PH reagent drops for testing pH of ionized water in larger 50cc glass bottle. Label features pH color chart. Simply add 2-3 drops into small amount [1-2 tablespoons] of water. Shake or swirl and observe color change. The 50cc bottle uses the same formula reagent as the 10cc bottle, but is just 5 times more volume. Note: Reagent has a shelf-life of about 2 years.