Asymmetric reactions catalyzed by chiral phosphine-metal complexes have been studied. Optically active ferrocenylphosphines are unique ligands in that structural modification can be readily made by introduction of a desired functional group on the side chain according to the demand of the reaction type, and they have been demonstrated to be effective for the following catalytic asymmetric reactions: 1) Gold-catalyzed asymmetric aldol reaction of isocyanoacetate.2) Rhodium-catalyzed asymmetric hydrogenation of trisubstituted acrylic acids.3) Palladiumcatalyzed asymmetric allylic amination and alkylation.4) Palladium-catalyzed asymmetric hydrosilylation of dienes.5) Nickel-catalyzed asymmetric cross-coupling formin g axially chiral binaphthyls. New catalytic asymmetric reactions have been developed. They are palladium-catalyzed asymmetric disilylation of α, β-unsaturated ketones forming optically active β-hydroxy ketones and rhodium-catalyzed asymmetric hydroboration of styrenes.

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Potential-pH diagrams and anodic oxidation behavior of antimony electrode were studied in buffer solution of various pH.
The antimony electrode was prepared from granular antimony of two kinds purity; one was 99.9% and the other was 99.999%.
Those granular antimony were m elted at 950 K in vacuum and atmosphere. The electrolyte of various buffer solution of pH 2-13 was used.
The results show that potential-pH diagr ams is different by deaerated buffer solution and air saturated buffer solution. The value of the potential of the electrode in deaerated buffer solution for pH range 6-13 is given approximately by the relation
E(scE)0.230-0.0591 pH
which is equilibrium equation of
Sb+ 2 H ₂ 0 = H S bO₂+3 H₊+3 _e
Calvanostatical anodic oxidation resulted in the formatio n of a Sb20, on antimony, and a HSbO2 outer layer produced dissolved antimony ion.
The formation ratio of Sb₂0₃ layer was increas ed with amounts of charge passed.

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Large area (60 mm x 200 mm) and high radioactive β sources of 3H and ¹⁰⁹Cd were prepared by LB method for the experiment of neutrino mass measurement. The sources consist of two-molecular film of cadmium icosanoate; cadmium [³H]icosanoate for ³H source and ¹⁰⁹Cd icosanoate for ¹⁰⁹Cd calibration source. For their preparation, new LB trough equipped with surface pressure generating system by air was developed. The uniformity of the LB film prepared was investigated by autoradiography and photometry. During the course of these experiments, the procedure for the preparation of uniform LB film with good reproducibility was established. The radioactivities of the prepared sources were --40 mCi for 3H and 200μCi for ^i"Cd, and those were used for the measurement of neutrino mass.

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A series of V-P mixed oxide catalysts with P/V atomic ratio of 0.75-4.70 were prepared to investigate the oxidation state and the P/V composition of the catalyst surface by XPS measurements. When the catalyst precursor (VOHPO., 0.5 H20) was calcined at 500°C for 2 h under N₂ flow, the valence of vanadium on the surface were four, while the calcination in air at 500°C for 2 h resulted in the dominance of V5+ on the surface (Fig.1). Under the catalytic reaction condition, a part of the V4+ ion of the catalysts calcined under N₂ flow was oxidized to V⁵⁺ when P/V <1.0 (Fig.2), while the V5+ ions on the surface of the catalysts calcined in air was reduced to V⁴⁺ when P/V>1.0 (Fig.3). This indicates that the phosphorus in excess of P/V=1.0 plays a role to stabilize V⁴⁺ on the surface during the catalytic reaction.
The BE value of P 2p shifted slightly in the region P/V=1.0-4.1 (Figs.2 and 3), indicating a change in the chemical bonding of phosphorus at that region.
The P/V atomic ratios at the surface of the catalysts w ere estimated from the XPS intensities of P 2p and V2P_3/2 as a function of the P/V (atomic) ratio of the catalyst bulk (Fig.4). As a result, it was found that the surface P/V ratios were always higher than the bulk P/V ratios when the bulk P/V exceeded 0.85. Very interestingly, the surface P/V ratios exhibited a plateau with a surface P/V atomic ratio of 1.6-1.9 for both of the catalysts calcined in air and N₂. The importance of the plateau in relation to the selective maleic anhydride (MA)formation was suggested from the correlation between the MA selectivity and the surface P/V ratio (Fig.6), which showed that the MA selectivity increased steeply when the surface P/V ratio exceeded 1.0 and reached a maximum at the P/V ratio corresponding to the plateau. It is suggested that the phosphorus-enriched surface layer with the plateau composition is responsible for the selective MA formation from butane.

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In order to study the effect of pretreatment conditions on the amount of CO-uptake of supported noble metal catalysts, We prepared a series of Cl-free supported a 5 wt% Pt, Pd, Rh, and Ru catalysts. The amount of the CO-uptake was determined by a convention al'pulse-adsorption apparatus at room temperature with He used as the carrier gas under various pretreatment conditions.
The amount of CO-u p take on Pt and Pd catalysts increased with increase in the O₂ concentration of the carrier gas, because CO reacted with adsorbed oxygen on the metal surface, and the produced CO₂ was absorbed on Al₂O₃ support. On the other hand, for Rh and Ru catalysts, the amount of CO-uptake decreased since the adsorbed oxygen on the metal surfa ce suppressed CO chemisorption at room temperature. These phenomena are interprete d in terms of the activities of CO-pulse oxidation. It is recommended to purify the carrier ga s by an oxygen scavenger such as activated copper, manganese oxide or molecular sieve at the liquid nitrogen temperature.
The amount o f CO-uptake was also affected remarkably by the H₂ reduction temperature and the air oxidation temperature. In order to burn off carbonaceous deposits on th e catalysts, the air oxidation above 300°C is desirable. The pretreatment temperatures should be 300-400°C for Pt, 400---450°C for Rh, and 300°C for Pd, since the oxidation over 500°C of Pt and Rh catalysts and the reduction above 300°C of Pd catalyst induce sintering of noble meta l. However, as for Ru catalyst, the amount of CO-uptake increased as the pretreatment temperature was higher.

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Transchlorination of polychlorobenzenes and benzene into chlorobenzene was carried out in the presence of catalyst under various reaction conditions. Activated charcoal seemed to be a suitable carrier, whereas the transchlorination did not proceed smoothly on active alumina. Rare earth metal chlorides enhanced remarkably, as promoter, the catalytic reactivity of palladium(II) chloride supported on activated charcoal. These promoters were found to sho w the similar effectiveness for the transchlorination.
The transchlorination was main ly performed by use of PdCl₂/CeCl₃supported on activated charcoal. The results obtained, for the transchlorination of o-dichlorobenzene (o-DCB) and benzene into chlorobenzene are summarized as follows. ( 1 ) It was considered to be adequate that 1.0 g of palladium chloride was supported on 50 g of activated charcoal. ( 2 ) Ch lorobenzene was obtained in good yield at 35000 f or a long time. ( 3 ) The selectivity of chlorojb enzene increased with increasing the molar ratio of benzene to o-DCB. (4) The transchlorination into chlorobenzene was increased by the increase in the contact time.
Trichlorobenzene, tetrachlorobenzene and hexachlorobenzene were als o transchlorinated with benzene into chlorobenzene in good yield. While the electron-releasing substituents accelerated the transchlorination of o-DCB and mono-substituted benzene, the electron-withdrawing groups diminished it. Therefore, it seemed to be reasonable that the transchlorination of polychlorobenzenes and benzene into chlorobenzene was an electrophilic reaction analogously to the chlorination of benzene with chlorine.

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Chlorobenzenes were disproportionated on activated charcoal supported with PdCl₂/CeCl₂, accompanied by the isomerization, as follows.
_??_
Bromobenzene was also disproportionated into benzene and dibromobenzenes at 350°C. Chlorobenzenes were formed by the displacement of bromine with chlorine generated from palladium(II) chloride at the early period for the disproportionation of bromobenzene. Therefore, palladium(II) trihalides anion (PdX₈θ) seemed to play an important role at the intermediate step of reaction.
It was considere d that the disproportionation of o-dichlorobenzene (o-DCB) into chlorobenzene and trichlorobenzenes proceeded according to the following reaction mechanism.
_??_
The disproportionation of bromobenzene was faster than that of chlorobenzene. The similar product composition was obtained from the transchlorination of chlorobenzene and trichlorobenzene as well as the disproportionation of o-DCB. There is a reversible relation between the transchlorination and disproportionation. That is to say, it could be confirmed that the disproportionation was an equilibrium reaction and proceeded smoothly at the same reaction conditions as that of transchlorination.

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The adsorptive property of indium(III) in the sulfuric acid leaching soln. of zinc slag with chelate resins containing aminomethylphosphonic acid moiety, aminocarboxyl moiety or oxime group, and extractants containing quinolynol moiety or oxime group in the molecule, was examined. Aminomethylphosphonic acid moiety containing chelate resin (MC-95) gave an excelent indium(III) adsorption without effection of protons or sulfate ions in the leaching soln. Indium(III) was adsorbed on MC-95 by Langmuir type reaction. Its saturation adsorption capacity of indium(III) was 0.901 mmol⋅g^-1 and K was 1.55 m³⋅mol^-'.
The sulfuric acid leaching soln. of zinc slag which the component is 98 m g Indm^-3-6.2 0 g Fe⋅dm^-3-123 g Zn⋅dm^-3-8.1 mg Ni⋅drn^-3-pH 0.7, was passed through the resin column, thereafter the 4 mol⋅drn-8 sulfuric acid aq. soln. was passed to elute metal ions exceptindium(III), then lastly a mixed soln. containing 4 mol⋅dm-3 hydrogen chloride and 2.5 moldm^-3 amononium chloride, was passed to elute indium. The quantity ratio of indium vs. total metal in the eluate was 92.8%.

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A hydroxyapatite (HAp) has been synthesized using as a P-sour c e phytin contained in rice bran. Phytin was extracted from the oilless rice bran by HCI solution. The mixtures of CaCO₃, (O.7 g) and Ca(OH)₂ (O.3 g) were added to the extract of 200 ml containing phytin to obtain the precipitate of calcium phytate including CaCO₃. Finally the precipitate fired at 1000°C for 3 h to yield HAp powders.
In this paper, the formation process of calcium phytate were observed with TEM and the composition of the fired HAp powders were examined by using X-ray diffraction, IR measurement etc.
The density of HAp powder obtained was 3.12 g/cm³. While shape of HAp powder was spherical particle of about 0.2 pm in diameter. It was also confirmed that the spherical HAp maintained a stable HAp structure even in the heat treatment at 1300°C, but decomposed into CaO, α-TCP, α-Ca₂P₂O₇, β-Ca₂P₂O₇ at 1400°C. t Synthesis of Hydroxyapatite Powder from Rice Bran as Starting Materials. M.

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The stability constants (log K_CuAL⁽¹⁾ and log K_CuAL⁽²⁾) of the ionic species of [CuAL]⁺ and [CuAL]⁺ produced from the imidazole- and alkylimidazoles-copper(II) acetate complex es, [CuA₂L₂] (A=C14₃C00, L=HIm[1], 1-CH₃⋅Im [2], 2-CH₃HIM[3], 4-CH₃⋅HIm [4 ], 2-C₂H₅.⋅ HIm [5], 2-(CH₃)₂CH⋅HIm [6] ) were determined by a potentiometry in the aque ous solution acidified with acetic acid at 25+0.1°C. The ionic strength of the sample solution was adjusted at 0.1 with potassium nitrate. The stability constants on the substitution site of methyl group decreased in the order of [1 ] (4.61) >[ 2 ] (4.41)> [4 ] (4.34) > [ 3 ] (4.29)for logK⁽¹⁾_CUAL, and [4 ](3.8 5) > [2 ] (3.56) > [ 1] (3.32) > [3 ] (3.14) for logK⁽²⁾_CUAL, respectively. On the other hand, the stability constants on the kinds of alkyl groups bonded at the 2-position decreased in the order of [ 3 ] (4.29)> [5](3.84)> [ 6] (3.55) for logK⁽¹⁾_CUAL, and [ 5 ] (4.0 6) >[ 6 ] (3.9 0) >[3] (3.14) for log K⁽²⁾_CuAL respectively. These orders are main ly explained by the relation of steric hindrance between alkyl groups and acetate ion.

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The calibration of a glass-reference electrode pair with liquid-junction was examined for measurements of the hydrogen ion concentrations (10^-2-10^-7moldm^-3) at high ionic strengths. The relation between pH-values (pH) based on the pH scale standardized with pHstandards and hydrogen ion concentrations (h) is expressed by the relationship pHm=M⋅ph+C where ph= log h. The M-value is related to liquid-junction potentials between the salt bridge and two pH-standards. The M-value of 1.008+0.002 was obtained for the three buffer systems (strong acid, acetic acid, and dihydrogenphosphate) at ionic strengths 0. moldm^-3 (KCI, NaC1, and KNO₃). The C-value, which is dependent on the ionic st rength and on the kind of the supporting electrolyte, is a function of the activity coefficient rpf, the hydrogen ion (yH) and of the liquid-junction potential between the salt bridge and the sample (Es). The values of log yH4-(δE/S), where S is the response slope of the glass electrode, calculated from the values of M. and C for hydrochloric acid, were consistent with those of our previous impel-0 regarding the liquid-junction potentials within ±0.01 pH unit. The C-value of weak acids is directly influenced by an uncertainty in the dissociation constant used. The calibration line proposed previously, pHm=ph + A, is an approximate relationship which can be derived from IiHm=-M. ph+C. A decrease in the pH-value of a strong acid accompanied by addition of a neutral salt can be explained by a decrease in the C-value with increasing ionic strength.

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A differential pulse polarographic method has been studied for the determination of uranium(VI) by using the catalytic current. The peak currents at 1.20 V vs. SCE were proportional to the concentration of uranium(VI) in the range of (4 x 10^-7-4 x 10^-6)mol⋅dm^-3under the optimum conditions as follows nitric acid concentration 5.0 x 10^-2 mol⋅dm^-3, hydroquinone concentration 2.0 x 10-2 mol⋅dm^-3, pH 2.0. The relative standard deviation was 2.6% (n=5) for 1.0x106 mol⋅dm^-3 level of uranium(VI) determination. The determinatio n was interfered by the coexistence of iron(III) and manganese(II) more than 14 and 50 times amounts of uranium, respectively. This method was successfully applied to the determination of uranium(V) in manganese nodules after removing the interfering ions (Fe(III), Mn(II)) by using 0.2 mol-dm^-3sulfuric acid as eluent with an anion-exchange resin (Amberlite IRA-410) column (24 cm x 0.6 cm I. D. ), followed by uranium(VI) elution by 1 moldm^-3hydrochloric acid.

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A simple and rapid preconcentration method for the determination of cobalt in natural waters is described. The proposed method is based on the extraction with 0.1 m/ of solvent in a centrifuge tube, and a preconcentration factor of 200 times is obtainable using 20 m/ of sample. The optimum preconcentration conditions were examined. The surface water sam ples, seawater, river water and lake water, were pretreated by filtering or heating under the acidity of 0.1 mol/l hydrochloric acid. The trace amount of cobalt in sample solution was extracted as thiocyanato complex with trioctylmethylammonium chloride in 1, 2-dichlorobenzene, and determined by graphite furnace atomic absorption spectrometry using a pyrolytic graphite coated tube. At the sampling points, three methods of pretreatment and the micro solvent extractionwere performed. The organic phases separated were stored in a refrigerator, and determined in the laboratory within a day (Methods A to C). And furthe r, the stored samples, filtered/acidified and unifiltered/acidified, were supplied to the proposed method in the laboratory (Methods D and E). The untreated samples were also stored, and determined. The results show that the contents of labile or extractable species in the filtered sample do not vary so much by acidification and during the storage in a refrigerator. In the case of seashore waters, the dissolved or filterable cobalt is seemed to be almost labile or extractable. In the case of land, waters, the cobalt contents in lake water are seemed to be lower than those in river water. The lower limit of determination (10σ) was found to be 0.011 n g/m/ of cobalt in the initial solution. The relative standard deviation was 1.1% fo r O.1 n g/ml of cobalt in artificial sea water (n=10). Interferences of many metal ions can be effectively reduced by masking with diammonium hydrogencitrate.

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4-Fluoreneacetic acid [6]was prepared from fluorene [1] via 5 steps. Acid schloride [7]was cyclized with AlC13 to give 4 H-cyclopenta[def]phenanthren-8-ol [8 ] accompanied by the 8, 9-dione [9]. Oxidation of the mixture of [8] and [9] with H₂O₂ in acetic acid gave 4, 5-fluorenedicarboxylic acid [10]. Dichloride [11] was converted into 5-alkoxycarbony1-4fluorenecarboxylic acids [12] with alcohols. Reaction of [11] with alkylamines gave 5-(Nalkylcarbamoy1)4-fluorenecarboxylic acids [13], which were easily cyclized with H₂SO₄ in acetic anhydride to give N-substituted 4, 5 -fluorenedicarboximides [14]. Reactions of [l0]. with urea gave 4, 5-fluorenedicarboximide [14a] and with NH₂OH. HC1 gave a condensed cyclic compound [16]containing -CONHOCO- moiety, respectively. Reduction of 5-methoxycarbonyl4-fluorenecarboxylic acid [12 a] with LiAlH₄ gave a lactone [15].

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1, 8-Fluorenonedicarboxylic acid [5] was synthesized via four steps from fluorene and many new 1, 8-disubstituted fluorene derivatives were derived therefrom by the conversion of two carboxyl groups. Thus, 1, 8-bis(methoxycarbonyl)- [10], 1, 8-bis(ethoxycarbonyl)- [10], 1, 8-bis(hydroxymethyl)- [13], 1, 8-bis(bromomethyl)- [14], 1, 8-dicarbamoyl- [20] and 1, 8diaminofluorenone [21] were synthesized. Diazo reactions of [21] led to 1, 8-dihyroxy- [23], 1, 8-dimethoxy- [24], 1, 8-difluoro-[25], 1, 8-dichloro- [26], 1, 8-dibromo- [27] and 1, 8 diiodofluorenone [28]1, 8-Dicarboxyl- [6] and 1, 8-bis(hydroxymethyl)-9-fluorenol [12], together with some fluorene derivatives such as 1, 8-dicarboxy- [7], 1, 8-bis(methoxycarbonyl)[8], 1, 8-bis(hydroxymethyl)-[9], 1, 8-bis(iodomethyl)- [15], 1, 8-dimethyl- [16], 1, 8-bis(bromomethyl)- [17]and 1, 8-bis(mercaptom. ethyl)fluorene [18] were also obtain ed. Furthermore, several attempts to prepare fluorenophanes with a bridge between 1, 8-positions were made.

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2-Amino-3-chloroquinoxaline was formed by bubbling NH₃ gas into a formamide solution of 2, 3-dichloroquinoxaline, and the addition of NH₄C1 into the reaction mixture caused the formation of 2, 3-diaminoquinoxaline. Bis(3-amino-2-quinoxalinyl)amine was obtained by bubbling NH₃ gas at a higher temperature into formamide solution of 2, 3-dichloroquinoxaline. The oxidation of 5, 11-dihydro-5, 6, 11, 12-tetraazanaphthacene with potassium permanganate gave 1, 4-dihydro-1, 4, 9, 10-tetraazaanthracene-2, 3-dione. Some discrepancies in the melting point data for the known compounds were ascribed to chemical transformation to intra- or intermolecular condensation products.

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This study was undertaken to elucidate the nature of initiator for the plasma-initiated polymerization of styrene. By rapid passage of styrene vapor through the plasma zone generated by radio-frequency discharges, oily product could be collected. The oligomer with molecular weight of 1300 was isolated from the oil. The oligomer was found to initiate the radical polymerization of styrene and methyl methacrylate, where the polymer conversion and molecular weight increased with reaction time. The polymerization rate was O.3 power with regard to oligomer concentration and 1.5 power with regard to monomer concentration. From the pyrolysis gas chromatographic analysis of the resulting polymer and the ESR spectral measurements of the spin adducts obtained from the reaction of the oligomer with 2, 4, 6-tri-t-butylnitrosobenzene, the oligomer was found to serve as thermal iniferter to induce the radical polymerization. On the other hand, it was observed that a low-pressure plasma for a short period in a vapor of styrene in sealed ampule produced an oligomer similar to the described above. Thus, it has been suggested that the plasma-produced oligomer can act as thermal iniferter for the plasma-initiated polymerization of styrene. t Study on Synthesis of Macromolecule by Use of Plasma Technique. I II.

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The polymerization of acrylamide was carried out at 40°C using (2, 2'-bipylidine)cobalt(II)complex as an initiator. Although the polymerization proceeded constantly by reacting the aqueous solution of cobalt(II) complex with acrylamide in the atmosphere of hydrogen, the polymerization was accelerated at the conversion of approximately 40% and then completed at that of 70%. The average molecular weight of the polymer was 1 to 7 x10⁴. The polymerization did not occur in the atmosphere of nitrogen. The polymerization smoothly proceeds, however, under the atmosphere of nitrogen by reacting acrylamide with the CoOD complex, which absorbed hydrogen. The reaction is prevented in the presence of air. It was confirmed that p-benzoquinone inhibits the polymerization. The copolymer composition curve for the copolymerization of acrylamide with potassium acrylate agreed with that of ordinary radical initiator. The rate of polymerization of acrylamide in the presence of Co(II)complex was expressed by the following equation.
Rp = k [Co(II) complex]^0.5[Acrylamide]^1.4
The apparent activation energy of the polymerization was estimated to be 61.1 k J/mol. The above information and the result obtained from the behaviour of Co(II) complex at the initial stage of polymerization indicate that the active species of polymerization is the Co(II)complex, which absorbed hydrogen, and the polymerization reaction is initiated following the complex formation of hydridocobalt complex and acrylamide.

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The thermally processed silver (TPS) film used in this study is a special type, which _remains photoinsensitive until subjected to preliminary heat treatment. Emulsion composition containing iodine molecules or triphenyl phosphite enneaiodide (PI 9) was investigated to clarify two kind of roles of the iodine molecules, which have in different ways, as silver iodide (AgI) sources and oxidizing agents for latent image (Ag°). In the case of the emulsion excluded sensitizing agents such as N-methylpyrrolidone (NMP), the TPS film is observed increasing in count of X-ray diffraction peak of AgI grains (2 θ=23.8°) by the preliminary heat treatment at 100°C. The half-value breadth of X-ray diffraction peak of AgI remains unchanged by heat treatment. This result do not shows the growth of the AgI grains, b ut the increase of the fine AgI grains. In the TPS films containing NMP, on the other h and, the narrow AgI peaks of X-ray diffraction show that PI 9 is allowed to react in situ completely with silver behenate at room temperature to give the large grains of AgI. Because the preliminary heat treatment for the TPS films containing NMP does not affect the X-ray diffraction patterns around 2θ=23.8°, it would be surmised that another reaction than the extinction of iodine molecules gives photosensitivity to the TPS films.
In order to interpret inclusively all results of the experiment of the sensitivity, the fading of the latent image and the X-ray diffraction, it is proposed that oxidizing agents produced from iodine molecules and oxidizing catalysts such as mercury (J1) ion synergistically work on photoinsensitivity.

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Three kinds of titanyl(IV)-oxalato compounds were obtained as powders by mixing an aqueous solution of TiOSO₄⋅_nH₂O with an aqueous solution of K₃[Cr(OX)₃]⋅3H₂O, K₃[Fe(0X)₃]⋅3H₂O or K₃[Co(OX)₅]⋅3 H₂O0. The compositions of these compounds were foun d to be (TiO)₂(OX)(OH)₂(H₂)₄ (Fri-Cr1), (TiO)_g(OX)(OH)₂(H₂O)₂ ([Ti-Fe]) and (TiO)₁₉Co(OX)₆(SO₄)8(OH)₁₂(H₂O)₁₃ ([Ti-Co]), respectively. Traces of chromium or iron w ere contained in the corresponding compounds. The Ti/M atomic ratios (M=Cr, Fe or Co) were about 45, 120 or 19, respectively. All of these compounds released almost all water molecules at about 200°C and gave their oxides above 500°C. The powder X-ray diffraction spectra suggested that titanium(IV) oxides formed by igniting at about 850°C in air were anatase-, rutiie-type and the mixture of both types for [Ti-Cr], [Ti-Co] and [Ti-Fe], respectively.

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A local structure around the Cu atom in the complete amorphous film with the composition of Bi₂Sr₂CaCu₂O_xglass was investigated by the Cu EXAFS (extended X-ray absorption fine structure) analysis. Using Bi₂Sr₂CaCu₂Ox crystals (Cu-O=1.91Å) as a reference sample, the average Cu-O distance of the glass was estimated to be 1.89Å. The glass-forming ability of the glass was discussed on the basis of coordination of the Cu atom.

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Chlorination of a mixture of amorphous silica and active carbon was investigated at 700-900 °C. The initial reaction rate increased linearly with the molar ratio of C/SiO₂ of 1-3. The reaction took place by the simultaneous contact of SiO₂, C and CI, . The rate-determining step was the chemical reaction at 700-800 °C, but changed gradually into gas diffusion with increase in the reaction temperatures above 850 °C. The apparent activation energy below 800 °C was about 2 x 10² kJ/mot.

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