James Moir was the eldest son of Dr James Moir, a classical scholar and headmaster of Aberdeen Grammar School. James junior studied at the University of Aberdeen, where he graduated in 1897 simultaneously as Bachelor of Science (BSc) and Master of Arts (MA), with triple first-class honours in chemistry, mathematics, and natural philosophy (physics). After three years as assistant to Professor F.R. Japp at the University of Aberdeen he obtained a two year scholarship in 1900 to continue his chemical research at the City and Guilds Central Technical College, London. On the basis of this work the University of Aberdeen conferred the degree Doctor of Science (DSc) on him in 1902.
Moir emigrated to the Transvaal Colony for health reasons in September 1902 and for a short time was science master at Jeppe High School in Johannesburg. In 1903 he was appointed as chemist in the newly established Rand Mines Laboratory of H. Eckstein and Co., Johannesburg. His first scientific paper in South Africa, "A new and rapid method of detecting and estimating gold in cyanide solutions", was delivered before the Chemical, Metallurgical and Mining Society of South Africa in September 1903 and published in its Journal (Vol. 4, pp. 125-127). It was followed by "Thio-carbamide [now thiourea]- a new solvent for gold" (Ibid, 1905/6, Vol. 6). From 1902 he served also as analyst to the Miners' Phthisis Committee.
In May 1904 Moir accepted a post as technical chemist in the Department of the Commissioner of Mines of the Transvaal Colony. He investigated the chemistry of the cyanide process for extracting gold from its ore, presenting a paper at the second annual congress of the South African Association for the Advancement of Science on "The cyanide process from the standpoint of modern chemistry" (Report, 1904). Several more papers by him were published in the association's Report in later years. He also contributed significantly to the study of dust particles in mine air that cause miners' phthisis and reported on "The vitiation of the air in Transvaal mines" (1905/6), "Witwatersrand mine air: Recent investigations" (1906/7), and "Recent investigations on dust in mine air and the causation of miners' phthisis" (1915) in the Journal of the Chemical, Metallurgical and Mining Society of South Africa. Among several other papers by him in the same journal two dealt with "Suggestions for a new atomic theory" (1909) and "Atomic weights and a new theory of chemical affinity" (1912/13). In 1912 he attended the International Congress of Applied Chemistry in New York as a government delegate.
In 1914 Moir became government analyst at the Government Chemical Laboratories in Johannesburg, a post he held until his death in 1929. He was an excellent organic chemist who, from 1916, studied the relationship between the chemical structure of organic substances and their colour. This work was published in a series of 26 short papers under the general title "Colour and chemical constitution" in the Transactions of the Royal Society of South Africa. The series was terminated by his death. Other papers by him in the same journal dealt with, among others, "The spectrum of ruby" and "The genesis of the chemical elements" (1908-1910), "On the spectrum of oxygen..." and "Notes on the spectra of the precious emerald and other gem-stones" (1910-1912), and "Valency and chemical affinity" (1913). With G.H. Stanley* he edited A text-book of Rand assay practice (Cape Town, 1924, 276p). The book had an impressive list of contributors and remained an authoritative source for almost 30 years. The first ten volumes of the Journal of the South African Chemical Institute, published during 1918-1927, included 25 notes and papers by him. In 1917 he was appointed as a member of the commission of examiners for the Government Certificate of Competency in Assaying.
Moir was mainly an organic chemist, but his publications indicate that he also made contributions to inorganic chemistry. These related mainly to gold extraction using the new solvent thiourea, removal of cyanide using ferrous sulphate, and investigations into the "purple of Cassius". He was also a theoretical chemist who played a role in the development of atomic theory (Loyson, 2014a, 2014b).
In addition to his work in chemistry Moir was an enthusiastic amateur astronomer. At his house in Auckland Park, Johannesburg, he had an equatorially mounted 130 mm refracting telescope and a large equatorial type sundial. The latter was fitted with a device of his own design by means of which the shadow was still cast on the south face when the sun was north of the equator. It was described in "A new type of accurate sundial or solar clock" in the Report of the South African Association for the Advancement of Science in 1918. He was a foundation member of the Johannesburg Astronomical Association and both he ande his wife were elected on its committee in September 1919. The association established a Mars Observing Section, with Dr Moir as director. When the association was absorbed into the new Astronomical Society of South Africa in 1922 he became a foundation member of the latter, as well as the thorough and energetic director of its Mars Observing Section. The section did good work, particularly at the time of the close opposition in 1924, and he led it until his death. He was also a keen observer of occultaions of stars by the moon and published a paper on "A rapid approximate method of calculating the occultation of stars by the moon (for the central Transvaal)" in the Report of the South African Association for the Advancement of Science (1918). In 1927 he visited England mainly to observe the total solar eclipse at Southport on 29 June that year. At the time of his death he was one of the Astronomical Society's representatives on the South African National Committee in Astronomy.
Moir was a Fellow of the (British) Chemical Society, a Fellow of the Institute of Chemistry (1916), and from 1905 a member of the British Association for the Advancement of Science. More importantly, he played an active role in several South African scientific societies. He was elected a foundation Fellow of the Royal Society of South Africa in 1908, served as a member of its council on several occasions, and as vice-president in 1911. He joined the Chemical, Metallurgical and Mining Society of South Africa in 1902, serving on its council from 1905, as joint vice-president from 1906, and as president for 1910/11. In 1921 he received the society's first research medal for chemistry, and two years later was elected an honorary life member. By 1903 he was a member of the South African Association for the Advancement of Science. He served on its council from 1907, on its Committee for the Standardising of Weights and Measures in South Africa in 1908, as president of Section B (which included chemistry) in 1921, and was awarded the association's South Africa Medal (gold) in 1919. In 1912 he became a foundation member of the South African Association of Analytical chemists and served on its council from the start, for many years. This association became the South African Chemical Institute in 1921. He was president for 1915/6, and again for 1924/5. Despite the fact that he was often in very bad health he continued his work and associated activities with enthusiasm and was the author of some 140 scientific publications. His contributions to science were commemorated in the James Moir Memorial Lectures, which were delivered about every three years under the auspices of the South African Chemical Institute. The institute also established a James Moir Memorial Fund, from which an annual award was made for the best MSc thesis on a chemical or metallurgical subject at South African universities. Moir married Gertrude Wilson in 1914, but they had no children.