Unfortunately, the chemical compound Cu3I8 does not exist. Perhaps you have entered the chemical formula incorrectly.
You might be thinking of CuI, also known as Copper(I) iodide. This is an inorganic compound with the formula CuI. It is a white or pale brown solid, odorless, which may turn green when exposed to moist air. The chemical properties of CuI include the ability to react with strong acids to form iodine and copper(II) ions, or react with alkalis to form alkali iodides and copper(II) hydroxide.
Please note that when working with chemical compounds, always adhere to the safety rules of the laboratory and only conduct experiments under the guidance of an experienced supervisor.