Thermal decomposition of sulfur hexafluoride SF₆(gas), which is important for the preparation of electrical equipments, has been investigated. SF₆ was heated with various metal pieces in a stainless steel vessel at 250°C to confirm that the thermal decomposition product was SO₂ (Table 1). The amount of SO₂ depended on the kind of metal (Table 2). When SF₆ and silicon steel plate were heated at 150, 200, and 250°C, the amount of SO₂varied with temperature and moisture in a vessel (Fig.1). X-Ray microanalyzer showed the formation of fluoride and sulfide on a surface of steel heated in SF₆, whereas that of sulfide only on a surface of copper (Figs.2, 3). The amounts of fluoride ion on a surface of silicon steel and on an inner surface of a test vessel, heated with.SF₆ at 150, 200, and 250°C, increased with increasing temperature (Table 3). Silicone resin laminates, heated in SF₆ at 250°C, changed mechanical and electrical characteristics (Table 4). Benzene was detected in SF₆ which was heated with silicone resin laminates (Fig.4) and infrared spectra of acetone, extracts from these laminates, indicated that phenyl group was removed from polymethylphenylsiloxane (Fig.5). HF, produced by the thermal decomposition of SF₆, would take part in this reaction.

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The deacylations of p-nitrophenyl carboxylates possessing acyl chain length, n, from n=2 to n=16 by hydroxamic acids (benzohydroxamic acid, r-phenylbutyrohydioxamic acid, decanehydoxamic acid, sebacohydroxamic acid, and 2-hexyldecanehydroxamic acid) with or without hexadecyltrimethylammonium bromide (CTAB) were performed to investigate the catalytic activities and substrate-selectivity of the acids.Among the nucleophiles employed, 2-hexyldecanehydroxamic acid, which has the hydrophilic moiety (hydroxamic acid) bound to the branching hydrophobic portion, enhanced markedly the deacylation-rate of the esters in the presence of CTAB. Furthermore, in the presence of CTAB, a characteristic micellar catalysis was observed in the deacylation of p-nitrophenyl decanoate having an appropriate acyl chain length (n=10) selectively enhanced by each of hydroxamic acids employed.

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The preparation of iron phosphates by the reaction of Fe₂O₃ with H₃PO₄ was investigated under varyingreaction conditions, such as a mixing ratio P₂O₅/Fe₂O₃ (R) of phosphoric acid to iron oxide, heating temperature, heatingtime, heatingrate and water vapor pressure in the heatingatmosphere.Crystalline iron phosphates formed in the reaction of Fe₂O₃ with H₃PO₄ at a temperature range of 100-700°C consisted of 8 kinds of compounds : A and B types of iron(III) dihydrogen orthophosphate Fe(H₂PO₄)₃, iron (III) hydrogen pyrophosphate FeHP₂O₇ neutral iron (III) pyrophosphate Fe₄(P₂O₇)₃, II type of iron(III) dihyrogen triphosphate FeH₂P₃O₁₀ A and C types of iron (III) polyphosphate Fe(PO₃)₃ and an unknown compound. 1) The A and B types of Fe(H₂PO₄)₃ were formed at R=3-4 at a low temperature below 200°C. The A type was especially formed at R=4 at 125°C, while the B type at R=3 at 125°C. 2)Pyrophosphate FeHP₂O₇ was easily formed at R=3 by heating for 5h in an electric furnace, in a sealed tube, in a water vapor, and in dry air. Further, Fe₄(P₂O₇)₃ was easily formed at about R.1.5 at 250-300°C. 3) The II type of FeH₂P₃O₁₀ was formed at R=3-4 in a temperature range 275-400°C, but only as a mixture with iron (III) pyrophosphate or iron (III) polyphosphate, not in a pure form. 4) The temperature at which Fe(PO₃)₃ formed was dependent on the mixing ratio R; with increasing mixing ratio, the temperature of its formation shifted to a lower temperature. At R=4, Fe(PO₃)₃ began to form at about 275°C. At 500°C, the C type of Fe(PO₃)₃ waseasily obtained ateither in an electric furnace/or a sealed tube or in a water vapor. On the other hand, the A type of Fe(PO₃)₃ was obtained atR=3 byheating in a vacuum, and its yield closely related with heating rate in the primary heat treatment. 5)At R.1-2 in a temperature range 150-250°C, an unknown compound was formed, and it was always obtained as a mixture with Fe₂O₃.

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The oxidation of sodium sulfite with nitrogen monoxide was proceeded by bubbling 780 ppm of nitrogen monoxide gas at a flow rate of 2. 8 l/min through the aqueous sulfite solutions (0.250-0.400mol/l) in the range of temperature 25-70°C and of pH 5.78-7.90. NO slowly reacted with HSO₃^- to produce N₂O and SO₄^2-at pH above 8 in the absence of Fe (II)-edta. However, it rapidly reacted in the presence of Fe(II)-edta, producing various nitrogen-sulfurcompounds such as HON(SO₃)₂^2-, N(SO₃)₃^3-, HN(SO₃)₂^2-, etc. The reaction products differed remarkably according to the reaction conditions applied. Thus, HON(SO₃)₂^2- was quantitatively produced at 25°C, and N(SO₃)₃^3-, HN(SO₃)₂^2- and SO₄^2- 70°C. S₂O₆^2-was produced to a significant extent when oxygen was contained in the reaction gas. N₂O was slightly produced at pH above 8. A possible oxidation pathway of sulfite in solution with NO was suggested based on these observations.

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The formation of silicon carbide powders by the vapor phase reaction of the SiH₄-CH₄-H₂ system was studied at the temperature of 1000-1400°C. The powder products consisted of β-SiC and silicon at low reaction temperatures, but they became pure SiC at 1400°C. The SiC particles were spherical and hollow. The particle sizes were 0.01μm to 0.15μm, and they decreased when the reactants were heated sharply. On the other hand, solid SiC particles, were produced under the conditions that the reactants were heated very sharply and the effective reaction temperature was increased.
It is concluded that the formation of hollow SiC particles from the SiH₄-CH₄-H₂ system occurs by a two-step process: the formation of silicon particles, by the pyrolysis of SiH₄ and their carburization with methane. The solid SiC particles obtained when the effective reaction temperature was increased, were considered to be formed by the nucleation ofSiC and its growth.

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The coercivity of an acicular chromium dioxide powder remarkably increased when electroless cobalt plating was applied to it by using cobalt sulfate. A particlesize of the chromium dioxide powder, starting material, was 0.8μ in length, 1:15 in shape ratio, and the magnetic properties of the powder were 92emu/g in saturation magnetization (σ_a) and 500Oe in coercive force at 10 kOe of applied field. Plating solution was a cobalt(II) sulfate solution containing sodium phosphinite as a reducing agent. During an experiment, the bath was stirred sufficiently to bring about high dispersion of a particle. The bath temperature was kept at 80°C. The plating time varied from 0.5 to 10 minutes.The coercive force of particles remarkably increased to maximum, 970Oe, at the beginning of aplatingas shown in Fig. 2. It might be possible that an increase in coercivity of particles is caused by bonding of chromium with cobalt via oxygen ion, for instance, Co-O-Cr, Co-O-Co etc. and notpossible that an increase in coercivity neither depends on a decrease in a particle interaction nor on an increase in a magnetostriction of a particle.The temperature dependence of the coercivity and the magnetization of cobalt plated particles has been more improved than that of, original chromium dioxide particles.

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The author has developed an improved method for the separation of red mud from an alkaline solution of bauxite (South Eastern Asia). The experimental results are summerized as follows. (1) The reduction of iron (III) oxide in bauxite by hydrogen with the aid of nickel catalyst was achieved in alkaline solution to produce magnetic iron (II) diiron (III) oxide. (2) The sedimentation rate of the magnetized mud was greater than that of non-magnetized one, except in the liquid medium of low density. However, when the liquid density was too low, the sedimentation rate decreased, and when the density became ca. 1.004, the mud almost stopped in falling. The reason of this decrease may be explained in terms of the peptization of the mud particles. The role of sodium ion was discussed in this regard. (3)A filtration apparatus of magnetized mud was devised. This was a filtration layer consisting'of iron powder placed in magnetic field. By this apparatus the separation of aluminate solution from the mud could be made completelyand rapidly.

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Sensitivity in spectrophotometry can be extremely enhanced by measuring the higher-order derivative value, instead of the absorbance, by using an automatic recording spectrophotometer and analogue differentiation amplifiers. Sensitivities obtained for α, β, γ, δ, -tetrakis (1-methylpyri-dinium-3-yl)porphine [T(3-MPy)P] and its copper(II) complex in n'th-order derivative spectrophotometry (n=1-4) are about 4.5ⁿ times that in the ordinary spectrophotometry. Fundamental studies for the determination of copper at ppb level or lower have been carried out from the viewpoint of application of the derivative spectrophotometry to ultramicro analysis. As a result, a sensitive, simple and practical determination method based on measurement of the 2nd-order derivative value of the Soret band of the copper (II)-T(3-MPy)P complex is developed. According to the proposed method, as low as 1 ppb of copper in drinking water can be determined with satisfactory accuracy and precision without any preconcentration treatment.

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Phenylfluorone reacted with copper (II) to form various water-soluble chelates in the presence of hexadecylpyridinium bromide and some monodentate ligand such as nitrite or pyridine. A red chelate of copper was formed in the presence of hexadecylpyridinium bromide and nitrite and its absorption maximum was found at 570nm. The absorbance was constant in the range of pH 4.5 to 5.0. The molar absorptivity was 4.54 × 10⁴lmol^-1cm^-1 at 570nm and the Sandell sensitivity was 0.0014μg Cu/cm² for log(I₀/I).0.001. The calibration curve prepard at 570nm was linear for the copper concentration up to 1.88 × 10^-5mol/l. The molar ratio of copper to phenylfluorone in the complei was estimated to be 1 : 2 in the presence of both hexadecylpyridinium bromide and nitrite. On the other hand a reddish violet chelate of copper was formed in the presence of hexadecylpyridinium bromide and pyridine and its absorption maximum was found at 595nm. The absorbance was constant in the range of pH 9.0 to 10.0. The molar absorptivity was 8.84 × 10⁴lmol^-1cm^-1 at 595nm and the Sandell sensitivity was 0.00072μμg Cu/cm² for log(I₀/I)=0.001. The calibration curve prepared at 595 nm was linear for the copper concentration up to 1.26 × 10^-5 mol/l. The molar ratio of copper to phenylfluorone in the complex was estimated to be 1 : 1in the presence of both hexadecylpyridinium bromide and pyridine.

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Solvent extraction of lithium with thenoyltrifluoroacetone (TTA) was carried out by using 23 organic solvents. The organic solvents having electron donor oxygen(alcohols, esters, ketones, and ethers) were used. The mechanism of this extraction was the formation of an adduct between an oxygen containing organic solvent and a lithium chelate of TTA. This adduct is readily soluble. Adducts Li(TTA)₂.2S (S : solvent) were extracted with organic solvents other than alcohols. This extraction was explained in terms of a dispersion force between solvent and solute and a coodrinating effect of oxygen containing solvents.

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The adsorption behaviors of phosphate ion in water and of phtsporus in the effluent from a sewage treatment plant by thirteen ion exchange resins which were loaded with iron (III) ion were investigated. The ion exchange regins inveitigated in This study were Amberlite IR 120 B, 200 C, Diaion WK 10, WK 11, WK 20, Amberlite IRC 50, Fumiace, Dowex A 1, Diaion CR 10, CR 11, CR 12, Uniselec UR 10 and UR 40, as shown in Table 1. The concentration of phosphate ion in the resion, Q, and in the aqueous phase, C, after equilibration of acetate buffered solution, followed the Freundlich's law of Q=KC^1/n. Similar results were observed on the effluent from a sewage treatment plant. The constant K and 1/n were found to be useful parameters for evaluating the iron(III)-loacted cation exchange resins as the adsorbent for phosphate ion. The most prospective one was Dowex Al-Fe(III) (1/n=0.46, log K=0.60). The adsorbed phosphate ion was able to be eluted- by the treatment with 2 mol/l sodium hydroxide, and the resin was eventuallytreated with 0.1 mol/l hydrochloric acid for the next adsorption cycle.

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Dehydration reaction of 2-methyl-3-(substituted phenyl)-2-propanols (MPP) with aluminum bromide (AlBr₃) was carried out in a mixed solvent of decaline and 1-hexanol. A marked induction period was observed in the first stage of a dehydration. The lapse of induction time decreased with increasing electron releasing ability of the substituent. The dehydration rate was of the first-order with respect to MPP and of the second-order with respect to AlBr₃. The same was true the dehydration reaction of the compounds described below, regardless of the kinds of tertiary alcohols and Lewis acids used. The dehydration rate increased with increasing electron-releasing ability of substituent (ρ=-0.8). The negative value of the reaction constant suggests that the reaction preceeds under an E₁elimination mechanism. The activation energies of the dehydration reactions of these substituted tertiary alcohols with AlBr₃ were estimated to be 10-14 kcal/mol.In this dehydration reaction a good linear relation exists between activation energies and activation entropies ; a sign of each slope is positive. The mechanism of this dehydration reaction was considered to be two reaction stages : first, initial formation of alkoxyaluminum dibromide by the dehydrobrornination reaction of a 1 : 1 addition complex produced from alcohol and catalyst, and second, subsequent dehydration of alkoxyaluminum dibromide upon further addition of hydrogen bromide-catalyst complex.

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When POCI₃-NH₂CHO adduct was allowed to react with p-cresol and its derivatives (o-methyl-, o-t-butyl-, o-bromo-) in formamide at 100-120°C, N-f ormy1-6, 12-epimino-2, 10-dimethy1-6 H, 12 H-dibenzo [d, g][1, 3]dioxocins [1a-d] were formed. Acid treatment of [1a] at a room temperature gave N-formyl-1, 1-bis (2-hydroxy-5-methylphenyl) methylamine [2a], and hydrolyiis of [1a] at 50-60°C for 8 hr afforded 1, 1Lbis (2-hydroxyL5Lmethylphenyl) methylamine [3a] which was identical with the product obtained by the reduction of 2, 2′-dihydroxy-5, 5′-dimethylbenzophenone oxime, When [2a] or [3a] was allowed. kto react with POCI₃-NH₂CHO adduct in formamide, [1a] was formed. Structure of dibromo compound [1d] was Confirmed by X-ray crystal refraction.

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The selective hydrogenation of 2, 3-dimethyl-1, 3-butadiene(DMBD) to monoenes with Ni(acac)₂-Al₂(C₂H₅)₃Cl₃-P(C₆H₅)₃(Ni:Al₂:P=1:10:5) catalyst was investigated. DMBD was hydrogenated in toluene at 40°C under 1 atm of H₂ to give 2, 3-dimethy1-1-butene and 2, 3-dimethy1-2-butene selectively, the ratio being about 2 : 1 in the initial stage (Fig.1). The monoenes formed were isomerized rapidly just before the completion of selective hydrogenation, while, even after its completion they were not practically hydrogenated to 2, 3-dimethylbutane. These results suggest that a π-allylic nickel complex is a reactive intermediate for the selective hydrogenation. The overall rate of hydrogenation, measured by 112 absorption, can be represented by the form : R=k[H₂][Ni], k=10^9.1 exp (-13200/R T) lmol^-1sec^-1, where [H₂] and [Ni] are the concentrations of H₂ and Ni(acac)₂, respectively. The activation parameters are ΔH^≠=12.6 kcal mol^-1 and ΔS^≠=-19 cal deg^-1mol^-1. The kinetic resulsts can be interpreted in terms of the following mechanism and suggest that the latter step is the rate-determining step and the C₆H₁₀ + Ni-H ⇔ Ni(π-C₆H₁₁) Ni(π-C₆H₁₁) + H₂ ⇒ C₆H₁₂ + Ni-H equilibrium prior to the step lies almost entirely in the right under the conditions investigated.

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The catalytic reduction (5% platinum on carbon carrier and under 1 atm of H₂) of nitrobenzene [1a] and o-nitrotoluene [1b] with hydrogen was carried out in sulfuric acid-methanol solution at a room temperature. The products were aniline [2a], o-toluidine [2b], and o-as well as p-methoxyanilines. o- and p-Methoxyanilines were considered to form in terms of the Bamberger-typeirearrangement of phenylhydroxylamines [9]which are the intermediates formed in the catalytic reduction of nitrobenzenes to anilines. In the reduction of [lb] more 4-methoxy-2-methylaniline [4b] was obtained than 6-methoxy-2-methylaniline [3b] as s rearrangement product. The maximum yield of [4b] was 56% under the typical reaction conditions, while that of [3b] was in every case lower than 1%. The yield of [4b] increased to 70% by the addition of a small amount of dimethyl self oxide to a reaction medium. In the reduction of [la], the total yield of rearrangement products (o- and p-anisidine ([3a], [4a])) was 13% or below, and olp ratiovaried significantly from 0.2 to 12 with an amount of sulfuric acid. Although in the rearrangement of phenylhydroxylamine [9a] in sulfuric acid-methanol solution, almost constant o/p ratio ([3a]/[4a] ratio, O.20-0.22) was observed, this ratio increased to 0.31-0.48 in the presence of Pt-C catalyst. The result indicates that when [9] are adsorbed onto a catalyst surface, the rearrangement to o-position becomes energetically more favorable than that to p-position.

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2, 7-Dialkoxyphenanthrenes with long alkyl chains have been synthesized by the alkylation of the corresponding hydroquinone. The products show liquid crystallinebehavior when the carbon number of the alkyl groups is 6-14. They are all smectic as judged by DTA and the microscopic observations. The results are shown in Fig. 2 and Table2.

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The effects of alkali metal (Li, Na, Rb and Cs) and tetraalkylammonium (n-Bu₄N and Me₄N (TBA and TMA, respectively)) chlorides on the conformational transition of poly(α-L-gluta-mic acid) in aqueous solution were studied by means of potentiometric titration, viscosity and optical rotation measurements. Poly(α-DL-glutamic acid) was used to obtain pK₀ value with a reasonable accuracy. The midpoint of pH of the helix-coil transition shifts toward a low value with decreasing crystallographic radius of the cation, viz., Li>Na>Rb>Cs≈MA>TBA. However, the plots of the helix content, θ, against the degree of neutralization, α, conform to 'a single transition curve for the alkali metal salts, indicating that the apparent pH dependence of the transition is the results of the influences of the salts on the dissociation of PLGA. The dependence of θ on the salt concentration shows antagonistic effects of TBAC1 and NaCI ; the former enhances the helix content with concentration, while the latter acts reversely. The free energy of coil to helix transition of uncharged PLGA molecules, ΔF°, is -245±5 cal/residue mol at 25°C, irrespective of the alkali metal species, while they are -200 and -270 cal for TMA and TBA salts, respectively. In the presence of 0.1 mol/l of these salts, the helix initiation parameter, σ, of . PLGA is evaluated from the θ-pH curves for 15-50°C. The temperature dependence of σ is discussed in terms of various interactions that possibly participate in the helix initiation.

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Binding of 4-aminoazobenzene (D-I) or 4-[bis(2-hydroxyethyl)amino]azobenzene (D-II) to poly (N-butyl-2- or -4-vinylpyridinium bromide) (C₄P2VP or C₄P4VP) or poly (N-octyl-2-vinyl-pyridinum bromide) (C₈P2VP-I[Degree of Quaternization, DQ=32.2%] and C₈P2VP-II [DQ=42.6%]) was determined by means of solubility measurements, spectrophotometry and dynamic dialysis technique.
While the solubility of the dyes was proportional to C₈P2VP-II concentration up to 7 g/l C₄P2VP didn't show any solubilizing effect on these dyes (Fig. 1). Spectral shift of absorption maximum, caused by the addition of C₈P2VP-II into an aqueous Sφresen buffer solution of these dyes, corresponded to the absorption spectra of these dyes in nonpolar solvent (Figs. 3 and 4). The results revealed that apparent binding constant, K_app, obtained by solubility, spectrophotometry, and dynamic dialysis measurements, depended on the concentration of the dye (Table 2). The binding of the dyes to C₈P2 VP-I in an aqueous acetate buffer solution at 25°C, observed by dynamic dialysis measurement, showed sigmoidal increase with increasing concentration of the free dye (Fig. 6). By applying McGhee and von Hippel's theory to Klotz and Scatchard plots (Figs. 7 and 8), positive cooperativity in the dye binding was confirmed. The number of consecutive residues covered by a bound dye, n, the intrinsic binding constant, K, and the cooperativity parameter, ω were as follows : 7.5, 17.5, and 350 for D-I and 16, 40, and 180 for D-II, respectively. An enhanced solubility caused by the addition of C₈P2VP can be attributed to the cooperative binding of the dye on the three types of "isolated", "singly contiguous", and "doubly contiguous" sites (Fig. 9).

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Wet-oxidation of various amides was investigated. It was found that amides were decomposed by two competitive mechanisms : thermal cleavage of their C-N bond followed by the oxidation of the resultant acids and amine-fragments and direct reaction of oxygen with amides. Their reactivity was correlated with the carbon content in the molecule, and this relationship between the carbon content and the reactivity is useful for the evaluation of the effectiveness of wet-oxidation in the treatment of amides. Although amides were considerably refractory to wet-oxidation, the degree of their biodegradation was improved after the oxidation. Therefore, it was indicated that a combined use of wet-oxidation and biodegradation should be effective for the treatment of amides.

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Oxidative dehydrogenation of 1-butene was examined over Bi-Ti oxide catalysts (Bi/Ti=4/3) prepared with various methods (Table 1). The method of preparation affected the selectivity. to butadiene significantly. A catalyst of Bi-Ti(III), obtained from bismuth nitrate and titanium sulfate, was most effective. Noncrystalline Bi₄Ti₃O₁₂ seems to be effective for this dehydrogenaton reaction. Formation of butadiene was also observed even in the absence of gaseous oxygen(Fig. 1). This formation was probably accompanied by subtraction of lattice oxygen in Bi₄Ti₃O₁₂. A redox mechanism similar to the one proposed for the case of Bi-Mo oxidewas suggested for the oxidative dehydrogenation over Bi₄Ti₃O₁₂ catalysts.

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A new method was found for N-alkylation of amines and amides with alcohols in homogeneous liquid-phase. Addition of small amounts of ammonium halide to the reactants attained successfully high yields of N-alkyl or N, N-dialkyl derivatives of starting amines and amides at 280-320°C in the atmosphere of nitrogen. This N-alkylation reaction gave N, N-dialkylaniline from aniline, N-alkyl-α-pyrrolidone from α-pyrrolidone, N-alkyl-α-piperidone from α-piperidone, N, N-dialkylformamide from formamide (starting material : ammonium formate), and N, N-dialkylacetamide from acetamide (starting material : ammonium acetate).

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Bis(4-anilino-3-penten-2-onato)copper(II) [1] reacted with p-substituted benzoyl chloride (R, a : NO₂, b : Cl, c : H, d : CH₃, and e : OCH₃) and pyridine (2.3 molar ratios to [1] in benzene at 8±2°C for an hour to give C-aroylated product, 4-anilino-3-(p-substituted, benzoyl)-3-penten-2-one [3] (41-86% yield), and 4-substituted benzanilide [4] (-10%). Bis(4-anilino-3-penten-2-onato)nickel(II) [2] was allowed to react similarly with them in the absence of pyridine to give [3] (53-85%) and [4] (-11%). The more the electron attractive substituent at benzene ring, the higher was the yield of [3] (Table 1). The stereochemical structures of all of [3] were (E)-isomers on the basis of the IR and PMR spectral data shown in Table 2 and of the comparison of spectroscopic data with the C-acetylated product, 3-acety-4-anilino-3-penten-2-one [5] (ν_C=O) of the free acetyl group : 1669 cm^-1, ν_C=O of the intramolecular hydrogen-bonded acetyl group : 1592 cm^-1, δ_NH : 1569 cm^-1, and proton signal of NH group : 13.72 ppm (broad)).

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A series of triethylaminium salt of acylated sulfuric acids [1] was synthesized in excellent yield from the triethylaminium salt of a higher fatty acid and the adduct of triethylamine-sulfur trioxide in 1, 2-dichloroethane under mild reaction conditions. R-C =O -O-SO₂-O^(-) HN⁽⁺⁾(C₂H₅)₃ [1]
The melting points of the salts thus obtained were as follows mp 35.5-38.2°C for lauroyl group (R=C₁₁H₂₃), mp 46.0-47.5°C for myristoyl group (R=C₁₃H₂₇), mp 57.5-60.0°C for palmitoyl group (R=-C₁₅H₃₁) and mp 64.0-67.0°C for stearoyl group (R=C₁₇H₃₅).

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The optical activation of N-benzoylphenylglycine (RS[1]) was realized when its salt of (R)-1-phenylethylamine (R[2]) was refluxed in 100 times its weight of toluene followed by gradual concentration of the solution to a half its original volume. The product which contained 71.7% of S[1]-R[2] was obtained in a 77% yield. The degrees of asymmetric transformation from R[1]-R[2] to S[1]-R[2] were measured under various conditions. The attempt to obtain optically pure S[1] from RS[1]-R[2] was made successfully by modifing above procedure. R[1] also was obtained in the same way when RS[1]-S[2] was used instead of RS[1]-R[2].

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A convenient synthetic method has been developed for the preparation of N, N′-dithiobis-(amines) from hindered amines : the reaction of 2, 2, 6, 6-tetramethyl-4-piperidinoile [1a] with S₂Cl₂-DMF in the presence of sodium acetate in hexane at 5-10°C gave bis(2, 2, 6, 6-tetramethyl-4-oxopiperidine-1-yl) disulfide [2a] in a good yield. Under the same reaction conditions, disulfides [2b-e] of other hindered amines were obtained.

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Fractionation of poly(α-L-glutamic acid) (PLGA) was carried out on DEAE cellulose column by NaCl gradient in an aqueous solution. PLGA with increasing molecular weight was eluted with NaCl concentration. M_w/M_n of unfractionated PLGA was evaluated to be 1.19 from the viscosity measurements.
The effect of molecular weight of PLGA on the helix-coil transition was examined by means of potentiometric titration and optical rotation measurements. The titration curves were independent of molecular weight in the region of degree of dissociation, α>0.35, while they were dependent on it in the region, α<0.35, where the polymer precipitated partially. The relation between helix content of the polymer, θ, and pH was represented by a single curve, regardless of molecular weight.

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