National Smelting Company
Corporate brand
UnclaimedA British government-created smelting company whose Avonmouth works later became a major zinc, cadmium, lead and chemical-processing site.
Last updated November 4, 2026
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Overview
National Smelting Company was a British state-created industrial enterprise associated with the development of the Avonmouth smelting works near Bristol, England. It was formed during the later stages of the First World War under the Ministry of Munitions, at a time when the British government was seeking greater control over strategic metals and chemical production. The company’s public industrial mandate was to establish zinc-smelting and sulphuric-acid capacity at Avonmouth Docks. Behind that industrial programme, the site was also used for the production of dichloroethyl sulphide, commonly known as mustard gas, for Britain’s wartime chemical-weapons effort. The Avonmouth project reflected both military necessity and supply-chain concerns. Before the war, much of Britain’s zinc ore came from Australia but was processed in Germany. Establishing domestic refining capacity therefore had strategic value independent of the chemical-weapons programme. Construction of the chemical plant began in 1917, and production started in spring 1918. The plant produced mustard gas using the Despretz–Niemann–Guthrie process, with the material sent to shell-filling facilities in Britain. Because chemical warfare conflicted with the Hague Conventions, the programme was conducted under official secrecy and was presented publicly through the cover of nationalised smelting activities. The human consequences of the wartime operation were severe. A Ministry of Munitions medical report recorded extensive illness and occupational injuries among the predominantly female workforce. The related filling operations at Chittening also recorded large numbers of cases of illness. These wartime activities remain the most controversial aspect of the company’s history, linking an apparently conventional metals enterprise with chemical-weapons manufacture. After the First World War, demand for zinc and sulphuric acid declined sharply. The company experienced commercial difficulties and was taken over by British industrialists with interests in metals and chemicals. It was subsequently revived under the name Commonwealth Smelting Company. In 1929, it was acquired by Australia’s Imperial Smelting Corporation. The smaller works were gradually closed or consolidated, while production was concentrated at Avonmouth, which became known as the Britannia smelting works. The Avonmouth site became particularly important in the history of non-ferrous metallurgy because the Imperial Smelting Process was developed there. This technology enabled zinc and lead to be recovered together in a blast-furnace operation and helped make the works a major integrated base-metal facility. From 1967, the site operated what was described as the world’s largest and most efficient zinc blast furnace. Its industrial complex also included plants and support facilities for sulphuric acid, cadmium, beryllium, hydrofluoric acid, aluminium sulphate, ammonium sulphate, battery acid, phosphate products, refrigerants and laboratory research. Corporate ownership changed as the wider metals industry consolidated. Imperial Smelting Corporation merged with Zinc Corporation in 1949 to create Consolidated Zinc. Consolidated Zinc later combined with the Rio Tinto Company, producing the Rio Tinto–Zinc Corporation and its associated Australian interests. These corporate developments ultimately connected the Avonmouth works to the modern Rio Tinto group, although the National Smelting Company itself no longer operated as an independent enterprise. Lower-cost smelting capacity elsewhere reduced the competitiveness of the Avonmouth works. Zinc production ceased during the 1990s, but the site continued for several years as a stockholding and distribution centre. Production and related industrial operations finally ended in 2003. The former works subsequently entered a complicated redevelopment process. In 2012, SITA UK began work connected with a recycling facility, but reports of mustard-gas-type symptoms among construction workers led to Ministry of Defence testing. A mustard-gas shell was later discovered and removed by military explosive-ordnance specialists, and the site was closed while further testing took place. Ministry of Defence clearance was eventually granted in late 2013. Plans then proceeded for a large Asda supermarket distribution centre and a SITA UK recycling plant.
History
National Smelting Company emerged from the British government’s First World War effort to secure strategic metals and chemical capacity. The Ministry of Munitions, led by Winston Churchill, nationalised a number of smaller smelting interests and used the new company as the public framework for building a large works at Merebank, near Avonmouth Docks. The stated purpose was to process zinc and manufacture sulphuric acid. This was strategically significant because Britain depended on imported zinc ore and much of its pre-war smelting had been carried out in Germany. The Avonmouth project also concealed a chemical-weapons installation. Britain planned to produce dichloroethyl sulphide, or mustard gas, despite the prohibitions on poison weapons contained in the Hague Conventions. Construction began in 1917, and the plant entered service in spring 1918. It manufactured mustard gas by the Despretz–Niemann–Guthrie method at a reported rate of approximately 20 tonnes per day. The material was transported to British shell-filling facilities, including Banbury, Chittening and Hereford. The associated workforce experienced serious occupational harm. A report covering the plant’s first six months recorded about 1,400 illnesses among roughly 1,100 mainly female workers, along with fatal accidents and hundreds of burn injuries. After the Armistice, the company faced a sharp fall in demand for zinc and sulphuric acid. Commercial difficulties led to a takeover by British industrialists, who reorganised the business as Commonwealth Smelting Company. In 1929, Imperial Smelting Corporation acquired the company. Production was consolidated at Avonmouth, while smaller installations were closed. The works became known as the Britannia smelting works and developed into a major centre for non-ferrous metallurgy. The site’s most important technological contribution was the Imperial Smelting Process, a combined zinc-and-lead recovery method developed and refined at Avonmouth. The process allowed both metals to be recovered from suitable concentrates in a single blast-furnace system. The works expanded into a broad industrial complex with zinc, lead, cadmium, chemical-acid, laboratory and engineering facilities. In 1967 it operated the world’s largest and most efficient zinc blast furnace, according to contemporary descriptions. Ownership continued to follow the consolidation of the international metals industry. Imperial Smelting Corporation and Zinc Corporation combined in 1949 to form Consolidated Zinc. Consolidated Zinc later merged with the Rio Tinto Company, creating the Rio Tinto–Zinc Corporation and related Australian operations. These entities formed part of the corporate lineage leading to Rio Tinto, although the original National Smelting Company had ceased to be an autonomous operating brand. The Avonmouth works eventually lost competitiveness as lower-cost smelters were built elsewhere. Smelting ended during the 1990s, but the site continued as a storage and distribution location until 2003, when zinc, cadmium, lead and sulphuric-acid production finally stopped. Redevelopment began in the 2010s. SITA UK’s plans encountered environmental and safety concerns after workers experienced symptoms associated with mustard gas and a shell was discovered. The Ministry of Defence and Defence Science and Technology Laboratory examined the site, and explosive-ordnance specialists removed the shell. Clearance was granted in late 2013, allowing plans for an Asda distribution centre and a SITA UK recycling facility to proceed.
- 2013
Redevelopment receives Ministry of Defence clearance
[1]Following testing and removal of a mustard-gas shell, the former industrial site was cleared for redevelopment.
- 2003
Production ceases
[1]The remaining production of zinc, cadmium, lead and sulphuric acid ended after the site’s decline as a competitive smelting location.
- 1967
Large-scale zinc blast furnace operation
[1]The Avonmouth works became home to a zinc blast furnace described as the largest and most efficient in the world.
- 1949
Imperial Smelting Corporation merges into Consolidated Zinc
[1]Imperial Smelting Corporation combined with Zinc Corporation, creating Consolidated Zinc and further consolidating ownership of the Avonmouth works.
- 1929
Acquisition by Imperial Smelting Corporation
[1]National Smelting Company was acquired by the Australian Imperial Smelting Corporation, beginning a long period of integration into international metals groups.
- 1923
Avonmouth plant construction completed
[1]The broader chemical project was completed after wartime delays and was reported to have cost £800,000.
- 1918
Mustard-gas production starts
[1]The chemical plant entered operation in spring 1918 and supplied dichloroethyl sulphide for British shell-filling operations.
- 1917
Construction of the Avonmouth chemical and smelting works begins
[1]Construction began at Merebank, Avonmouth Docks, for zinc smelting, sulphuric-acid production and a concealed mustard-gas manufacturing plant.
Products and positioning
A strategic British metals and chemicals enterprise whose identity evolved from wartime state industrial production into a major integrated non-ferrous smelting operation.
Base metals
Zinc
Zinc was the principal long-term product of the Avonmouth works. The site was created partly to establish domestic British zinc-smelting capacity and later became a major industrial centre using the Imperial Smelting Process. Zinc production continued through the twentieth century before becoming uneconomic against lower-cost international alternatives.
Base metals
Lead
Lead was recovered alongside zinc at the integrated Avonmouth works. The Imperial Smelting Process was significant because it permitted the combined treatment of suitable zinc-and-lead concentrates, supporting the site’s role as a large non-ferrous metals complex.
Specialty metals
Cadmium
Cadmium was produced as part of the site’s broader non-ferrous refining operations. A dedicated cadmium plant was listed among the works’ late-1960s facilities. Cadmium production ended with the closure of the remaining Avonmouth operations.
Industrial chemicals
Sulphuric acid
Sulphuric acid was one of the original products planned for the Avonmouth complex and remained part of its integrated chemical and metallurgical infrastructure. The works included a sulphuric-acid plant and associated chemical-processing facilities.
Chemical warfare agent · 1918
Mustard gas
During the final year of the First World War, the Avonmouth chemical plant manufactured dichloroethyl sulphide, or mustard gas, for use in British chemical-weapons shells. This was a secret wartime activity conducted under the cover of the company’s public smelting mandate and is not a commercial product associated with the later industrial business.
Brand decisions
2012
Begin redevelopment of the former worksStrategyBackground
The closed industrial site was targeted for reuse as a distribution and recycling complex.
Action taken
SITA UK began redevelopment, but construction was suspended after health concerns and the discovery of a mustard-gas shell led to military and scientific testing.
Aftermath
After Ministry of Defence clearance in late 2013, plans proceeded for an Asda supermarket distribution centre and a SITA UK recycling plant.
1990
Wind down Avonmouth smelting operationsStrategyBackground
Smelting became less competitive as lower-cost production capacity developed elsewhere in the world.
Action taken
The Avonmouth site ceased smelting during the 1990s and shifted toward stockholding and distribution before final closure.
Aftermath
The site remained operational in a reduced logistics role until production and related industrial activity ended in 2003.
1929
Sell the company to Imperial Smelting CorporationM&ABackground
Post-war reductions in demand for zinc and sulphuric acid created commercial difficulties for the company.
Action taken
After an intervening reorganisation as Commonwealth Smelting Company, the business was acquired by Australia’s Imperial Smelting Corporation.
Aftermath
Operations were consolidated at Avonmouth, supporting development of the Imperial Smelting Process.
1917
Create a state smelting company at AvonmouthStrategyBackground
Britain needed domestic zinc-processing capacity during the First World War, while the Ministry of Munitions also required a concealed facility for chemical-weapons production.
Action taken
The government nationalised smaller smelting interests under National Smelting Company and commissioned a new Avonmouth zinc-smelting and chemical complex.
Aftermath
The project established the industrial site that later became the Britannia smelting works and a major centre for zinc and lead metallurgy.
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