The depression of pyrrhotite containing sphalerite is very difficult on account of the copper ion activation during the zinc flotation process. Accordingly, the mineral particles to be floated by the copper ion activation are so many that the flotation machine overloads. Thus, the grade and recovery of zinc in the zinc concentrates are remarkably lowered. Therefore, it has been said that the zinc flotation is disturbed considerably in the case where pyrrhotite exists in Sphalerite.
In this paper, the authors pursued on many problems for the separation of sphalerite and pyrrhotite and discussed on how to separate the above minerals from the detailed investigation of the past paper.
At first, the authors attempted to discuss on the copper ion adsorption of sphalerite and pyrrhotite. As compared the copper ion adsorption on sphalerite with the copper ion adsorption on pyrrhotite, it is recognized that the copper ion adsorption on sphalerite proceeds in all pH values, but the copper ion adsorption on pyrrhotite depends remarkably on the pH value. With the increase of the iron contents in sphalerite, the copper ion adsorption on sphalerite decreases in the case where oxygen is sufficiently dissolved in the flotation pulp and the pH is high enough. On the other hand, the copper ion adsorption on pyrrhotite scarecely proceeds in the above-stated conditions. Bushell and his collaborators carried out the flotation tests for the separation of sphalerite and pyrrhotite by using oxygen. They confirmed that the separation of sphalerite and pyrrhotite is possible. As a reason, they surmised that the copper ion adsorption is hindered because of the formation of the insoluble and protective film such as ferric hydroxide, ferric oxide, or basic iron salt in the case where the pH is high enough and oxygen is sufficiently dissolved in the flotation pulp to oxidize iron of mineral surface.
As the above mentioned, it is considered that the dissolved oxygen in the flotation pulp is one of the most important factors.

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In the first place, microscopic property, X-ray diffraction profile and oxidation property were measured as the specific property of the minerals. In the second place, influence of the specific property on the flotation behavior, particularly pH value of the pulp was investigated.
The main results obtained are as follows :
1) The crystallinity of pyrite from sulphur mine is lower than that of ordinary one. A difference of crystallinity is also recognized in pyrites from various sulphur mines.
2) The oxidation rate of pyrite increases with a decrease of its crystallinity.
3) As concerns pyrite, marcasite and their mixture, the converged equilibrium pH value of the pulp decreases and intensity of the convergence increases with an increase of the oxidation rate.
4) The converged equilibrium pH value of the pulp has a close connection with the critical pH value of flotation.

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Leja and other investigators had reported many instances of interaction of frothers and collecters in flotation. The important and yet to be studied aspect which pertains to the characteristics of flotation froth seems to be the coadsorption of the both reagents on mineral surfaces.
The auther confirmed this interaction by (a) Hallimond tube flotation tests of pyrites and Cu-activated zincblende, (b) measuring the increase in surface tension of clear solutions taken out from the solutions containing NaEX and some one kind of frothers in which galena, chalcopyrite or pyrite was agitated and conditioned and (c) the difficult depression of pyrite which was previously floated in nearly neutral solution containing NaEX and a f rother. Because of the coadsorption and fixation of f rothers on mineral surfaces, frother concentration in ore pulp decreases, and if the dosage of frothers is insufficient, the mineralized froth becomes too thick and dry, even when NaEX, not mentioning the use of higher xanthates, is used.

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