Patent US5378634 - Labelling color for detecting methamphetamine - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More ??Sign inAdvanced Patent SearchPatentsA labelling color which includes a pentamethine of the following formula (1): ##STR1## wherein R1, R2, R3 and R4 each are a C1-6 alkyl group, and X is an anion....http://www.google.com.au/patents/US5378634?utm_source=gb-gplus-s