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利用分光光度法测定有色配合物稳定常数K稳值的方法一般为连续变化法,目前所采用的单曲线法对研究配位比大和离解度大的配合物不准确,又由于双曲线法需要同时作两条等摩尔连续变化曲线．其测定过程繁琐,也不方便应用。故作者在本文中提出一种新的设想,即取单曲线法和双曲线法两者的优点来建立第三种方法──单曲线改进法。 相似文献
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本文以PH电位法,在25.0±0.1℃及离子强度I=0.10mol/dm~3条件下,测定了N-乙酰基-DL-缬氨酸的质子化常数,并系统研究了该配体与十五种稀土元素的配位作用。发现在所研究PH范围内,生成1∶1配合物,稀土与N-乙酰基-DL-缬氨酸配合物稳定性呈现“钆断效应。”此外,对钇的位置进行了讨论。 相似文献
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李可群 《渭南师范学院学报》2010,25(5):41-43
提出了整数斜率点应用于萃取法测定配合物稳定常数的方法,即在金属离子分配比对数值lgD对自由配体浓度负对数pL一阶微分曲线上找出整数斜率点i-c（i=0,1,2,…,n）及其对应的pL值,i为配离子MLi配位数,c为被萃取配离子MLc配位数.在这些pL值分别有lgD=lgλc＋（lgβc-lgβi）＋（i-c）pL＋lgΦMLi,max,式中λc为被萃取配离子在有机相与水相的分配常数,β为配合物累积稳定常数,ΦMLi,max为水相中配离子MLi的最大分布系数.式中略去lgΦMLi,max,当i=c,0时分别得到lgλc和lgβc的初值,其他i值时得到相应累积稳定常数对数值的初值.将上述初值代入上式lgΦMLi,max中可得到新的值,逐步迭代直至两次结果相等即为计算结果.文章使用了两个配合物体系进行计算,它们相邻两级稳定常数对数值差值最小仅为0.3,计算结果与真值一致. 相似文献
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对酯水解的动力学常数测定实验进行改进,通过使用带恒温装置的紫外可见分光光度计,在一定pH值和恒温条件下测定具有三脚架型的二乙烯三胺锌配合物催化磷酸双酯BNPP水解的吸光度随时间的变化,进一步求算出催化磷酸双酯水解的二级速率常数,有助于学生掌握测定配合物催化酯水解的动力学参数。 相似文献
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8-羟基喹啉修饰环糊精可发射8-羟基喹啉基团的荧光,环糊精和8-羟基喹啉基团存在自包结现象,当该修饰环糊精加入金刚烷衍生物后,金刚烷衍生物和修饰环糊精形成更稳定的包合物,可以把环糊精自包结的8-羟基喹啉基团顶出环糊精空腔,从而引起饰修环糊精荧光强度的变化。通过测定荧光强度的变化值,测得修饰环糊精与金刚烷衍生物配合物的稳定常数为LogKs=4.015。 相似文献
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从误差分析角度,分析了分光光度法测定邻菲琳-亚铁离子配合物稳定常数的计算公式中误差传递,结果表明对于稳定常数过高的配合物,由于其解离组分浓度太小,致使其间接测量的相对误差大,经误差传递后,最终使平衡常数K的相对误差远远超过允许范围(如500%),测定结果失去意义。 相似文献
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采用pH电位滴定法测定了Cu(Ⅱ)—水杨酸配合物在离子强度为0.10mol.L-1(KNO3)条件下的pH值,用半整数作图法得出了Cu(Ⅱ)—水杨酸配合物的逐级稳定常数:lgk1=9.90,lgk2=7.32。 相似文献
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本文应用解析法以质子等衡式为依据,先分别算出强,弱酸的酸度,再用加合公式把它们加合起来,以算出混酸溶液的PH,该法比原有方法简便,适用性广,算出的结果也较准确。 相似文献
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脲醛树脂胶粘剂具有价廉、使用简单等特点,但其耐水性较差。文章从甲醛与尿素摩尔比,酸碱性调节,加入改进剂及其改进剂的加入量等方面进行了研究,结论为控制甲醛与尿素摩尔比为1.6,以弱碱-弱酸-弱碱方式调节体系的PH值,以苯酚作为改进剂能够得到耐水性能较好的胶粘剂。 相似文献
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A trinudear Mn（II） coordination complex Mna （HEDTA）2-10H20 （EDTA=ethylene diamine tetraacetic acid） 1 has been synthesized and characterized by X-ray crystal structure determination. In addition, IR spectrum, thermogravimetric analysis, electron paramagnetic resonance （EPR） spectra and magnetic susceptibility of this complex are discussed. X-ray determination indicates that six- and seven-coordinate modes between Mn（Yl） and H4EDTA exist alternately in 1. Furthermore, detailed discussion of magnetic ordering in tile temperature range of 2-300 K reveals the antiferromagnetic interactions in the complex. 相似文献
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Technology-supported learning innovation in cultural contexts 总被引：1，自引：0，他引：1
Jianwei Zhang 《Educational technology research and development : ETR & D》2010,58(2):229-243
Many reform initiatives adopt a reductionist, proceduralized approach to cultural change, assuming that deep changes can be
realized by introducing new classroom activities, textbooks, and technological tools. This article elaborates a complex system
perspective of learning culture: A learning culture as a complex system involves macro-level properties (e.g., epistemological
beliefs, social values, power structures) and micro-level features (e.g., technology, classroom activities). Deep changes
in macro-level properties cannot be reduced to any component. This complex system perspective is applied to examining technology-supported
educational change in East Asia and analyzing how teachers sustain the knowledge building innovation in different contexts.
Working with the macro–micro dynamics in a learning culture requires a principle-based approach to learning innovation that
specifies macro-level changes using principle-based instead of procedure-based terms and engages teachers’ deep reflection
and creative engagement at both the macro- and the micro-level. 相似文献
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以工业级乙二胺和环氧丙烷为原料经开环加成和催化环合两步反应合成了2-甲基哌嗪,两步反应收率分别为84.9％和73.9％,总收率为62.7％。采用活性镍为催化剂,实验验证产品性能良好,经GC分析产品纯度超过98％,外观呈白色结晶体,成本较低,此法适合于工业上大规模生产。 相似文献
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在混合弱酸滴定中,化学计量点时PH值计算、终点误差计算,分步滴定判据是三个必须明确的问题,本文对混合弱酸滴定的这三个问题作一探讨。 相似文献
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采用氯化钡改性的方法制备氯化钡改性膨润土。研究了振荡时间、废液的pH值、改性膨润土的用量、吸附温度、亚甲基蓝的初始浓度对改性膨润土吸附性能的影响,通过单因素试验和正交试验获得最佳吸附条件。建立了等温吸附模型,考察改性膨润土的再生能力。实验结果表明：当吸附温度为25℃,吸附剂用量为0.5g,吸附时间为20min,亚甲基蓝的浓度为70mg/L,溶液的pH值为7时,钡基改性膨润土对亚甲基蓝的吸附率达到93.25%,吸附符合Langmuir等温吸附模型,热再生率较高。 相似文献
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This article reviews current scholarship about how to promote change in instructional practices used in undergraduate science, technology, engineering, and mathematics (STEM) courses. The review is based on 191 conceptual and empirical journal articles published between 1995 and 2008. Four broad categories of change strategies were developed to capture core differences within this body of literature: disseminating curriculum and pedagogy, developing reflective teachers, enacting policy, and developing shared vision. STEM education researchers largely write about change in terms of disseminating curriculum and pedagogy. Faculty development researchers largely write about change in terms of developing reflective teachers. Higher education researchers largely write about change in terms of enacting policy. New work often does not build on prior empirical or theoretical work. Although most articles claim success of the change strategy studied, evidence presented to support these claims is typically not strong. For example, only 21% of articles that studied implementation of a change strategy were categorized as presenting strong evidence to support claims of success or failure of the strategy. These analyses suggest that the state of change strategies and the study of change strategies are weak, and that research communities that study and enact change are largely isolated from one‐another. In spite of the weak state of the literature, some conclusions related to the design of change strategies can be drawn from this review. Two commonly used change strategies are clearly not effective: developing and testing “best practice” curricular materials and then making these materials available to other faculty and “top‐down” policy‐making meant to influence instructional practices. Effective change strategies: are aligned with or seek to change the beliefs of the individuals involved; involve long‐term interventions, lasting at least one semester; require understanding a college or university as a complex system and designing a strategy that is compatible with this system. © 2011 Wiley Periodicals, Inc. J Res Sci Teach 48: 952–984, 2011 相似文献
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校际合作改进薄弱学校是支教的一种方式,浙江省优质Z中学和薄弱D中学以文化濡染、深度合作的方式,帮助薄弱校改进成长,已产生明显效果,彰显了独特的文化意义。按照文化变迁和整合理论来看,这种支教方式体现了人类文化是可以实现有意识变迁的,不过需借助人类学习文化的功能方式才能实现,需要借助文化整合,使不同的文化要素和组成部分相互适应,结合成一个有机整体,薄弱学校的文化变迁便可真正完成。 相似文献
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山楂也称红果、山里红,在我国有极其丰富的资源.山楂红色素中含有可溶性糖、酸和黄酮类物质,属于天然花青素类色素,具有抗氧化和消除自由基的作用,有一定的药用和保健价值[1-3].山楂红色素安全、无毒且含有一定的营养成分,可用于食品着色和饮料的配制等.同时这种色素主要存在于 相似文献