读者园地

问 :为什么燃烧 碘量法测定钢铁中硫其结果不能用理论值计算 ?浙江读者———陈琦读者园地　　答 :燃烧 碘量法测定硫的基本原理可用以下反应方程式表示。试样在高温下通氧燃烧生成ＳＯ2 :4ＦｅＳ +7Ｏ2 2Ｆｅ2 Ｏ3+4ＳＯ2 ↑3ＭｎＳ +5Ｏ2 Ｍｎ3Ｏ4 +3ＳＯ2生成的ＳＯ2 在酸性淀粉溶液 (或淀粉水溶液 )中吸收生成Ｈ2 ＳＯ3:ＳＯ2 +Ｈ2 ＯＨ2 ＳＯ3生成的Ｈ2 ＳＯ3用ＫＩＯ3或Ｉ2 标准溶液滴定 :ＫＩＯ3+5ＫＩ +6ＨＣｌ 3Ｉ2 +6ＫＣｌ+3Ｈ2 ＯＨ2 ＳＯ3+Ｉ2 +Ｈ2 ＯＨ2 ＳＯ4 +2ＨＩ过量的Ｉ2 与淀粉指示剂作用呈蓝色 ,指示终点的到达。由…     

Excel在理化检验中的应用

对食用盐中碘和盐业部门的加碘食盐 (根据调查加碘食盐中碘均以碘酸钾形式加入 )中的碘含量进行监测时 ,由于此项工作样本量多 ,为了避免人为误差 ,可运用Ｅｘｃｅｌ电子表格的数据处理功能 ,对测定的大量数据进行统计计算 ,提高其准确度。1　原理碘盐中的碘酸钾在酸性环境中 ,加入过量的碘化钾析出碘 ,以淀粉作指示剂 ,用硫代硫酸钠标准溶液滴定并计算其含量 :ＩＯ- 3+ 5Ｉ- + 6Ｈ+3Ｉ2 + 3Ｈ2 Ｏ　　　2Ｎａ2 Ｓ2 Ｏ3+Ｉ2 2ＮａＩ+Ｎａ2 Ｓ4 Ｏ62　食盐中碘含量检测称取碘盐 10 .0 0 0 0 ｇ置于 2 5 0ｍｌ碘量瓶中 ,加无碘水 5 0ｍｌ使盐…     

读者园地

2　光度测定法目前常用的测定钢铁中氮的光度法有两种 ,即纳氏试剂法与靛酚蓝法。2 1　纳氏试剂法2 1 1　方法的概要应用纳氏试剂 (Ｋ2 ＨｇＩ4 )光度法测定钢铁中氮已有很长历史。在碱性介质中 ,纳氏试剂与氨反应生成碘化汞铵络合物 ,呈柠檬黄色 :2Ｋ2 ＨｇＩ4 +ＮＨ3 ·Ｈ2 Ｏ +3ＮａＯＨＯＨｇＮＨ2 ＩＨｇ+3Ｈ2 Ｏ +3ＮａＩ +4ＫＩ反应的最佳碱度为 0 .0 9ｍｏｌ·Ｌ- 1,碱度增大虽可使测定的灵敏度有提高 ,但显色后的溶液易产生混浊 ,碱度降低 ,则其灵敏度也降低。显色时 ,氮的浓度超过 0 .6 μｇ·ｍｌ- 1时 ,将产生红褐色沉淀。如…     

电化学方法简便测定芬顿反应产生的羟基自由基

1　引　　言由于羟基自由基的反应活性大、寿命短、存在浓度低 ,直接测定存在一定的难度。因此 ,建立快速、简便的测定方法 ,对自由基理论研究和抗氧化药物筛选有重要意义。水杨酸、2 脱氧 Ｄ 核糖和ＤＭＳＯ是测定羟基自由基常用的分子探针。其中 ,ＤＭＳＯ与羟基自由基反应 ,主要的生成物有甲基亚磺酸 (Ｉ)及甲醛 (ＩＩ)等。·ＯＨ +(ＣＨ3) 2 ＳＯＣＨ3ＳＯ2 Ｈ +·ＣＨ3(1)·ＣＨ3+Ｏ2 ＣＨ3ＯＯ· (2 )2ＣＨ3ＯＯ·ＨＣＨＯ(ＩＩ) +ＣＨ3ＯＨ +Ｏ2 (3)　　有报道通过测定上述反应生成的甲基亚磺酸或来间接定量测定羟基自由基 ,也有…     

漂白剂对酸碱指示剂作用的实验探索

1　问题的提出中学化学教科书介绍的漂白剂有Ｎａ2 Ｏ2 、Ｃｌ2 、ＳＯ2 等 ,漂白作用的机理分别是Ｎａ2 Ｏ2 和Ｃｌ2 与水反应生成的Ｈ2 Ｏ2 和ＨＣｌＯ是强氧化剂 ,能氧化染料和有机色素使它们褪色 ;ＳＯ2 则能跟某些有色物质化合而生成不稳定的无色物质。另外有习题表明 ,Ｃｌ2 与湿润的蓝色石蕊试纸作用时 ,能使石蕊试纸先变红后褪色。变红是氯气与试纸上的水反应生成了酸 ,褪色是反应产物中的ＨＣｌＯ具有强氧化性 ,能起漂白作用。那么 ,Ｎａ2 Ｏ2 和ＳＯ2 等漂白剂对石蕊的作用如何 ?包括Ｃｌ2 在内的常见漂白剂对其他常见酸碱指示剂…     

铁矿中全铁、二氧化硅和氧化钙的测定

铁矿的质量检查和入炉铁矿全铁、二氧化硅和氧化钙的测定 ,是中小型铁厂化验室相当繁重的一项日常工作 ,表现为试样数量多 ,测试频率高 ,同时要求较快地报出结果。采用既经济又快速实用的分析方法 ,对指导高炉生产有着十分重要的意义。1　试验部分1.1　主要仪器与试剂72 1ＳＸ分光光度计钨酸钠溶液 :5 0ｇ·Ｌ- 1,称取Ｎａ2 ＷＯ4 ·2Ｈ2 Ｏ 5ｇ溶于 5 0ｍｌ水中 ,加磷酸 10ｍｌ,用水稀释至 10 0ｍｌ ,摇匀。三氯化钛溶液 :将 15 0～ 2 0 0ｇ·Ｌ- 1三氯化钛用盐酸 (1+ 1)稀释 3倍硫酸铜溶液 :2 0ｇ·Ｌ- 1硫 磷混酸 :Ｈ2 ＳＯ4 ∶Ｈ2 ＰＯ…     

废水中硫化物的快速分光光度法测定

1　引　　言滴定法和亚甲蓝法是目前广泛使用的硫化物测定法。亚甲蓝法灵敏度高 ,选择性好 ,但反应速度慢 ,重现性较差。本文用Ｋ2 Ｃｒ2 Ｏ7代替Ｆｅ3+,实验结果表明 :在Ｈ2 ＳＯ4 溶液中 ,Ｋ2 Ｃｒ2 Ｏ7+对二乙氨基苯胺 +Ｓ2 -显色反应即刻完成 ,表观摩尔吸收系数为 5 42× 10 4 Ｌ·ｍｏｌ-1·ｃｍ-1,比原乙基蓝法灵敏度提高 40 % ,线性范围为 0～ 0 .6ｍｇ/Ｌ。采用蒸馏分离方法 ,用ＮａＯＨ作吸收液 ,提出了一种适于水样中硫化物测定的快速分光光度法。方法简便快速且检测灵敏度高 ,已用于水和废水中硫化物的测定。2　实验部分2 1　…     

常压气相氧化羰基化合成碳酸二乙酯

碳酸二乙酯是一种重要的有机化工原料,可广泛用于合成农药如脱叶灵,医药如喹啉酮衍生物,中间体3-氧硫代羧酸酯,还可用于电子管阴极的镀层[1-3]。生产碳酸二乙酯的传统方法为:无水乙醇与光气反应生成氯甲酸乙酯,氯甲酸乙酯继续与乙醇反应生成碳酸二乙酯后经水洗蒸馏制成。使用光气为原料对设备的要求较高。我们在常压下气相羰基化合成碳酸二乙酯[4]:2ＮＯ+Ｃ2Ｈ5ＯＨ+0.5Ｏ2→2Ｃ2Ｈ5ＯＮＯ+Ｈ2Ｏ(1)ＣＯ+2Ｃ2Ｈ5ＯＮＯ→(Ｃ2Ｈ5Ｏ)2ＣＯ+2ＮＯ(2)产生的一氧化氮可与氧气和乙醇进行反应再生为亚硝酸乙酯,符合原子经济反应且几乎不放出对…     

复盐K3Na(SO4)2的热化学研究

钾芒硝是一种成因复杂的复盐[1～ 3 ] ,并且由于钾芒硝Ｋ3 Ｎａ(ＳＯ4 ) 2 与硫酸钾石 [Ｋ3 Ｎａ(ＳＯ4 ) 2 或Ｎａ2 ＳＯ4 ·3Ｋ2 ＳＯ4 ]的化学组成相同 ,未能确定二者是否属于同一种复盐[4 ,5] 。我们合成了复盐Ｋ3 Ｎａ(ＳＯ4 )2[3 ] ,用溶解量热法测定了Ｋ3 Ｎａ(ＳＯ4 )2 和反应物 [Ｎａ2 ＳＯ4 (ｓ) +Ｋ2 ＳＯ4 (ｓ) ]的溶解焓 ,通过设计热化学循环计算出复盐的标准生成焓 ,为我们了解钾芒硝和硫酸钾石是否为同一复盐 ,并为进一步研究其成因和组成提供参考。1　实验部分1 1　试剂与仪器Ｋ2 ＳＯ4 (ｓ)和Ｎａ2 ＳＯ4 (ｓ)为Ａ .Ｒ .…     

氨回收液中二氧化碳的测定

煤制气的副产品氨在回收时 ,工艺上对氨溶液中二氧化碳含量要求十分严格 ,因为二氧化碳与氨水形成碳酸铵结晶堵塞管道和腐蚀管道。原设计手册中的分析方法是先将氨溶液中的二氧化碳蒸出 ,用氢氧化钡溶液吸收 ,再用硫酸标准溶液滴定。该方法不但所需时间长 ,氢氧化钡溶液易吸收二氧化碳而形成碳酸钡沉淀 ,而且误差大。本法用过量氢氧化钠溶液吸收氨溶液中二氧化碳 ,再用硫酸滴定混合碱的滴定方法。在消除氨、硫化氢及氰化氢的干扰后 ,能快速准确地测定氨溶液中的二氧化碳含量。吸收和滴定反应如下 :ＣＯ2 +2ＮａＯＨ =Ｎａ2 ＣＯ3 +Ｈ2 Ｏ2Ｎ…     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

物质分配系数的测定实验改进

实验教学目的是从解决实际问题出发,以实验技术训练和实验设计思想培养为目标。介绍了将单一的物质分配系数测定实验改进为综合实验,提高了实验效果及实验资源利用率。     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.