We have discovered the first case of enantiomeric resolution by simple recrystallization of a series of racemic crystals, although in principle this sort of enantiomeric resolution was believed to be impossible for more than a century since the mechanical resolution of enantiomeric conglomerates by Pasteur and the discovery of the “preferential crystallization” technique by Gernetz. We have referred to this new phenomenon of enantiomeric resolution as the “preferential enrichment” in the mother liquor. By means of X-ray crystallographic analysis and construction of the binary melting point phase diagram, it has been found that the racemic crystals of the compounds, which show the preferential enrichment phenomenon, can be classified into a highly or fairly ordered mixed crystal composed of the two enantiomers, while those of the analogous compounds, which fail to show the phenomenon, are classified into a less ordered mixed crystal of the two enantiomers. By comparison of the presumed enantiomeric association mode in solution with the enantiomeric arrangement in the crystal, we propose a mechanism of the polymorphic transformation during crystallization closely associated with the preferential enrichment phenomenon.

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An indirect potentiometric determination of anions (or cations) using a precipitation reaction and a standard addition method which does not require the adjustment of an ionic strength and a solvent composition of the sample of a water—organic solvent mixture is proposed.
A certain volume (V_r) of the aqueous solution (reactant) containing the precipitant cation A of a known concentration c_r is added to the sample of the water—organic solvent mixture of volume V containing the analyte anion B of a concentration c_x. If the composition of formed precipitate is A_mB_n, the condition of V_r ≥ mc_xV/(nc_r) needs to be satisfied. After addition of the reactant, an A-selective electrode and a reference electrode are immersed to the sample and this solution is titrated with the aqueous solution (standard-1) containing A of a known concentration c_s1, where added volumes and the final added volume of the standard-1 are denoted with v_s1 and v_s1⁰ respectively. The electromotive forces (E₁) corresponding to added volumes (v_s1) of the standard-1 are measured. Subsequently the same sample solution of volume V and the reactant of volume V_r are added to the titrated sample. This solution is titrated again with the aqueous solution (standard-2) containing A of a known concentration c_s2 ( >c_s1) and having the same ionic strength as that of the standard-1. The electromotive forces (E₂) corresponding to added volumes (v_s2) of the standard-2 are measured.
If E₁ and E₂ corresponding to v_s1 and v_s2 that satisfy a condition of v_s2 = 2v_s1 − v_s1⁰ are read off from two titration curves, and a side reaction coefficient considering an ion association of A in the solution of E₁ measurement is almost the same as that in the solution of E₂ measurement, the following equation is held concerning with the concentration c_x of B:
_{&nikkashi_2001_83;} (y = [nc_s1/nc_rV_r − mc_xV]x + g)
where y = 10^ΔE/S, x = v_s1{(c_s2/c_s1) − y}, ΔE = E₂ − E₁, and S and g are the response slope of the A-selective electrode and a constant respectively. This c_x is determined from the slope of linear plots of y vs. x.
The present indirect method can be applied to determinations of the hexacyanoferrate (II) in the media of water—ethanol and water—1,4-dioxane mixtures with almost the same precision as in aqueous solutions by using a silver ion as the precipitant and a silver ion-selective electrode as an indicator electrode.

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To make use for separation and qualitative analysis of phosphonium ions, paper electrophoresis method was applied to the analysis of 40 kinds of phosphonium ions (RR₃′P⁺) obtained from the reactions of trimethyl-, triethyl-, tributyl- and triphenylphosphine (R₃′P) with methyl-, ethyl-, propyl-, butyl-, benzyl-, acetylmethyl-, benzoylmethyl-, methoxycarbonylmethyl-, ethoxycarbonylmethyl- and cyanomethyl halides (RX). Good correlations were found between the average mobilities and the molecular structural parameters such as molecular weights, molecular volumes, and molecular surface areas. The slopes for the regression line between the average mobilities of each phosphonium ion and the structural parameters tend to increase with the increase of the pH of the buffer solution used. It was proved that this behavior serve to differentiate and analyze the phosphonium ions according to the substituents on the phosphonium ions.

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A simple and sensitive method is described for the determination of tin in iron and steel by differential pulse anodic stripping voltammetry at a gold-coated glassy carbon electrode. Tin(IV) could be quantitatively electrodeposited by the addition of high concentrations of bromide. The interference of the iron(III) matrix was eliminated by reducing it to iron(II) with L(+)-ascorbic acid. Pre-electrolysis was carried out in 0.3 mol dm⁻³ hydrochloric acid—0.1 mol dm⁻³ nitric acid containing 2 mol dm⁻³ sodium bromide and 0.2 mol dm⁻³ L(+)-ascorbic acid at a potential of −0.5 V vs. Ag/AgCl for 300 s. The deposits were stripped at a scan rate of 40 mV s⁻¹ to 0 V vs. Ag/AgCl. The calibration (peak height vs. tin(IV) concentration) graph in the presence of 1000 μg cm⁻³ Fe(II) was linear over a concentration range 8.4 × 10⁻⁹ to 3.4 × 10⁻⁷ mol dm⁻³ of tin(IV) and passed through the origin, with a relative standard deviation of 4.3% for 20 ng cm⁻³ (n = 5). The detection limit (3σ) was 2.8 × 10⁻⁹ mol dm⁻³. There were serious interferences due to overlapping stripping peaks of cadmium(II) and copper(II). The determination of 120 to 400 μg g⁻¹ of tin in iron and steel was achieved with good precision and accuracy within 50 min without any preliminary separation of the matrix. The proposed method is applicable to the determination of tin down to 1 μg g⁻¹ levels in scrap iron.

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From the knowledge of the reactivity of amines with urushiol as a main component in lacquer tree paint, effect of addition of the primary amines to the lacquer tree paint on the curing process and the light resistance was investigated to get an insight into a relationship between the curing reaction of lacquer tree paint and the molecular structure of the amines as additives. Lacquer tree paint films were added with primary amines such as diamines, star-burst-style polydiverged polymer (dendrimers) bearing amino groups, or other amino compounds, cured, and photo-irradiated.
Although primary amines immediately reacted with urushiol, their reactivity was dependent on the neighboring group of amino groups and the reaction smoothly proceeded for the amines having primary amino groups separated by long polymethylene chains. Steric structures of the amines seemed to greatly affect the reaction of amines with urushiol and the inhibition of curing reaction of lacquer tree paint film.
Furthermore, diamines and star-burst-style polydiverged polymer (dendrimer of first generation) with 4 primary amino groups worked as a nucleation reagent for microcrystallization in the lacquer tree paint films and made curing at low humidity possible.

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Valuable information from 2D-NMR spectra should be used for structure elucidation. A system named “Spec2D” as a structure elucidation system has been developed in order to propose plausible structures for unknown compounds using H-H COSY spectral information. A knowledge base for the system has been constructed beforehand. It consists of information about correlation between chemical shifts of ¹H-NMR spectra and the corresponding substructures represented by HYPER code. The knowledge base is incorporated with networks of spin-spin coupling information from cross peaks in the H-H COSY spectral data which have been derived from fully assigned ¹H-NMR data in our databases. For the structure elucidation the system requires information of chemical shifts, the number of protons of each signal, and signal connections derived from the cross peak information of H-H COSY spectrum of an unknown compound. The system does not require any molecular formula. The requisite information is only ¹H-NMR and H-H COSY spectra of the unknown compound in question. The system extracts substructures consistent with input spectral data from the knowledge base. A small number of consistent substructures should be survived by means of the cross peak information and the extracted large fragments of the substructures. Furthermore, the substructures are combined into larger substructures using coupling information of the cross peaks. Referring to the assignments of the substructures, these are combined into complete structures in the final combination procedure. In a verification module the system predicts the chemical shifts and the cross peaks for every candidate structure proposed in the structure generation step and compares them with the input spectrum of the unknown compound. The system calculates scores of the predicted spectra representing similarities of chemical shifts and cross peaks. The most plausible structure for the unknown compound is ranked at the higher position in the list of candidate structures. Finally, the system proposes the plausible candidate structures.

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Oxidation of sulfurous acid (H₂SO₃) to sulfuric acid (H₂SO₄) by dissolved oxygen (O₂) in an aqueous solution was remarkably enhanced by freezing. The concentration of sulfurous acid in a sample solution which froze in a −10 °C refrigerant for 60 min decreased by about 50%, and three freeze/thaw cycles resulted in perfect conversion into sulfuric acid. The difference of reaction rates in −20 °C and −10 °C refrigerants indicated that the rate-determining step of the reaction was the growth rate of ice formation in the sulfurous acid in an aqueous solution. The yield of sulfurous acid oxidation in a −10 °C refrigerant was higher than that in a −20 °C refrigerant.

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The chemical reaction which was occurred by ultrasonic irradiation for CN⁻ ion in aqueous solution was examined. The concentration of the CN⁻ ion in aqueous solution decreased from 4.0 × 10⁻³ mol dm⁻³ to 3.3 × 10⁻³ mol dm⁻³ by 300 min irradiation. While pH value of the ion aqueous solution containing CN⁻ ion increased from 10.40 to 10.97 by the 300 min irradiation. The reaction for the change of the concentration of CN⁻ (or OH⁻) for ultrasonic irradiation time was almost described with first-order kinetics. Insoluble fine particle with white color formed in the aqueous solution by the ultrasonic irradiation. It became clear that the potassium element was not included in the fine particle from experiment on flame reaction. The fine particles were dissolved at a little quantity in methanol, and it was shown that the proton did not exist in the particles from ¹H-NMR measurement using the methanol solution. From FT-IR measurement for the fine particle, the absorption of 1390.4 cm⁻¹ and 1100.2 cm⁻¹ which originated from the stretching vibration of single bond of CN was measured, the absorption of 2075.1 cm⁻¹ which originated from the stretching vibration of triple bond of CN was not measured. It become clear that fine particles were the tabular crystal from the scanning electron microscopy and that it is a macro molecular substance which consists of single bond of C–C and C–N.

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