Check the listing for details. pH Indicator Test Drops, pH 2.0-10.0, 0.5 pH Intervals, 100 Tests. Condition: New. Listed at 13.80 USD. This product contains one 10 ml bottle of pH indicator solution and a 20 ml screw top plastic bottle. The 10 ml bottle of pH indicator solution will provide roughly 100-150 pH testings while the 20 ml screw top bottle was added to make pH testing faster and easier. By having a screw bottle with your pH test kit, you can readily test your solutions on the go. Simply fill your 20 ml plastic bottle halfway, add 1-2 drops of pH indicator, and then match your solution's color against the color chart provided to determine your pH. To further the reliability of our products we randomly test each shipment we receive across multiple pHs to ensure product quality and reliability. pH Drop Instructions 1. Apply 1-2 drops of pH indicator per 10 ml of the solution you would like to measure. The color of your solution will change instantly. 2. Match this color against the color chart provided to obtain the pH. 3. The number next to the color on the chart is your solution's pH. The pH scale ranges from 1 (very acidic) to 14 (very basic), 7 is neutral.