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"Rapid Determination of Boric Acid in Nickel Plating Solution" by the addition of Na₂C₂O₄and thus preventing the precipitation of Ni(OH)₂during titration, has previously been reported. In this paper, the exact amount of glycerine and the complexing possibility of oxalate with nickel has been determined by means of conductivity titrations. This experimental work has been supported by the mathematical application of the Debye-Hu¨ckel and mass action equations as well as statistical analysis. The results were: (1) For determining boric acid in nickel plating solution, 20㎖ of 400㎖/ℓglycerine was sufficient, since 97% of the H₃BO₃was dissociated by this addition. (2) In the absence of Na₂C₂O₄, the continious precipitation of Ni(OH)₂a during titration with NaOH even past end-point for boric acid determination resulted in considerable analytical error. (3) In the presence of Na₂C₂O₄during titration, Ni^(++) combined with C₂O₄^(--) to form NiC₂O₄. The solution with this precititate of very fine, colloidal, transparent particles, remained quite clear for approximately 2 hours. Therefore it was shown that the presence of Na₂C₂O₄prevents the formation of gross Ni(OH)₂ precipitation by forming NiC₂O₄instead of a complex salt with Ni^(++), which did not interfere with the visible determination of the end-point for boric acid with NaOH titation. This observation may be interpreted in the light of the previously published solubility ratio for NiC₂O₄and Ni(OH)₂: 0.3㎎/100g H₂O (25℃), and 1.3㎎/100g H₂O (25℃), respectively. Precipitation of the less soluble, albeit transparent salt, NiC₂O₄, precluded therefore the precipitation of the Ni(OH)₂salt.

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After our investigation on the improvement of welding techniques in Korea under the contract by the MOST-USOM Research Project Code No 660∼19, it has been already reported as foregoing section that a title has fundamental study on the arc weld for the steel plates(-on the mechanical properties and welder qualification-). This is a secondary report succeeding to it. Therefore, to get the results for tensile and impact values for the deposited metal from their specimens, when the generally rolled mild steel plates are welded with four kind of domestic covered arc electrodes, prepared tests are experimentally carried out. Then, such the results gained have been discussed. As one of the performance of it, the tensile strength σ_B and yielding point σ_y are presented higher values more than its standards, while the elongation are not given satisfactory values in several data and the impact values are considered to keep its standards except the results of two specimen.

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The settling velocity, sediment volume and floatability of scheelite particles under various concentration of oleic acid are studied by using turbidimeter, modified mass cylinder and Hallimond Tube respectively. The results were compared with the flocculation and dispersion phenomena of the particles in the solution and floatability of scheelite minerals. Measuring the amount of adsorption by using gas chromatography, it was found out that the amount of adsorption was increased gradually according to the concentration increment of oleic acid. And also, it was found the formation of poly molecular layer of oleic acid at the concentration more than 10^(-4) M/l.

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The phase boundaries for the YCd₃-Zn pseudo-binary section of the yttrium-cadmium-zinc ternary system are presented. The boundaries were studied through differential thermal analysis, metallographic, electron micro-probe analysis, neutron activation analysis, and x-ray diffraction studies. A ternary compound, whose composition was established to be (YCd₃)Zn₂, which decomposes peritectically at 757℃ was found in this section. Two other compounds, whose compositions were thought to be Y₃Cd₄Zn_7 and ∼Y₂CdZn_(14), which decompose congruently at 840 and 875℃ in the range of 10.0∼25.0 w/o Zn and 32.0∼90.0 w/o Zn, respectively. X-ray diffraction studies revealed that Y₃Cd₄Zn_7, is orthorhombic and (YCd)₃Zn₂, and∼Y₂Cd Zn_(14), are hexagonal and monoclinic, respectively, with. a=15.103±4, c=14.985±6Å (YCD₃)₃Zn₂, and a=10.234±7, b=9.038±5, c=6.822±9Å , β=99.40˚(∼Y₂CdZn_(14))

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The development of welding techniques in Korea are still in the infant stage, as compared with the standards achieved by the advanced nations of the world. However, the improvement of welding techniques has been appeared as important problem in the field of the construction of manufactural plants in our country. On request of the Economic Planning Board, Republic of Korea and the United States Operations to Korea, the research investigation with the title of Improvement of Welding Techniques in Korea has been cooperatively carried out by our research members who are staff of the Mechanical Engineering Department at Yonsei Engineering Research Center in Yonsei University, Seoul, in accord with the contract signed on October, 1966. Then, the final report was submitted in July, 1967. The contents of this report contains a part of experimental works in above study. When the generally rolled mild steel plates taken as the base metal are welded with several covered arc electrodes of domestic, the weld joint efficiency in tension test and the results in guided bend test are discussed. And also, the standards of welder qualification in the guided bend test are studied under the consideration domestic situations.

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Flotation tests of molydenite, chalcopyrite and cosalite were carried out by Hallimond tube with various xanthates and depressing agents. Molybdenite and cosalite showed that they have maximum flotability at about pH 6.0 while chalcopyrite has at pH 4.0-8.0 range. Oxidizing reagent, potassium permanganate is effective depressant of chalcopyrite on the selective flotation of molybdenite and chalcopyrite. On the other hand, potassium dichromate depresses cosalite on the selective flotation of molybdenite and cosalite or chalcopyrite and cosalite.

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Thermodynamic properties of zinc and iron were derived from zinc-vapor pressures in equilibrium with B.C.C. Solutions of zinc and iron at 703.5˚, 757˚,793˚, and 900℃ measured by Wriedt using an isopiestic method. Gibbs free energy change difference of liquid zinc and weight pct in iron was computed by the both as standard states of pure B.C.C. elements and pure liquid zinc. The difference of computed values by both standard states shows quite small. It was determined that. an equation for the Gibbs free energy change between liquid zinc and weight pct in iron. Activities of iron for each temperature were derived with Gibbs-Duhem integrations by a graphical method using log r and were compared with values obtained by Wriedt using Gibbs-Duhem integrations of the form involving the α function. It was found that both values show a firely good coincidence.

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Corrosion survey were covered about forty industrial plants which were deeply related to corrosion problem. This study was discussed them under six sub-divisions, such as fertilizer plants & oil refinery, thermal power plants, water plants, general chemical plants, fiber plants & paper mills, and shipyard, port, and railroad facilities. Corrosion problem in fertilizer plants & oil refinery were considered as the most importance. Generally main corrosion problems were: 1) water treatments in pipelines, heat exchangers, and boilers etc., 2) corrosion problem by fuels such as Banker C and coal etc., and 3) underground pipe lines by low soil resistivity, salt contents, and biological attack etc.

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