粗盐提纯方法改进探究

采用控制变量法结合粉末X射线衍射表征技术探究了粗盐提纯实验中影响沉淀形态、结晶度以及实验时间和产品产率的因素，实验结果表明：第2次过滤实验的最优条件是机械搅拌速度为1 r/s，粗盐用量为8 g，煮沸时间为12 min。该条件下沉淀全部以晶体形式析出，产品产率高达76.25%。     

以粗盐为原料提纯氯化钠的问题探讨

为培养学生的创新性思维和实验探究能力,师生共同探讨“以粗盐为原料提纯氯化钠”实验的几个问题。分离和提纯物质都是除掉杂质吗?煅炒粗盐时,为什么会发生轻微的爆炸现象?沉淀法除去SO42-、Ca2+等杂质时,盐水一定要煮沸吗?为除去过量的Na2CO3,溶液的pH应该控制在什么范围?     

基于“大清河盐场”实地观摩考察的初中化学项目式学习*—食盐的“旅程”

食盐的工业生产是一个理想的基于实际问题解决的教学素材。盐场的生产环境安全可考察,学生可以完整地了解所有生产环节,与溶液及粗盐提纯的部分关联较为紧密。本课程以“食盐的旅程—从自然界中的盐到餐桌上的盐”为项目主题,开展初中化学“溶液和粗盐提纯”的教学。通过赴大清河盐场考察,针对食盐生产过程中纳潮、晒盐、收盐、洗盐中的问题展开讨论,解释生产过程的核心环节和关键问题,模拟食盐生产过程,自主建构饱和溶液、溶解度等概念,掌握溶解、过滤、蒸发等基本操作技能,建立物质分离的模型。     

“萃取”教学的2个问题与对策

萃取作为高中生进入高中最先接触的新知识,是“化学必修1”第一章(从实验学化学)第一节(化学实验基本方法)的2个难点之一(另一难点为粗盐提纯中试剂的顺序).在教学中,学生理解与掌握得好坏不仅影响成绩,而且关乎学生学习兴趣的发展.如果依据新课程理念,从教师教的角度剖析实际教学过程,将发现萃取的教学过程在教材的处理、概念的形成等方面仍存在一些值得探讨的问题.     

四组份混合物分离提纯方案的设计与实践

四组份混合物分离提纯方案的设计与实践张本才（陕西师范大学化学系，西安７１００６２）混合物的分离提纯是有机化学各个研究领域都不可缺少的内容，并且往往是能否获得研究成果的关键步骤。因此，在大学学习有机化学实验期间，如何精选合适的混合物分离提纯实验，培养学...     

“电离与离子反应”的单元教学设计与实施*——食盐精制:从微观角度看粗盐中可溶性杂质的去除

在“食盐精制:从微观角度看粗盐中可溶性杂质的去除”的单元教学中,通过初识粗盐中的杂质、微观角度看氯化钠、微观角度看粗盐溶液、微观角度认识除杂方法、设计除杂方案并实施等活动,促进学生理解与应用电离、离子反应等核心概念,引领学生解决真实问题,形成解决除杂实验问题的基本思路,实现能力素养的发展。经过多轮次教学改进,结合教学实践及其教学效果抽提出“聚焦核心概念和学生必做实验,实现认识能力的进阶与实际问题解决过程高度融合”“通过学科实践及实验探究,建立宏观、微观、符号关联,突出证据推理,构建思维模型”“通过持续性评价活动,外显学生的前概念,促进概念转变,形成化学学科思维方式”等教学策略。     

精盐和粗盐的竞争

在美洲，对于地方性甲状腺肿的病因曾有过争论，其中有一种观点认为这是一种传染病。例如在美国的弗吉尼亚地区，１９００年之前从未发现过甲状腺肿。１９００年以后，陆续出现了一些甲状腺肿患者，并逐渐增多。经过研究人们生活情况的变化发现，问题原来出在食盐上。１９００年以前人们食用的是卡那瓦河谷地区生产的棕黄色粗盐，而１９００年以后，从密执安州和俄亥俄州运来了精盐。精盐洁白如雪，粗盐自然不是竞争的“对手”。粗盐虽粗，颜色也不好看，但含有当地人体不可缺少的碘，精盐虽白，却不能满足当地人对碘的需求。所以，当人们舍…     

废电池在初中化学实验的贡献

在学生做过基本操作训练实验和粗盐的提玩实验以后,我增加了“废电池的再生利用”。这个实验是一方面基本操作训练的进一步强化,特别是对过滤操作实验,同时,也使学生提高了学化学的兴趣。实验后学生的信息反馈表明喜欢化学的达到100%,较开始学习时的88%提高了不少。     

实验作业是适合初三学生年龄特征的重要实验形式

中学化学教学大纲(修订草案)中,对于化学实验给予了较大的重视和注意。除了教师所进行的演示实验已经明确的规定外,把学生实验部分又分为两种形式进行:一种是实验作业,这是跟教师讲解教材相结合的实验;一种是实习作业,这是在学完一个题目或部分教材以后,在教师指导下,由学生单独或分组进行实验。大纲说明中指出“……实验作业能够使学生更充分地了解教材内容,帮助他们获得实际的技能和技巧……,实验作业……,特别在低年级里进行的次数应该多一些,实习作业的次数应该随着年级的升高而增加……”。这是十分恰当的指示,现在把我在教学中的一些体会写出来。希同志们指正,以便能更好地改进教学。初二学生进入初三时,虽然对于学习化学有着莫大的兴趣,但是他们对于仪器,设备和实验操作是生疏的,在这种情况下,如果在教师的示范讲解之后学生立即进行实验,那么学生的困难就将减少。譬如,在处理初三年级第一章第四节“物质的提纯法”的教材时,我曾采用过二种教法:第一种,用一节课作课堂教学(演示与讲述法相结合);另一节课进行“粗盐的提纯”与“制取蒸馏水”二项实习作业。第二种教     

血清中硫脂质的提纯及其结构分析

应用离子交换及硅胶柱色谱法分离提纯血清中酸性脂质,并采用薄层色谱法(TLC)、TLC免疫染色法、质谱法及溶化分解等方法分析血清中硫脂质的种类及结构。实验确定了样品的提纯体系,证实胆固醇硫酸及脑硫脂是血清中的主要硫脂质。     

四磺酸酞氰锌四钾盐的合成与表征

四磺酸酞氰锌四钾盐的合成与表征;四磺酸酞氰锌四钾盐;磺酸邻苯二甲酸单钾盐;磺酸邻苯二甲腈单钾盐;     

2007年重庆市璧山县和云阳县抽样地区环境碘含量调查分析

为了解重庆市抽样地区自然环境中的碘含量,为碘盐的合理摄入和防治碘相关疾病提供依据,采用多级整群随机抽样法,选择重庆市渝东地区云阳县和渝西地区璧山县为调查点,在两县经济状况中等的乡镇各抽取3所乡镇小学的8～10岁儿童各30名作为调查对象,以直接滴定法(GB/T13025.7-1999)检测了其家庭食用盐碘含量;采用随机抽样方法抽取两县居民饮用水样和土壤样,以GB5750-85中砷铈催化分光光度法测定了水碘含量,反向放大比色法测定了土壤碘含量。结果表明,检测两县居民食盐样本556份,璧山县与云阳县食盐碘均数分别为30.41和35.78mg/kg;抽取两县居民饮用水样87份,两县水碘中位数分别为6.50和2.78μg/L;水碘含量10μg/L的水样分别占73.33%和100%;抽取两县浅表层土壤样品88份,两县土壤碘中位数分别为8.20和7.56mg/kg。提示两抽样县均属于碘缺乏地区,需要通过食盐加碘防治碘缺乏病。可根据各地区具体情况,考虑适当调整食盐含碘量。     

Synthesis and anion exchange properties of a Zn/Ni double hydroxide salt with a guarinoite structure

In this study, the first route to synthesize a compound with the guarinoite structure (Zn,Co,Ni)₆(SO₄)(OH,Cl)₁₀·5H₂O is reported. Zn/Ni guarinoite is obtained from the reaction of NiSO₄·7H₂O with solid ZnO in aqueous solution. The resulting green Zn/Ni guarinoite ((Zn_3.52Ni_1.63)(SO₄)_1.33(OH_7.64)·4.67H₂O) was characterized by X-ray diffraction, infrared spectrometry, UV–Visible spectrometry and thermal analysis. It is shown that its structure is similar to the one described for the layered Zn sulfate hydroxide hydrate, i.e. brucite layers with empty octahedra presenting tetrahedrally coordinated divalent atoms above and below the empty octahedra. Ni atoms are located in the octahedra and zinc atoms in tetrahedra and octahedra. In this structure the exchangeable anions are located at the apex of tetrahedra. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the Zn/Ni guarinoite is composed of aggregates of hexagonal plates of several hundreds of nanometers. Due to its interest for industrial or environmental applications, the exchange of sulfate groups by carbonates has been investigated. Results show a limited exchange and a higher affinity of the Zn/Ni guarinoite for sulfates compared to carbonates.     

Recent application of acidic 1,3-azolium salts as promoters in the solution-phase synthesis of nucleosides and nucleotides

Acidic 1,3-azolium salts are prepared from Brønsted acids and 1,3-azoles such as imidazole, thiazole, and oxazole. Acidic imidazolium salts are frequently employed as promoters for the synthesis of nucleotides using the phosphoramidite method in a solution phase. Recently, it was revealed that thiazolium and oxazolium salts catalyzed Vorbrüggen-type N-glycosylation reactions to give nucleosides. These reactivities are attributed to the stronger Brønsted acidities of the thiazolium and oxazolium salts relative to those of the imidazolium salts. This digest focuses on recent progress in the applicability of acidic 1,3-azolium salts as promoters in the solution-phase synthesis of nucleosides and nucleotides.     

汽液平衡盐效应中的沸点变化(英文)

测定了在恒压(100.0kPa)条件下若干含盐双液系(甲醇-水,乙醇-水,正丙醇-水)的沸点变化.实验结果表明引起溶液沸点降低 反常现象"发生的必要条件是易挥发组分被盐析或难挥发组分被盐溶.经热力学分析表明上述实验结果是一个具有普遍意义的结论.     

漫谈食盐与工业盐

本文针对人们普遍关注的工业盐中毒问题,对食盐与含有亚硝酸钠的工业盐进行了比较,介绍了工业盐对人体健康的危害、工业盐中毒的原因及预防措施,探讨了区别食盐与工业盐的方法。     

Combined study of thermochemical properties of nitroform and its salts

A combined method for determination of the standard enthalpies of formation of nitroform and its salts was proposed. The enthalpies of dissolution of nitroform and its ammonium, hydrazinium, guanidinium, and potassium salts in water were measured. The enthalpy of combustion of hydrazinium salt of nitroform was determined by a combustion calorimetry, and its standard enthalpy of formation was calculated. The enthalpy of formation of trinitromethyl anion in indefinitely diluted aqueous solution −24.94±0.79 kJ mol⁻¹, was calculated on the basic of the data obtained for enthalpies of formation and dissolution of ammonium and hydrazinium salts of nitroform. Standard enthalpies of formation of nitroform and its salts were calculated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2451–2454, December, 1998.     

Thermal analysis study of imidazolinium and some benzimid azolium salts by TG

The imidazolinium and benzimidazolium bromide salts with pentafluor substituents on N atom were synthesized. The structures of imidazolinium and benzimidazolium bromide salts obtained were conformed by ¹H and ¹³C NMR, ¹⁹F NMR and elemental analysis. It was found that pyrolytic decomposition occurs with melting in salts. The imidazolinium and benzimidazolium bromide salts were studied by TG-DTG and DTA from ambient temperature to 1000°C in nitrogen atmosphere. The decomposition occurred mainly in one stage and the values of activation energy E, frequency factor A, reaction order n, enthalpy change ΔH ^#, entropy change ΔS ^# and Gibbs free energy ΔG ^#, of the thermal decomposition were calculated by means of Coats-Redfern (CR), MacCallum-Tanner (MC) and van Krevelen (vK) methods. The activation energy value obtained by CR and MC methods were in good agreement with each other while those obtained by vK were found to be 10–12 kJ mol⁻¹ larger.     

食用菌中 Ca、Mg 含量的测定

采用FAAS法对食用菌中微量元素 Ca、Mg 的含量分别在无释放剂和加入锶盐和镧盐作释放剂条件下进行了测定.结果发现,加入锶和镧盐均能提高大多数试样 Ca、Mg 元素含量的测定灵敏度,且镧盐的释放效果明显高于锶盐,但有个别反常现象.对比锶盐和镧盐作释放剂条件下的测定结果和加标回收率,也表明镧盐作释放剂的回收率更接近100%.