Acids are sour in taste and change the colour of blue litmus to red. Acidic nature or ions that shows that the substance is acidic are h+ ions.

Bases are bitter and change the colour of the red litmus to blue. Basic nature or ions that shows that the substance is basic are OH- ions or decrease in h+ ions.

Litmus is a natural indicator turmeric is another such indicator these are basic in nature we can also use synthetic indicators such as methyl orange and phenolphthalein to test for acids and bases.

There are some substances whose order changes in acidic or basic medium these are called olfactory indicators. Like Vanilla, onion and clove can be used as olfactory indicators.

Salt formed by the combination of hydrochloric acid and sodium hydroxide solution which is called sodium chloride. This is a salt that we use in food. Sea water contains many salt dissolved and it sodium chloride is separated from these salts. Deposits of solid sold are also found in several part of the world. This large crystals are off tin brown due to impurities this is called rock salt.