In 1852 one of his pupils found that adding iodine to the urine of a dog that had been fed quinine produced unusual green crystals. Herapath noticed while studying the crystals under a microscope that they appeared to polarize light and patented the discovery for optical use as Herapathite. He described it as artificial tourmaline, a semi-precious gem. He went on to develop new analytical techniques for the detection and analysis of alkaloid compounds based on the optical and chemical characteristics of their iodo-sulphates. He also designed a new combustion blowpipe for organic analyses and developed spectroscopic techniques for detecting traces of blood.
