'Chronoprints' Identify Samples by How they Change Over Space and Time (image) American Chemical Society Share Print E-Mail Caption A new method identifies substances by examining how they change after being immersed in liquid nitrogen. Credit American Chemical Society Usage Restrictions Please credit the American Chemical Society. 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.