He was born in Bristol, the eldest son of William Herapath, Professor of Chemistry at Bristol Medical School and educated at London University, where he was awarded M.B. in 1844. He worked as a surgeon at Queen Elizabeth Hospital, Bristol and St Peter's Hospital, Bristol and was awarded M.D. in 1851. He published many articles in medical, chemical, and other scientific journals and was vice-president of the Bristol Microscopical Society. 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. In 1854 he was elected a Fellow of the Royal Society of Edinburgh, his proposer being Philip Kelland. In 1859 he was elected a Fellow of the Royal Society. His candidature citation read: "''The discoverer of the Optical and Chemical Characters of the sulphate of Iodo-quinine. The author of four papers in the Philosophical Magazine 1st On the Optical Properties & Chemical Characters of the Sulphate of Iodo-quinine,2nd On the Chemical Analysis of the same remarkable salt - 3rd On the Discovery of Quinine and Quinidine in the Urine of Patients under Treatment, 4th On the Manufacture of large Optical plates of Sulphate of Iodo-quinine. The inventor of a new polarizing medium, as an efficient substitute for the Tourmaline. Distinguished for his acquaintance with the science of Chemistry. Eminent as a Chemist, Physiologist, and Microscopist". In 1864 he became ill and died in 1868 and was buried in Bristol's Arnos Vale Cemetery.
Family
He married Lucy Kynaston, daughter of Cabot Kynaston of Penally, Pembrokeshire with whom he had a son and five daughters.
Legacy
The embedding of microscopic crystals of herapathite in a clear film was later patented by Edwin H. Land as a polarizing filter, under the name of Polaroid.
