The single crystals of CrB, Cr₃B₄ and CrB₂ have been prepared by the reaction of elementary chromium with boron in molten aluminum flux under an argon atmosphere. The optimum mixing atomic ratios of raw materials (B/Cr and Al/Cr), reaction temperature and reaction time are as follows: B/Cr =0.8, Al/Cr =28.9, 1500°C and 10∼20 h for CrB; B/Cr =1.33, Al/Cr =28.9, 1500°C and 10 h for Cr₃B₄; B/Cr = 2.0, Al/Cr = 28.9∼38.2, 1500°C and 10∼20 h fo r CrB₂. Under these conditions, CrB single crystals are obtained as pillars and prisms grown in the direction of ‹100› and ‹001›, Cr₃B₄ as thin plates and thick trapezoidal plates with well-developed (010) faces, and CrB₂ in the forms hexagonal prism extending in the ‹0001› direction and thick hexagonal plates with well-developed (0001) faces. The latti ce constants, densities and Vicker's microhardness are as follows:
CrB(orthorhombic); a=2.977+0.002Å, b=7.862±0.003Å, c= 2.931 ± 0.001Å D=6, 04 ± 0.03 g/cm³, H_v=1960∼2340 kg/mm²
Cr₃B₄(orthorhombic); a = 2.996 ± 0.001Å, b=13.005 ± 0.004Å, c=2.950 ± 0.001Å. D=5.72 ± 0.02 g/cm³, H_v=2130∼2340 kg/mm²
CrB₂(hexagonal); a=2.9730 ± 0.001Å, c=3.074 ± 0.001Å D=5.16 ± 0.03 g/cm³, H_v=2070∼2290 kg/mm²

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A solid solution tends to have a compositional fluctuation. A new method was developed to determine the extent of compositional fluctuation and applied to the (Ba, Pb)TiO₃ system. The method revealed that the (Ba, Pb)TiO₃ solid solution, prepared by a conventional solidsolid reaction, always has compositional fluctuation.
(Ba, Pb)TiO₃ solid solution having little compositional fluctuation was prepared by a new process, a solid solid reaction between titanium dioxide and co-precipitate of lead and barium carbonates. Compared with a conventional wet method, which requires simultaneous precipitation of all the constituent cations, the proposed method has an advantage that only a simultaneous precipitation of the cations in the same site is necessary.
The (Ba, Pb)TiO₃ having compositional fluctuation exhibits a coexiste nce of tetragonal and cubic phases over a wide range around the Curie temperature, On the other hand, for the (Ba, Pb)TiO₃ having no compositional fluctuation, the transformation from tetragonal phase to cubic phase occurs suddenly.
Compositional fluctuat ion appeared to the (Ba, Pb)TiO₃ having no compositional fluctuation, when it was fired again at relatively high temperatures. This phenomenon may be related the evaporation of PbO. Therefore, firing for a long period at a high temperature is not always appropriate in order to obtain the material with no compositional fluctuation.

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Faujasite type zeolite was synthesized from co-precipitated silica-alumina gel prepared from “Shirasu”, volcanic ash distributed widely in Southern Kyushu.
Ground Shirasu was first mixed with solid sodium hyd roxide and heated at 300°C to obtain a dry mixture Shirasu-Na₂O, which was then neutralized with 2 mol. dm^-8 HCl solution. Silica-alumina gel co-precipitated was mixed with a calculated amount of sodium hydroxide solution, aged at 25°C for 1 h, and heated at 90°C for 5 to 50 h.
The amount of faujasite formed in solid phase was affected by H₂O/Na₂O molar ratio, Na₂O/(SiO₂+ Al₂O₃) molar ratio and the addition of seed crystals of faujasite type zeolite. In the region of lower Na₂O/(SiO₂+Al₂O₈) molar ratio, gmelinite and chabazite was produced instead of faujasite. In the region of higher Na₂O/(SiO₂-Al₂O₃) molar ratio, zeolite P was formed as a major crystalline phase. The addition of seed crystals of faujasite increased the formation field of faujasite, and decreased especially the crystallization of chabazite and gmelinite. The formation field of zeolite P also decreased, but not so notable. The addition of seed crystals of faujasite decreased mainly the yield of zeolite whose framework structure is similar to that of seed crystals.

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Effects of silicone-oil treatment were investigated in order to prepare fine acicular Fe particles with a high coercivity. The Fe particles were prepared by hydrogen reduction of fine acicular α-FeOOH particles which were treated with silicone oil dissolved in 2-butanone. The size and shape of Fe particles were examined using an electron microscope while the coercivity was measured by a vibrating sample magnetometer. Fe particles obtained from nontreated α-FeOOH were large in size due to sintering between the Fe particles and nonacicular in shape. These particles had a low coercivity. Desirable Fe particles were obtained when silicon oil-treated α-FeOOH was reduced at 550°C. The Fe particles were 0.35 μm in length, the length-to-diameter ratio being 6 and the coercivity 110 kA/m.
Thermal decomposition products of the silicone oil used were examined by IR-sp ectroscopy. The silicone oil adsorbed on α-FeOOH decomposed to SiO during reduction. The SiO possibly obstructs the sintering and aids in keeping the acicular shape.

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In the reaction of thiophenol [1], 4-methylbenzenethiol [2], 4-nitrobenzenethiol [3], α-toluenethiol [4] and 1-dodecanethiol [13] with DMSO-SbCl₅(1:1) complex, the corresponding sulfides were given over 81% yield under the mild conditions (Table 1 and Table 2).1, 2-Dithiolane [11] and 1, 2-dithiane [12] were also obtained in high yields of 90.7% and 73.2% respectively in the reaction of 1, 3-propanedithiol [5] and 1, 4-butanedithiol [6] with the complex. Both DMSO and SbCl₅ in the complex seem to be concerned as an oxidant as shown in the following equation.
4RSH + DMSO SbCl₅→ 2R-S-S-R (CH₃)₂S SbCl₃ + 2HCl H₂O
When tribenzylamine was added in each reaction mixture of [1], [2], [3] and [4] with the complex, the yield of the corresponding sulfides increased in the range of 3% to 10% (Tnble 7).

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The mercury content of seawater is very low, as little as one nanogram per liter. A pre-concentration is therefore required for the determination of mercury at ppt levels in seawater.
The recommended procedures are as follows ( a ) A seawater sample is acidified with sulfuric acid and then mercury is reduced with tin( II) chloride. Nitrogen gas is passed through the sample solution and any mercury evolved is trapped on a porous gold collector and determined by cold vapor atomic absorption spectrometry. ( b ) Seawater samples are treated with sodium hydroxide, copper(II) ions and tin(II) chloride, and the mercury is determined as in ( a ). ( c ) Seawater samples are treated with a mixture of sulfuric acid and potassium peroxodisulfate solution and heated on a water bath, followed by ( a).
Dissolved inorganic mercury, dissolved inorganic mercury p lus a part of the organic mercury and suspended mercury, and the total mercury can be determined by procedures ( a ), ( b)and ( c ), respectively.
Seawater samples were collected from Kagoshima Bay and from the open ocean (the East China Sea) during the period 1981∼4983 and the distribution of mercury and its various chemical forms were investigated. Levels of mercury determined by procedures ( a ), (b)and ( c ) were found to be in the range of 1.5∼5.4 (mean 2.3₉), 1.6∼43.3 (mean 3.2₇)and 1.7∼17.6 ng/l (mean 5.7₃ ng/l) for 37 samples taken from Kagoshima Bay and 1.3∼-2.9(mean 1.8₉), 1.4∼3.2 (mean 2.2₈) and 2.8∼5.2 ng/l (mean 3.6₀ ng/l) for 27 samples taken from the East China Sea, respectively.
Mean levels of mercury [ ( a ), ( b ), ( c ) ] for Kagoshima Bay were 1.2₆, 1.4₃ and 1.5₉ times higher than those for the East China. From these results, it is considered that factors such as urbanization activies around Kagoshima City, geological circumstances and submarine volcanic activities of Northern Kagoshima Bay have produced significant changes in the seawaters of Kagoshima Bay.

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The racemic structures of (+)-a-methylbenzylammonium salts of substituted benzoic acids (substituent=p-OCH₃ (MTB), o-CH₃ (OMB), m-CH₃ (MMB), p-CH₃ (PMB), H(BA), 0-C1(OCB), m-Cl (MCB), m-NO, (MNB), p-NO₂ (PNB)) have been studied. The racemic structures of the (6plusmn;)-salts were determined on the basis of the comparison of enthalpies of fusion of the (6plusmn;)-salt with those of the corresponding ()-salt, binary phase diagrams of melting point, and free energies of formation of racemate. These results indicated that (+)-MTB, OMB, MMB, PMB, and MCB salts form racemic compounds, that (+)-PN B salt is an ideal solid solution, and that (±)-OCB and MNB salts are conglomerates. The (±)-BA salt was suggested to be a mixture of racemic compound and conglomerate spe cies by the binary phase diagram of melting point, ternary phase diagram of solubility, and infrared spectra of the (±)- and (-)-salts. The optical resolutions by preferential crystallization of (v)-OCB and MNB salts have been carried out at 10°C in ttrahydrofuran, and these (-)-salts can be obtained with optical purity of 86∼400%.

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The reaction of 1-azabicyclo[2.2.2]octane (ABCO) with p-toluenesulfonyl halides [1a-c] and p-toluoyl halides [7a-c] in benzene has been investigated. p-Toluenesulfonyl chloride [1a] and p-toluenesulfonyl bromide [1b] gave 4-(2-haloethyl)-1-(p-tolylsulfonyl)piperidines [2a, b respectivity] in good yields. In the reac tions, [1b] reacted faster than [1a] (Fig.1, Table 2). The reaction of ABCO with p-toluenesulfonyl iodide [1c] resulted only in decomposition of [1c] and no sulfonamide [2c] was detected in the reaction mixture. At the earlier stage of the reaction of [1b] with ABCO, a quaternary ammonium type intermediate deposited in the reaction mixture as a white precipitate [PPT-1] (Table 2), which gave 1-(p-tolylsulfonyl)piperidine or 4-(p-tolylsulfonyl)morpholine by the reaction with the corresponding amines (Scheme 2). The reactions of ABCO with phenyl chloroformate [5] and p-toluoyl halides [7a-c] gave the corresponding carbamate [6] and carboxamides [8a-c], respectively. The reactions showed a similar pattern as those with sulf onyl halides (Table 3, 4).
The react ivity of [7a-c] toward the amine was in the order: iodide [7c] bromide [7b]chloride [7a], and in accordance with the order of the softness of the halides in terms of the HSAB principle.

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Cyanamide was found to promote effectively the condensation reaction of primary amines with carboxylic acids in an appropriate solvent such as diethyl ketone at its refluxing temperature to give the corresponding amides. To investigate the promoting effect of cyanamide, the condensation rates of aniline with benzoic acid under various conditions have been determined by GLC. The facile condensation was promoted by the use of a large excess of both cyanamide and benzoic acid versus aniline and depended on the reaction temperature rather than the nature of the solvent. On the basis of the yields of the substituted benzanilides prepared from substituted anilines and substituted benzoic acids, it was also found that the electron-releasing substituent attached on the amine and the electronwithdrawing one on the carboxylic acid accelerated the condensation. From these results, a reaction mechanism is discussed.

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Electron transfer from cis-dialkylcobalt (III) complexes, cis-[R₂Co(bpy)₂]ClO₄ (R =Me, Et; bpy =2, 2'-bipyridine), to strong organic oxidants (2, 3-dichloro-5, 6-dicyano-pbenzoquinone, 2, 3-dicyano-p-benzoquinone, tetracyanoethylene, and 7, 7, 8, 8-tetracyano-pquinodimethan)in acetonitrile results in the cleavage of a pair of the cobalt-alkyl bonds to yield the coupled products (R-R) exclusively. The cleavage of the cobalt-alkyl bonds of cis-[R₂Co(bpy)₂]⁺ with weaker organic oxidants such as p-benzoquinone was catal yzed significantly by Mg(ClO4)2 and HClO₄. The presence of both Mg(ClO₄)₂ and HClO₄ showed a much larger catalytic effect than that of Mg(ClO₄)₂ or HClO₄ alone. It has been studied a correlation of the logarithm of rate constants with the difference of the redox potentials between cis-[R₂Co(bpy)₂]⁺ and the oxidants in the absence and presence of Mg(ClO₄)₂, and presence of both Mg(ClO₄)₂ and HClO₄. Then, the role of Mg(ClO₄)₂ and HClO₄ in the cleavage of the cobalt-alkyl bonds of cis-[R₂Co(bpy)₂]⁺ with p-benzoquinone derivatives was found to be due to the increased electron-accepting property of the oxidants, resulting in the acceleration of electron transfer from cis-[R₂Co(hnv)₂]⁺ to the oxidants.

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Temperature effect on isomer distributions under kinetic conditions and equilibrium conditions in sulfonation with sulfuric acid and in hydroxysulfonylation with p-hydroxybenzenesulfonic acid of phenol was studied.
It was found that in the sulfonation under both conditions, kinetic control and thermodynamic control, o/p ratio decreased with raising temperature, and that in the hydroxysulfonylation, on the other hand, with raising temperature, the kinetic ratio (2, 4'/4, 4') were decreased, but the thermodynamic ratio (2, 4'/4, 4') increased.
Isokinetic temperatures of these reaction were -24°C and 36°C, respectivily.
It was concluded from thermodynamic parameter obtained that o-hydroxybenzenesulfonic acid was more stable than p-isomer, and in verse, 4, 4'-clihydroxydiphenyl sulfone was more stable than 2, 4'-isomer.

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In order to examine the influence of the conformation of two vicinal hydroxyl groups upon the stabilization of poly(vinyl chloride), bis(2-ethylhexyl) esters of stereoisomeric tartaric acids (DOT) were combined into PVC together with unpoisonous Zn/Ca synergetic soaps. Each tartrate showed better compatibility with the PVC-DOP system than tartaric acid. Specific rotation of meso-DOT did not change during the course of esterification and on heating in the presence of ZnCl₂ which would be produced from the metal soap and hydrogen chloride. meso-DOT and dl-DOT slowed down the appearance of zinc burning and the former exhibited the marked synergetic effect as a second stabilizer more than the latter in combined use with synergetic soaps. This is thought to be based on the ease of masking ZnCl₂ with the vicinal hydroxyl groups and the carboxyl groups near the hydroxyl g roups.

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Poly[oxy-1, 4-phenyleneimino(2, 5-dicarboxyterephthaloyl)imino-1, 4-phenylene] (PA) was prepared by low-temperature solution polymerization using N, N-dimethylacetamide as an organic solvent.
In orde r to achieve enhanced mechanical properties of poly[N-(oxy-1, 4-phenylene)-N'(1, 4-phenylene)pyromellitimide] (PI) films, PA films prepared by casting were drawn in N, N-dimethylformamide/aq. mixture (40: 60, v/v) and heat-treated under various conditions (conversion to polyimide). The mechanical properties were investigated by means of stressstrain curve, birefringence, and x-ray diffraction pattern.
The values of Young's modulus and strength at break of the films drawn and heat-treated under tention were 10.4 x 10¹⁰ dyn/cm² and 51.8 kg/mm², respectively. These are about 4.4 and 6.2 times as large as those of undrawn PI films.

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The elementary reactions and the rate-determining step were proposed on the basis of experimental results of oxidative polymerization of 2, 6-xylenol with the catalyst composed of manganese chloride, 2-aminoethanol, and methanol.
The rate-determining step was speculated to be in the process of formation of quinone acetal intermediate (Eq.10). The oxidation of the manganese complex with oxygen, the coordination of phynoxide ion to manganese, the one-electron oxidation, the redistribution reaction of the quinone acetal, and the re-oxidation of the manganese complex catalyst were all regarded to be sufficiently rapid. Furthermore the redistribution reaction was assumed to proceed under the desirable control within coordination sphere of the manganese complex catalyst.
The eq uations drived on the above-mentioned assumption to account for the relationships such as the extent of reaction (p) vs the reaction time, p vs the residual monomer, p vs the polymer yield, and p vs the molecular-weight distribution were shown to be in good accordance with the experimental results (Figs.1 to 4) enough to support the validity of the proposed kinetics and reaction mechanism.

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In order to explain theoretically the easiness of the polymerization of vinyl monomer, the perturbation energies, ΔE, of the reaction of CH₃CH-R with CH₂=CH-R were calculated by the unrestricted MO method. First, the geometries of the monomers and the radicals were obtained by ab initio unrestricted Hartree-Fock MO method. Then the parameters of MO (eigenvalus, net charges and 'coefficients) were calculated.
Δ was calculated by the unrestricted frontier MO method, according to the following ea uation,
ψ_α and ψ_β indicate the occupied frontier α-MO and the vacant frontier β-MO. R_r8, ε and 4Δ were estimated to be 2.3 Å, 2.3 and -3.9 eV, respectively. The calculated Δ Were coordinated with the activation energies, Ep_??_, of the radical propagation reaction in literature, and a straight line was obtained, as shown in Fig.4 (in Text). Accordingly, the relationship between Ep_??_ and Δ was established as the following equation, Ep_??_ =c-γΔE

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A study on the termination reaction in the radical polymerization of vinyl monomers was carried out by the unrestricted frontier MO method. As the model of the propagating chain, the radicals of the structure of CH₃-CH-R were adopted. Their stru ctures and necessary parameters were written in the preceding paper (Vinyl Polymerization.427). ( 1 ) Recombination termination: pertrubation energies ΔE_C were calculated, accordin g to the Et_??_. ( 2 ) in Text.4Ec were coordinated with the observed “overall” activation energies, ΔE_C. An approximately straight line was obtained. ( 2 ) Disproportionation term ination: the II-abstraction reaction takes place between the MO of ψα and ψβ of the first radical and the σ-HOMO and σ^*-LUMO of the second radical. The perturbation energy, ΔE_D, was calculated, according to Eq. ( 4 ) in Text. However, it is clear that ΔE_D does not give the realzik, value, because at the transition state, the reacting second radical loses the hyperconjugation energy and gains a part of π-bond energy. (3) Hydrogen abstraction reaction from the ester group (COOCH₃) of 1-methyl-1-(methoxycarbonyl)ethyl radical was also discussed.

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New isopropenyl-1, 3, 5-triazines, e. g., 2-amino-4-(methoxy [1] and ethoxy [2])-6isopropeny1-1, 3, 5-triazines and 2-anilino-4-(methoxy [3]and ethoxy [4])-6-isopropenyl1, 3, 5-triazines were prepared by the reaction of the corresponding N-amidino-O-alkylisourea with methacryloyl chrolide.2, 4-Diamino-6-isopropeny1-1, 3, 5-triazine [5] was also prepared by the reaction of biguanide with methacryloyl chloride. The homopolymerization of these monomers and their copolymerizations with styrene, methyl methacrylate and methyl acrylate (M₁) were carried out in dimethyl sulfoxide at 60°C using azobisisobutyronitrile as an initiator. The copolymerization parameters (r₁, r₂, Q₂ and e₂) were determined for these monomers. Monomer reactivity ratios obtained were r₁ < 1 and r₂ < 1. The glass transition temperature (T_g) of the copolymers of [1]∼[5] with methyl methacrylate and methyl ac rylate were determined by differential scanning calorimeter.

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New isopropenyl-1, 3, 5-triazines, e. g., 2-amino-4-(p-methoxy[ 1 ] ethoxy[2], propoxy J, isopropoxy[ 4 ], butoxy[ 5 ] and isobutoxy[ 6 ] carbonylanilino)-6-isopropenyl-1, [3] 3, 5triazines were prepared by the reaction of corresponding 1-(p-alkoxycarbonylphenyl)biguanides with methacryloyl chloride or by the transesterification. The homopolymerization of these monomers and their copolymerization with styrene and methyl methacrylate (M₁) were carried out in dimethyl sulfoxide at 60°C using azobisisobutyronitrile as an initiator. The copolymerization parameters (r₁, r₂, Q₂ and e₂) were determined for these monomers. Thermal polymerization of [2] ∼ [6] was studied by DSC measurement. The ceiling temperature (T_c ; 162∼169°C) and the heat of polymerization (ΔH_p ; -10.5∼-11.2 kcal/mol) were obtained from DSC data.

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Polyelectrolyte complex membranes consisting of [2-(diethylamino)ethyl]dextran hydrochloride, sadium salt of (carboxymethyl)dextran, and sulfated poly(vinyl alcohol) have been prepared. The membranes prepared in high hydrogen ion concentration were stable in alkaline and acidic solutions. Those prepared under low concentration of hydrogen ions were damaged in alkaline solutions. The transport behavior of alkali metal ions through those membranes was much effected by the hydrogen ion concentration which played the role of a driving force. It was suggested that affinity of the carrier and the degree of changes in chemical and physical properties of the polyelectrolyte complex membrane with hydrogen ion concentration controlled the active and selective transports through the membrane.

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The photographic properties of photopolymerizable composition initiated by organic peroxide and sensitizer combination were investigated under ultraviolet, visible light and laser exposure. The photopolymerizable layer consists of four components: binder polymer[poly(N-vinyl-2-pyrrolidone)] (PVP), multifunctional monomer (pentaerythritol triacrylate), organic peroxide and sensitizing dye. Since organic peroxides have sensitivity only in a short wavelength region of ultraviolet light (ca.290 nm), , it is difficult to use them as the photoinitiator of imaging materials. However, by the addition of sensitizing dye such as pyrylium or thiopyrylium salt, the range of spectral sensitivity was extended toward a longer wavelength region (ca.600 nm). The organic peroxide of peroxy ester structure exhibited high sensitivity values. The sensitivity of photopolymer which was initiated by di-t-butyl diperoxyisophthalate sensitized with 4-(4-butoxyphenyl)-2, 6-bis(4-methoxypheyl)thiopyry, lium tetrafluoroborate was 27 μJ/cm² for ultraviolet light and 80 μJ/cm² for 488 nm argon laser light under an inert atmosphere. The photopolymer was found to follow the reciprocity law under a laser scanning exposure with very high intensity. The sensitivity was increased with increasing average molecular weight of binder polymer. The binder polymers can be classified into two groups by their sensitivities. The group including PVP and its copolymers exhibited high sensitivity compared with other polymer groups. In the PVP solid matrix, the rate of polymerization had a large value much higher than that obtained in poly(vinyl butyral) because of the interaction between the binder polymer and the monomer. The main reason for the sensitivity gap observed between the binder polymers used was due to the difference in the rate of polymerization of these polymers. The thermal stability, or the storage stability was much improved by the addition of α-tocopherol without effective lowering of the photosensitivity.

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Bis[1-(4-dimethylaminopheny1)-2-phenylethanedithione]nickel(0), a Q-switch dye for neodium lasers, was unstable and easily bleached by photo-illumination. This bleaching was caused by photochemical reaction with a trace amount of peroxides contained in solvent. In order to stabilize, this dye was included by cyclodextrin and dissolved in water. This complex was not photobleached even in the presence of radicals.

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As polarographic behavior of catalytic wave by controlled current method has been rarely investigated, a current scanning polarograph was constructed and catalytic wave of vanadium (III)-EDTA was measured for comparing it with the result which was already obtained by using conventional polarograph. Although diffusion and catalytic currents (i_d and i_c) were influenced by the reversibility of the supporting electrolyte as shown in theory, the rate constant, k_obs, of the redox reaction between vanadium(II)-EDTA and nitrate ion was in agreement with that obtained by ordinary polarography. So, it may be allowed to use a current scanning polarograph for the measurements of catalytic phenomena in polarography.

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In the reduction of 1, 2-dibenzoylethylene [1a, b] with aluminum isopropoxide, the addition of aluminum chloride increased the yields of furan derivatives [5], [6] or [7].
The cis-isomer was isomerized to trans- under the reduction conditions. Prom cis-a, pdibenzoyistyrene [2], 2, 3, 5-triphenylfuran [8] was obtained without aluminum chloride, and 3-alkoxy-2, 4, 5-triphenylfurans [9] and [10] were readily formed in the pres ence of aluminum chloride.
The structures of products [6], [7], [9] and [10] were established on the basis of spectral data (Table 5).
Probable mechanisms for the formation of the furan ring are shown in Scheme 1.

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It has previously been reported that 7, 7'-dihydroxy-4, 4'-dimethyl-3, 4-dihydro-4, 6'-bicoumarin C 4 J was obtained from the reaction of resorcinol [1] J with methyl acetoacetate [2]. The reaction of [5], diacetate of [4] with aluminum chloride has no w been studied.
The products were found to be 2, 4-diacetylresorcinol [6], 4, 6-diacetylresorcinol [7], 2, 4, 6-triacetylresorcinol [8] and 4, 6-dimethyl-2 H, 8 H-benzo [1, 2-b : 5, 4-b'] dipyran-2, 8-dione mainly on the spectroscopic evidence. Expected Fries reaction products of [5] [9] were not obtained.
The plausible mechanism for the formation of [6]∼[9] is discussed briefly (Scheme 3).

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The direct short time leaching of molybdate(VI) ion from low grade molybdenite ore (MoS₂; 2.1%) was carried out by the use of a microautoclave and the effects of temperature, oxygen over pressure, and NaOH concentration were examined. Both oxygen over pressure and NaOH concentration were found to control the extraction of molybdate(VI) ion. The dissolution of silica, however, was not affected by oxygen over pressure. Laboratory small batch studies have shown that molybdenite can be readily dissolved in dilute NaOH solution (0.2∼0.6 moldm^-3) under 150∼200°C and 5 MPa of oxygen over pressure, leaving Si, Al, Fe, Ca, and Mg in the residue.

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