过氧化钠的实验室制备

在碱金属元素一章的教学中,金属钠的化学性质中安排了钠在空气中的燃烧实验,目的是观察钠的颜色反应和燃烧产物过氧化钠的颜色和状态。教材中是在燃烧匙内进行该实验的,由于燃烧匙凹陷、且暴露在空气中,得到的通常是灰色糊状物质,学生很难观察到过氧化钠淡黄色颗粒状现象,更无法进一步检验产物的化学性质,为此改用下列方法进行该实验效果较好。     

过氧化钠是呈白色还是淡黄色

高中化学教材认为过氧化钠是淡黄色固体,这是一种旧观点。笔者认为过氧化钠是白色固体。钠在空气中燃烧的产物是白色的Na2O、Na2O2和淡黄色的NaO2组成的混合物;钠在空气中燃烧的产物颜色主要是由NaO2的存在引起的,过氧化钠并不是淡黄色物质。所以,应该恢复过氧化钠是白色固体的真相,不能再以讹传讹了。     

钠在空气中燃烧生成过氧化钠的热力学讨论

从热力学基本原理出发,探讨钠在空气中燃烧生成过氧化钠的原因,得出过氧化钠是钠在空气中燃烧反应的最稳定产物的结论。     

介绍一种燃烧产物的收集验证装置

物质在空气中的燃烧 ,是中学化学中常见的实验。观察燃烧现象 ,验证燃烧产物是学习掌握可燃性物质性质、组成必然涉及的过程。通常的实验中 ,由于燃烧产物难于富集、火焰颜色及烟等因素的影响 ,使产物的观察难以进行 ,同时由于燃烧产物中还包括燃烧不完全的气体 ,这些气体的扩散 ,很容易造成空气污染。笔者设计了一套气体产物收集及验证的简易装置 ,利用负压引导气体流向 ,使气体产物易于富集 ,便于观察 ,很好地防止了空气的污染。而且操作简便易行 ,效果较好。以H2 S燃烧产物的观察和分析为例说明其原理。仪器 :漏斗、试管、广口瓶、烧杯…     

钠的两个性质实验的创新设计

钠是典型的金属元素,在中学阶段,研究钠的化学性质主要包括2个方面:一是钠与非金属(主要是氧气)的反应,即钠在空气中燃烧;二是钠与水的反应.钠在空气中燃烧的实验多数教材采用的方法是在石棉网上加热,这种方法不仅实验成功率低,而且会损坏石棉网,造成不必要的浪费;人教版普通高中课程标准实验教科书<化学1(必修)>采用的方法是钠在坩埚中燃烧[1],用这种方法实验,学生不容易观察到实验现象,演示效果较差.钠和水的反应,不容易收集到反应时生成的气体,气体产物的检验成为实验的难点,3套新课程标准高中化学教材中都略去了该项实验操作.为了克服以上困难,我们对上述2个实验进行了改进.     

煤中钠在燃料初期行为的研究

煤中钠是影响增压流化床（PFBC）和整体煤气化（IGCC）发展的一个重要因素。本文对煤中钠分别在800℃和900℃以及富氧和贫氧两种气氛下燃烧初期的释放规律进行了研究。结果表明,煤中钠在燃烧初期变化不大,钠的释放将主要发生在煤燃烧的后期。不同形态钠在燃烧初期的变化规律不同。随燃烧时间的增加水溶钠线性减小,盐酸溶钠线性增加。醋酸铵溶钠在燃烧初期总体表现为增加,不可溶钠则总体减少。研究显示,不同形态钠在燃烧初期存在转化,并主要表现咪水溶钠向盐酸溶钠的转化。温度和气氛对钠释放的影响主要取决于煤种。     

一种含氢燃料火焰降温观色筒的设计和应用*

针对酒精灯火焰呈黄色的解释争议进行研究,以降低环境温度和减少氧气浓度为方向,设计了可观察环境温度变化对含氢燃料火焰颜色影响的仪器。对乙醇、丁烷、蜡烛等燃烧火焰进行降温测试,发现含氢燃料正常燃烧火焰颜色一般为黄色、降低环境温度后变为极淡的蓝色(光亮条件下)的规律,证明了燃烧过程中水分子处于激发态是导致火焰颜色由蓝色变为黄色的重要原因,钠元素的焰色反应不是酒精灯火焰呈黄色的唯一原因。对丁烷喷枪火焰颜色的降温测试,意外观察到4种疑似氢原子光谱的可见光谱线,为今后寻找该谱线提供了可借鉴的方向。研究过程可作为基于真实情境的研究素材,通过问题的发现、仪器的改进和规律的总结,提高学生运用化学知识解决真实问题的能力,培养学生的核心素养。     

"乙醇与钠的反应"实验改进

1问题的提出笔者在课堂演示人教版教材《化学2(必修)》第三章第三节实验3-2乙醇与钠的反应时,学生提出2个问题:(1)乙醇为易挥发液体,且钠与乙醇反应放热,故放出的氢气中含有一定浓度的乙醇蒸气。教材中通过气体燃烧产物的检验,判断钠与乙醇反应放出     

火焰原子吸收法偏转与不偏转燃烧头测定高浓度钠的不确定度分析

对使用火焰原子吸收法测定钠时,采用偏转与不偏转燃烧头的方式对高浓度钠的测定结果进行不确定度分析。结果表明,对钠含量较高的食品,采用将燃烧头偏转一定的角度,测定结果的准确度更高,这是由于避免了在不偏转燃烧头的情况下,对样品进行高倍稀释作用而引入的不确定度。     

如何使钠在空气中燃烧的主要产物为过氧化钠

钠在空气中燃烧是一个既简单又复杂的化学反应。按照现有教材提供的实验方法以及其他有关该实验的改进措施,实验所得到的实验现象并不能足够支持教材教学所希望的结论。钠只有在足够的温度下与足量氧气充分反应主要产物才能是淡黄色的Na2O2。     

Osmotic and activity coefficients of aqueous bile salt solutions at 25, 37, and 45°C

Osmotic coefficients measured by vapor pressure osmometry are reported for aqueous bile salt solutions at 25, 37, and 45°C. Solute activities decrease rapidly with increasing concentration due to premicellar association and micelle formation. In all cases, activities of the dihydroxy bile salts are lower than those of the trihydroxy bile salts. Osmotic coefficients and activity coefficients increase with increasing temperature. It is suggested that hydrophobic forces contribute substantially to the stability of primary bile salt aggregates and micelles.     

胆酸盐在酸性介质中自聚集作用的共振瑞利散射光谱及其分析应用研究

研究了牛磺胆酸钠、甘牛胆酸钠、胆酸钠和脱氧胆酸钠等四种胆酸盐在酸性介质中的聚集作用对共振瑞利散射光谱的影响及其分析应用. 结果表明: 在一定浓度的HCl, H₂SO₄或HNO₃溶液中, 四种胆酸盐均能自聚集形成粒径增大的聚集体. 该聚集体能导致溶液RRS显著增强, 并产生了新的RRS光谱. 不同胆酸盐在同种介质中的反应产物具有相似的光谱特征, 最大RRS波长分别位于349 (HNO₃介质), 359 (H₂SO₄介质)和369 nm (HCl介质). 在一定范围内, 胆酸盐的浓度与散射强度(ΔI_RRS)成正比. 对于不同的体系其检出限在12.0～21.8 ng/mL之间. 方法灵敏度高, 选择性较好, 而且十分简便快速. 可用于市售蛇胆川贝液和血清样品中胆酸盐的测定.     

Facile Stabilization of the Sodium Metal Anode with Additives: Unexpected Key Role of Sodium Polysulfide and Adverse Effect of Sodium Nitrate

Sodium metal is an attractive anode for next‐generation energy storage systems owing to its high specific capacity, low cost, and high abundance. Nevertheless, uncontrolled Na dendrite growth caused by the formation of unstable solid electrolyte interphase (SEI) leads to poor cycling performance and severe safety concerns. Sodium polysulfide (Na₂S₆) alone is revealed to serve as a positive additive or pre‐passivation agent in ether electrolyte to improve the long‐term stability and reversibility of the Na anode, while Na₂S₆‐NaNO₃ as co‐additive has an adverse effect, contrary to the prior findings in the lithium anode system. A superior cycling behavior of Na anode is first demonstrated at a current density up to 10 mA cm^?2 and a capacity up to 5 mAh cm^?2 over 100 cycles. As a proof of concept, a high‐capacity Na‐S battery was prepared by pre‐passivating the Na anode with Na₂S₆. This study gives insights into understanding the differences between Li and Na systems.     

30%亚硫酸氢钠溶液样品中Cl~-和SO_4~(2-)的同时测定

建立了采用离子色谱测定 30%亚硫酸氢钠溶液样品中的氯化钠和硫酸钠含量的新方法。采用IonPacAS14分析柱,选择三乙醇胺为亚硫酸氢钠的稳定剂,以丙酮为有机改进剂,淋洗液组成为 1 5mol/LNa2CO3 3 5mol/LNaHCO3 10% (体积分数) (CH3 )2CO,流速为 1 0mL/min,抑制电导检测。实验结果表明,氯离子、硫酸根离子分别在 0.05~1.5mg/L,0.20~15mg/L时,其峰面积与质量浓度呈线性关系,相关系数均大于 0.999,检出限分别为0 01mg/L和 0 03mg/L。该法用于实际样品分析,操作便捷,结果可靠。     

Mechanism of glass ampoule breakage prevention during the freeze-drying process of sodium thiopental lyophilization products on addition of sodium chloride

Glass ampoule breakage during the freeze-drying process was prevented by the addition of sodium chloride to the formulation of lyophilization products of sodium thiopental. In order to clarify the ampoule breakage prevention mechanism, the physicochemical behavior of the freeze-drying process was monitored by simultaneous XRD-DSC measurements and thermal mechanical analysis (TMA). During the freezing process of formulated solution, the smaller heat of fusion of crystallized ice with the addition of sodium chloride was observed in comparison to that without sodium chloride. Although a greater amorphous portion remained, a higher crystal habit of hexagonal ice was reproducibly observed in the XRD patterns with the addition of sodium chloride during the freezing process. In the measurement of TMA, the scattering of the thermal expansion rate of formulated solution was significantly reduced by the addition of sodium chloride. These observations indicated that the addition of sodium chloride minimized the scattering of the thermal expansion rate and might be a cause for the inhibition of glass ampoule breakage during the freeze-drying process.     

Studies on the Effects of Salt and Surfactant in Wet Phase Separation of Polysulfone

This study investigates the effect of additives in the nonsolvent water in terms of cloud point during the phase inversion of Polysulfone (PS) in dimethyl formamide (DMF). The exponential pattern is observed with PS concentration (0.2 to 0.6% (w/w)). It needs a low amount of water to get the cloud point at low temperature. The cloud point varied with the nature of water matrix and depended on the amount of salt, as well as the PS amount. The presence of salts (sodium chloride and sodium sulfate) lowers the cloud point of the solution. The network distribution of the particles at the cloud point is disturbed in the presence of salt. The requirement is more for Sodium lauryl sulfate (SLS) added water to reach the cloud point in the low range of PS solution up to 0.3% PS (w/w). The morphological and distribution pattern of PS particles are very different compared to PS particles produced from pure water. XRD study of PS particles produced from the mixed water system reflects relatively more amorphous character with respect to PS particles from pure water. The presence of both surfactant and salts in water systems also influences the cloud point in synergistic manner.     

Crystal Structure of a New Form of Sodium Octoborate β-Na2B8O13

Single crystals of a new form of sodium octoborate, β-Na₂B₈O₁₃, were obtained fortuitously from a complex Na₂O-B₂O₃-P₂O₅ mixture, and studied. The compound is monoclinic, space group P2₁/c; the unit cell parameters are a=11.731(4) Å, b=7.880(3) Å, c=10.410(4) Å, β=99.883(3)°; Z=4. The crystal structure was solved from 1653 reflections until R₁=0.0444; it consists of two infinite, independent, and interleaved boron-oxygen networks containing a complex borate anion (B₈O₁₃)²⁻ formed by six BO₃ triangles (Δ) and two BO₄ tetrahedra (T), which can be viewed as a B₅O₁₀ group linked to a B₃O₇ group; this leads to a Fundamental Building Block (FBB) with the shorthand notation: 8: ∞³ [(5:4Δ+T)+(3:2Δ+T)]. This FBB is identical to that described in other octoborates such as α-Na₂B₈O₁₃ and Ag₂B₈O₁₃. However, some subtle differences exist in the interlinking of the octoborate anions found in these three compounds, which explains their different structure and unit cell parameters.     

自动电位滴定法测定工业碳酸钠中氯化钠含量

采用自动电位滴定法,用硝酸银标准溶液作为滴定剂,测定工业碳酸钠中氯化钠含量。方法检出限为0.13mg/L,不同含量氯化钠样品加标回收率为99.7%~100.3%,相对标准偏差(n=5)为0.17%~2.0%,方法简单、快速,精密度和准确度高,适合大批量快速分析样品。     

毛细管电泳法测定注射用头孢哌酮钠他唑巴坦钠中目标成分

建立了毛细管区带电泳法同时测定注射用头孢哌酮钠他唑巴坦钠中目标成分含量的方法。采用石英毛细管(75 cm×75 μm i.d.,有效长度63 cm),以40 mmol/L硼砂溶液为背景电解质(BGE),以氢氯噻嗪为内标,分离电压12.0 kV,检测波长220 nm,重力进样10 s(高度10 cm)。实验结果表明,头孢哌酮钠与他唑巴坦钠分别在0.25～3.96 g/L和0.062～0.99 g/L范围内呈良好的线性关系,相关系数(r)分别为0.9995和0.9996。精密度和重复性均良好,相对峰面积的相对标准偏差(RSD)均小于3%,制剂在208 min内稳定,回收试验结果符合方法学要求。该方法简单、准确、耗费少、污染小,可用于注射用粉针剂头孢哌酮钠他唑巴坦钠中头孢哌酮钠和他唑巴坦钠的定量分析。     

复合硝基酚钠盐的胶束电动力学毛细管色谱分析

本文在自行研制的高效毛细管电泳仪上建立了复合硝基酚钠盐的胶束电动力学毛细管色谱分析方法。用５０ｍｍｏｌ／Ｌ十二烷基硫酸钠、ｐＨ＝９．０的硼酸盐缓冲溶液，在２０ｋＶ电压下分离了５－硝基愈创木酚钠、对硝基酚钠、邻硝基酚钠，此法用于Ａｔｏｎｉｋ型植物生长调节剂的定量分析，相对偏差小于２％，回收率在１０１％￣１０５％之间。