自动电位滴定法测定铁矿中水溶性氯化物

应用自动电位滴定法,在pH＞2的微酸性乙醇-水(4+1)溶液中,用0.002 mol·L-1硝酸银标准溶液为滴定剂,测定了铁矿石样品中水溶性氯化物.试样用水在95℃温度条件下浸取使其水溶性氯化物溶出,共存的硫化物的干扰采用在微碱性条件下加入过氧化氢并煮沸至无小气泡产生可予以消除,对试样的预处理方法,以及各项影响测定的参数(如溶液介质,被滴定液的酸度及温度,滴定速度及搅拌速度等)做了试验并予以优化.方法的检出限(S/N=3)为2.0μg,用标准加入法做了回收率试验,结果在99.9%～100.4%之间.     

玮晖水务剩余污泥中磷释放的正交试验研究

以开封玮晖水务剩余污泥为对象,研究了不同条件(释放时间、温度、pH、溶剂用量和振荡频率)对污泥磷释放的影响。利用正交试验优化实验条件,得到富磷上清液,并对释磷效率进行了分析。结果表明:在一定条件下,溶剂用量、溶液pH、释放时间以及温度均存在一个最佳值;各因素对污泥磷释放影响的重要性排列顺序是:溶剂用量﹥pH﹥温度﹥释放时间,在溶剂体积50 mL,pH为2,温度为30℃,振荡时间4 h的释放条件下,磷的释放率达到82.12%。污泥在强酸性和强碱性的环境中,污泥释磷效果比较好,溶液初始pH分别是1和13时,污泥磷释放效率分别达到了76.92%和83.75%,大约是中性条件下释磷效率的2倍。     

聚异戊二烯橡胶中钕的分光光度测定

本文用硝酸和高氯酸分解试样,在pH1.5的乙酸钠-盐酸缓冲溶液中,以偶氮氯膦Ⅲ为显色剂,用分光光度法测定了聚异戊二烯橡胶中钕的含量,Al~(3+)、Fe~(3+)的干扰以EDTA掩蔽。主要试剂乙酸钠-盐酸缓冲溶液:50毫升1M乙酸钠与60毫升1M盐酸、140毫升水混合后,再细调至溶液pH为1.5(用pH计测量);钕标准溶液:称取0.1170克氧化钕(纯度99.9%),用10毫升盐酸(1+1)溶解,移入1000毫升容量瓶中,以水定容,摇匀。此溶液每毫升含钕0.1毫克,使用时再稀释至所需浓度。     

Na2EDTA滴定法测定粗二氧化碲中铅含量

建立了用氢溴酸消除锑、砷、锡干扰,用硫酸将铅形成硫酸铅沉淀,再用EDTA络合滴定法测定粗二氧化碲中铅量的方法。试样用硝酸、盐酸溶解,用硫酸沉淀铅,氢溴酸消除锑、砷、锡的干扰后,过滤分离其他共存元素,以乙酸-乙酸钠缓冲溶液溶解硫酸铅沉淀,在pH=5.0～6.0时,以二甲酚橙作指示剂,用Na_2EDTA溶液滴定溶液中铅含量。实验结果表明,氢溴酸加入量为15mL,酒石酸加入量为10mL,沉淀体积为50～60mL,沉淀时间1h以上时,方法相对标准偏差(RSD)在0.10%～1.1%,加标回收率为97.1%～102%,满足粗二氧化碲中铅量的生产控制检测要求。     

磷矿及磷肥中氧化钙测定方法改进

为了解决磷矿及磷肥中氧化钙酸溶不完全和消除测定过程中磷酸根、镁、铁等的干扰,对磷矿和磷肥中氧化钙的测定方法进行改进。对不同酸溶解体系选择、酸用量、加热时间、干扰掩蔽实验、pH值等条件进行实验,确定采用10 mL王水、3 mL氢氟酸分解试样,加入2 mL盐酸溶解盐类,加入10 mL糊精和5 mL三乙醇胺溶液掩蔽Mg^2+、Fe^3+、PO4^3-、Al^3+的干扰,无需过滤,在pH≈7时预加EDTA至溶液清亮,再加入KOH调节溶液pH>13,加入适量的钙黄绿素指示剂,用EDTA溶液滴定至绿色荧光消失,测定磷矿和磷肥中氧化钙。实验结果表明,三个磷矿石标准样品和磷肥监控样氧化钙测定的相对标准偏差(RSD,n=11)为0.21%~1.1%。实际磷矿和磷肥样品中氧化钙测定值与国家标准方法测定结果一致。     

微波消解试样-氢化物发生-原子荧光光谱法测定铁矿石中砷

应用氢化物发生-原子荧光光谱法测定了铁矿石中微量砷。试样用硝酸、盐酸及氟氢酸的混合酸在微波消解仪中消解处理。经试验选定微波消解程序为:①消解功率650 V;②以5℃.min-1速率升温至170℃,保持20 min;③冷却20 min,在所得溶液中加入饱和硼酸溶液使游离氢氟酸络合,再加入硫脲及抗坏血酸溶液作掩蔽剂后定容为50 mL,在仪器工作条件下进行砷的测定。设置样品溶液的进样量为1.0 mL,10 g.L-1硼氢化钾溶液的加入量为0.5 mL。在制作标准曲线时加入一定量的铁以抵消基体铁的干扰。砷的质量浓度在0.90~100μg.L-1范围内与相应的荧光强度之间呈线性关系。方法的检出限(3s)为0.40μg.L-1。按所提出的方法测定了铁矿石标准样品中砷量,所得结果与认定值相符。     

易熔合金中铋的测定

本文研究了易熔合金中铋的直接滴定条件。用盐酸-硝酸分解试样,加过量酒石酸络合锡、锑、铋等,既消除了锡、锑的干扰,又防止了铋的水解。由于锡、锑的酒石酸络合物较铋的酒石酸络合物稳定,控制硫脲加入量。在pH1—2时用EDTA直接滴定铋,终点变化敏锐。在拟定条件下,由于控制滴定的pH较低,     

EDTA滴定法测定矿石中铅含量的方法改进

对以往测定铅的方法进行了改进。消解样品的体系为盐酸-硝酸-硫酸和氟化铵,氟化铵(200 g/L)的加入量为3 mL;硫酸加入量为10 mL,浓度为1+1;硫酸铅沉淀静止时间为45 min;除去铋干扰的方法为调节溶液的pH值用EDTA溶液进行分步滴定;将过滤后的滤液进行回收测定,与滴定的结果相加以得到最终结果,滤液中铅含量的大概范围为0.13 %~0.27 %。本方法的精密度为0.12%~0.15% ,准确度为0.24%~0.43%。     

石墨炉原子吸收光谱法测定土壤及农产品中痕量铍

土壤试样用浓硝酸及过氧化氢在ETHOS 1型微波消解仪中按预设程序进行消解,所得消解溶液蒸发至近干后定容为25.0 mL供石墨炉原子吸收光谱法(GF-AAS)分析用。农产品试样先置于浓硝酸及高氯酸中浸泡过夜,然后置于电热板上加热消解至溶液呈深棕色,再加入硝酸-高氯酸(3+1)混合酸适量,加热蒸发至冒高氯酸烟,冷却,定容为25.0 mL供GF-AAS分析。分取10μL试样溶液,按预设的仪器工作条件测定其含铍量。在试样溶液中加入氯化钙溶液作为基体改进剂,铍(Ⅱ)的质量浓度与相应的吸光度值在4.0μg.L-1范围内呈线性关系。方法的检出限(3s/k)为0.4 pg。应用此方法测定了土壤及菠菜标准物质,测定结果均与证书值一致,测定值的相对标准偏差(n=6)均小于5%。     

测定锑的新方法——重铬酸钾容量法

锑的容量法测定一般都沿用经典的硫酸铈和溴酸钾容量法,此法须在70—80℃下,在20%盐酸介质中滴定。如试样中含铁量高时,用甲基橙作指示剂,终点不明显。本文研究了在0.5—2M硫酸溶液中,以铁(Ⅱ)为诱导剂(使铁(Ⅱ)和锑(Ⅲ)的摩尔比>1:1)的容量法,从而确立了二苯胺磺酸钠为指示剂,用重铬酸钾标准溶液滴定锑的条件,终点敏锐。砷对滴定虽有干扰,但在测定条件下,砷(Ⅲ)与重铬酸钾不是定量反应.试样中砷含量在5%以下,对锑的测定无影响。试样中含有铁(Ⅱ),经与硫酸-硫酸钾高温熔矿     

Pollution-free method for the determination of iron in iron ore

A method for the determination of total iron in iron ores and concentrates is described which avoids the use of mercuric chloride. The sample is decomposed either by an acid attack or by fusion with sodium peroxide. The hot sample solution in about 6M hydrochloric acid is treated with hot 10% stannous chloride solution till pale yellow, followed by addition of a slight excess of 2% titanous chloride solution; the excess is then oxidized with perchloric acid (1 + 1). The solution is rapidly cooled in ice-water, and the iron (II) is titrated with potassium dichromate (sodium diphenylsulphonate as indicator). The results show the same degree of precision, accuracy, and degree of interference as those obtained by the standard stannous chloride-mercuric chloride method.     

Silver-reductor method for determination of iron in iron ores and iron-ore sinters

A new technique for the quick dissolution of iron ore, magnetite and sinter products has been developed. The sample is dissolved with thioglycollic acid and hydrochloric acid, the excess of thioglycollic acid is oxidized, and the iron is reduced in the silver reductor.     

Hepcidin in iron metabolism

Hepcidin, which has been recently identified both by biochemical and genomic approaches, is a 25 amino acid polypeptide synthesized mainly by hepatocytes and secreted into the plasma. Besides its potential activity in antimicrobial defense, hepcidin plays a major role in iron metabolism. It controls two key steps of iron bioavailability, likely through a hormonal action: digestive iron absorption by enterocytes and iron recycling by macrophages. In humans, this could explain that low levels of hepcidin found during juvenile haemochromatosis and HFE-1 genetic haemochromatosis are associated with an iron overload phenotype. Conversely, an increase of hepcidin expression is suspected to play a major role in the development of anemia of chronic inflammatory diseases. However, the regulatory mechanisms of hepcidin expression are multiple, including iron-related parameters, anemia, hypoxia, inflammation and hepatocyte function. Therefore, many physiological and pathological situations may modulate hepcidin expression and subsequently iron metabolism. A better knowledge of the biological effects of hepcidin and of its expression regulatory mechanisms will clarify the place of hepcidin in the diagnosis and treatment of iron-related diseases.     

Determination of metallic iron, iron(II) oxide, and iron(III) oxide in a mixture

A procedure is described for the estimation of metallic iron, ferrous oxide, and ferric oxide when present together. The sample is treated with bromine dissolved in ethanol, and filtered. Iron in the filtrate is titrated iodometrically, and corresponds to the metallic iron present in the mixture. The oxide residue is dissolved in hydrochloric acid under a carbon dioxide atmosphere. The iron(II) formed, equivalent to FeO present, is titrated with a standard vanadate solution, and the total iron(III) (FeO + Fe₂O₃) in the titrated solution is then estimated iodometrically.     

Nanophase iron phosphate, iron arsenate, iron vanadate, and iron molybdate minerals synthesized within the protein cage of ferritin

Nanoparticles of iron phosphate, iron arsenate, iron molybdate, and iron vanadate were synthesized within the 8 nm interior of ferritin. The synthesis involved reacting Fe(II) with ferritin in a buffered solution at pH 7.4 in the presence of phosphate, arsenate, vanadate, or molybdate. O2 was used as the oxidant to deposit the Fe(III) mineral inside ferritin. The rate of iron incorporation into ferritin was stimulated when oxo-anions were present. The simultaneous deposition of both iron and the oxo-anion was confirmed by elemental analysis and energy-dispersive X-ray analysis. The ferritin samples containing iron and one of the oxo-anions possessed different UV/vis spectra depending on the anion used during mineral formation. TEM analysis showed mineral cores with approximately 8 nm mineral particles consistent with the formation of mineral phases inside ferritin.     

Thermal dissociation of iron carbonyls during growth of iron whiskers

Methods for the preparation of iron whiskers in chemical transport reactions of thermal dissociation of iron penta- and dodecacarbonyls and carbidocarbonyl clusters Fe₅C(CO)₁₅ were described. The morphology, structure, and chemical composition of the whiskers were studied. The main factors determining the growth rate and mechanical properties of the whiskers were revealed. A model for the mechanism of thermal dissociation of iron carbonyls was proposed. This process was shown to be a chain radical ion reaction initiated via the scheme of activating complex formation. Analogies between the thermal dissociation of iron carbonyls in the adsorption layer and the known radical ion processes in the liquid and gas phases were found.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1826–1836, September, 2004.     

Transferrins in the metabolism of iron

The main physicochemical characteristics of the transferrins, their physiological role, and questions of reticulocyte-transferrin interaction and the biosynthesis of transferrin are discussed.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 139–151, March–April, 1984.     

Complexometric determination of magnesium in nodular cast iron and alloyed cast iron roll samples

A complexometric method for the determination of magnesium in nodular cast iron, alloyed cast iron and roll samples has been developed. The bulk of the iron is removed by ether extraction and the phosphate as zirconium phosphate. The other elements are removed by extraction with dithiocarbamate into chloroform. Magnesium is then titrated with EDTA at pH 10, with Eriochrome Black T as indicator. Calcium interferes, but is very rarely present in such cast iron samples.     

Mono-Substitution of iron pentacarbonyl catalyzed by polynuclear iron carbonyl anions

The specific formation of LFe(CO)₄ (L = PPh₃, P(OPh)₃, P(OMe)₃ can be achieved by the reaction of Fe(CO)₅ with L in the presence of a catalytic amount of iron carbonyl anion. A convenient synthetic procedure was developed in which the iron carbonyl anion catalyst is generated in situ. It is shown that the mechanism does not proceed by the simple cleavage of the Fe₂(CO)₈^2? or Fe₃(CO)₁₁^2? anions, because triphenylphosphine reacts with these anions in the absence of Fe(CO)₅ to produce (PPh₃)₂Fe(CO)₃.