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71.
Nb6.74Ta5.26S4 has been prepared by high temperature techniques. The crystal structure has been determined from single crystal X-ray diffraction data (R/Rw = 0.0588/0.0655). The compound crystallizes in the orthorhombic space group Pnma with unit cell dimensions a = 959.11 (26) pm, b = 336.37 (10) pm, and c = 3282.51 (74) pm. The orthorhombic cell contains four formula units. Its structure is similar to that of Nb-rich sulfides, rather than to that of Ta-rich sulfides. The metal coordinations are capped distorted cubic prisms and pentagonal prisms while the coordinations of sulfur are capped trigonal prisms. 相似文献
72.
Xin Sheng Li Yao Jun Zhang Qin Xin Chun Xin Ji Yan Fen Miao Li Wang 《Reaction Kinetics and Catalysis Letters》1996,57(1):177-182
Volumetric H2-uptake measurements on an Mo2N (79 m2g–1) sample reduced at 673 K have been carried out and the uptake isotherms in the temperature range of 308–623 K have been determined. Both the total and reversible hydrogen uptake increased with the uptake temperature. The irreversible hydrogen uptake increased abruptly when the uptake temperature was raised up to 423 K. The maximum of irreversible hydrogen uptake was measured at 473 K. The HIR/Mo ratio calculated from the uptakes obtained in the temperature range of 308–623 K varies in the range of 0.0010–0.0202. One possible mechanism for hydrogen adsorption is proposed to be heterolytic dissociation on Mo-N paris, in which the molybdenum atoms are in unsaturated coordination. 相似文献
73.
74.
A selective titrimetric determination of Pb after separation by a modified method of precipitation as its sulphate is proposed. Pb(II), present as the perchlorate, is precipitated by gentle boiling in 3.6M H(2)SO(4) presaturated with PbSO(4) and free from any extraneous anions. The customary time-consuming evaporation to fumes of sulphuric acid is dispensed with. The precipitate is collected, and dissolved in excess of HEDTA, the surplus of which is back-titrated with Zn(II) at pH 5.0-5.5. Use of Catechol Violet and Xylenol Orange as a mixed indicator gives a sharper end-point. The standard deviation of the proposed method for 60 mg of lead is 0.35 mg. The method has been successfully used to determine Pb in non-ferrous alloys. 相似文献
75.
76.
Kang De Yao Tao Peng Han Bao Feng Yu Ying He 《Journal of polymer science. Part A, Polymer chemistry》1994,32(7):1213-1223
The aqueous swelling kinetics of a series of crosslinked chitosan (cr-CS) with glutaraldehyde (GA) interpenetrating polyether hydrogels have been studied as functions of pH, the N-deacetylation degree of chitosan, the amount of crosslinking agent, the electrolyte composition in solution, temperature, and gel composition. Based on these results, the swelling mechanism of the hydrogels was discussed. The release profiles of chlorhexidini acetas from the semi-IPN were also investigated. © 1994 John Wiley & Sons, Inc. 相似文献
77.
Hong-Chang Yao Song Gao Li-Min Zheng Xin-Quan Xin 《Journal of solid state chemistry》2004,177(12):4557-4563
Hydrothermal reactions of copper (II) nitrate with 1-hydroxycyclohexanephosphonic acid [C6H10(OH)PO3H2] or Δ1-cyclohexenephosphonic acid [C6H9PO3H2] have resulted in three new copper phosphonates, namely, Cu(C6H10(OH)PO3)(H2O)2 (1), Cu(C6H10(OH)PO3) (2) and Cu(C6H9PO3)(H2O) (3). Compound 1 has a dinuclear structure in which two {CuO5} square pyramids are bridged by two {CPO3} tetrahedra through corner sharing. The dimers are connected through intermolecular hydrogen bonds, forming supramolecular layers. Both compounds 2 and 3 show layer structures typical for metal mono-phosphonates, in which the inorganic metal-containing layers are separated by cyclohexane or cyclohexene groups. The magnetic studies show that ferromagnetic interactions are mediated between copper centers in compound 1. In compounds 2 and 3, antiferromagnetic interactions are dominant. 相似文献
78.
茂基稀土胺化物(MeCp)2YbNPh2(THF)与异氰酸正己酯(n-HexylNCO)按11摩尔比反应, 分离出产物{(MeC5H4)2Yb[OC(NPh2)N(n-hexyl)]}2. 产物经元素分析和核磁共振表征, 并测定了其晶体结构. 配合物属三斜晶系, R-3空间群, 晶胞参数为a=2.9533(11) nm, b=2.9533(11) nm, c=1.5873(6) nm, V=11.9896(80) nm3, Z=9, Dc=1.562 mg·m-3, μ=3.536 mm-1 (Mo Kα), F(000)=5670, R=0.034, Rw=0.064. 该化合物具有二个对称氧桥的双分子结构, 并存在着由氮原子向中心金属镱分子内配位而形成的三环骨架, 中心金属镱的配位数是九, 整个分子呈中心对称. 相似文献
79.
Hong-Wen Hu Xu-Dong Wei Cun Li Hong-Zhe Sun Yi-Ming Yao Zhong-Yuan Zhou Kai-Bei Yu 《中国化学》1992,10(3):278-284
The reaction of m-chlorobenzaldoxime dehydrodimer with styrene gives two 1:1 adducts.The main product 7 is a bisnitrone. The minor product 8 has been shown by X-ray diffraction anal-ysis to possess the structure: ArCH(N=O)CH_2CH (Ph)O--N=CHAr. The two C=N bonds areall in Z configuration. The structure of the adducts from benzaldoxime dehydrodimer and styrene isalso assigned. 相似文献
80.
文中直接取硫酸样品3ml于装有约10ml水的25ml比色管中,加入碘化钾溶液2ml,用水稀至刻度。加入甲基异丁酮5ml,萃取lmin,分层后,在有机相中测定铅、镉、铜含量;在水相中测定锌含量。方法的加标回收率为98.9%~103%,精密度1.8%~4.3%,标准曲线法和标准加入法结果相近,倍比试验结果亦相吻合,方法快速简便、准确,适合于工业中的快速分析。 相似文献