Dissolution of cellulose in ethylene diamine/salt solvent systems

Investigation of the dissolution of cellulose in Ethylene Diamine (EDA)/Potassium thiocyanate (KSCN) solutions by infrared spectroscopy (FTIR) and thermal analysis (DSC) indicated that changes to the solvent during freeze thaw cycling of mixtures was consistent with increased interaction between cellulose and solvent. Thermal transitions in the system, however, occurred at temperatures outside the range used in thermal cycling to promote dissolution. Further exploration of the dissolution and mixing process indicated that mixing was the limiting step in solution formation. The dissolution of two types of cellulose with different molecular weights (Degree of Polymerization (DP)=210 and >1000) was studied using EDA/KSCN solution as the solvent. The solubility and the dissolution rate of cellulose depended on both the solvent composition and cellulose molecular weight. Cellulose could dissolve faster in the solvent with lower salt concentration but the highest cellulose concentration was obtained in the solvent with 30~35% KSCN. Rheological measurements showed that cellulose solutions exhibited viscous solution behavior at low KSCN concentration but primarily elastic behavior at high salt concentration.     

Inorganic-Organic Hybrid Materials: Synthesis and X-Ray Structure of N,N′-Dimethylimidazolium Salts [(Me2Im)2][Cd2(SCN)6] and N,N′-Dicyclohexylimidazolium [(Cy2Im)2][Cd2(SCN)6]·C3H6O

Two novel N,N′-dialkylimidazolium thiocyanate-cadmium complexes [(R₂Im)₂][Cd₂(SCN)₆] for R=Me (3), and cyclohexyl (4) have been synthesized and characterized by single-crystal X-ray diffraction. Compound 3 crystallizes in the monoclinic unit cell dimensions of 17.468(3), 7.7273(12), 10.6750(16) Å, 104.833(2)°, and space group C2 with two [(Me₂Im)₂] [Cd₂(SCN)₆] per unit cell. The two cadmium atoms in 3 are octahedrally coordinated in 4N2S and 2N4S coordination environment, and linking into one-dimensional zigzag chains. Compound 4 belongs to the monoclinic space group Cc with unit cell of dimensions 13.3049(12), 17.5550(16), 20.8012(19) Å, 101.494(2)°, and four [(Cy₂Im)₂][Cd₂(SCN)₆]·C₃H₆O per unit cell. The cadmium atoms in 4 are all 3N3S hexa-coordinated with six bridging SCN⁻ ions in an fac configuration and form infinite zigzag polymeric chains. The infinite chains in 3 form an approximate hexagonal array, making triangular channels which are occupied by N,N′-dimethylimidazolium ions, whereas the chains in 4 form layered structure, and the layers are stacked perpendicularly with respect to the orientation of the infinite anionic chains alternatively. N,N′-dicyclohexylimidazolium cations and solvent molecules fill in between layers.     

A study on the mechanism of dissolution of the cellulose/NH3/NH4SCN system. I

Ammonia/ammonium thiocyanate (NH₃/NH₄SCN) is an excellent swelling agent and solvent for cellulose, even at a high degree of polymerization. Because polymorphic conversion in cellulose has been a long-standing, perplexing, troublesome problem, we have undertaken to study that mechanism. Solid state CP/MAS ¹³C-NMR and X-ray analysis proved to be very useful analytical techniques for the task. It appears that during temperature cycling, specific cellulosic inter- and intramolecular hydrogen-bonds are broken as polymorphic conversion proceeds sequentially from the polymorph I to III, and finally at total solvation to amorphous. This proceeds correspondingly via transformation of the polymorph conformations of CH₂OH from trans-gauche, “tg,” to gauche-trans, “gt,” to gauche-gauche, “gg.” © 1994 John Wiley & Sons, Inc.     

Synthesis and Crystal Structure of a Three-dimensional Cd(Ⅱ) Coordination Polymer [Cd(μ1,3-SCN)(μ3-pco)]n (pco = Pyrazine-2-carboxylate 4-oxide Anion)

The three-dimensional complex [Cd(μ1,3-SCN)(μ3-pco)]n has been synthesized with μ1,3-SCN- and pco as mixed bridged ligands. The crystal belongs to monoclinic, space group P21/n with a = 10.3777(16), b = 6.2592(9), c = 13.150(2) (A), β= 97.317(2)°, V=847.2(2) (A)3, Z= 4,C6H3CdN3O3S, Mr = 309.575, Dc = 2.427 g/cm3, F(000) = 592 and μ = 2.804 mm-1. The structure was refined to R = 0.0255 and wR = 0.0550 for 1712 observed reflections (I＞2σ(I)). In the crystal the Cd(Ⅱ) ions are coordinated by μ1,3-SCN- and μ3-pco bridge ligands to form a three-dimensional structure.     

Simultaneous determination of halide and thiocyanate ions by potentiometric precipitation titration and multivariate calibration

Halide and thiocyanate ions can be determined by a precipitation titration with silver nitrate as the titrant, and the end-point can be evaluated by a potentiometric method, in which generally a silver indicator electrode is used as the indicator electrode and a double-junction Ag–AgCl electrode as the reference electrode. However, when mixtures of halide and thiocyanate are titrated, it is difficult to determine these components individually for there are overlapping steps in the potentiometric titration curves, especially in the case that there are obvious differences between concentrations of the components. In this paper, the linear equation for the potentiometric precipitation titration of a mixture of halide and thiocyanate ions was developed and it was then used for determining the components in the mixtures simultaneously with the aid of multivariate calibration methods. By application of this model, 27 synthetic mixtures with three- and four-component combinations of chloride, bromide, iodide and thiocyanate with low concentration levels from 1.8×10⁻⁴ to 6.2×10⁻⁴ mol l⁻¹ were analyzed and acceptable results were obtained.     

某些助剂对明胶的凝胶强度的影响的研究

众所周知,物理力学性能是照相明胶的一种很重要的属性。在各种彩色及黑白胶片都面向高温快速加工发展的今天,这种属性就显得更为重要。提高胶片的物理力学性能,一方面要从提高明胶本身的胶冻强度着手,例如减少明胶中溶胶组份(分子量小、冷水中溶解度高),提高明胶中的α和β组份的相对含量,减少分子量过大的组份等等。     

不同吸收剂影响大气中二氧化硫测定的探讨

对盐酸玫瑰苯胺光度法测定大气中二氧化硫时所用的3种吸收剂（四氯汞钾、甲醛及三羟乙基胺）的吸收效果及方法的准确性、灵敏度等条件作了比较试验。结果表明,与另两种吸收剂相比,采用甲醛作吸收剂,吸收效果最好,测定的灵敏度,精密度和准确度也都占优,其检出限在三者中最低。用甲醛替代四氯汞钾,除了上述优点外尚可避免使用较大量的汞盐,有利于环境保护。     

硝酸钠-硫氰酸铵-溴化十六烷基三甲基铵体系浮选铜

浮选分离;硝酸钠-硫氰酸铵-溴化十六烷基三甲基铵体系浮选铜     

Simultaneous Determination of Copper,Lead and Cadmium by Oscillopolarography

Copper, Lead and Cadmium determination is important for preventive medicine in environmental for food,water,blood,urine,air and so on,Which play a very important role in health,Including,human's toxic harmful symptoms:tenderness, pain,dizziness, fever, fatigue, loss of appetive, liver,neurosis and brain disease.There have been a lot of methods dealing with the measurements of Copper, Lead and Cadmium in Health Laboratory Technology,among wich atomic absorption spectrometry is considered to be the best one,but the proposed oscillopolarography method can be satisfactorily applied to the simultaneous' determination of Cu(Ⅱ),Pb(Ⅱ) and Cd(Ⅱ) in water sample with out any pre-treatment.     

Polyfluorinated hydrazones in organic synthesis

The oxidation of 1,1,1,5,5,5-hexafluoro-4-trifluoromethylpentane-2,3-dione bishydrazone (1) with SeO₂, HgO, and Hg(OAc)₂ was studied. The use of selenium dioxide leads to 1,1,1,5,5,5-hexafluoro-4-trifluoromethylpent-2-ene (2) and C₁₂H₄F₁₈Se₂. 1,1,1,5,5,5-Hexafluoro-4-trifluoromethylpent-2-yne (4) and C₆H₂F₉HgC₆H₂F₉ were obtained by the oxidation of bishydrazone1 with mercuric oxide. The oxidation of compound1 with mercuric acetate in diglyme affords 1,1,1,5,5,5-hexafluoro-4-trifluoromethylpenta-2,3-diene (6). Alkyne4 is isomerized to allene6 at 130 °C. For Part 3, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 677–680, April, 1998.