Aboundance of iron are resources in Manchukou has been drawing public attention, but the development of the iron are deposits in Korea has been overlooked by most people.
The iron ores in Korea are magnetite, hematite, limonite or the mixture of these. The magnetite mines constitute 33% of the iron mines operating, however, magnetite constitutes 99% of the iron are reserve. This fact presents one outstanding advantage in the discovery of iron mines in Korea, as magnetite deposit can readily be prospected magnetically. Furthermore, the advancement of the geophysical prospecting in recent years has enable one to apply magnetic prospecting to are deposits in which the magnetite is of the secondary importance. Non-magnetic iron ores can now be prospected according to the nature of deposit and the topography of the area, by electrical, gravitational or seismic method.
Examining the results of the prospecting magnetically or at times magnetically and electrically the Manchurian type deposit of Mosan Iron Mine, contact deposits of Kosho and Tansen Iron Mines, magnetic segregation deposit of Joyo Iron Mine and placer deposit of Shuotsu district, in 1938-1939, the author discusses the importance and the effectiveness of the geophysical prospecting, especially, magnetic prospecting, in the development of iron are resources in Korea and calls attention of the public.

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In this paper, authors described the results of an experimental investigation which carried out to study whether the characteristics of CA-7 type pneumatic-hamrnerpicic were influenced by the compressed air pressure and the primary pressure of the spring of the testing machine.

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This work consists of: (I) a study of the flotative properties of calcite in a nearly pure state and (II) application of this experimental information to concentrating lowgrade limestone by flotation.
(I) The experiments were performed with a 50-gram flotation machine of the M. S. type made of stainless steel. The pulp was made of 50 grams of the sample and 200 c.c. of distilled water.
The pH of the tailing solution was determined by means of a potentiometer with a saturated calomel and an antimony electrodes, or a calorimetric comparator.
The are used was massive calcite, containing 94.75% CaCO3, from the Yosida Quarry, Hukuoka, Japan. The sample was crushed and them ground (dry) to pass through 65-mesh. The-65+200-mesh material was separated from the-200-mesh material by dry screening.
The-65+200-mesh calcite was more floatable than the-200-mesh calcite when oleic acid in the pulp was less than 360g/t, but the-200-mesh calcite was more floatable than-65+200-mesh calcite with sodium oleate or over 360g/t oleic acid. This tendency may be attributable to the fact that the rate of flocculation of the-200-mesh calcite was increased by the addition of oleic acid.
Oleic acid with sodium oleate floated more calcite than did oleic acid alone. Small quantities, e.g. about 100g/t, of another frother such as camphor white oil with oleic acid or sodium oleate, increased the floatability of calcite.
The influence of the pulp temperature was experimented. The temperature of the pulp at the beginning of the flotation was 5°, 10°, 20°, 30° and 40°. respectively. In the range 5°-20°., it rose during the flotation process and became 15°-29°. at the end of 20 min. In the range 30°-40°., however, the pulp temperature dropped to 28°-32°. at the end of the same flotation duration. With 450g/t oleic acid, the variation in the floatability of-200-mesh calcite was most marked when the pulp temperature after the flotation was in the range 17°-25°. With 400g/t sodium oleate, it was considerable in the range 24°-29°. It was observed that small quantities, e. g. about 100 g/t, of another frother such as camphor white oil with oleic acid or sodium oleate floated calcite very effectively irrespective of the final pulp temperature.
With 270g/t oleic acid, calcite floated most at-50+200-mesh; the-150+200-mesh calcite floated most in the solution of distilled water with the pH value of 8.4. In the case of calcite, acid pulps are unstable because acid decomposes calcite.
The depressors were sodium silicate, citric acid, sodium meta-phosphate, copper sulphate, aluminium chloride, chromium nitrate, iron sulphate and gum arabic among which the most effective ones being citric acid and sodium meta-phosphate. The depressing action of copper sulphate with oleic acid was more marked than with sodium oleate.
Potassium dichromate or manganese sulphate had a tendency to slightly depress and sodium carbonate activated, especially with oleic acid, the flotation of calcite.
(II) The experiments were performed with a 150-gram flotation machine of the M. S. type made of stainless steel. The pulp was made of 150 grams of the sample and 450 c.c. of tap water.
The Manchurian limestone containing 70% CaCO₃ and 26% SiO₂ was crushed and then ground (dry) to pass through 200-mesh. The pulp was conditioned for 10 min. and froth was collected for 30 min.
Reagents: 100 g/t copper sulphate, 500 g/t Na₂02S10₂ and 1, 100 g/t oleic acid. Assay: 87.9% CaCO₃ in concentrate and 28.4% CaCO₃ in tailing. Recovery: 87.1% CaCO₃.
Reagents: 200g/t potassium dichromate, 500g/t Na₂O2SiO₂ and 1, 100g/t oleic acid. Assay: 88.4% CaCO₃ in concentrate and 22.5% CaCO₃ in tailing. Recovery: 91.3% CaCO₃.

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