Following his time in Leyden, Hutton returned to London and thence back to Edinburgh in the summer of 1750. He was 24 years old. Prospects for establishing a medical practice were apparently few and probably did not hold great attraction for him without being able to indulge his fascination in chemistry.
One of those with whom he shared his chemical experiments as a youngster was a close friend, James Davie. They had together experimented on the nature and production of sal ammoniac from soot, which was to form the basis of a successful manufacturing business in which they were partners and from which they profited well.