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71.
The electrical conductivities of aqueous solutions of NaCF3SO3, KCF3SO3, and Ni(CF3SO3)2 have been measured at 25‡C in the concentration range 1 to 25X 10-3 mol-dm-3 The data approach the Onsager limiting law at low concentrations, leading to a limiting molar ion conductivity for the CF3SO
3
−
ion of 44.5±0.2 S-cm2-mol-1, based on standard values for the cations. Using a simple size parameter for unsymmetrical polyatomic ions, based on the
ion geometry, it is shown that the well known empirical relation between the molar conductivities of symmetrical ions and
their radii can be extended to include certain polyatomic anions including CF3SO
3
−
. The results suggest that the CF3SO
3
−
ion is either a weak structure breaker in aqueous solution or neutral in this respect. 相似文献
72.
A rigorous side by side comparison of miniature planar potassium-selective electrodes with hydrogel and potassium hexacyanoferrate(II)/(III) doped polypyrrole (PPy/FeCN) based inner contacts is presented. The planar electrodes were manufactured by screen printing as four- and five-site arrays on ceramic substrates. These electrode arrays were incorporated into a flow-through cell, which could accommodate nine electrode sites. Two identical flow cells were connected in series and the effect of the inner contacts on the analytical performance of the respective electrodes has been critically evaluated. The time necessary to reach steady state conditions has been determined and the effect of experimental parameters (temperature, ambient light intensity, CO2, and O2 concentration of the sample) on the potential stability of the electrodes was analyzed. At controlled temperature, the drift of the planar potassium electrodes with hydrogel and PPy/FeCN solid contact were 0.11±0.02 mV h−1 and 0.03±0.007 mV h−1, respectively. The experimental data proved that there is no aqueous film formation between the PPy/FeCN film and the potassium-selective solvent polymeric membrane. 相似文献
73.
固固相反应合成牛磺酸水杨醛钾与锑、铋的配合物 总被引:2,自引:0,他引:2
合成了牛磺酸水杨醛钾,并采用室温固固相反应法合成了牛磺酸水杨醛钾与三氯化锑和三氯化铋的配合物,其组成为:K2MC18H20O8N2S2 (M = Sb, Bi)。两种配合物的晶体结构均属于单斜晶系,锑配合物的晶胞参数为:a = 1.2869 nm, b = 1.7636 nm, c = 1.9917 nm, β= 93.79埃活榕浜衔锏木О问篴 = 1.4770 nm, b = 2.0334 nm, c = 2.0149 nm, β= 94.05。红外光谱表明N、Cl原子参与了配位,中心离子的配位数为5。 相似文献
74.
75.
K. V. Titova O. A. D'yachenko V. V. Gritsenko G. V. Shilov 《Russian Chemical Bulletin》1993,42(1):30-35
Potassium fluoride peroxosolvate KF-H2O2 was obtained upon action of a 30% aqueous solution of hydrogen peroxide on solid potassium fluoride dihydrate. As compared to other peroxosolvates, KF-H2O2 is characterized by the highest thermal stability: the decomposition rate constantk
1, at 120°C is 1.4 10–3 min–1, the enthalpy of H2O2 addition to KF is 8.1 kcal/ mol. The correlation between the high stability of KF-H2O2 and the absence of catalytic properties of KF towards H2O2, and the formation of strong intermolecular O-H...F and intramolecular O-H...O hydrogen bonds in the crystal is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 38–44, January, 1993. 相似文献
76.
柠檬酸三丁酯是浅黄色的液体,可作为固定相,文献记载它被制备成色谱柱的最高使用温度为150℃。鉴于最高使用温度低的限制,柠檬酸三丁酯作为色谱固定相时,一些分子量大的化合物不能使用该柱分析。本文将其作为固定相用溶胶-凝胶法制备毛细管气相色谱柱,并在色谱柱上初步研究了一系列低沸点有机物的分离和保留行为,发现其对醇类、胺类、芳烃等有很好的分离效果。同时使用该种方法制得的毛细管柱能承受的最高温度现为240℃,这对提高柠檬酸三丁酯的利用价值有较好的意义。 相似文献
77.
Cory Momany Marvin L. Hackert Jyotsna Sharma Narinder S. Poonia 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):343-354
Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]2DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal2DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]2DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)2DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)2DB24C8 and (NaSal)2DB24C8 molecules. The crystals are monoclinic,P21/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, Å3,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na2- and K2-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K2-crown being nearly planar and the Na2-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na2-molecule; 82.7° K2-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K+K+ and Na+Na+ distances in the respective molecules are 3.95 and 3.34 Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages). 相似文献
78.
Comparison
of the fragility index of different eudragit polymers determined by activation
enthalpies
Gabriella Csóka A. Gelencsér Dorottya Kiss Eszter Pásztor I. Klebovich Romána Zelkó 《Journal of Thermal Analysis and Calorimetry》2007,87(2):469-473
The present study aimed to apply fragility
index (m) of polymers in the determination
of the optimal amount of plasticizer in polymer films. The fragility index
of different Eudragit polymers (RS, RL, EPO) was assessed by differential
scanning calorimerty (DSC), applying the Arrhenius connection (logq–1/T
g).
The fragility of Eudragit EPO films proved to be the highest, while in the
case of RS and RL, the increase of the alkyl-chain length caused the increase
of fragility. Studying the effect of plasticizer (triethyl citrate, TEC) on
the m value of Eudragit RL and RS films,
a near linear reduction of the fragility index could be observed between 5–30%
TEC concentration, but above 30%, this value leveled out to constant. 相似文献
79.
低浓度HPAM/AlCit交联体系的27Al NMR研究 总被引:2,自引:0,他引:2
用27Al NMR谱研究了高分子量低浓度的部分水解聚丙烯酰胺(HPAM)与柠檬酸铝(AlCit)体系交联反应过程中Al的化学位移和Al的自旋-晶格弛豫时间的变化. 结果表明, HPAM与AlCit反应后, 与HPAM分子链上的羧基发生配位交联的Al的化学位移向低场移动, 而不参与交联反应的AlCit分子结构中Al的化学位移基本不变. HPAM/AlCit交联体系中存在三种形态的Al, 分别对应三种不同的自旋-晶格弛豫时间. 当HPAM的质量浓度≤200 mg/L时, HPAM与AlCit反应过程中交联态Al的自旋-晶格弛豫时间τ13随反应进行变小, HPAM与AlCit主要发生分子内交联反应. 当HPAM的质量浓度≥250 mg/L时, HPAM与AlCit反应过程中交联态Al的自旋-晶格弛豫时间τ13随反应进行变大, HPAM与AlCit主要发生分子间交联反应. 相似文献
80.
碘酸钾存在下极谱催化波法测定陈皮甙 总被引:2,自引:0,他引:2
基于陈皮甙在KIO3存在下产生的极谱催化波,拟定了测定陈皮甙的新方法。在 0.55 mol/L HAc-0.01mol/L NaAc(pH 4.00±0.05)-1.0×10~(-3)mol/L KIO3缓冲溶液中,陈皮甙催化波的峰电位为-1.35 V(vs,SCE),它的一阶导数峰峰电流与陈皮甙浓度在2.6 × 10~(-7)~2.6 × 10~(-6)mol/L范围内呈线性关系(r=0.9970,n=6)。本方法比现有的电化学方法灵敏度高一个数量级。可用于直接测定中草药贯众水提液中陈皮甙含量。 相似文献