James Apjohn (1796-1886) was a renowned and respected chemist and physicist who lived and worked in Dublin during the 1800s. He was known internationally for his work on hygrometry and the Apjohn dewpoint. A mineral from Algoa Bay, South Africa, which proved to be an effloresced manganese alum was analysed and described by Apjohn to great acclaim. Subsequently it was named 'Apjohnite' in his honour. James Apjohn (1796-1886) Apjohn was born on 1st September 1796 at his father's property, Sunville, in Pallasgrean, Co. Limerick. He attended the Tipperary Grammar School for four years before entering Trinity College Dublin in 1814 under the tutorship of Rev. Dr. Wall. Apjohn graduated with a B.A in 1817 and took his degree of M.B in 1821. His debút as a lecturer on science took place in the Cork Institution in 1824. He continued lecturing throughout his career and was popular for his lucid style and well devised experiments. In some cases his lectures were so well at...