Ballantyne was the son of Thomas Ballantyne and his wife Jane. After attending Garnethill School, Ballantyne studied at Glasgow and West of Scotland Technical College. In 1887 he became assistant to the City Analyst of Glasgow. At the same time, he deepened his training in the laboratories of Wallace Tatlock & Clark and those of R.R. Tatlock, Thomson & Redman.

In 1896, Ballantyne settled in London as a consulting chemist, specializing in patent law in relation to chemical processes and cognate matter. From 1916 to 1928, Ballantyne was a director at Thermit Ltd. From 1928 to 1937 he was director of Lever Brothers and Unilever. From 1937 until his death, Ballantyne was advisory director at Lever Bros and Unilever Ltd.

Ballantyne was classified as an important target by the National Socialist police forces at the end of the 1930s because of his leading position in the British economy; Ballantyne was named in the Nazi’s ‘Black Book’: the wanted arrest list drawn up by the Nazis in the event of a successful Nazi invasion in 1940.

Ballantyne was a Fellow of the Chemical Society and the Royal Institute of Chemistry. He died in 1956.