The researchers found that they can use a chemical called chloranil to measure acidity levels in very strong acids like anhydrous hydrogen fluoride and superacids. By using both hydrogen and chloranil electrodes, they created a chart showing acidity levels in hydrogen fluoride. They also discovered a new value for the autoprotolysis constant of hydrogen fluoride. The indicator system they developed can show acidity levels in hydrogen fluoride on a scale, ranging from pH 0 in water to extremely high acidity levels in superacids.