Explosives and Fish are Traced with Chemical Tags (2 of 2) (image) FECYT - Spanish Foundation for Science and Technology Share Print E-Mail Caption The black chips represent the quantity of a chemical element with natural isotopic abundance whereas the blue and green chips indicate the quantity of the same element with altered isotopic abundance. The "color" of the element shows its isotopic distribution, which can be measured using a mass spectrometer. In the first image the proportion between blue and green chips is 1:3 whereas it lies at 1:1 in the second image. This ratio, which defines the tag, is independent of the amount of black chips. Credit J.I. García Alonso et al. Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.