This is a small ampule of high-purity (99.96%) heavy water. The "purity" of the sample is listed as 20% because that's the weight-percent of hydrogen (deuterium actually) in heavy water.
This is a spare from the beautiful periodic table display that Max Whitby and I recently installed at DePauw University.
Source: Max Whitby of RGB
Contributor: Max Whitby of RGB
Acquired: 1 November, 2003
Text Updated: 11 August, 2007