James Scott Maclarin was born on 8th November 1864 in Unst, Shetland, the son of Robert Campbell Maclaurin and Martha Joan Spence.

He went to Auckland Grammar School and began as an assistant to a chemical analyst. Auckland University College was being established and began offering science degrees. James and his younger brother Richad Maclaurin were enrolled in 1888. James graduated in 1892 with a BSc and began working for honours on a new cyanide process for extracting gold from low-grade ores.

James married Dorcas (Cas) Macky on 27th December 1893 in Paterangi, New Zealand. Cas (b. 23rd April 1873, Otahuhu) was the daughter of William Macky and Ann Goodfellow. An older sister, Catherine Cochrane Macky, had married an older brother of James, William Gilbert Maclaurin, six years earlier.

James and Cas had four children:

• Helen Baird Maclaurin b. 13th March 1895 who married William Irwin Hunt (b. 1891) in Wellington on 8th August 1923. William was a farmer. They had family. William died on 9th August 1976 and Helen on 7th September 1990.

• Catherine Anne Maclaurin b. 25th January 1897 in Auckland who married John Murdoch McKenzie (b. 1st December 1891, Auckland) on 22nd December 1921 in Wellington. John was the son of John McKenzie and Mary Smith. He was a minister, BA, LLB. Catherine and John had family. She died on 24th September 1975 and is buried in Wellington. John died there on 9th February 1981.

• Colin Campbell Maclaurin b. 2nd October 1898 who married Dorothy Knyvett Mirams (b. 15th April 1899) in 1925. He was a doctor (MBChB). Colin and Dorothy had family. He died on 8th April 1979 and Dorothy on 26th June 1991.

• William Macky Maclaurin b. 4th April 1904 who married his cousin Winifred Joan Maclaurin (b. 1899) in Wellington on 14th September 1926. Winifred was the daughter of Edward Thomas Woodford Maclaurin and Winfred Ball. William, like his elder brother Colin Maclaurin, was also a doctor (MBChB). William and Winifred had family. William died on 5th May 1987 and Winifred on 29th September 1986.

James won first class honours for his work on the cyanide process and in 1895 was awarded the 1851 Exhibition Scholarship, which would have enabled him to undertake two year's research work anywhere in the world. In view of his young family, he declined in favour of the security of his existing position. The prize consequently went to the next best candidate, an Ernest Rutherford who went to Cambridge, England and subsequently won a Nobel Prize for Physics.

In 1901 James was appointed the New Zealand government's colonial analyst. He subsequently built up the Colonial (subsequently the Dominion) Laboratory. He died on 23rd November 1939 in Wellington and Cas on 28th February 1963.