共查询到20条相似文献，搜索用时 68 毫秒
1.
冯泳兰 《衡阳师范学院学报》1993,(6)
在表面活性剂DDMBA 存在下,0.64～0.80mol/LHCl 介质中,Ge(Ⅳ)与香草基荧光酮(VF)形成橙黄色配合物。其λ_(max)为500nm,显色反应具有很高的灵敏度和选择性,表观摩尔吸光系数ε为1.48×10~5 L·mol~(-1)·cm~(-1)。Ge 含量在0～8ug/2Sml 符合比尔定律。该法不经任何分离直接应用于矿石、铅锌矿渣中微量锗的测定,获得满意的结果。 相似文献
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研究了2—(3,5—二氯—2—吡啶偶氮)—5—二甲氨基苯胺与铑(Ⅲ)的显色反应,在PH4.0～5.2范围内,试剂与铑(Ⅲ)形成稳定的紫红色配合物、配合物形成后,提高酸度至0.72～mol.L~(-1)盐酸溶液,其中最大吸收峰红移至614nm,,灵敏度显著提高,表观摩尔吸光系数ε_(614)=1.40×10~5L·mol~(-1)、cm~(-1),铑含量在0～0.72μg、mol~(-1)内符合比尔定律。所拟方法操作简便,灵敏度高,用于储化剂中微量铑的测定,获得满意结果。 相似文献
3.
在5．3mol·L－1的H2SO4介质中．锗与4．5-二溴苯基荧光酮，十二烷基硫酸钠生成三元配合物。其λmax为509nm，表观摩尔吸光率为1．77×105L·mol-1·cm-1．锗量在0～7μg／25mL遵守比耳定律。显色反应具高选择性，各种低价和高价金属离子均不干扰测定。测定了有机锗口服液中微量锗。 相似文献
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宁明远 《邵阳学院学报(社会科学版)》1994,(5)
钇—铬天青S—邻菲罗啉—澳化十六烷基三甲铵体系在PH=9.0-11.5的酸度范围内形成稳定的绿色四元配合物,其λ_(max)=630nm,摩尔吸光系数达1.08×10~5L·mol~(-1)·cm~(-1)。在钇浓度为2—25ug/25ml时符合比耳定律,可用于镍基合金中钇的测定。 相似文献
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本文介绍椭圆与双曲线的一个有趣性质,并说明其应用. 性质 1 设P点是椭圆b2x2+a2y2=a2b2(a>b>0)上异于长轴端点的任一点,F1、F2为其焦点,记∠F1PF2=θ,则|PF1|·|PF2|=2b2/1+cosθ 简证:由椭圆定义有|PF1|·|PF2|=2a (1) 在△PF1F2中,由余弦定理有|PF1|2+|PF2|2-2|PF1|·|PF2|cosθ=4c2 (2) (1)2-(2)化简得 相似文献
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在 pH =5的邻苯二甲酸氢钾 -氢氧化钠的缓冲溶液中 ,钴 (II)与双水杨醛乙二胺形成黄色配合物 .该黄色配合物的λmax =380nm ,ε =5 .5x10 3L·mol- 1 ·cm- 1 ,Co(II)的质量浓度为 0～ 4 7mg 10ml时符合比尔定律 .本方法用于测定VB12药物中的钴结果良好 相似文献
7.
在pH=5的邻苯二甲酸氢钾-氢氧化钠的缓冲溶液中,钴(Ⅱ)与双水杨醛乙二胺形成黄色配合物.该黄色配合物的λmax=380nm,8=5.5x103L·mol-1·cm-1,Co(Ⅱ)的质量浓度为0～47mg/10ml时符合比尔定律.本方法用于测定VB12药物中的钴结果良好. 相似文献
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研究了3’-甲氧基-4’-羟基苯基荧光酮光度法测定微量钼的方法。在HCl介质中,溴化十六烷基三甲铵 (CTMAB)存在下,3’-甲氧基-4’-羟基苯基荧光酮(MHPF)与钼(VI)显色,形成摩尔比为2:1的红色配合物。配合物最大吸收波长位于522nm,表观摩尔吸光系数ε522为1．03×105L·mol-1·cm-12．4×105L·mol-1·cm-1,钼含量在0-0．48 mg／L范围内符合比耳定律。研究的新光度方法应用于食物样品中微量钼的测定,结果满意。 相似文献
9.
本文成功地建立了以微晶石蜡柱为固相萃取剂,以2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(5-Br-PADAP)为显色剂的固相萃取光度法测定痕量铁的新方法,并采用正交试验法考查了测定条件.方法基于在pH=4.5的缓冲溶液中,铁(Ⅱ)与5-Br-PADAP形成稳定的配合物,在λ=742nm处进行测定,其摩尔吸光系数为ε742=2.61×105L·mol-1·cm-1,检测限为0.218μg·L-1,铁含量在0-0.4μg·mL-1范围内服从比尔定律.该方法用于水样中痕量铁的测定,结果满意. 相似文献
10.
在常规条件下 ,当 pH值为 3,Ge与H8X的物质的量比为 1∶1时 ,合成了乙二胺四甲叉膦酸 (简称EDTMP)与锗的固体配合物 ,用元素分析、红外光谱和热分析进行了表征 .配合物的组成为 :GeH4X·4H2 O ,X =(O3 PCH2 ) 2 NCH2 CH2 N(CH2 PO3 ) 2 .配合物具有一维链状配位聚合结构 . 相似文献
11.
罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
12.
Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
14.
邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献