离子选择电极电位滴定法连续测定瓷土中的钙镁含量

本工作制定了用离子选择电极电位滴定法连续测定瓷土中钙镁含量的分析方法。以硫化银电极为指示电极,EGTA—Ag 为液体指示剂,不须另取试液可用 EGTA和 CyDTA 连续滴定钙和镁。在 pH=9.5—10.0,在25ml 的一份试液中加入5毫克分子酒石酸钾钠,可隐蔽 Fe~(3 )、Al~(3 )、Ti~(4 )等干扰离子。EGTA、CyDTA 的浓度分别是1×10~(-3)M、5×10~(-3)M。实验发现:CyDTA 同钙(镁)的反应速度快于 EDTA同钙(镁)的反应速度,且在 CyDTA 滴定曲线上的电位突跃范围比在 EDTA 滴定曲线上的电位突跃范围宽。当钙(镁)氧化物的含量由0.1—3%时,可以测定得到准确的结果。     

电位滴定法测定酸性镀锌溶液中氯化锌浓度

通过采用EDTA为滴定剂,钙电极为指示电极,双盐桥甘汞电极为参比电极,实现了酸性镀锌溶液中氯化锌含量的自动电位滴定.向待测液中加入Ca-EDTA(乙二胺四乙酸二钠钙)作为置换剂,增大了滴定终点时的电位突跃.实验考察了电极的种类、滴定剂预加体积、滴定剂的最大增量和最小增量、pH缓冲溶液和Ca-EDTA的加入量等对测定结果...     

利用氟电极测定玻璃纤维中的氟含量

介绍了利用电极电位法测定玻璃纤维中氟含量的原理、试剂和方法。从测定数据的平行性和准确度等方面和标准样品给定值进行了对比,证明此方法完全可以应用于玻璃纤维的氟含量测定中。电极电位法和GB/T 1549-94《钠钙硅铝硼玻璃化学分析方法》中采用的比色法相比,分析步骤少、操作简单、干扰因素少、且容易克服。     

pM电极电位滴定法测定硅酸盐试样中的钙镁

提出了以汞膜电极作为电位滴定法连续测定硅酸盐样品中钙和镁的指示电极，以ＥＤＴＡ为滴定剂，在ｐＨ≥１２时滴定钙，ｐＨ＝１０时滴定镁，终点电位有明显的突跃，对溶液ｐＨ值的影响等方面作了详细的研究，所述条件下的滴定具有较好的选择性，方法简单、快速、准确。     

电位滴定法测定苯甲酸钠含量

研究以pH玻璃电极为指示电极，甘汞电极为参比电极，电位滴定法测定苯甲酸钠含量，滴定终点由电位突跃来判断。此法简便、快速、准确，相对标准偏差为0．29％，相对误差为0．85％，测定结果与，药典法基本一致。     

国内化肥文摘

电位法测磷铵、磷酸和磷矿中的铝含量——成都科技大学,骆美芹等,《离子选择电极通讯》,1984,2,87～91 氟离子选择电极作指示电极,甘汞电极作参比电极,标准NaF溶液作滴定剂,测定磷铵、磷酸和磷矿中的铝含量。用氟电极作指示电极测定磷矿等试样中的铝含量目的在于简化磷肥厂用E、D、T、A的络合滴定法。测定了磷铵、磷酸和磷矿中的三氧化二铝含量得到了较为满意的结果。本法测定铝时,钙和硅不干扰,用     

电位滴定法测定电泳漆槽液中锌离子含量

取一定量的电泳漆槽液，用蒸馏水稀释后，加入醋酸铵缓冲溶液，使溶液ｐＨ＝６．５～６．８。以铜离子选择电极为指示电极，饱和甘汞电极为参比电极，用铜试剂标准溶液进行电位滴定。用二级微商法计算滴定终点，而间接求出电泳漆槽液中Ｚｎ＾２＋的含量。以铅离子选择电极为指示电极，用硝酸铅标准溶液进行电位滴定，用类似的方法即可测定电泳漆槽液中ＰＯ＾３－４的含量。     

自动电位滴定法测定米糠中维生素B1含量的方法研究

研究了以银电极为指示电极,饱和甘汞电极为参比电极,用自动电位滴定法测定维生素B1含量。探讨了该分析方法的工作电极的选择、滴定剂浓度等实验条件。在最佳实验条件下,对维生素B1含量进行测定,并与紫外分光光度法加以比较。实验均用AgNO3标准溶液滴定,通过电位突跃来判断滴定终点。该方法的标准偏差约为4.51×10-4,相对标准偏差为0.78%,加标回收率为99.2%~100.7%。     

酸性光亮镀铜溶液中Cl-测定

以往采用目视比浊法和沉淀滴定法测定酸性光亮镀铜溶液中Cl^-含量,测定结果不够精确,或滴定终点不明显使测定误差较大采用电位分析方法在弱硝酸酸性介质中,Cl^-与Ag^ 反应生成AsCl沉淀,以银电极为指示电极,双盐桥型饱和甘汞电极为参比电极,用AgNO3标准溶液进行电位滴定,通过被测试样电位滴定曲线突跃确定终点,可以准确测定酸性光亮镀铜溶液中Cl^-含量。该方法新颖,操作简便,测定结果准确。     

氟离子选择电极-标准加入法测定豆腐中的氟

研究采用离子选择电极-标准加入法测定豆腐中的氟含量.氟离子选择电极和饱和甘汞电极与待测含氟溶液构成原电池,通过测定加入标准溶液前后的电位值计算试液中氟的浓度.所测豆腐样品的氟含量为1.135 mg/kg,测定平均偏差为0.08 mg/kg,平均相对偏差为7.0%.     

Conductivities of calcium chloride and calcium chloride-sodium chloride solutions saturated in calcium carbide and unsaturated in calcium oxide

The specific conductivity variation of the named solutions vs temperature in the range 750–950°C and vs the sodium chloride molar fractions have been measured. The specific conductivity increases sharply with increasing sodium chloride M fraction and reaches a maximum when the M fraction ratio of sodium chloride to calcium carbide is nearly two. This experimental result has been interpreted by assuming interactions between calcium carbide and sodium chloride, and constitutes a verification of a previous thermodynamic result obtained by the same authors.     

Hydrates of calcium ferrites and calcium aluminoferrites

The series of substances C_xF, where x = 1, 2, 3, 4 and C₂A_yF_1?y, where $\text{y}\text{=}\text{1}\text{3}\text{,}\text{1}\text{2}\text{,}\text{2}\text{3}$, have been studied by X-ray diffraction, scanning electron microscopy and Mossbauer spectroscopy, after hydration at temperatures from 4° to 180°C. A new phase, probably C₄FH₁₉, was formed at 4°C. C₃FH₆ forms in the CaOFe₂O₃H₂O system, but it is metastable and decomposes to form calcium hydroxide and hydrous ferric oxide or, at higher temperatures, hematite. The hydration of C₂A_yF_1?y at 4°C produces hexagonal tetracalcium aluminoferrite hydrates and hydrous ferric oxide, which convert at 21°C and above to the cubic C₃(A,F)H₆. The substitution of iron for aluminium in the lattice destabilizes this compound, which decomposes to form calcium hydroxide, hematite and C₃AH₆.     

Inorganic cements for biomedical application: calcium phosphate,calcium sulphate and calcium silicate

Inorganic cements have found utility in tissue replacement since the late nineteenth century, one of the first examples being calcium sulphates in the augmentation of bone defects. In the intervening period of time countless formulations of calcium phosphate, sulphate and silicate cement have been researched and as a result, many are now commercially available for a variety of biomedical applications. This review summarises the applications, formulations, advantages and drawbacks of such inorganic cements, suggesting future work that will drive progress in this area into the future of biomaterials research.     

Kinetics of calcium sulfoaluminate formation from tricalcium aluminate,calcium sulfate and calcium oxide

The formation kinetics of tricalcium aluminate (C₃A) and calcium sulfate yielding calcium sulfoaluminate (C₄A₃$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C₃A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca₃Al₂O₆ + CaSO₄ → Ca₄Al₆O₁₂(SO₄) + 6CaO was the primary reaction < 1350 °C with and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca₄Al₆O₁₂(SO₄) + 10CaO → 6Ca₃Al₂O₆ + 2SO₂ ↑ + O₂ ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C₄A₃$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C₄A₃$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca^2 + and SO₄^2 − were the diffusive species in both the formation and decomposition reactions.     

由氯化钙制备纳米碳酸钙研究

随着国民经济的发展,对纳米碳酸钙的需求量越来越大.基于化工生产中大量副产氯化钙,以氯化钙和碳酸铵为原料,对制备纳米碳酸钙进行了研究.实验研究了添加剂、反应温度和反应物浓度等工艺条件对产物粒径的影响,并采用XRD和TEM对产物进行了初步分析.实验结果表明:不同的添加剂对产物粒径以及形貌具有一定的影响,当氯化钙和碳酸铵配料比为1.0:1.0 mol/mol、反应温度为15℃和氯化钙浓度为0.3 mol/L时,以有机醇A和磷酸系化合物G为添加剂制备的产物为方解石型球状碳酸钙,粒径在50 nm左右.     

电石渣制备纳米碳酸钙的研究

电石渣与氯化铵、水按一定的比例混合，过滤后得到澄清的浸取液，再利用液-液连续碳化法制备纳米碳酸钙。实验结果表明，该工艺所制备碳酸钙的晶型为立方体、平均粒径40～50nm。此种规格的碳酸钙在涂料、塑料行业有广泛的应用前景。     

Oxidative coupling of methane over calcium chloride-promoted calcium chlorophosphate

CaCl₂-promoted calcium chlorophosphate catalysts exhibited high catalytic performance for oxidative coupling of methane (OCM), while unpromoted calcium chlorapatite and calcium chlorophosphate exhibited poor catalytic performance. The presence of CaCl₂ also yielded high ethene selectivity. Partial substitution of the calcium with transition metals, such as zinc, lead and nickel further enhanced the catalytic performance at 973 K; the optimum extent of substitution was about 4%. At 1023 K, however, the effect of substitution appeared to be little. Too excessive substitution gave rise to a decrease of the activity. At 1023 K, the highest C₂ yield of around 22% was obtained with the C₂ selectivity of 56–59%. The C₂H₄ selectivity was also high, around 50%. Production of a significant amount of H₂ was observed over the CaCl₂-promoted calcium chlorophosphate catalysts. We propose that the major pathways for the production of H₂ are the steam reforming and partial oxidation of ethane and ethene which accompany simultaneous production of CO.     

利用副产品碳酸钙分解制石灰的工程化分析

文章论述了利用碳酸钙滤饼分解制石灰,目的是解决磷石膏综合利用的二次污染问题,只有先解决了碳酸钙产品的出路才能确保硫酸铵装置的顺利实施。根据滤饼的特性,从生产原理和技术方案比选,认为选用回转窑煅烧分解制石灰是可行的,同时也阐明了随着杂质的带入对煅烧分解工程化技术和最终产品质量可能会产生一定的影响,需采用切实有效的对策措施。     

Colorful calcium sensors

(R)evolution of protein-based calcium sensors: Expanding the toolbox of genetically encoded calcium sensors with new colors and traits is important for understanding calcium signaling and its relation to other intracellular pathways. Campbell and co-workers have used a new directed-evolution strategy to develop a rich palette of new sensors, including the first red-shifted, genetically encoded calcium sensor.