碘-聚乙烯醇显色法标定硫代硫酸钠溶液

聚乙烯醇和碘能够发生显色反应，在碘量滴定法的一些测定中，可以用聚乙烯醇代替淀粉作指示剂指示终点。分别用碘、碘酸钾作基准试剂，聚乙烯醇、淀粉作指示剂，对硫代硫酸钠溶液进行标定，测定结果基本一致。     

过氧化氢水溶液中过氧化氢含量分析的简便方法

用氧化还原滴定法测过氧化氢含量，是测定过氧化氢含量的经典方法，但存在着影响因素多，操作周期长，分析费时、费力的缺点。此法根据不同浓度的过氧化氢水溶液同一温度下的密度差别来分析过氧化氢水溶液中过氧化氢含量，分析了其可靠性，指出该方法具有准确、简便、易掌握的优点。     

用于环己烷氧化混合产物的分析方法

针对环己烷空气液相氧化混合产物的不同特性，采用了不同的测定方法：环己基过氧化氢采用间接碘量法定量；酸和酯采用酸碱滴定法定量；环己醇和环己酮等有机物采用气相色谱法，但进样前先加入三苯基膦以避免环己基过氧化氢的干扰。该方法回收率为96．62％～101．69％，相对标准偏差为1．12％～5．09％。     

碘化钾碘蓝分光光度法测定微量过氧化氢

基于在酸性介质中 ,过氧化氢与碘化钾、淀粉的显色反应 ,建立了碘化钾碘兰分光光度法测定微量过氧化氢方法。过氧化氢浓度在 0～ 2 5μg/2 5m L范围内有良好的线性关系 ,方法的相对标准偏差 1 .2 % ,回收率 97.2 %～1 0 1 .2 % ,检出限为 2 .0× 1 0 -3 mg/L。并应用于雨水、空气中微量过氧化氢的测定。     

甲状腺肿大率与尿碘、盐碘关系的探讨

为了解甲状腺肿大率与尿碘“分离”现象产生的原因 ,用B超检查甲状腺肿大率 ,用酸消化砷 -铈接触法测定尿碘 ,用直接滴定法测定盐碘。结果表明 ,全市甲状腺肿大率为 7 1% ;尿碘中位数为 2 0 5 5 μg/L ,盐碘中位数为 43 4× 10 -6。甲状腺肿大率与尿碘水平无明显相关性 ,与盐碘浓度也无差异显著性。提示出现病情与尿碘分离现象 ,可能存在其它致甲肿的原因。     

碘量紫外分光光度法测定碳氢燃料过氧化值

建立测定碳氢燃料过氧化值的碘量紫外分光光度法。样品溶于乙醇中，加入0.50 mL冰乙酸，用饱和碘化钾-乙醇溶液定容至10 mL，避光显色90 min，过氧化物在酸性条件下与碘化钾反应生成黄色的I₃^-，在360 nm处测定吸光度，计算过氧化氢的含量。过氧化氢的质量浓度在0.106 1～1.061μg/mL范围内与吸光度线性关系良好，相关系数为0.999 8，方法检出限为0.015μg/mL。样品加标回收率为97.3%～103.6%，测定结果的相对标准偏差小于5%(n=6)。该法适用于测定碳氢燃料的过氧化值。     

牛血红蛋白催化分光光度法测定过氧化氢

在pH 4.8的0.1mol·L-1柠檬酸-0.2mol·L-1磷酸氢二钠缓冲介质中,于43℃水浴加热60min,牛血红蛋白对过氧化氢氧化邻苯二胺的反应有明显的催化作用。试验结果表明:过氧化氢浓度在8.24×10-6~2.31×10-4 mol·L-1范围内与相应吸光度的增加值ΔA呈线性关系,检出限(3s/k)为4.50×10-8 mol·L-1。据此提出了牛血红蛋白催化分光光度法测定过氧化氢的含量。采用此法测定消毒液和雨水中过氧化氢的含量,测定值的相对标准偏差(n=5)分别为0.081%和1.6%,消毒液中过氧化氢的测定值与滴定法测定结果相符。以上述2种试样作基体用标准加入法进行回收试验,测得回收率分别为99.3%和97.3%。     

铁(Ⅲ)置换氧化还原滴定法测定维生素C片剂及针剂中抗坏血酸

基于将测定抗坏血酸的碘滴定（药典）法和铁铵矾滴定法相结合,即先用铁铵矾基准物氧化碘化钾置换出相当量的12,再在维生素C药物溶液滴定中让相当量的12定量氧化抗坏血酸。合适的反应条件是：乙酸介质,碘离子过量,室温置暗处置换反应10min。将该法用于维生素C药物中抗坏血酸的测定,结果与药典法结果相符。     

水溶性聚合物和两亲聚合物：聚（丙烯酰胺－co－丙烯酸钠）－g－聚（β－胺基丙酸）接枝共聚物

合成了端丙烯酰胺基聚（β－胺基丙酸）大分子单体，用端基滴定法和１Ｈ－ＮＭＲ法测定了大分子单体的分子量，用＾１＾３Ｃ－ＭＮＲ和氢氧化钠水解法测定了支化度，在水溶液中用硫酸亚铁／异丙苯过氧化氢氧化还原引发体系引发丙烯酰胺，丙烯酸钠与聚（β－胺基丙酸）大分子单体的共聚反应，合成了聚（丙烯酰胺－ｃｏ－丙烯酸钠）－ｇ－聚（β－胺基丙酸）用１Ｈ－ＮＭＲ和滴定法测定了接枝共聚物的组成。溶液性质的数据表明，与部分     

碘离子选择电极测定S2O82-与I-反应动力学参数

水溶液中S_2O_8~(2-)氧化I~-的反应是典型的二级离子反应,常选为大学物理化学实验.但该实验一直沿用滴定法和碘钟法,因而存在着操作繁锁费时、无法确定任意时刻的反应物浓度及引入其它试剂使体系复杂等缺点. 为了克服上述缺点,本文根据离子选择电极和化学动力学原理,提出一种新的能系统地进行S_2O_8~(2-)与I~-反应动力学实验的方法,它包括反应级数、反应速度常数、反应活化能的测定以及考察离子强度、催化剂对反应速度的影响.作者采用碘离子选择电极(以下简称碘电极)电位法跟踪反应中I~-浓度的变化,可由     

Titrimetric Microdetermination of chloral hydrate by amplification reactions

A simple titrimetric method for estimation of 0.1–5 mg of chloral hydrate is presented. It depends on oxidation of an alkaline solution of chloral hydrate with a chloroform solution of iodine, removal of excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate produced, giving 6-fold amplification. Alternatively, the iodide formed is oxidized with periodate, masking of the excess of periodate with molybdate at pH 3, and iodometric titration of the iodate, giving 24-fold amplification. The coefficient of variation does not usually exceed 2%, for above 1 mg of chloral hydrate but increases to 3.8% at the 0.1-mg level.     

Titrimetric determination of silver,chloride and bromide in glasses

Titrimetric methods are described for the determination of total silver, free silver or free halide (Cl, Br and I), and bromide (or iodide) in glasses. Total silver is titrated potentiometrically with standard bromide solution after hydrofluoric—sulfuric acid sample decomposition followed by sodium hydrogensulfate fusion for volatilizing hydrogen halide. Free silver is determined similarly on a separate sample without the fusion step. For glasses containing excess of halide, free halide is titrated potentiometrically with standard silver(I) solution after dissolution of the sample in ice-cold hydrofluoric—nitric acid. Total bromide (or iodide) is determined by iodometric titration after oxidation to bromate (or iodate) with hypochlorite solution. The methods have been applied to a wide range of complex glass compositions and results are compared with values obtained by controlled-potential coulometry and x-ray fluorescence analysis.     

Analysis of peracetic acid solutions

In the estimation of peracetic acid in aqueous solution, hydrolysis of the peroxy group must be taken into account. The best volumetric method is an indirect one using cerium(IV) as the oxidant, followed by iodometric titration of the excess of cerium(IV). A spectrophotometric estimation of the hydrogen peroxide present, based on the peroxytitanium(IV) complex is satisfactory if measurements are made at known time intervals and extrapolated to zero time.     

Iodometric determination of potassium permanganate by arsenious oxide following iodide reduction in presence of borax-boric acid buffer and barium chloride

Summary An iodometric method for the determination of potassium permananate is described following its reduction to MnO₂ in presence of boraxboric acid buffer at PH 8–10 by iodide and titration of the liberated iodine with standard arsenious oxide solution. Excess BaCl₂ is added to coagulate the colloidal MnO₂ whose otherwise partial reduction by iodide is prevented thereby.Sincere thanks of the authors are due to Prof. S. S. Joshi, for his kind interest in the work.     

Iodometric microdetermination of hydrazines by amplification reactions

Two new, simple, rapid, and accurate iodometric amplification methods are described for the micro and submicro determination of hydrazine. The first depends on oxidation with a chloroform solution of iodine and removal of its excess, oxidation of the resulting iodide with bromine, and iodometric titration of the liberated iodate. The second method is based on oxidation with periodate at pH 8, masking of the excess of periodate with molybdate at pH 3, and iodometric titration of the iodate. The order of amplification involved in the two methods is 6- and 3-fold, respectively. Micro amounts of hydrazine sulphate and dihydrochloride were determined satisfactorily by both methods, the average recoveries being 98.6 and 99.4%.     

Titrimetric microdetermination of isoniazid by amplification reactions

An amplification method for the determination of (0.01–2.0 mg) isoniazid is described. It depends on oxidation of the isoniazid sample solution with a chloroform solution of iodine and removed of its excess, oxidation of the resulting iodide with bromine, and iodometric titration of the liberated iodate after 6-fold amplification. Alternatively, the liberated iodine is reduced to iodide, and again oxidized to yield 36 iodide ions for every iodide ion originally present. The coefficient of variation does not usually exceed 1.5% for above 0.5 mg of isoniazid but increases to 3.6% at the 0.01-mg level.     

The influence of hydrogen peroxide and pH on the Mohr titration

The official Japanese method for determination of chloride in hot-spring waters requires any H(2)S present to be oxidized with hydrogen peroxide in ammoniacal medium. When this was done, and the solution was titrated with silver nitrate at pH 9.7, the indicator colour changed from yellow to brownish grey, owing to reduction of silver ions to the metal by hydrogen peroxide. The effect can be eliminated by adjusting the pH to 7.0-7.5 before the titration.     

Determination of chloride by displacement of hydrogen cyanide from mercury(II) cyanide

A method, based on the passivity of mercury(II) cyanide in dilute sulphuric acid and its reaction with hydrochloric acid to produce hydrogen cyanide, has been developed for the determination of small amounts of chloride. Hydrogen cyanide, distilled from a mercury(II) cyanide-halide-dilute sulphuric acid system is found by iodometric measurement to be directly proportional to the amount of chloride or bromide and of hydrogen ion in acids such as sulphuric acid. A linear correlation also holds for iodide but the stoichiometry is different, the titration values being about three times larger than expected. By conversion of the cyanide into a dye by means of the pyridine-pyrazolone reagent, 0.014-0.43 mug ml chloride concentrations have been determined. The method is also applicable to bromide and sulphuric acid in small amounts but not to fluoride and iodide. Results are reproducible to within +/-2%.     

Micro and submicro iodometric determination of arsenite and sulphite ions by amplification reactions

Two methods are described for the micro and submicro iodometric determination of arsenite and sulphite ions involving 3- and 6-fold amplification reactions, respectively. The arsenite method is based on oxidation with an excess of periodate, masking of the unreacted periodate with molybdate, and final iodometric titration of the iodate released. The sulphite method depends upon oxidation with iodine and removal of its excess by extraction with chloroform, and oxidation of the iodide formed to iodate, which is determined iodometrically as usual. The two methods are simple, rapid, and accurate. The average recoveries obtained are 99.9 and 99.3% for arsenite and sulphite, respectively.     

Enzymatic determination of choline in milk using a FIA system with potentiometric detection

The development of a FIA system for the determination of total choline content in several types of milk is described. The samples were submitted to hydrochloric acid digestion before injection into the system and passed through an enzymatic reactor containing choline oxidase immobilised on glass beads. This enzymatic reaction releases hydrogen peroxide which then reacts with a solution of iodide. The decrease in the concentration of iodide ion is quantified using an iodide ion selective tubular electrode based on a homogeneous crystalline membrane. Validation of the results obtained with this system was performed by comparison with results from a method described in the literature and applied to the determination of total choline in milks. The relative deviation was always < 5%. The repeatability of the method developed was assessed by calculation of the relative standard deviation (RSD) for 12 consecutive injections of one sample. The RSD obtained was < 0.6%.