Bromothymol blue solution is used as an indicator to determine the rough pH of a substance. It is prepared from a powder, household items and common laboratory chemicals that can be obtained through a scientific supply house individually or as a kit. The mixed bromothymol blue solution will turn yellow in an acidic solution and blue in basic solutions. Add 0.1 g of bromothymol blue powder to 10 mL of 4 percent sodium hydroxide solution in a large beaker. Combine 20 mL of alcohol to the sodium hydroxide/bromothymol blue solution. Dilute the mixture with 1 L of distilled water in a large container. The solution should be dark blue in color. If the solution appears green, use a pipette to slowly add sodium hydroxide drop by drop to the solution until it changes to blue.