Science Buddies: "Ask an Expert"

So I did this project 3 times and got the same results. I tested half the salt cups with vinegar and the other half with vinegar. The salts without vinegar with iodide turned pink or light pink. The salts with vinegar all turned black. What is the reason for both and what does it mean?

Hi Ryderckellis,

I'm assuming that you're working on the project described here:

https://www.sciencebuddies.org/science- ... nt-of-salt

If you carefully follow the project procedure a salt sample that contains iodide will give a purple colored solution at the end of the test. A salt sample without iodide will not change color. You should add vinegar to all of the test solutions as described in the procedure. It's possible that your tests without vinegar did not show a color change (to purple) because acid is required to make the reaction work.

I hope this helps. Please ask again if you have more questions.

A. Norman