硅钼蓝分光光度法测定磷铁合金中硅

硅钼蓝光度法测定硅在冶金领域中已有广泛应用[1-3],但大都是应用于低磷合金,然而对于磷铁合金(磷质量分数高达30%)中硅含量的测定通常采用氟硅酸钾滴定法[4],也有文献报道采用十二烷基硫酸钠作保护剂,用硅钼蓝光度法测定[5]。本工作采用草酸破坏磷钼、砷钼杂多酸,在高酸度下消除磷干扰,用硅钼蓝光度法测定硅的含量。1试验部分1.1仪器与试剂721型分光光度计。无水亚硫酸钠溶液:30g·L-1。     

孔雀绿-磷钼杂多酸光度法测定钢铁中磷

钢铁中磷的测定目前多采用磷钼蓝光度法及磷钒铝黄光度法,但前者的吸光度稳定时间短,不适用于成批试样的分析;后者的吸光度稳定时间虽然较长但灵敏度低。文献报道了孔雀绿-钼磷杂多酸光度法测定矿石中微量磷的条件,指出此法灵敏度比磷钼蓝光度法高,吸光度24小时不变。本文研究以孔雀绿-磷钼杂多酸光度法则定钢铁中磷的条件,表明,在0.28—     

铋磷钼蓝光度法测定钼精矿中磷

磷是钼精矿中有害杂质元素之一,对其后序加工的产品质量有很大影响。钼精矿中磷的测定方法有磷钒钼黄光度法、有机试剂萃取-钼蓝光度法。其不是灵敏度低就是操作繁琐。本文采用铋磷钼蓝光度法,操作简便、快速,灵敏度高。结果令人满意。     

分光光度法快速测定钢铁中的锰、磷、硅

用硝酸、过硫酸铵溶解试样,在较高温度下,分别用过硫酸铵光度法测定钢铁中的锰含量,铋磷钼蓝光度法测定磷含量,抗坏血酸硅钼蓝光度法测定硅含量。方法简便、快速、灵敏、准确并已应用于锰、磷、硅自动分析仪。     

钢铁及矿石中微量砷的测定——砷锑钼蓝光度法

利用磷锑钼三元络合物的钼蓝光度法,已广泛地应用于磷的测定。而砷锑钼三元络合物的钼蓝光度法的研究和应用还比较少见。本文在前人工作的基础上,研究了砷锑钼络合物的组成,钼蓝生成条件及应用。拟定了一个以砷化氢分离,砷锑钼蓝光度法测定钢铁及矿石中微量砷的方法。 (一)试剂及仪器碘溶液:碘0.5克,碘化钾5克,加少量水溶解后,加碳酸氢钠5克,加水至500毫升。     

光度法测定生铁和铸铁中磷

利用氟化钠-氯化亚锡还原钼蓝光度法测定磷是钢铁中直接快速测磷的方法。在酸性介质中,磷酸与钼酸铵生成磷钼杂多酸,再用氯化亚锡还原,形成钼蓝。当无铁基存在时,色泽呈纯蓝色,形成的磷钼杂多蓝很稳定;当有铁基存在时,特别是分析含磷量较高的试样时,因发色后的磷钼蓝色泽极不稳定,颜色由深蓝色向     

磷砷共存时磷的快速测定

磷砷共存在某些钢材中.由于砷钼杂多酸形成条件与磷钼杂多酸形成条件相似,因此砷对磷的测定有干扰.目前采用的方法为消除砷测磷的干扰.普遍采用正丁醇-三氯甲烷萃取光度法.但萃取分离,只能解决低含量磷和砷的定量分离,不能解决高砷试样的测定.本法利用酒石酸抑制砷钼杂多酸的形成,以抗坏血酸为还原剂,磷钼蓝光度法测定,省略了分离步骤,方法简便快速,重现性和稳定性良好.     

光度法测定含钡铁合金中磷

含钡铁合金如硅钡、硅铝钡、硅钙钡等均为新型铁合金 ,其在冶金行业中的应用正越来越广泛 ,但无相应国家标准分析方法。本法采用硝酸 ,氢氟酸溶解样品 ,高氯酸冒烟赶尽氟化物。采用铋盐存在下抗坏血酸还原磷钼蓝光度法测磷含量[1] 。本法分析周期短 ,准确度高 ,完全可满足分析要求。1　试验部分1.1　主要仪器与试剂72 1型分光光度计磷标准溶液 :5 μｇ·ｍｌ-1硝酸铋溶液 :5ｇ·Ｌ-1,硝酸 (1+3)介质。1.2　试验方法称取纯铁 0 .15ｇ ,氯化钡 0 .3ｇ于 30 0ｍｌ聚四氟乙烯烧杯中 ,加浓硝酸 10ｍｌ ,氢氟酸 2ｍｌ ,高氯酸2ｍｌ,置电热板上蒸至…     

磷钨钼钒杂多蓝光度法测定钼的探索

本文研究了磷钨钼钒四元杂多酸及其还原产物杂多蓝的形成条件、光度性质、组成和在测定高速钢中高钼的应用。试验表明,磷钨钼钒杂多蓝光度法测定钼具有新颖性、高选择性、较高准确性和简便性,适于高速钢中>1％Mo的测定。     

赤霉素还原-钼蓝光度法测定钢铁中硅

作者曾以赤霉素为还原剂,对磷钼杂多酸的还原反应进行了研究,并应用于钢铁中磷的光度测定,结果满意。本文是前文研究的继续,以赤霉素作还原剂-钼蓝光度法测定钢铁中硅。方法的灵敏度和选择性均比其它常用的还原剂高,生成的钼蓝颜色和还原剂本身均稳定。经试验表明,在2.16—9.36N硫酸酸度溶液范围内,并置沸水浴中加热3分钟,硅钼杂多酸可被定量还原成钼蓝,吸光度较高且恒定。其最大吸收位于810nm,表观摩尔吸光系数为3.51×10~4,     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

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.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.