[jhernandezf]

Hi
I made a test to look for iodine in salt.  I used one recommended by UNICEF  : Salt becomes purple when lemon juice is mixed with it.  Perfect, but I do not know why this occurs. Why lemon does that on salt.

Any help on this will be greatly appreciated

Thanks
Johanny

[english]

Isn't iodine solid purple?  Does this mean you're getting a deposition of iodine when you add lemon juice?  Possibly a redox reaction?

[Arkcon]

Is there starch present, in your sample or your test reagent salt?  The iodine, is it free iodine (the brown or purplish-black crystals, with a lustrous almost metallic sheen) or is it a salt of iodine (can be white in color)?

*[EDIT]*

It appears you were performing a test, something like this one:
http://www.unicef.org/uzbekistan/reallives.html
but, some more specifics about your application are needed.