There must be a considerable difference in floatabilities among the sulphide minerals to be floated if the differential flotation is applied. This is effected by controlling and addition of reagents. And though if it is possible to separate each mineral experimentally or in laboratory scale, sometimes it cannot be practiced from the economical point of view.
The author obtained experimentally the relative floatabilities of several important sulphide minerals, and found that the separation of galena from sphalerite, and chalcopyrite from sphalerite were easy, but the separation of galena from chalcopyrite was difficult more or less.
He concluded that flotation combined with some wet metallurgical process was recommendable with a sulphide are composed of mainly copper, lead and zinc.

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The results of experiments on flotation of rhodochrosite and pyrolusite are shown. Rhodochrosite floats easily by pine oil and sodium-oleate, and pyrolusite somewhat harder than rhodochrosite by the same procedures. Thus possibility of concentration of manganese ore by flotation was ascertained.

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Size of a mineral particle in flotation depends flrst upon the natural size of Hoatablemineralintherawore, andsecondlyonthemostappropriatesizeofmineral to float. In this paper the sizes based upon the screening analyses of flotation concentrates from various mills in Japan are dealt with.
As a recent trend of practice, concentrates as rich as possible are desired, and for this purpose very flne grinding is indispensable, especially with a complex sulphide ore. At the Hitachi mill the size below 300 mesh takes up over 90%; at the Besshi mill, more than 80%; at Ikuno (for copper ore), more than 60%; at Ashio, more than 50%. In this manner it is ascertained that the size flner than 300 mesh holds the greater part of the metal to be extracted.
In conclusion, importance and scientific interests are found in connection with such fine particles as 300-mesh-through.

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Floatability depends on the lustre of mineral, the tarnished mineral being disturbed to float.
It is difficult to determine the degree of tarnishing by any chemical analysis. The author determined it photometrically by Ostwald photometer. Chalcopyrite was treated with hydrogenperoxides of various concentrations, and in this way tarnishing was effected. Flotation was carried out on these samples. The relation between floatability and Brightness of mineral is as follows

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The writer gives an outline of the mechanism of flotation based upon the explanation made by G. H. Buchanan, Chief Technologist of American Cyanamid Co. Mr. Buchanan compared the flotation phenomena with the balloon accension.
Summing up, in his comparison:
The mineral particle is the aeronant.
The gangue … is the crowd.
The oil bubble … is the balloon.
The promoter … is the rigging.
The depressor … is the sand bag.
The regulator … is the weather.
Finally the writer of this paper added the theory of slime coating advanced by A. F. Taggart, T. C. Taylor, and C. R. Ince.

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Gold occurs in almost every districts in Chosen, and the deposits are genetically classified as: first, quartzose fissure filling deposits (majority of gold in Chosen comes from these deposits), secondly, metamorphic metasomatic deposits, and thirdly, igneous deposits. Generally, ores are associated with sulphides, such as pyrite, galena, sphalerite, pyrrhotite, arsenopyrite, chalcopyrite, bismuthnite and stibnite to a considerable amount; pyrite, galena and sphalerite are essential, pyrite being most predominant, and other sulphide minerals are accessory.
Amalgamation and cyaniding have been applied to the oxidized ores near the surface hitherto, and as the mine became deep the unaltered sulphides had to be worked, and sometimes such ores were not amenable to direct amalgamation and cyaniding. Therefore rich sulphide are was preliminarily hand-picked as much as possible, and then amalgamation and cyaniding were applied, being followed by tabling for recovering the fine sulphides together with gold from the amalgamation and cyaniding tails. But the extraction was very low. These sulphide concentrates were sold to the smelter.
Recently, flotation is applied to such ores; two systems are incorporated:
(1) Amalgamation and cyaniding in conjunction with flotation and tabling;
(2) Flotation in conjunction with tabling.
Ball-milling in stead of stamp-milling is also adopted and accordingly the extraction of gold is remarkably increased.
Gold ores in Chosen will be entirely concentrated by flotation in future.

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For the cleaning of slack delivered from coal washery the flotation process was utilized commercially at Imperial Steel Works since 1924. The flotator consists of five pneumatic cells provided with impellers. Flotation feed: 60% passes through 200 meshes screen, ash contents 22-24% in average, consistency 5%. Flotation oil: coal tar, its consumption being 0.14% of feed. Waste from flotation plant, containing 70% of ashes, is utilized as lining materials for ovens.

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Hosokura Lead and Zinc Mines, which is one of the most important lead and zinc producing mines in Japan, has been taken its ownership by the Kyoritsu Mining Company three years ago.
As there are a numger of veins, some of them being so big as 2 miles in length with the breadth of 5 to 30 feet, the company has intended to develop the mines, and to improve the gravity concentration will substituting with flotation process, and also to extend the electrolytic zinc plants.
In 1928, the company has started the proposed undertakings. first commencing with the opening of a new shaft, called Kanten Shaft, to sink it down below the levels thereto worked. Newly, air compressors of Rand and Ingersoll make have been introduced to have more effective results in working the mines. Two of 500 H. P. Diesel engines of Sulzer make were installed in order to supply enough power in case of want of hydro electric power in mid summer or in severe winter. At the same time, several improvements were made in many parts in the mills and metallurgical plants.
When the company intended to proceed on to put up a new flotation plants ousting the gravity concentration, there came an unexpected depression in the prices of zinc and lead, which were so low as quite unknown in the past historical records. Such coonditions made the company to postpone all the further undertakings in the mines as well as in the metallurgical plants.
But many experiments made in Hosokura as well as in a testing mill in Salt Lake City, U. S. A. showed that the differential flotation process is well suited for the ores of Hosokura, the extraction percentage of both lead and zinc concentrates being higher than 80%. As such excellent recoveries of both metals were obtained by flotation, much superseding the present gravity concentration, the company has for a temporary purpose put up a small flotation plant to treat the tailing coming from the present concentration mill, instead of supplanting the entire mill of the present existence. This tailing is of still containing 8% of zinc, and 90% of it is of very fine pulp below 200 mesh. For this tailing, flotation process has been applied to recover the zinc in it. From such refuses, hither thrown away into the dump, more than ¥20, 000 has been recovered in one year as net profit, after paying off all expenses incurred upon the metal produced.
All about the erectioin and the working details in this flotation plant, are fully described in this essay in Japanese, hereby submitted.

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The Osarisawa copper mill was reconstructed at the end of 1930 after two years from its start. Many fundamental investigations were carried out in connection with this reconstruction.
The capacity of the mill is 1, 300-4, 400 tons per day, being doubled before the mill was improved. Formerly, hand-picking, jigging and tabling were predominant and flotation was subordinate. All flotation system was adapted in the new mill, and modern and efficient crushing machines and flotation machines were equipped, and good organized, and in this way the mill was run very efficiently.
The ratio of concentration is 16-47 against 5-6 in earlier time. The concentrate assays 20-25% copper, tails assays 0.17% copper and extraction of copper is nearly 90%. The concentrated are is basic, which requires silicious flux, and the auriferous acidic are is charged in smelting.

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