An anion-exchange chromatographic study on boron isotopic fractionation at 2 MPa at 293 K

To study boron isotopic fractionation at high pressure, column chromatography operated in the breakthrough manner was performed at 2.0 MPa at 25.0 degrees C. The fractionation factor (S) between boron adsorbed onto strongly basic anion-exchange resin and boron in solution was obtained as 1.013, which was smaller than the values at 0.1 MPa (atmospheric pressure) found in literature. The pressure dependence of S was discussed based on the polymerization of boron in the solution and resin phases and on the occurrence of the pressure dependent isotope effect relating to the molar volume changes of boron species upon isotope substitution.     

Photochemistry of peroxoborates: borate inhibition of the photodecomposition of hydrogen peroxide

The UV absorbance and photochemical decomposition kinetics of hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. At higher pH borate/boric acid inhibits the photodecomposition of hydrogen peroxide (molar absorptivity and quantum yield of H(2)O(2) and HO(2) (-), (19.0+/-0.3) M(-1) cm(-1) and 1, and (237+/-7) M(-1) cm(-1) and 0.8+/-0.1, respectively). The results are consistent with the equilibrium formation of the anions monoperoxoborate, K(BOOH)=[H(+)][HOOB(OH)(3) (-)]/([B(OH)(3)][H(2)O(2)]), 2.0 x 10(-8), R. Pizer, C. Tihal, Inorg. Chem. 1987, 26, 3639-3642, and monoperoxodiborate, K(BOOB)=[BOOB(2-)]/([B(OH)(4) (-)][HOOB(OH)(3) (-)]), 1.0+/-0.3 or 4.3+/-0.9, depending upon the conditions, with molar absorptivity, (19+/-1) M(-1) cm(-1) and (86+/-15) M(-1) cm(-1), respectively, and respective quantum yields, 1.1+/-0.1 and 0.04+/-0.04. The low quantum yield of monoperoxodiborate is discussed in terms of the slower diffusion apart of incipient (.)OB(OH)(3) (-) radicals than may be possible for (.)OH radicals, or a possible oxygen-bridged cyclic structure of the monoperoxodiborate.     

298.15K下Li2B4O7-H2O体系水蒸汽分压及渗透系数的等压测定和离子相互作用模型

在已有研究含硼体系的文献中仅考虑了硼酸根B4O7^-2或B(OH)4^-和H3BO3的存在，而对Li2B4O7-H2O体系具有多种硼物种聚合平衡体系的热力学性质的研究尚未见报道．本文用等压法研究了Li2B4O7-H2O体系于298．15K下浓度由稀到过饱和溶液的平衡气相蒸汽压及渗透系数．考虑了水溶液中多种硼物种的存在，以Pitzer方程为基础，建立了可描述该含硼体系的离子相互作用模型。     

Rapid accurate isotopic measurements on boron in boric acid and boron carbide

A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry.     

生物质空气－水蒸气气化制取合成气热力学分析

基于Gibbs自由能最小化原理，计算了包括H2O(l)和C(s)在内的，生物质空气 水蒸气气化体系热力学平衡，对比分析了常压气化和加压气化的特点，通过回归分析得到了不同压力下，气化产物中可燃气体分率最高时的水蒸气/生物质质量比（S/B，Steam to Biomass Ratio）与空气当量比（ER，Equivalence Ratio）的关系曲线，为探讨适于制取合成气的气化工艺和条件提供初步的理论指导。研究表明，相对于常压气化，加压气化体系的平衡温度较高，平衡状态下可燃气体分数较低，但CH4含量明显增加；一定温度和当量比下，加压气化使得气化产物中可燃气体分数达到最高所对应的S/B比增大，即需要消耗更多水蒸气；通过调节S/B比，可以比较方便地控制产物中H2和CO的比例。以常压为例，T=1173K，S/B=0.17时，气化产物中H2/CO约为1.1∶1，而S/B=1.02时，气化产物中H2/CO约为2∶1；不同压力下最佳S/B比和ER有很好的线性关系，温度为1173K时，最佳S/B比与压力及ER〖的关系为S/B=－1.48×ER－4.49 E×10－5×p2 + 5.83 E×10－3×p + 0.32。     

Determination of borate ion-pair stability constants by potentiometry and non-approximative linearization of titration data

Borate anions, B(OH)(-)(4), are known to associate with alkali and alkaline-earth metal cations in sea-water. The borate cation ion-pairs are of the general form MB(OH)((n-1)+)(4), where M(n+) is the cation. In this work, the cation borate stability constants (K*(MB)) have been evaluated for Na(+), Li(+), Mg(2+), Ca(2+) and Sr(2+) where K*(MB) = [MB(OH(4))((n-1)+)]/[M(n+)][B(OH)(-)(4)]. The K*(MB) values were obtained from values found for the stability constant of boric acid (K*(B)) in various electrolyte media at 25 degrees and an ionic strength of 0.7. Acid-base potentiometric titrations were performed in the electrolyte media with a standard Pt/H(2) electrode and a junctionless Ag/AgCl reference electrode to monitor the emf. A non-approximative equation was used to linearize the titration data. The values obtained were: K*(Lib) = 0.89 +/- 0.02, K*(NaB) = 0.44 +/- 0.01, K*(MgB) = 13.6 +/- 0.7, K*(CaB) = 11.4 +/- 0.15, K*(SrB) = 3.47 +/- 0.06. The values for K*(MB) correlate with the charge-density parameter z(2)/(r + 0.85), where r is the radius of the cation. The speciation of boron in sea-water was predicted from the K*(MB), data for the major cations present.     

Volumetric properties of the glycyl group of proteins in aqueous solution at high pressures

Sound speeds have been measured for aqueous solutions of alanine and the peptides alanylglycine (alagly), alanylglycylglycine (ala(gly)(2)), alanylglycylglycylglycine (ala(gly)(3)) and alanylglycylglycylglycylglycine (ala(gly)(4)) at T=298.15 K and at the pressures p=0.1, 5.0, 10.0, 20.0, 40.0, 60.0, 80.0 and 100.0 MPa. A method is described whereby reliable partial molar volumes at infinite dilution, Vo2, partial molar isentropic compressions at infinite dilution, Ko(S,2), and partial molar isothermal compressions at infinite dilution, Ko(T,2), for the solutes can be derived from the sound speed data. These results were used to obtain partial molar volumes, isentropic and isothermal compressions for the backbone glycyl group of proteins, CH(2)CONH, over the pressure range p=0.1 to 100.0 MPa. The variations of these properties with pressure are discussed in terms of the likely glycyl-group-water interactions.     

Determination of boron isotopic variations in aquatic systems with negative thermal ionization mass spectrometry as a tracer for anthropogenic influences

A technique for precise boron isotope ratio measurements with a high detection power has been developed by negative thermal ionization mass spectrometry (NTIMS). Relative standard deviations in the range of 0.03-0.3% have been obtained for the determination of the (11)B/(10)B isotope ratio using nanogram amounts of boron. Ba(OH)(2) has been applied as ionization promoter for the formation of negative thermal ions. By adding MgCl(2) better reproducibilities of the measurement have been achieved. A possible interference of BO(-)(2) ions at mass number 42 by CNO(-) could be excluded by the sample preparation technique used. Contrary to other NTI techniques no dependence of the measured isotope ratio on the boron amount used has been observed. Anthropogenic and natural saline influences in ground water have been successfully identified by boron isotope ratio determinations with this NTIMS method, due to the different isotopic composition of boron in natural and anthropogenic substances. In sewage, the boron isotope ratio is substantially influenced by washing powder, which contains low (11)B/(10)B ratios (expressed in delta(11)B values normalized to the standard reference material NIST SRM 951). In contaminated ground water, low delta(11)B values are normally correlated with high boron and high chloride concentrations. On the other hand, delta(11)B shifts to higher values in less contaminated samples. For ground water with saline influences, only the delta(11)B determination, and not the boron or chloride content, allowed the correct identification of this natural source of contamination.     

有孔虫中硼的分离及其正热电离质谱法测定

针对大洋钻探计划(0DP)钻孔中有孔虫数量少、硼含量低的特点，改进了硼特效树脂和阴、阳混合离子交换树脂相结合进行分离硼的方法，成功地实现了硼的分离，并且首次采用正热电离质语法测定了有孔虫中硼同位素的比值。由于硼的分离过程不产生同位素分馏，测定结果令人满意。     

Standard partial molar volumes of aqueous glycolic acid and tartaric acid from 25 to 350 degrees C: evidence of a negative Krichevskii parameter for a neutral organic solute

Apparent molar volumes have been determined using a high-pressure vibrating-tube densimeter for aqueous solutions of glycolic acid (HGly = HOCH(2)COOH) and tartaric acid (H(2)Tar = HOOCCH(OH)CH(OH)COOH) at temperatures from 25 degrees C to 350 degrees C and pressures as high as 20 MPa. The resulting standard partial molar volumes (HGly,aq) are relatively independent of temperature until 315 degrees C, at which point (HGly,aq) deviates sharply toward negative values. This suggests that the Krichevskii parameter, A(Kr) = lim(x(2) --> 0) , which describes the discontinuities in standard partial molar properties at the critical point of water, is negative. Almost all aqueous nonelectrolytes are characterized by positive Krichevskii parameters. This is the first negative value reported for any organic molecule that is not an ion or zwitterion and only the third ever observed directly for a neutral species (the others are B(OH)(3) and H(3)PO(4)). The standard partial molar volumes for H(2)Tar(aq) are also relatively independent of temperature until 275 degrees C, suggesting a similar behavior. However, the onset of thermal decomposition prevented measurements at temperatures above 300 degrees C.     

Partial molar volumes of organic solutes in water. VI.o-Chlorophenol andp-chlorophenol at temperatures from 298 K to 573 K and pressures up to 30 MPa

Density data for dilute aqueous solutions of two isomeric chlorohydroxybenzenes (chlorophenols) obtained in the temperature range 298.15 K to 573.15 K and at either atmospheric pressure, or at pressures close to the saturated vapour pressure of water, and at pressures up to 30 MPa are presented together with partial molar volumes calculated from the experimental data. The data were obtained using either a high-temperature and high-pressure flow vibrating-tube densimeter for measurements at elevated pressures or a commercial vibrating-tube cell DMA 602HT for measurements at atmospheric pressure.     

Determination of isotopic ratio of boron in boric acid using laser mass spectrometry.

A reflectron time-of-flight mass spectrometer (RTOFMS) with a laser ablation ion source was used to determine the isotopic ratio of 10B/11B present in boric acid solutions, using graphite as the matrix. The atom % 10B values obtained were within +/-1% of the actual ones. The determination of the boron isotopic ratio using this method is, in comparison to other methods, faster, less expensive and easier to perform. The results are compared with the values determined using thermal ionization mass spectrometry.     

Fullerenols revisited as stable radical anions

The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene.     

Experimental and computational studies on the molecular energetics of chlorobenzophenones

The standard (p degrees = 0.1 MPa) molar enthalpies of formation, Delta(f)H(m)degrees, of crystalline 2-, 3- and 4-chlorobenzophenone and 4,4'-dichlorobenzophenone were derived from the standard molar energies of combustion, Delta(c)U(m)degrees, in oxygen, to yield CO(2)(g), N(2)(g), and HCl x 600H(2)O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The Calvet high-temperature vacuum sublimation technique was used to measure the enthalpy of sublimation, Delta(cr)(g)H(m)degrees, of the compound 2-chlorobenzophenone. For the other three compounds, the standard molar enthalpies of sublimation, at T = 298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapor pressures of these compounds, measured by the Knudsen-effusion technique. From the values of Delta(f)H(m)degrees and Delta(cr)(g)H(m)degrees, the standard molar enthalpies of formation of all the compounds, in the gaseous phase, Delta(f)H(m)degrees (g), at T = 298.15 K, were derived. These values were also calculated by using the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d) computational approach.     

Phase behaviour of three homologues of the discotic hexa‐n‐alkoxyanthraquinones under pressure

The phase transition behaviour of three homologous discotic mesogens, the hexa‐n‐alkoxyanthraquinones HOAQ(n), n indicating the number of carbon atoms in the alkoxy group, was investigated under hydrostatic pressures up to 500?MPa using a high pressure differential thermal analyser. The T vs. P phase diagrams of HOAQ(6), HOAQ(8) and HOAQ(9) were constructed for solution‐ (Cr₀) and melt‐crystallized (Cr₁) samples of the compounds. HOAQ(6) shows the reversible Cr₀–rectangular columnar phase (Col_r)–hexagonal columnar phase (Col_h)–isotropic liquid (I) phase sequence at atmospheric pressure. The stable Col_r phase of HOAQ(6) has a decreased temperature range with increasing pressure and then the Col_r phase disappears under pressures above about 350?MPa; instead the Cr₀–Col_h–I phase sequence is exhibited. For HOAQ(8), the solution‐grown sample exhibits the stable Cr₀–Col_h–I phase sequence at atmospheric pressure. Applying pressure to the solution‐grown sample induces the formation of the stable Col_r phase in the pressure region between 10 and 350?MPa, leading to the Cr₀–Col_r–Col_h–I phase sequence. The pressure‐induced Col_r phase disappears under higher pressures. The melt‐cooled sample of HOAQ(8) shows the formation of the metastable crystal (Cr₁), unknown mesophase (X) and Col_r phases at lower temperatures under atmospheric pressure, and exhibits the reversible Cr₁–X–Col_r–Col_h–I phase sequence on subsequent thermal cycles. The metastable phase sequence was observed under pressures up to 100?MPa, but the phase transitions were too small to be detected under higher pressures. In HOAQ(9) the stable Cr₀–Col_h–I phase sequence is observed at all pressures, while the melt‐cooled sample shows the metastable Cr₁–Col_r–Col_h–I phase sequence under pressures up to 300?MPa. The metastable Col_r phase disappears under higher pressures.     

Phase behaviour of three homologues of the discotic hexa-n-alkoxyanthraquinones under pressure

The phase transition behaviour of three homologous discotic mesogens, the hexa-n-alkoxyanthraquinones HOAQ(n), n indicating the number of carbon atoms in the alkoxy group, was investigated under hydrostatic pressures up to 500 MPa using a high pressure differential thermal analyser. The T vs. P phase diagrams of HOAQ(6), HOAQ(8) and HOAQ(9) were constructed for solution- (Cr₀) and melt-crystallized (Cr₁) samples of the compounds. HOAQ(6) shows the reversible Cr₀-rectangular columnar phase (Col_r)-hexagonal columnar phase (Col_h)-isotropic liquid (I) phase sequence at atmospheric pressure. The stable Col_r phase of HOAQ(6) has a decreased temperature range with increasing pressure and then the Col_r phase disappears under pressures above about 350 MPa; instead the Cr₀-Col_h-I phase sequence is exhibited. For HOAQ(8), the solution-grown sample exhibits the stable Cr₀-Col_h-I phase sequence at atmospheric pressure. Applying pressure to the solution-grown sample induces the formation of the stable Col_r phase in the pressure region between 10 and 350 MPa, leading to the Cr₀-Col_r-Col_h-I phase sequence. The pressure-induced Col_r phase disappears under higher pressures. The melt-cooled sample of HOAQ(8) shows the formation of the metastable crystal (Cr₁), unknown mesophase (X) and Col_r phases at lower temperatures under atmospheric pressure, and exhibits the reversible Cr₁-X-Col_r-Col_h-I phase sequence on subsequent thermal cycles. The metastable phase sequence was observed under pressures up to 100 MPa, but the phase transitions were too small to be detected under higher pressures. In HOAQ(9) the stable Cr₀-Col_h-I phase sequence is observed at all pressures, while the melt-cooled sample shows the metastable Cr₁-Col_r-Col_h-I phase sequence under pressures up to 300 MPa. The metastable Col_r phase disappears under higher pressures.     

Borate-catalyzed reactions of hydrogen peroxide: kinetics and mechanism of the oxidation of organic sulfides by peroxoborates

The kinetics of the oxidation of substituted phenyl methyl sulfides by hydrogen peroxide in borate/boric acid buffers were investigated as a function of pH, total peroxide concentration, and total boron concentration. Second-order rate constants at 25 degrees C for the reaction of methyl 4-nitrophenyl sulfide and H(2)O(2), monoperoxoborate, HOOB(OH)(3) (-), or diperoxoborate, (HOO)(2)B(OH)(2) (-), are 8.29 x 10(-5), 1.51 x 10(-2) and 1.06 x 10(-2) M(-1) s(-1), respectively. Peroxoboric acid, HOOB(OH)(2), is unreactive. The Hammett rho values for the reactions of a range of substituted phenyl methyl sulfides and hydrogen peroxide, monoperoxoborate or diperoxoborate are -1.50 +/- 0.1, -0.65 +/- 0.07 and -0.48 (two points only), respectively. The rho values for the peroxoborates are of significantly lower magnitude than expected from their reactivity compared to other peroxides. Nevertheless the negative rho values indicate positive charge development on the sulfur atom in the transition state consistent with nucleophilic attack by the organic sulfides on the peroxoborates as with the other peroxides. The kinetic parameters, including the lack of reactivity of peroxoboric acid, are discussed in terms of the differences in the transition state of reactions involving peroxoboron species with respect to those of other peroxides.     

An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally. The results show the clear positive relationships between boron concentration and δ11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic fractionation between inorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis that B(OH)4- is the dominant spe-cies incorporated into the biogenic calcite structure. The isotopic fractionation factors α between synthetic calcium carbonate precipitate and parent solutions increase systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072 at pH 8.60 for seawater and from 0.9826 at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopic fractionation factor of larger than 1 in synthetic calcium carbonate precipitated from seawater/saline water at higher pH is observed, which implies that a substantial amount of the isotopically heavier B(OH)3 species must be incorporated preferentially into synthetic inorganic carbonate. The results propose that the incorporation of B(OH)3 is attributed to the formation of Mg(OH)2 at higher pH of calcifying microenvironment during the synthetic calcium carbonate precipitation. The preliminary experiment of Mg(OH)2 precipitated from artificial seawater shows that heavier 11B is enriched in Mg(OH)2 precipitation, which suggests that isotopically heavier B(OH)3 species incorporated preferentially into Mg(OH)2 precipitation. This result cannot be applied to explain the boron isotopic fractionation of marine bio-carbonate because of the possibility that the unusual environment in this study appears in formation of marine bio-carbonate is infinitesimal. We, however, must pay more attention to this phenomenon observed in this study, which accidentally appears in especially natural environment.     

Ion Exchange Extraction of Boron from Aqueous Fluids by Amberlite IRA 743 Resin

The ion exchange characteristics d Amherlite IRA 743 resin for extracting boron from aqueous fluids have been investigated in detail. The results show that AmherHte IRA 743 resin, a boron specific ion exchange resin, can quantitatively extract boron as the B (OH)4- spedes from weakly basle solution. Some exchangeable anions such as CI- and SO4^2- are present, resulting in an increase in pH value of the loeded solution within the nan, and the boron in natural aqueous fluids with low nH is also extracted by Amberlite IRA 743 resin. However, the voiume of loaded solution must be restricted. The maximum voiume of loaded solution giving quantitative extraction of boron decreases for sample soh.,tiom of lower pH value. Warm HCI solution is more effective than room temperature HCI solution for eluting boron from Amberllte IRA 743 resin.     

Optimization of conditions for the determination of boron by a ruthenium(II) complex having diol moiety: A mechanistic study

Two ruthenium(II) complexes, [Ru(bpy)(2)(dhbpy-H(-1))](+) and [Ru(bpy)(2)(dhphen)](2+) (bpy=2,2'-bipyridine, dhbpy=3,3'-dihydroxy-2,2'-bipyridine, dhphen=5,6-dihydroxy-1,10-phenanthroline) were examined for use as a colorimetric reagent for the determination of boron. The reactions of boric acid with these two complexes were thermodynamically and kinetically studied in detail in order to specify the reactive species and to set up optimum condition for the determination of boron. The detailed analysis of the kinetic data for the reaction of the latter water-soluble complex showed that both boric acid and borate ion were reactive in an alkaline solution. The thermodynamically and kinetically optimum pH for the determination of boron was ca. 9 at 25 degrees C. A spectrofluorimetric determination of boron with the latter complex was attempted at 600nm with excitation at 360nm, and at pH 8.9 using CHES (N-cyclohexyl-2-aminoethanesulfonic acid) buffer. It was found that a trace amount of boron as low as ca. 2x10(-5)M ( approximately 1ppm) could be detectable.