首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 953 毫秒
1.
今年2月8日是俄罗斯天才的化学家门捷列夫(1834—1907)诞生125周年纪念。特选此译文刊出以为纪念。  相似文献   

2.
苏联共产党第十九次代表大会的决议指示出化学教师应该提高关于综合技术教育的教学质量,更密切地联系学习与生活,使学生认识重要化学生产的科学原理。氨的制造是属于重要化学生产之列的。研究氨的制造是具有重要的教育教养意义。这课题的材料,可以提供作复习和更深入地去认识以前所熟悉的物质的性质和扩大瞭解关于反应进行的条件,以及在工业上的管理方法.在八年级末学期已经学过硫酸的制造,从而熟悉了一些化学工业制造原理,如阶段的划分和流水作业的装置,扩大反应物质的表面,逆流原理,温度和压力的影响,热的交换等等,在研究氨的制造中巩固了这些原理,并且增加了关于适当的压力和循环作业的利用等概念。  相似文献   

3.
王勇 《化学教育》1991,12(5):33-33
一、反应原理在放电条件下,N2和O2能直接化合生成无色的一氧化氮。放电N2+O2(?)2NO一氧化氮在常温下很容易和O2化合,生成棕色并有刺激性气味的NO2。二、仪器及药品打气球、贮气瓶2个(一个标出刻度)、两口玻璃球(容积140ml)、铁架台、铁丝电。  相似文献   

4.
前言有机试剂是用于化学元素和化合物的测定、分离与浓集、掩蔽的有机化合物。这类化合物数量很多,在分析化学中得到极其广泛的应用。有机试剂结构及其与反应性能之间关系的研究是有机试剂理论研究的基本问题。早在本世纪二十年代Feigl就提出了分析功能团的概念。这个概念广泛地应用于有机试剂的研究中,并不断得到丰富和发展。这一概念的出现,为人们研究有机试剂结构与反应性能的关系奠定了基础。随着现代科学技术的不断发展,X射线衍射、红外光谱、拉曼光谱等现代技术也相继用于有机试剂的研究,使人们对有机试剂的认识进一步加深。此外近代迅速发展起来的络合物结构理论、量子化学方法以及计算技术也被用于有机试剂的研究中,从而使得从理论上  相似文献   

5.
对公认的Clapeyron方程的推导的不同意见   总被引:1,自引:1,他引:1  
对公认的Clapeyron方程的推导的不同意见郭余年,赵凤云(吉林工学院轻化工程系长春130012)Clapeyron方程问世干热力学第二定律成立之前。第二定律建立以后,赋予了它以新的内容,使其成为描述单元系任意温度(压力)、任意两相平衡的普遍公式。...  相似文献   

6.
以直线交叉法为依据,根据最小二乘原理,采用Matlab GUI工具设计了一款用于计算二元共聚合反应竞聚率的图形用户程序。与传统的求解竞聚率方法相比,该图形用户程序具有设计原理简单、计算快捷的特点;同时程序提供界面简洁、交互友好的数据输入平台,实用性强。实际应用表明:采用该款图形用户程序所测得的数据与微机动态搜索法、Tidwell-Mortimer法相近,而比采用斜率截距法计算竞聚率的最小差方和更小,并且也避免了采用斜率截距法由于所用方程的非对称性造成的计算结果的不一致性。  相似文献   

7.
将含不同负离子的苄基紫精分散在混合有PVP的MMA-HEMA共聚物基质中可制成耐水的光致变色膜。它们的光致变色速度的大小随紫精负离子的不同而有如下序列:V6(PF6^-)〉V5(BF4^-) ̄V4(ClO4^-)〉V3(CH3-苯环-SO3^-)〉V2(Br^-) ̄V1(Cl^-)。这与这些紫精在DMF中的溶解度以及在共聚物基质中的溶解性大小的序列相一致。负离子对这些光致变色膜在空气中的氧化退色速  相似文献   

8.
在氩气保护下,利用N-(正丁基)-N’(4-甲酰基苯氧戊基)-1.6,7,12-四-(4-叔丁基苯氧基)-3,4,9,10-苝酰亚胺和N-甲基甘氨酸产生的亚胺叶立德与富勒烯反应,合成了含富勒烯的苝化合物,用NMR、FT—IR、UV-Vis及TGA等方法对其结构和性能进行了表征和测试。研究结果表明此类化合物具有好的溶解性和高的热稳定性。  相似文献   

9.
自从本刊1975年第二期“金的快速测定”一文发表以后,读者来信提出了宝贵的意见,认为此法测定金时铊有干扰,且试样分解方法可能使金的结果偏低。过去,我们分析的样品中不含有铊,故对铊的干扰未作考虑。现经试验,在溴氢酸存在下,三价金在低温蒸干时,随时间、温度、溴氢酸用量的不同,均有部份金被还原造成结果偏低。铊的存在对金的测定有干扰。因此对金的快速测定作如下的补充。  相似文献   

10.
砷的光度分析法的进展   总被引:8,自引:0,他引:8  
文中着重介绍了近年来砷的光度测定方法的新进展,包括砷斑法、Ag(DDC)光度法、分单质银分散体系光度法、砷钼蓝光度法等。引用文献85篇。  相似文献   

11.
A miniature planar magnetron glow discharge source with a chamber volume of 60 ml has been designed and evaluated for the analysis of less than 1 μl of aqueous samples by atomic emission spectroscopy. Limits of detection for magnesium, silver, boron, europium and copper in the presence of a magnetic field are observed to be 3 to 40 times lower than for the source without a magnetic field when the measurements are made under the compromised discharge conditions for each type of source. Emission intensity in the presence of the magnetic field is found to increase as a square function of the discharge current. The improved detection limits for the magnetically enhanced glow discharge source are attributed to the increased current density of the discharge in the presence of the magnetic field which formed a plasma ring localized above the cathode surface. An RSD in the range 15–25% is observed for these measurements.  相似文献   

12.
Radiofrequency (rf) multipole ion guides are widely used to transfer ions through the strong magnetic field gradient between source and analyzer regions of external source Fourier transform ion cyclotron resonance mass spectrometers. Although ion transfer as determined solely by the electric field in a multipole ion guide has been thoroughly studied, transfer influenced by immersion in a strong magnetic field gradient has not been as well characterized. Recent work has indicated that the added magnetic field can have profound effects on ion transfer, ultimately resulting in loss of ions initially contained within the multipole. Those losses result from radial ejection of ions due to transient cyclotron resonance that occurs when ions traverse a region in which the magnetic field results in an effective cyclotron frequency equal to the multipole rf drive frequency divided by the multipole order (multipole order is equal to one-half the number of poles). In this work, we describe the analytical basis for ion resonance in a rf multipole ion guide with superposed static magnetic field and compare with results of numerical trajectory simulations.  相似文献   

13.
以Fe3O4磁粉和稳恒弱磁场作为磁场来源,研究了不同磁场条件对微生物/细菌生长及苯酚降解的影响。结果表明,1~4g/L磁粉加量对微生物生长有促进作用,使之提前进入对数增长期;投加量为4g/L时效果最好,加量超过6g/L会抑制微生物生长;磁粉添加使微生物生长静止期稳定性有所下降。适量磁粉和弱磁场作用可促进苯酚与微生物共代谢,能明显提高苯酚的去除率。4g/L磁粉、100mT恒弱磁场作用下,22h对苯酚的去除率分别可达96%、90%,无磁场对照组仅为85%。  相似文献   

14.
A theoretical analysis is presented of the signals observed with different systems that employ the Zeeman effect for background correction in analytical atomic absorption spectrometry.Magnetic modulation of the primary source of radiation offers basically the same possibilities as the deuterium background correction system. Correction for wavelength dependent background absorption is possible only when the magnetic field is applied to the absorbing vapour. Similar expressions are obtained for constant or variable magnetic fields directed either perpendicular or parallel to the optical axis. However, mere magnetic modulation of either the source or the atomizer cannot correct for non-absorbed lines.It is demonstrated that simultaneous correction for non-absorbed lines and background absorption can be attained with a variable magnetic field applied to the atomizer, by taking measurements at three discrete, different field strengths.  相似文献   

15.
The fundamental characteristics of a new type of glow discharge source as designed by Grimm are described. The source incorporates a permanent magnet which causes the electrons in the plasma to execute a spiral motion about the lines of force of the electric field leading to enhanced collisional excitation, sputtering and light output as compared to the conventional source. The performance of the magnetic field glow discharge source in the analysis of mild and stainless steels is evaluated.  相似文献   

16.
张勇  朱亚先 《分析化学》1995,23(11):1348-1353
本文介绍了一种自行设计的能将外加磁场效应引入现有分子发光分析仪器的外加磁场装置,讨论了装置的组成、特点和分子发光分析法中的实际应用以及该装置在研究生命科学、生物体系磁效应等方面的潜在意义。  相似文献   

17.
The magnetic field glow-discharge source (MFGDS) has been evaluated in the analysis of mild and alloyed steels. Its performance, as described by precision, line—background intensity ratio and the quality of calibration curves, was compared to results obtainable with the conventional Grimm glow-discharge source (GDS). The analytical performance was found to be comparable in the analysis of mild steels but difficulties, exhibiting themselves as the splitting of calibration curves, were encountered in the analysis of alloyed steels on account of their differing magnetic properties.  相似文献   

18.
An experimental study was conducted to investigate the effects of several operational parameters in the emission spectra, in the 400-850 nm wavelength region, of a laboratory Argon plasma source. In particular, the emission spectra of the inductively coupled plasma and the Helicon plasma modes of operation were compared. Comparisons of spectra point to a significant increase in the ionization fraction of the plasma for the Helicon mode of operation. The spectral measurements allow one to determine the major trends in the plasma electron density for various parameters such as power delivered to the helical antenna, propellant mass flow rate, and applied external magnetic field intensity.Analysis of a prominent Argon single ion line, at 434.8 nm, points out that the plasma electron density increases linearly with the power delivered to the helical antenna, and that there is an optimum propellant mass flow rate for maximum ionization fraction. Additional analysis of the same line shows that above a minimum applied axial magnetic field intensity, the variation in the magnetic field strength has little effect on the plasma electron density.  相似文献   

19.
Enhancements of the order of 100% in the mass transport limited current for electrodeposition have been observed in magnetic fields of order 1 T. The effect of the field is to induce convection in the solution and it is equivalent to rotating the electrode or stirring the solution. In this communication, a quantitative comparison is made of the magnitude of various body forces which have been proposed to account for the experimentally observed effects, with a view to identifying the likely source of the field enhancement. When the magnetic field is uniform, the Lorentz force and the electrokinetic force both contribute significantly to the field enhancement.  相似文献   

20.
The effects of the external magnetic field has been investigated on the K XRF cross sections of Fe, Co, Ni, and some of their compounds by using an energy dispersive X-ray fluorescence spectrometer. The samples were irradiated by using the γ-rays of 59.537 keV emitted from an 241Am radioisotope source of 100 mCi. The samples were prepared from pure foil of Fe, Co, Ni, and some of their compounds. The external magnetic fields have been applied two opposite directions and the magnitude of the external magnetic field has been fixed at 0.400 T and −0.400 T. The measured K XRF cross sections have been compared with the calculated theoretical data and interpolated values of Puri et al. Our experimental results show that the K XRF cross sections have been affected by the external magnetic field.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号