The universal indicator
is a piece of paper
soaked in a chemical
that changes properties (most often color
) depending on the pH
of the chemical
s it comes in contact with.
Although they have been used before that, the first mention of universal indicators are by the Dutch chemist H.M. van Urk in 1928.
Universal Indicator is also a series of early acid (hence the name, acid->pH->UI) recordings released by Rephlex Records from 1989 to 1995. Although the information is a little sketchy, this is what is known:
Notice how the catalog numbers are famous Roland analog audio equipment.
Note: www.joyrex.com is currently down, and that's the only place I can find out how many copies were made of UI:Blue and Yellow. or if any of you know & will /msg me.