Turmeric is used as a natural indicator. Turmeric is yellow in colour. Turmeric paper turns into red when it is dipped into basic solution. Turmeric paper does not change its colour with acid. The aqueous solution of this oxide turns turmeric paper red. It indicates that the oxide is basic in nature. Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides are different from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids. Hence, the element is a metal. For example, magnesium is a metal, it reacts with oxygen to magnesium oxide, which is basic in nature.