He was born in Beach Hill, County Armagh, Ireland, son of Thomas Simpson.
He attended Dr. Henderson's school at Newry before continuing to Trinity College, Dublin in 1832.
After attending a lecture in Paris by Dumas on chemistry he decided to study that subject, which he did at University College, London.
During this early part of his life he had started making the discoveries that placed him in the first rank of chemists of his time.
[1] In 1872 he was appointed Professor of Chemistry at Queen's College, Cork, a position he held until his retirement in 1892.