Potassium chloride
It is used to make potassium metal. Potassium chloride is heated very hot until it melts. Sodium metal is reacted with it. The sodium metal melts and boils to make sodium gas. The sodium gas reacts with the potassium chloride to make potassium gas and sodium chloride. It can be electrolyzed in a water solution to make potassium hydroxide. It is used in food processing. It can be used to execute people in a lethal injection. It is used instead of table salt sometimes. Normally it is half table salt and half potassium chloride. It can be used to extinguish fires. It was used to make packs that get hot when squeezed, but better chemicals are used now.