Chemical Reaction Vessel

As the vessel's contents are observed, it appears to be empty initially, with no remnants from previous reactions. Upon carefully adding the first substance, hydrogen peroxide (H2O2), to the vessel, it remains unchanged as there are no other substances present to react with it. Visually, the vessel contains only clear liquid hydrogen peroxide. Equation: H2O2 (l) → H2O2 (l) Substances in the vessel: Hydrogen peroxide (H2O2) Next, sodium iodide (NaI) is added to the vessel. As sodium iodide comes into contact with the hydrogen peroxide, a reaction takes place, resulting in the formation of water (H2O) and oxygen gas (O2). The reaction can be represented by the following equation: Equation: 2 H2O2 (l) + 2 NaI (aq) → 2 H2O (l) + O2 (g) + 2 NaOH (aq) Substances in the vessel after the reaction: Water (H2O), oxygen gas (O2), and sodium hydroxide (NaOH) are now present in the vessel, in addition to the remaining hydrogen peroxide (H2O2). Visually, the contents of the vessel may appear as a mixture of water and oxygen gas, with possible gas bubbles being released due to the formation of oxygen gas. The colorless sodium hydroxide may also be dissolved in the liquid, giving it a slightly alkaline property. What would you like to add to the vessel next? Please provide the chemical formula.