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21.
Apparent molal heat capacities
of some piperidine, morpholine, and piperazine derivatives in aqueous solution have been determined by adiabatic calorimetry
in the temperature range 20–55°C and in the molality range 0.2–1m. Comparison of experimental
values with those calculated through group contributions, found for monofunctional compounds, indicates strong interactions
between the hydrophilic centers. An interpretation is given of the possible mechanism of this interaction. Also, values of
ΔC
p
for the addition reaction of proton to nitrogen centers of mono- and bifunctional organic compounds are examined. 相似文献
22.
报道了用火焰原子吸收光谱法测定裂解汽油中铅的方法。用碘 二甲苯溶液对汽油进行氧化处理,用稀硝酸进行萃取,萃取后浓缩液用原子吸收光谱法进行测定。铅含量在0~7.0μg·ml-1范围内符合比耳定律。对汽油样品进行分析时,相对标准偏差小于3.95%,对样品进行加标回收试验,回收率为97.7%~101.7%,方法的精密度和准确度良好。 相似文献
23.
《Electroanalysis》2004,16(8):650-655
An analytical solution is developed for heterogeneous ECE processes occurring at channel electrode surface for both laminar and turbulent flow. The solution explicitly links the behavior of ECE processes and the parameters. A simple expression of the effective number of electrons transferred, covering all the reaction rate constants and different diffusion coefficients of the reactant A and the intermediate product B, is obtained. Excellent agreement with previous numerical and analytical results is shown . Parametric studies illustrate the effects of diffusion coefficients, hydrodynamic factors and reaction rate constants on the effective number of electrons transferred and the currents. 相似文献
24.
M. Paluch 《Colloid and polymer science》1998,276(7):648-652
The results of experimental studies of the adsorption at the solution/air interface from an aqueous mixture: 2,4,6-trimethylphenol–2,4,6-trichlorophenol
are presented. The surface properties of the above-mentioned mixture were studied by surface potential and surface tension
measurements. These measurements were carried out as a function of the concentration of 2,4,6-trimethylphenol aqueous solution
at a constant concentration of 2,4,6-trichlorophenol.
Using the results obtained and based on the Gibbs equation, Helmholtz formula and Motomura’s method the relative surface excesses
of adsorbed substances, effective dipole moments, surface molar fractions of solutes and miscibility of adsorbed films were
determined.
Received: 7 November 1997 Accepted: 26 February 1998 相似文献
25.
The composition range and (composite modulated) structure of compounds within the wide range non-stoichiometric LaSb2Snx, 0.1?x?0.75, solid solution is carefully investigated via a combined electron diffraction, XRD and electron probe microanalysis study. Evidence for metastability of the LaSb2Snx phase at the low x composition end of the solid solution is presented. Direct evidence is found for a reasonably (although by no means perfectly) well ordered Sn sub-structure which is, in general, mutually incommensurable with respect to a very well ordered underlying LaSb2 sub-structure along both a and c directions. The overall (3+2)-d superspace group symmetry is given along with a discussion of the consequences as regards the arrangement of the Sn atoms. The Sn sub-structure c-axis cell dimension shows very little variation with composition x providing direct experimental evidence of the importance of Sn-Sn metallic bonding (along one-dimensional [001] Sn strings) for the stability of the phase. 相似文献
26.
叙述了用θ-2θ型X射线衍射仪精确测定电解质溶液结构的新实验技术。设计制作了具有恒温功能的超厚液体样品池,并建立了样品池窗口强度的校正方法。优化了液体X射线衍射数据和结构参数精细化的计算机程序,获得了非常令人满意的实验结果。由θ-2θ型X射线衍射仪精确测定的径向分布函数与θ-θ型衍射仪自由散射比较,表明DRF分辨率有所提高。 相似文献
27.
Enthalpies of solution of sodium benzoate, potassium benzoate, and potassium halo-substituted benzoates are reported at 298.15°K
in water and in nine water-tert-butyl alchol mixtures. Transfer enthalpies from water to the mixed solvent go through a maximum for about 0.055 mole fraction
of alcohol. Additivity of ionic contributions in the enthalpies of transfer is verified. Substituent effects on the transfer
enthalpies of benzoates are discussed in terms of size of the solutes and cohesion of the solvent mixtures.
For Part V, see ref. 1. 相似文献
28.
G.B. Song C.Q. Han J.K. Liang Q.L. Liu F.S. Liu G.H. Rao 《Journal of solid state chemistry》2004,177(7):2394-2403
The subsolidus phase relations of the PrOx-CaO-CuO pseudo-ternary system sintered at 950-1000°C have been investigated by X-ray powder diffraction. In this system, there exist one compound Ca10Pr4Cu24O41, one Ca2Pr2Cu5O10-based solid solution, seven three-phase regions and two two-phase regions. The crystal structures of Ca10Pr4Cu24O41 and Ca2Pr2Cu5O10-based solid solution have been determined. Compound Ca10Pr4Cu24O41 crystallizes in an orthorhombic cell with space group D2h20−Cccm, Z=4. Its lattice parameters are a=11.278(2) Å, b=12.448(3) Å and c=27.486(8) Å. The crystal structure of Ca2Pr2Cu5O10-based solid solution is an incommensurate phase based on the orthorhombic NaCuO2 type subcell. The lattice parameters of the subcell of the Ca2.4Pr1.6Cu5O10 are a0=2.8246(7) Å, b0=6.3693(5) Å, c0=10.679(1) Å, and those of the orthorhombic superstructure are with a=5a0, b=b0, c=5c0. The Ca2.4Pr1.6Cu5O10 structure can also be determined by using a monoclinic supercell with space group C2h5−P21/c, Z=4, a=5a0, b=b0, and β=104.79(1)° or 136.60(1)°, V=5a0b0c0. 相似文献
29.
研究了采用显色剂 苦胺酸偶氮变色酸对化学镀钴基合金镀液中钴含量进行测定的试验条件,在pH11的氨 氯化铵缓冲溶液中,钴与显色剂配合物的最大吸收峰在650nm波长处,钴(Ⅱ)在0~60μg/25ml范围内服从比耳定律,表观摩尔吸光系数为3.1×104L·mol-1·cm-1。该法测定钴的选择性好,在大量镍存在下,也能准确测定,对镀液样品进行了测定,相对标准偏差小于1%,结果满意。 相似文献
30.
Transference numbers of HCl(aq) solutions at 25°C, from 0.01 to 13.6 mol-kg–1(m) have been obtained by measuring the emf of cells with transference using hydrogen gas/platinum electrodes. Good agreement is obtained at concentrations up to 1 m with all previous data, and our results strongly corroborate those of King and Spiro over the 2–8m concentration range. The transference numbers of the hydronium ion fit the empirical equation,
H
HCl
= 0.821 + 0.0457m
1/2 – 2.476×10–2m – 1.90×10–4
m
2 – 1.45×10–5
m
3 the maximum deviation in T
H
HCl
being 0.003. 相似文献