months or if the solution no longer turns blue with iodine, whichever is earlier.

What do you think?

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