Alexander Robertson was born on the Hatton Estate in Charlesfield, Auctherless, Aberdeenshire, Scotland on February 12, 1896. His father was Andrew Robertson, a farmer, and his mother was Jane Cantlay. He received his early education at Auchterless School and Turriff Higher Grade School and always intended to follow in his father’s footsteps as a farmer. He was an excellent student, however, and his mother encouraged him to go on to the University of Aberdeen instead. He excelled in the sciences and placed first in chemistry at the University.

At the start of the First World War, Robertson he enlisted in the Royal Engineers of the Special Brigade and worked on gas weapons and warfare. He then served in the military in France and was discharged in 1918 as a Lieutenant after surviving a gas attack. He was then able to finish his degree at Aberdeen.

In 1922, Robertson received a Carnegie Research Scholarship and worked for two years at the University of Glasgow under G. G. Henderson. At the end of the two years, he had completed his Ph.D. for work with terpenes. In 1924, he declined a Ramsay Memorial Fellowship for a Rockefeller International Science Fellowship. He worked for two years with Robert Robinson at the University of Manchester. At the close of the fellowship, he continued on at Manchester as a lecturer.

Robertson moved on to the University of London in 1928 and then to the London School of Hygiene and Tropical Medicine in 1930. Finally, in 1933 he became the organic chemistry chair at Liverpool, where he stayed until retiring in 1957. During his time there, Robertson established a strong research focus and one of the earliest microanalytical laboratories. His research throughout his career focused mostly on natural compounds and organic chemistry. He developed his interest in this work while earning his Ph.D. under Henderson.

After retiring from his academic and research work, Robertson joined the Advisory Council for Scientific and Industrial Research and the University Grants Committee. He also became an Advisor in Chemistry for the Carnegie Trust. He contributed time and knowledge to agricultural issues by becoming a member of the Rothamsted Agricultural Station and the Lawes Agricultural Trust.

Robertson married Margaret Mitchell-Chapman in 1926. They had a long and happy marriage. Mrs. Robertson died soon after his retirement in 1957 and he never entirely recovered from the loss. Robertson died on February 9, 1970 after being ill for a short time.