The document describes the process of oxidizing sodium iodide (NaI) to iodine (I2) using oxidizing agents like sulfuric acid (H2SO4), resulting in a purple solution. This color change indicates the presence of iodide ions (I-). The chemical reaction involved is also detailed in the document.

1. I2 is purple color. using oxidizing areagent to oxdize NaI to I2. through color
change, you can judge if the salt contains I- ion or not. such as use H2SO4 to oxidize it. 2 Na+ +
2 I- + 2 H+ + 2 HSO4- <-> 2 Na+ + I2 + HSO3- + HSO4- + H2O.
Solution
I2 is purple color. using oxidizing areagent to oxdize NaI to I2. through color
change, you can judge if the salt contains I- ion or not. such as use H2SO4 to oxidize it. 2 Na+ +
2 I- + 2 H+ + 2 HSO4- <-> 2 Na+ + I2 + HSO3- + HSO4- + H2O.