He was ordained in the
Church of Scotland in 1826 in
Gargunnock and translated in 1829 to
Saltoun in
East Lothian, replacing Rev Dr Gilbert Burnet. In 1833 he moved to the
Tron Kirk in
Glasgow. He then lived at 2 Richmond Street. Working from the base created by his predecessor, Rev Dr
Thomas Chalmers he did much "home mission" work in Glasgow and expanded the church into the poorer areas such as "The Wynds" of old Glasgow. . In 1838 it was Buchanan who chaired the debate on the "Auchterarder question", regarding the ability of a congregation to refuse a minister proposed by the local patron. This debate was the beginning of the schism which eventually led to the
Disruption of 1843. In this. Buchanan stood at the side of Chalmers and was part of the heated debate. The church split in two and he was thereafter a minister of the Free Church of Scotland. In 1857 he transferred to the Free College Church College on Lynedoch Street. In 1860 he succeeded
Very Rev William Cunningham as Moderator of the General Assembly, the highest position in the Free Church. He was succeeded in turn in 1861 by Rev
Robert Smith Candlish. From 1863 to 1873 he presided over the committee looking at the potential union of the Free Church with the
United Presbyterian Church, the Reformed Presbyterian Church and the Presbyterian Church of England, all being doctrinally similar. Although these talks were unsuccessful, large sections did merge in 1900. From 1872 until death he was an active member of the Glasgow School Board. In later life he lived at 2 Sandyford Place, a handsome Georgian terraced house in north-west Glasgow. == Death ==