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1．多元酸与碱的反应
如H3PO4溶液与Ba（OH）2溶液反应：
（1）将H3PO4溶液逐渐滴入Ba（OH）2溶液中；立即出现沉淀，后沉淀逐渐溶解．先后发生的反应为：2H3PO4＋3Ba（OH）2=Ba3（PO4）2↓＋6H2O，Ba3（PO4）2＋H3PO4=3BaHPO4↓，BaHPO4＋H3PO4=Ba（H2PO4）2． 相似文献
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宁明远 《邵阳学院学报(社会科学版)》2003,2(5):77-78
为提高铁系磷化效果，研究了一种新的常温磷化液，介绍了其配方、配制和磷化工艺，讨论了磷化液组成和工艺条件对磷化膜的影响，并对磷化膜的性能进行了检测．结果表明，该磷化工艺具有磷化液组成简单、污染少、成本低、磷化膜厚度适当、色彩均匀、耐腐蚀强等特点，具有广阔的应用前景． 相似文献
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通过对磷化参数的调整及分析,研究了不同影响因素下的磷化膜形貌特征。试验结果表明,磷化工艺适宜的实验条件为:磷化液温度:35℃～40℃;磷化时间:2～3min;总酸度浓度为120g/L、游离酸与总酸比为1:30;促进剂浓度:0.3gL～0.6g/L。 相似文献
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笔者采用火焰原子吸收光谱法测定了长江起点水域中的微量元素镉、铬、锰、锌、铜、镍6种元素，考察了不同种酸及酸度对硝化作用的影响和在体系中共存离子的相互干扰情况。用NH4H2PO4-Mg（NO3）2作为测定镉、铬的基体改进剂，得到了良好的测定结果，其标准加入回收率为96．5％-105％，相对标准偏差为1．1％-2．0％，检测限镉为0．040mg／L；铬为0．018mg／L；锰为0．020mg／L；锌0．096mg／mL；铜为0．064mg／mL；镍为0．035mg／mL。 相似文献
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“分别Na3PO4，NaH2PO4，NazHPO4三种溶液中滴加AgNO3溶液，其沉淀物：A．都是Ag3PO4B．分别是Ag3PO4，AgH2PO4，Ag2HPO4 C．都是AgH2PO4 D．都是Ag2HPO4。这是1987年全国化学竞赛试题第19题选择题，这道题正确答案为：A。资料显示磷酸的钠、钾、铵盐及磷酸的二氢盐都易溶于水， 相似文献
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从温度、酸度、磷化时间、添加剂、前处理等方面研究了中温锌钙系磷化液的影响因素，并将在各种不同条件下所制得的磷化膜的外观、耐蚀性、附着力等性能加以比较、测定，找到了最佳磷化条件。 相似文献
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采用液相沉淀法制取了Cs2（HSO4）2（H2PO4）,用XRD,IR标明其晶体结构。通过研究发现SO42-：PO43-=0.7：0.3时能够制得结晶良好的Cs3（HSO4）2（H2PO4）晶体,其电导率σ为2.52×10-3S/cm。 相似文献
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室温下,以Ti（S04）22-6g／L,H2021-2g／L,NaF3-5g／L,EDTA2-6g／L为转化液的主要成分,加入1-2g／LCe（N03）3 ．6H20促进转化膜的致密性和均匀性,控制转化液pH4．0-4．5,转化处理10min,在样品表面制备一层化学转化膜．通过中性盐雾测试和电化学测试表征转化膜的耐蚀性,采用冷场发射扫描电镜（SEM）观察转化膜的微观形貌,X射线能谱仪（EDS）分析转化膜的化学成分．结果表明：该转化膜耐蚀性优艮,EDS能谱分析得出这层颗粒状物质主要由Na,A1,F元素和少量的Mg,Ti,O元素组成,推断转化膜的主要成分为Na3AIF6,铈盐起到促进转化膜致密性和均匀性的作用． 相似文献
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赵亚丽 《晋城职业技术学院学报》2012,5(4):91-94
液膜分离是一种高效低成本的金属离子预富集手段,本文采用组成为载体P-204（8％）,表面活性剂Span-80（3％）,膜稳定剂液体石蜡（0．5％）,膜溶剂煤油（88．5％）,内相HC1的浓度2．0mol／L的液膜萃取体系,考察了萃取时间、外水相酸度、转速、乳水比的分离条件对镉萃取率的影响。,实验优化后的萃取条件为萃取时间10min、外水相pH=4．50、乳水比1：4、搅拌速度200r／min;将液膜分离与火焰原子吸收相结合检测镉、铜离子,结果表明,此法灵敏度高、检测限低、检测范围宽。 相似文献
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锅垢的成分是什么？有的同学会回答：碳酸钙．其实,锅垢的成分不一定都是碳酸钙,因此,清洗锅垢也要具体问题具体分析．锅垢的组成很复杂,通常为许多种化合物的混合体．根据其主要化学成分;锅垢有如下几个类型：l钙垢：其主要成分是CaCO3、C3SO4,其结构较疏松,如开水瓶内水垢,可用醋酸除去．z．镁垢：主要是Mg（OH）2和Mg3（PO4）2,可配制1％的稀盐酸除之．3．磷酸盐垢：主要成分是Fe3（PO4）2和NaFePO4;可用5％的磷酸溶液除之．4．硅酸盐垢：主要成分为钠沸石,Na2O,Al2O3·3SiO2·2H2O,方沸石Na2O·Al2O3·4SiO2… 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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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,(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
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 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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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献