In 1915, Mitsui Mining Company started the research on EElectrolytic production of Zinc, but, because of the unfavorable results of the experiments, the project was abandoned in 1919.
Durring 1930-1931, demand for distilled Zinc cooled down and the stock of distilled Zinc accumulated, but on the other hand, Zinc consumers demanded more electrolytic Zinc for fabrication. So, Miike Z.nc Works started the research on electrolytic production of pure Zinc with Kamioka Cocentrate. Some engineers of Mitsui Mining Company including the author inspected American and Canadian Zinc plants and the project to construct flash roasting plant and electrolytic Zinc plant according to the Trail and Tainton practice respectivly. Des'gncd capacity of the electrolytic Zinc pant has been 6, 000 tons of electrolytic Zinc per year. Mitsui Mining Company made a contract with Consolidated Smelting and Refining Company, B. C. for the application of the patent.
The whole plant was completed in September, 1936.
A Lurgi type multiple-hearth furnace was converted to flash roasting furnace and ball mill, air separator, are injector, waste-heat boiler and other necessary accessories were insatalled.
Advantages of flash roasting are:
1. Low sulphur content in calcine.
2. High concen ration of SO₂ in exit gas, correspondingly high extraction in H₂SO₄ mailing, and, therefore, possibility of mixing S0₂-poor D. L. gas with flash roaster gas.
3. No external heat is needed.
4. Utilization of waste heat as steam piped to electrolytic Zinc plant.
5. If Wedge-type roaster is available, it can be reconstructed easily, and, correspondingly, erection-capital is small.
6. Cost of operation is cheapest among various roasting processes.
Disadvantages of flash roasting are.
1. About 40% of charged are or 50% of calcine shows high sulphur which is not adequate to be used in distillation or electrolytic plant.
2. Repair cost of machines is comparatively high.
3. Electric power cost is comparatively high.
But advantages are more than enough to cancel disadvantages.
According to Mr. Tainton's findings, high acid-high current density process has been applied in electrolytic Zinc plant.
Batch leaching, Burt filter and two stage purification are carried out.
Electrolyte is composed of H₂SO₄ 19-20%, Zn 6-7%
Temperature of elecirolyte is kept between 40-50°C.
Current density is 750-800 amps/m².
Cathod deposits are stripped every 16 hours.
Electric power consumption is between 3, 800-4, 200K. W. H./T
Stripped deposits are melted with Ajax-Wyatt Low frequency indgetion furnace.
Parity of electrolytic Zinc Slab is 99.97-99.988%
First purification residue is treated for copper and cobalt.
Second purification residue is roasted and leached with H₂SO₄ and Cd-sponge is precipitated from the pregnant solution, purified and electrodeposited with insoluble anode electrolysis.
Purity or electrolytic Cadmium is around 99.98-99.99%.

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Researches on electrolytic production of Zinc were carried out in various laboratories in colleges and mining companies and some of the results were industriallized during 1910-1925, but the production figures of electrolytic Zinc during this period were too small as compared with that of distilled Zinc. Se7eral industrial plants for the mass production of electrolytic Zinc were erected successively since 1925 following the Tainton and Magdebvey processes.
During the last war, all of the electrolytic Zinc plants played important roles for the prouction of pure Zinc as a strategic material. Until 1911-1942, most of the plants showed favorable technical results with which they produced increased amounts of pure Zinc. But these high efficiencies were not comparable to American or German practice.
Because of the acutte demand for Zinci emergency productions were continned in all the plants, and, as a result, operating efficiencies began to retard due to the lack of adequate technical supervisions and the mobilization of skilled wokers and engineers. Even though some skilled engineers and workers endeavored to recover the plant efficiencies, actual data showed continuous slow down.
After the end of hostilities, plants restarted again to meet with the increasing domestic and foreign demands for pure Zinc, but the operators are fighting against the. hardship not only to overcome bottlenecks in Japanese economy but to regain technical standrds they had before the war.
Raseavhes on Zinc fuminy with leaching residues were carried out in several companies, but none of them could be industriallized after the war.
According to the situation of Zinc in the worldmarket, Japaness electrolytic Zinc plants should increase production at higher efficiencies as possible.
Residues and drosses should be treated for electrolytic Zinc-for the perfect utilization of natural resources. Managements should go further to set up a systim to inform and edueate young. enginees and average workers.
Scientific management and technical supervision based on actual daily report should be enforced for the efficient operation of the plants to the standard they secured before the war.
In the next place, scientists and engineers in this field should get a target to which every Zinc plant must approach. This target should be the technical-standard with whii h Amerieau electrolytic Zinc plants are furnishing every day.

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