Blue Soul returns to Whiskey Pickle with the second half of his "Litmus Test" series. This series is a metaphor based on the litmus test in chemistry, in which one is able to test the general acidity of a substance, but not its exact pH. It was in the 14th century that scientists discovered that litmus, a mixture of colored organic compounds obtained from lichen, turns red in acid solutions and blue in alkaline solutions and, thus, can be used as an acid-base indicator.