The Weldon process is a process developed in 1866 by

Walter Weldon Walter Weldon FRS FRSE (31 October 183220 September 1885) was a 19th-century English industrial chemist and journalist. He was President of the Society of Chemical Industry 1883/84. Life He was born in Loughborough on 31 October 1832, the son ...

for recovering

manganese dioxide Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cell ...

for re-use in

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

manufacture. Commercial operations started at the Gamble works in St. Helens in 1869. The process is described in considerable detail in the book, The Alkali Industry, by J.R. Partington,D.Sc. The common method to manufacture chlorine at the time, was to react manganese dioxide (and related oxides) with hydrochloric acid to give chlorine: : MnO₂ + 4 HCl → MnCl₂ + Cl₂ + 2H₂O Weldon's contribution was to develop a process to recycle the manganese. The waste

manganese(II) chloride Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the dihydrate (MnCl2·2H2O) and tetrahydrate (MnCl2·4H2O), with the tetrahydrate being the most common form. Like ...

solution is treated with lime, steam and oxygen, producing

calcium manganite(IV) Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

: : 2 MnCl₂ + 3 Ca(OH)₂ + O₂ →

CaO Cao or CAO may refer to: Mythology *Cao (bull), a legendary bull in Meitei mythology Companies or organizations * Air China Cargo, ICAO airline designator CAO *CA Oradea, Romanian football club *CA Osasuna, Spanish football club *Canadian Assoc ...

·2MnO₂ + 3 H₂O + 2 CaCl₂ The resulting calcium manganite can be reacted with HCl as in related processes: : CaO·2MnO₂ + 10 HCl → CaCl₂ + 2 MnCl₂ + 2 Cl₂ + 5 H₂O The manganese(II) chloride can be recycled, while the calcium chloride is a waste byproduct. The Weldon process was first replaced by the

Deacon process The Deacon process, invented by Henry Deacon, is a process used during the manufacture of alkalis (the initial end product was sodium carbonate) by the Leblanc process. Hydrogen chloride gas was converted to chlorine gas, which was then used ...

and later by the

Chloralkali process The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride (NaCl) solutions. It is the technology used to produce chlorine and sodium hydroxide (caustic soda), which are comm ...

References

Further reading