Chemicals for treating, purifying and cleaning water; chemicals for use in industry; water purifying, treating and cleaning chemicals for swimming pools and spas; magnesium chloride; magnesium preparations for treating, purifying and cleaning water; chlorine for swimming pools and spas; calcium; liquid chloride for treating, purifying and treating water; lithium; liquid lithium for treating, purifying and treating water; acids; chemical preparations for testing swimming pool and spa water