Effect of polypropylene glycol monomethyl ethers (polyPGME), such as mono-(1PGME), di-(2PGME), tri-(3PGME), and tetrapropylene glycol monomethyl ether (4PGME), on the floatability of galena with xanthate was investigated. α-terpineol and cineol were also used in the test as the reference. The floatability of galena was measured with a bubble pick up tube at 25°C. In order to investigate the adsorption property of poly-PGME at the liquid-gas interface, surface tension was measured with Du Nouy tensiometer at 20°C.
The floatability of galena with xanthate in the region of pH 4-10 increased in the presence of the poly-PGME as well as α-terpineol and cineol. The more the number of propylene group in the molecule of polyPGME was increased, the more the floatability of galena with xanthate was promoted. The adsorption property of the polyPGME at the liquid-gas interface decreased with decreasing the number of propylene group in the molecule. From these results, Dowfroth 250, α-terpineol, and cineol were comparatively discussed on the viewpoints of frothing property and selectivity for collecting of mineral particles in the practical flotation system.

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A microscopic method for the determination of the particle size distribution in ground minerals by means of a scanning electron microscope (SEM) was established.
1. A special sample holder, for this purpose, was used in order to take photographs of both the sample and the standard scale under the same conditions.
2. The pieces of micro-mesh sieves were used as a standard scale, and their lengths were measured precisely by an optical microscope and SEM.
3. Because this SEM is equiped with a special coil, the maximum deformation ratio of the micro photographs of the images was 3.5%.
4. Presentation of a better technique in sampling, counting and calculation of particle size analysis of quartz powder by the SEM.
5. The particle size distribution curve obtained by the SEM indicated a low proportion of the quantity of particles in the region of the small particle diameter, compared with the results of the sedimentation balance method.
6. A particle size analysis using the SEM, an optical microscope (OM) and a sedimentation balance (SB) was performed on a sample of spherical glass beads with larger particle sizes than those of the quartz powder. The particle size distribution curve based on the number of particles obtained by the OM indicated a low proportion in the region of small particle diameters compared with the curve obtained by the SEM. But the curves based on the weights of the particles obtained by the SEM, the OM and the SB were not so dissimilar.
7. It seems that the particles easily observed are overestimated by the microscopic method as compared with the sedimentation balance method.

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Ozone is known as a most powerful oxidant. In this paper, the decomposition of xanthate and xanthate metallic salts by ozone was examined to investigate the possibility of the application of ozone treatment in the flotation process. At first, potassium ethyl xanthate (KEX) solution was treated by ozone at various pH and it was observed that KEX was decomposed easily and rapidly even at relatively high concentration. Furthermore, it was found that the formation of sulfate ion (SO^2-₄) followed the decomposition of xanthate and so pH of the solution got lower remarkably. Potassium normal-amyl xanthate (KAX) was also decomposed. Next, copper ethyl xanthate (Cu(EX)₂), lead ethyl xanthate (Pb(EX)₂) and zinc ethyl xanthate (Zn(EX)₂) were treated respectively. These metallic salts were decomposed, too. Both Cu(EX)₂ and Zn(EX)₂ were decomposed completely at the adequate pH, but the maximum of the decomposition percentage of Pb(EX)₂ was about 70% in this experimental condition. And in the case of the decomposition of these metallic salts pH of the solution became lower after the ozone treatment when the initial pH was under about 11.

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