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1.
2.1.2 沉淀草酸稀土时草酸的加入量及溶液的酸度条件与稀土的氢氧化物和氟化物相比,草酸稀土沉淀的溶解度相对较大,因此,溶液体积不宜太大和稀土离子的量不宜太少是进行草酸稀土沉淀时的两项基本要求。为使草酸稀土的沉淀尽可能地完全,一般要求  相似文献   

2.
于pH5.5—6溶液中以EDTA络合滴定镍时,合金钢中所有常见干扰元素(如锰、铬、铜、钴、铝、锡、钛、锆、铈、稀土元素等)可在氨性柠檬酸盐存在下先使镍成丁二肟镍沉淀与其分离加以消除(预先使铬成六价,钴则以过氧化氢消除)。丁二肟镍沉淀中沾污的痕量铁、铜等可在络合滴定前以氟化物-抗坏血酸及硫脲联合掩蔽。本法利用二甲酚橙的酸碱及金属指示剂双重特性,能准确地调整滴定溶液酸度至pH5.5—6,再以锌盐反滴过量EDTA完成镍的测定。经含镍1—20%的各类标样验证,获得满意结果,适用于所有合金钢的常规分析,经适当处理也可适用于  相似文献   

3.
研究了在酒石酸盐存在下,以硫代硫酸钠为掩蔽剂,于醋酸盐缓冲溶液中,镍呈丁二酮肟镍沉淀与共存元素铁、铝、铅、铬、锌、钒、钛和铜等分离。然后于pH4.5~5.5的醋酸盐缓冲溶液中,以高灵敏度的显色剂2-(5-溴-2-吡啶偶氮)5-二乙氨基苯酚(5-Br-PADAP)作指示剂,用EDTA络合滴定镍。人工合成试样(含8%铁、30%铜、1%钴、55%镍等)的分析结果表明,在丁二酮肟镍沉淀中残留的铜、铁、钴量均分别低于11、5和1毫克。标准加料回收试验的回收率为99.7~100%。以本法和其他方法对照分析含镍54.97%的标样,结果很一致。由误差统计求出本法测定结果的变异系数为0.14%。试剂配制镍标准溶液(2毫克/毫升镍):EDTA-  相似文献   

4.
对于某些重金属离子,可以通过形成氯络离子交换吸附于阴离子交换树脂柱上,再利用各金属络阴离子稳定性的差别,以不同浓度的HCl淋洗进行分离回收。在工业实际应用中,人们总希望降低淋洗液的酸度,这对回收过程更为有利。对分析中的分离来说,降低淋洗液酸度也便于分离后的测定。本文对分离回收Co~(2+)、Fe~(3+);Co~(2+)、Mn~(2+)、Fe~(3+)所用树脂和低酸度洗脱等进行了探讨。实验结果表明:为了除去铁杂质回收钴或锰的离子交换分离或Mn~(2+)、Co~(2+)、Fe~(2+)的层析分离,不仅可在较浓的盐酸溶液条件下进行;也可以在较低浓度的盐酸和氯化钠的混合溶液中完成。增大淋洗液中NaCl的浓度,就可降低其中盐酸的浓度,可得到同样满意的结果。  相似文献   

5.
稀土在电沉积镍-钴合金中的作用   总被引:7,自引:0,他引:7  
由于稀土元素具有独特的电子层结构和化学性能,使稀土及其化合物在材料科学领域中的应用越来越广泛,尤其是稀土在电沉积过程中的研究及应用正日趋深入。这是因为在电镀溶液中加入少量的稀土化合物后,可以改善镀液的分散能力和深镀能力,提高电镀的电流效率,增加镀层的硬度和耐蚀性等[1 4],但有关稀土在电沉积镍 钴合金中的作用的研究还未见报道。本文研究了在硫酸盐体系镍 钴合金电镀液中加入少量的稀土化合物后对电沉积过程、合金电极的催化性能、合金镀层的形貌和成分的影响。1 实验方法基础镀液成分(g/L)为NiSO4·7H2O200,CoSO4…  相似文献   

6.
目前,常用的测定铜的方法中,铁、钴、镍等均为干扰元素,通常是在硝酸介质中,用硫代硫酸钠将铜以硫化物形式沉淀分离,再转化为溶液进行铜的容量法或比色法测定。把铜的硫化物沉淀转化为溶液时都要通过灰化、灼烧、溶解及硫酸冒烟,甚至加入熔剂熔融浸取等手续,这就使方法变得烦琐。  相似文献   

7.
金属铜钴镍中微量硅的光度法分析 ,由于有色离子的干扰 ,现行的方法中 ,常用萃取方法分离硅[1,2 ] ,使得分析流程长 ;使用有机溶剂污染环境 ,对操作者健康不利。本文采用铁氰化钾 亚铁氰化钾沉淀分离大量铜钴镍等离子 ,让微量硅留于溶液中 ,利用小体积 硅钼蓝吸光光度法较好地解决了大量有色离子中微量硅的分离与测定。1 试验部分1.1 仪器与试剂72 1型分光光度计 (上海第三分析仪器厂 )沉淀剂 :称取铁氰化钾、亚铁氰化钾各 3.8g于2 5 0ml烧杯中 ,加水约 5 0ml,微热溶解后 ,移入10 0ml容量瓶中 ,用水稀释至刻度 ,混匀。硅标准溶液 :以高…  相似文献   

8.
应用螯合树脂分离稀土,国外已有这方面的报告。本文介绍应用含有偶氮胂I特征结构的Asl螯合树脂进行微量稀土总量和部分轻、中、重稀土La、Nd、Lu之间的分离和测定。研究了AsI螯合树脂分离稀土的特性和条件,测定了树脂对稀土的交换容量、分配系数及分离因素等参数。采用不同酸度和浓度的a-羟基异丁酸为洗脱剂,进行柱上分离稀土实验,2.6小时能定量洗脱分离微克量的La、Nd、Lu离子。  相似文献   

9.
在乙酸缓冲溶液中(pH3.5),铜试剂能有效地沉淀分离铁、镍、钴、铜、钼、钨、钒、铌和大部分铬、锰、钛等干扰元素而不吸附铝,然后用EDTA进行滴定。残留的钛以及含少量锆或稀土的试样可以在滴定时用铜铁试剂进行有效的掩蔽。当铁、钴共存时,加入铜试剂能使部分Fe~(3+)还原为Fe~(2+),而Co~(2+),被氧化为Co~(3+),降低了对铁的分离效果,加入过氧化氢可以避免此现象的发生。本法适用于含锰≤2%,含钛<5%的高温合金、精密合金、钒铁、合金钢和铝青铜中铝(>0.4%)的测定。方法准确、快速。  相似文献   

10.
为有效去除稀土草酸沉淀废水中残留的草酸,采用电解氧化探索氧化分解废水中草酸的可行性。考察不同阳极、反应温度、反应时间、废水初始酸度等因素对氧化效果的影响。草酸的氧化速度随反应温度、电流和反应时间的增加而升高,随初始酸度的增加反而降低,确定了优化工艺条件。[C_2O_4~(2-)]=1.84 g·L~(-1),[H~+]=0.90 mol·L~(-1)的Eu草酸沉淀废水,在反应温度30℃,电流1.5 A,反应时间5 h,草酸的氧化率可达99%,废水中残留的草酸质量浓度仅为0.01 g·L~(-1),处理后的废水可直接返回稀土萃取分离,实现了工艺流程的闭路循环。  相似文献   

11.
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.  相似文献   

12.
KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.  相似文献   

13.
The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.  相似文献   

14.
Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.  相似文献   

15.
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.  相似文献   

16.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion.  相似文献   

17.
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.  相似文献   

18.
An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.  相似文献   

19.
20.
N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).  相似文献   

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