Edgar Arthur Ashcroft (5 September 1864 – 24 August 1938) was an Australian electrical engineer and metallurgist, best known for developing an early electrolytic process for extracting zinc metal from its sulphide ores.
Early Life and Career
Ashcroft was born in Sunderland, County Durham, England, the son of George Ashcroft, a civil engineer, and his wife Sophia, née Davey. He trained as a mechanical and electrical engineer for five years before being recruited by the Broken Hill Proprietary Co. Ltd (BHP) to travel to Broken Hill, New South Wales, Australia, to install an electric lighting plant at its facilities. While at BHP, he worked as an electrician and also experimented in the treatment of silver-lead sulphide ores, assisted by Dr. Carl Schnabel of Clausthal, Germany. In 1893, together with John Howell, he invented a steam generator that used hot slag as a heat source.
The Ashcroft Process
In 1894, Ashcroft patented a complex electrolytic process for recovering zinc from refractory sulphide ores. He was motivated by the vast quantities of zinc sulphide tailings at the Broken Hill mines, which were considered waste due to the expense and difficulty of existing extraction methods. After leaving BHP later that year, the process was tested successfully on a small scale at Broken Hill and in England, and was approved by Schnabel.
The Sulphide Corporation (Ashcroft Process) Ltd was floated in London in 1895 with a capital of £1,100,000, purchasing Ashcroft's patents and the Broken Hill Central Mine. At Cockle Creek, near Newcastle, New South Wales, the world's first electrolytic zinc works was erected in 1897 at a cost of £250,000, built to Ashcroft's specifications and under his control.
Commercial Failure
Although based on sound scientific principles, the process failed commercially. Ashcroft had over-estimated profits and under-estimated costs, and the problems involved in scaling up from laboratory to industrial production had been minimized. Despite major modifications, the plant was largely dismantled within a year. The Sulphide Corporation dissociated itself from Ashcroft and his process, reverting to conventional roasting methods. The Australian Mining Standard accused him of making "a very large amount of money in selling what he knew was worthless to his company," though this accusation was never substantiated.
Later Life
Ashcroft returned to England amid controversy. He joined James Swinburne and continued laboratory work on wet electrolysis systems for separating chlorides and related problems. He published in journals such as the Transactions of the Electrochemical Society in New York. In the early 1920s he described himself as a research chemist, and in 1933 his paper on "Chlorine smelting with chloride electrolysis" was read to the Institution of Mining and Metallurgy.
He retired to Ancrum House, Roxburghshire, Scotland, and died on 24 August 1938 at Polton, Midlothian. He was survived by his wife Irene, née Dulier.
Memberships
- Australasian Institute of Mining Engineers (councillor, 1895–1897)
- Institution of Mining and Metallurgy, London (member from 1895)
Legacy
Described by Sir Richard Threlfall as having "that peculiar combination of imaginative faculty with sound horse sense which, more than anything else differentiates the born inventor," Ashcroft's complicated process—consisting of twenty operations—failed commercially. However, the original Sulphide Corporation "advanced the electrolytic process further than any other individual or company in the world," contributing foundational knowledge to the eventual commercial success of electrolytic zinc extraction.
