The presence of salt that is sodium chloride cannot be tested at once. Two different tests are performed to show the presence of both sodium and chloride.
To test for the chloride ion:
Add few drops of aqueous solution of silver nitrate to aqueous solution of sodium chloride, white precipitate is seen which cannot dissolve in cold water and dilute nitric acid. This precipitate formed is soluble in solution of ammonium hydroxide to give a colorless diamine silver chloride solution.
To test for the sodium ion: Use a flame test.
Dip a wire of platinum in concentrated hydrochloric solution and hold it in the flame of the Bunsen burner until the flame no longer changes its color. Again dip the wire in hydrochloric solution and rub some sodium chloride on the wire and put it again in the burner, an intense yellow to orange color forms that shows the presence of sodium ion.
If the substance passes both the tests in the given way then it is salt (sodium chloride)
