Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Formation of CaF and AlF in the arc plasma and spectrochemical determination of Ca and Al

Summary The influence of chemical reactions in d.c. arc plasma on the atomic emission determination of traces has been investigated. The effect of added NH₄F on the intensity of spectral lines of Ca and Al was examined. A decrease of the spectral line intensities of Ca and Al in the presence of NH₄F occurred, if the sample had not been mixed in the electrode with NH₄F. The AlF band spectrum, transition A ¹ X ¹ , was observed in absorption of the arc radiation. Further, the axial intensity distribution of Ca, Al, Ga and Ag spectral lines and of the head of the green system of CaF band, has been measured. The depressive effect of fluorine on spectral line intensities of Ca, Al, Ga and Ag has to be connected with the processes in plasma. It is suggested that the formation of fluoride radicals could take part in this effect.

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Bildung von CaF und AlF im Bogenplasma und spektrochemische Bestimmung von Ca und Al

Zusammenfassung Der Einfluß von chemischen Reaktionen im Lichtbogenplasma auf die spektrochemische Spurenanalyse wurde erörtert. Die Wirkung einer Zugabe von Ammoniumfluorid auf die Intensitäten der Spektrallinien des Calciums und Aluminiums wurde untersucht. Wenn die Probe nicht in der Elektrode mit NH₄F gemischt war, wurde eine Intensitätserniedrigung von Ca- und Al-Spektrallinien in Anwesenheit von NH₄F beobachtet. Das AlF-Bandenspektrum, Übergang A ¹ X ¹ , wurde in Absorption der Bogenstrahlung beobachtet. Die Axialverteilung der Linienintensitäten von Ca, Al, Ga und Ag wie auch der Intensität der Kante des grünen Systems der CaF-Banden wurde untersucht. Die depressive Wirkung des Fluors auf die Linienintensitäten von Ca, Al, Ga und Ag sollte mit den Vorgängen im Plasma in Zusammenhang gebracht werden. Es kann vorausgesetzt werden, daß die Bildung der Fluoridradikale bei diesem Effekt eine Rolle spielt.

     

A mild and practical method for the regioselective synthesis of N-acylated 3,4-dihydropyrimidin-2-ones. New acyl transfer reagents

The treatment of 3,4-dihydropyrimidin-2-ones with n-BuLi at −78 °C, followed by quenching with various electrophiles furnished N3-substituted derivatives, regioselectively. Further, N1,N3-diacyl derivatives were found to transfer N1-acyl groups to nucleophilic sites.     

Small angle neutron scattering studies on nonaqueous dispersions of calcium carbonate Part 2. Determination of the form factor for concentric spheres

Colloidal dispersions of calcium carbonate, stabilised primarily by a surface active agent, in both toluene and dodecane have been examined by small angle neutron scattering. A model has been developed to simulate the scattering behaviour of the particles and is based on the idea of a concentric sphere with a homogeneous layer of adsorbed material surrounding a core particle. Computations based on the model show a wide variation of scattering behaviour with variation of the coherent scattering length of the dispersion medium. These predictions were confirmed by experiment. A method is described for analysis of the experimental data which leads to a determination of the thickness of the adsorbed layer, the radius of the core particle and the standard deviation of core particle radius.     

Zur Kenntnis des Calciumbromats und - iodats,Kristallstruktur, röntgenographische,IR- und Raman-spektroskopische und thermoanalytische Untersuchungen

On Calcium Bromated and Iodates – Crystal Structure, X-Ray, IR and Raman Spectroscopical and Thermoanalytical Investigations The phase relationships (and both decomposition and disproportionation)of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-Ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO₃)₂ · 6 H₂O oF 216, the isotypic Ca(BrO₃)₂ · H₂O and Ca(IO₃)₂ · H₂O mP 48, Ca(IO₃)₂ I (Lautarit) mP 36, Ca(IO₃)₂ II and Ca(BrO₃)₂. The Crystal structure of Ca(IO₃)₂ · H₂O (brüggenite) (space group P2₁/c, Z = 4) has been determined by single crystal X-ray diffraction (MoKα). The final R value for 3888 reflections with I_o > 3σ₁ is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO₃–ions as well as the strengths of H-bonds present in the respective hydrates.     

In situ neutron powder diffraction investigation of the hydration of tricalcium aluminate in the presence of gypsum

The hydration of a 1:3 molar ratio of tricalcium aluminate, Ca₃Al₂O₆, to gypsum, CaSO₄·2D₂O, was investigated at temperatures of 25, 50, and 80 °C using time-of-flight powder neutron diffraction combined with multiphase Rietveld structural refinement. It was shown that ettringite, Ca₆[Al(OD)₆]₂(SO₄)₃·∼26D₂O, was the first and only hydration product of the system, in contrast to a prior investigation which suggested the occurrence of a precursor phase prior to the formation of ettringite. Kinetics data showed that the hydration reaction is very sensitive to temperature: hydration at 25 °C was characterized by a single kinetic regime while hydration at higher temperatures consisted of two distinct kinetic regimes. The presence of two kinetic regimes was attributed to a change in either the dimensionality of the growth process or a change in the rate controlling mechanism in the hydration reaction.     

氯化钙/水-醇溶液稀释热

电解质溶液稀释热是溶液的重要热性质之一．由它可计算不同浓度下电解质的溶解热、表现相对摩尔焓、溶液中反应热和化合物生成热等．在电解质溶液理论研究中，稀释热也是重要的基础数据．由稀释热可推算溶液中组分的活度系数、渗透系数、相对偏摩尔焓及表观摩尔热容等[1-3]．在化工生产中，稀释热是化工过程能量计算不可缺少的数据．电解质水溶液稀释热已有不少研究[2，4]．但电解质混合溶剂体系稀释热报导甚少．随着加盐精馏技术、海水淡化技术等研究的进展，急需这方面数据．本文作者已报告了CaCl2／C2H5OH－H2O体系[5]和CaCl2／n－C…     

深圳市1408例儿童发中钙,铁,镁含量调查与分析

用火焰原子吸收法检测了深圳市１４０８例１３岁以下儿童发中钙，铁，镁的元素含量，并探讨了元素含量与年龄，性别的关系，结果显示，性别差异有显著意义，钙，镁含量随年龄增长有相似变化。     

以1,1,1-三(N-甲基-N_苯基氨基羰甲氧甲基)丙烷为载体的钙离子选择电极

报道了以三脚架化合物1,1,1_三 (N_甲基_N_苯基氨基羰甲氧甲基 )丙烷 (TMPP)为载体的钙离子选择电极的研制;探讨了增塑剂、载体浓度、pH等因素对电极性能的影响 ;结果表明电极对钙离子有较好的近能斯特响应 ,相应的斜率为27.6 mV/pcCa2+ ,线性响应范围为5×10-5 ～5×10-2 mol/L,检出限为2.3×10-5mol/L ;电极在pH4～13范围内具有强的抗干扰能力 ,并具有很好的重复性和稳定性 ;该电极作为钙离子选择电极 ,用于乳酸钙口服液中钙含量的测定 ,取得了满意的结果     

健儿三宝冲剂治疗儿童钙,铁,锌缺乏症164例临床观察

用健儿三宝冲剂治疗的儿童钙，铁，锌缺乏症，经临床观察，取得了较好的疗效。