36 沸点和蒸馏
Boiling Points of Pure Liquids
沸点的纯液体
Any given liquid, when admitted into a closed evacuated space, evaporates until the vapor attains a certain definite pressure, which depends only upon the temperature. This pressure, which is the p ressure exerted by the vapor in equilibrium with the liquid, is the vapor pressure of the liquid at th at temperature. As the temperature increases . the vapor pressure of a typical liquid x increases reg ularly as shown by the generalized vapor pressure-temperature curve BC, in Fig. 5.
任何给定的液体,当进入一个封闭的疏散空间,蒸发到蒸汽形成某种明确的压力,仅仅依赖于温度。这种压力,这是由蒸汽压力与液体平衡的,是液体的蒸气压在温度。随着温度的升高。这个压力，是通过在与液体平衡的蒸汽施加的压力，是液体在该温度下的蒸汽压，其随着温度的增加而增加。一个典型液体x的蒸汽压的增加经常如图五所示，广义蒸汽压-温度曲线BC。
At the temperature, Tp, where the vapor pressure reaches 101.3kPa. x begins to boil and Tp is call ed the NORMAL BOILING POINT of x. Every liquid which does not decompose before its vapor pressure reaches 101.3kPa. has its own characteristic boiling point. In general, the boiling point of a substance depends upon the mass of its molecules and the strength of the attractive
forces between them. For a given homologous series, the boiling points of the member compounds rise fairly regularly with increasing molecular weight.
在温度、Tp,那里的蒸汽压力达到101.3 kPa。开始煮和x Tp被称为正常沸点液体的x。在这个温度，当蒸汽压达到101.3 kPa时，液体x开始沸腾，这个蒸汽压力被叫做x的正常沸点。任何一种液体在它的蒸汽压达到101.3 kPa之前都不分解，每种液体的沸点都有其自身的特点。一般来说,一种物质的沸点取决于它的分子质量和它们之间的引力的强度。对于一个给定的同系物，其成员化合物的沸点随分子量的增加而增加。
Polar liquids tend to boil higher than nonpolar liquids of the same molecular weight, and associated polar liquids usually boil considerably higher than nonassociated polar compounds.
极性液体的沸点往往高于相同分子量的非极性液体，而相关的极性液体的沸点远远高于一般的极性化合物。
The boiling point is a characteristic constant that is widely used in the identification of liquids. Be cause of its marked dependence upon pressure and its rather erratic response to impurities, howeve r, it is generally less reliable and useful in characterization and as a criterion of purity than is the m elting point for solids1.
沸点是一个常数,广泛用于识别液体。然而，由于对压力的显著依赖性和对杂质的相当无规律的反应，沸点用于鉴别和作为纯度的判据方面，较之固体的熔点一般不太可信和较少使用。Boiling Points of Solutions
沸点的解决方案
The normal boiling point of any solution is the temperature at which the total vapor pressure of the solution is equal to 101.3kPa. The effect of any solute, Y, on the boiling point of X will depend, th en, upon the nature of Y. If Y is less volatile than X. then the total vapor pressure of the solution is lower, at any given temperature, than the vapor pressure of pure X.
正常沸点的任何解决方案都是在其溶液总蒸汽压力等于101.3 kPa时的温度。任何溶质，Y 在X上的沸点的效果将取决于Y的性质。如果Y比X难挥发。那么其总蒸汽压都比在任何
给定的温度下纯X的蒸汽压低。
Such a case is represented by curve B'C , in which the experimentally determined values tor the va por pressures of a solution are plotted against temperature. The vapor pressure of the solution does not reach 101.3kPa. until a temperature Tp' is attained. In other words, the presence of the less vol atile solute raises the boiling point of X from Tp to Tp'. A solution of sugar or salt in water is a fa miliar example of this type of solution.
根据溶质所确定实验值来绘制温度-蒸汽压力图，如曲线B'C所示。直到温度达到Tp'时，其溶液的蒸汽压才达到101.3 kPa。换句话说,较低挥发性溶质的存在使X的沸点从Tp提高到Tp’。这种类型的一个广为人知的例子就是糖或盐溶解在水中。
Figure 5. Generalized vapor pressure diagrams for a pure liquid (BO , for a solution in which the s olute is less volatile than the solvent (B'C), and for a solution in which the solute is more volatile t han the solvent(B"C").
图5。广义水汽压图表示纯液体(BC,溶液中溶质比溶剂(B 'C)难挥发，以及另一溶液中含有更不稳定的溶剂(B“C”)。
On the other hand, if Y is more volatile than X. then the total vapor pressure of the solution is higher than that of pure X, as shown by curve B"C". The vapor pressure of such a solution reaches 101.3kPa. at temprature Tp"; hence the effect of the more volatile solute is to lower the boiling po int of X from Tp to Tp". A solution of acetone in water is an example of this type.
另一方面,如果Y比X更易挥发。那么其溶液的总蒸汽压比纯X的高。,如图所示曲线B’’C’’所示。当一溶液的蒸汽压力达到101.3 kPa、温度达到Tp ",因此更多的挥发性溶质的作用是使X的沸点从TP降低到TP’’。丙酮在水中的溶液就是这种类型的一个例子。
In any solution of two liquids X and Y, the molecules of X are diluted by molecules of Y, and, con versely, the molecules of Y are diluted by molecules of X. Y ou would therefore expect the
vapor pressure due to X to be less than that of pure X; in fact, you might predict that the PARTIAL PRESSURE due to X would be proportional to the molecular concentration of X.
在任何溶液中的两种液体X和Y，X的分子被Y的分子稀释，相反,Y的分子被X的分子稀释。你因此会认为由此X的蒸汽压就小于纯的X。事实上,你可以预测,X的局部压力,与X 的组分的浓度成正比。
Similarly, the partial pressure of Y might be expected to be proportional to the molecular concentr ation of Y. This is, in fact, the relationship which holds for so -called ideal solutions. It is expresse d in Raoult's Law-the partial pressure of a component in a solution at a given temperature is equal to the vapor pressure of the pure substance multiplied by its mole fraction in solution. In symbols, for a solution of components X and Y.
同样地,局部压力的Y也许被希望是与Y的分子浓度成正比。 .这是,事实上,这种关系可以使用与理想溶液。这由拉乌尔定律表述为：溶液中成分的局部压力等于在给定温度下的纯物质的蒸汽压乘以该物质在溶液中的摩尔分数。用符号X和Y表示溶液的组分。
Px=Px0Nx
where Px = the partial pressure of X in solution,
Px=X在溶液中的分压
Px0= the vapor pressure of pure X at that temperature,
Px0 =纯X在该温度下的蒸汽压
Nx = the mole fraction of X in the solution.
Nx =X在溶液中的摩尔分数
Similarly.
相同的，
Py = Py0Ny
where Py = the partial pressure of Y in solution.
Py=Y在溶液中的分压
Py0 = the vapor pressure of pure Y at that temperature,
Py0 =纯Y在该温度下的蒸汽压
Ny = the mole fraction of y in solution.
Ny=Y在溶液中的摩尔分数
The total pressure, PT of the solution would be the sum of the partial pressures of X and Y.
溶液的总压，PT，是X和Y的分压的加和。
PT = Px+Py
Temperature-Composition Diagram for Solutions which Follow Raoult's Law. 溶液的温度—组成图遵循拉乌尔定律
These facts are represented graphically in Fig. 6 which shows a typical te mperature-composition diagram. This diagram is a temperature-compositi on plot of the experimentally determined values for the system benzene-t oluene, but it is representative of the plot for all solutions which are descr ibed by Raoult's Law.
根据事实，用图6来表示，图6是一个典型的温度-组成图。这个图是用实验方法对苯-甲苯系统测定值而得到，但对所有可以用拉乌尔定律来表示的溶液，这是一个典型的图。
Boiling points (ordinates) are plotted against composition expressed as m ole fractions (abscissae). Pure benzene (100 percent x ) boils at 80.1° (p oint A) and pure toluene (100 percent y ) at 110.6° (point B). All mixtur es of the two boil at intermediate temperatures, as shown by the liquid (lo wer) curve. This curve shows the temperature at which a mixture of benz ene and toluene of any given composition begins to boil. The vapor (uppe r) curve represents the composition of the vapor in equilibrium with the li
quid at any given temperature.
沸点（纵坐标）绘制对组成表示为摩尔分数（横坐标）。纯的苯(100% x)沸点为80.1℃(A点)、纯甲苯(100% y)的沸点为110.6℃(B点)。所有混合物的沸点在两个纯组分的沸点之间,如图所示液体(下图)曲线。该曲线显示了在任何给定的苯-甲苯的组成开始沸腾的温度。蒸汽(上面)曲线表示了在任何给定温度下气-液平衡时的组成。
For example . consider the changes which occur when a 20 mole per cent benzene — 80 mole per cent toluene solution (represented by point P) is heated. At 101.6°, corresponding to point L1 the liquid begins to boil. T he first trace of vapor which is formed is, of course,in equilibrium with th
e liquid at 101.6°. It has the composition 38 mole per cent benzene — 6
2 mole per cent toluene, as represented by point V1, and is therefore cons iderably richer than the liquid in benzene.
以20%的苯和80%的甲苯（P点）溶液被加热时出现的变化为例。在101.6℃,对应点L1液体开始沸腾。首次出现微量的蒸汽，它的组成在101.6℃是与液体平衡的。它由38%的苯和62%的甲苯组成，V1为代表点，因此比苯含量更大。
Figure 6. Temperature-Composition diagram of the system benzene-tolue ne.
图6 .温度—组成图苯-甲苯系统。
As the distillation proceeds, the concentration of toluene in the liquid pha se and the boiling point increase continuously,following the values repres
ented by L1B. Finally, at the end of the distillation, the liquid phase is pur e toluene boiling at 110.6℃. Similarly, the vapor becomes progressively richer in toluene also, following V1B. Always, however, it i s richer in benzene than is the liquid with which it is in equilibrium, as sh own by the points of intersection of any horizontal line with the vapor an d liquid curves2.
在精馏过程中，随着L1B所表示的值，甲苯在液相中的浓度和沸点逐步增加。最后，在精馏结束时，液相是纯的甲苯，沸点为110.6℃。同样地，根据V1B曲线，甲苯蒸汽也随之变浓。然而，蒸汽较之其处于平衡的液体总是富含苯的，正如任一水平线与蒸汽和液体曲线的交点所示。
Obviously, a single simple distillation could never separates 20:80 molar mixture of benzene and toluene into the pure components. But now consi der what would be accomplished if the first trace of vapor formed by disti llation of the mixture were cooled and condensed. It would, of course, for m liquid corresponding to point L2 of composition 38 mole per cent benz ene — 62 mole per cent toluene at 94.5°.
很明显,单一简单的精馏不能分离苯-甲苯20:80摩尔的纯组分混合物。但是现在考虑如果是通过精馏混合物使首先出现的微量蒸汽被冷却和浓缩的话可以实现。当然，这将会形成液体相应的点L2，在94.5℃的组成成分是38%摩尔的苯和62%摩尔的甲苯。
Now, if liquid L2 were distilled, the first trace of vapor formed would hav
e the composition 59 mole per cent benzene — 41 mole per cent toluene ( point V2) and when cooled would condense to liquid at 88° (point L3). This, in turn, may be further enriched in benzene as indicated on the grap h.
现在，如果液体L2被蒸馏，首先形成的微量蒸汽将会由59%摩尔的苯和41%摩尔的甲苯（点V2)组成，冷却到88℃时将得到冷凝液（点L3）。反过来，这可能进一步增加了苯在图上的显示。
01 THE ELEMENTS AND THE PERIODIC TABLE 01 元素和元素周期表 The number of protons in the nucleus of an atom is referred to as the atomic number, or proton number, Z. The number of electrons in an electrically neutral atom is also equal to the atomic number, Z. The total mass of an atom is determined very nearly by the total number of protons and neutrons in its nucleus. This total is called the mass number, A. The number of neutrons in an atom, the neutron number, is given by the quantity A-Z. 质子的数量在一个原子的核被称为原子序数,或质子数、周淑金、电子的数量在一个电中性原子也等于原子序数松山机场的总质量的原子做出很近的总数的质子和中子在它的核心。这个总数被称为大量胡逸舟、中子的数量在一个原子,中子数,给出了a - z的数量。 The term element refers to, a pure substance with atoms all of a single kind. T o the chemist the "kind" of atom is specified by its atomic number, since this is the property that determines its chemical behavior. At present all the atoms from Z = 1 to Z = 107 are known; there are 107 chemical elements. Each chemical element has been given a name and a distinctive symbol. For most elements the symbol is simply the abbreviated form of the English name consisting of one or two letters, for example: 这个术语是指元素,一个纯物质与原子组成一个单一的善良。在药房“客气”原子的原子数来确定它,因为它的性质是决定其化学行为。目前所有原子和Z = 1 a到Z = 107是知道的;有107种化学元素。每一种化学元素起了一个名字和独特的象征。对于大多数元素都仅仅是一个象征的英文名称缩写形式,一个或两个字母组成,例如: oxygen==O nitrogen == N neon==Ne magnesium == Mg
Veterinary Immunology and Immunopathology 141 (2011) 133–138 Contents lists available at ScienceDirect Veterinary Immunology and Immunopathology j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /v e t i m m Short communication Saccharomyces cerevisiae decreases in?ammatory responses induced by F4+enterotoxigenic Escherichia coli in porcine intestinal epithelial cells Galliano Zanello a ,b ,1,Franc ?ois Meurens a ,1,Mustapha Berri a ,Claire Chevaleyre a ,Sandrine Melo a ,Eric Auclair b ,Henri Salmon a ,? a Institut National de la Recherche Agronomique (INRA),UR1282,Infectiologie Animale et SantéPublique,F-37380Nouzilly (Tours),Indre et Loire,France b SociétéIndustrielle Lesaffre,Lesaffre Feed Additives,Marcq-en-Baroeul,France a r t i c l e i n f o Article history: Received 19October 2010Received in revised form 13December 2010 Accepted 31January 2011Keywords: Saccharomyces cerevisiae Enterotoxigenic Escherichia coli Pig Intestinal epithelial cells Cytokines Chemokines a b s t r a c t Probiotic yeasts may provide protection against intestinal in?ammation induced by enteric pathogens.In piglets,infection with F4+enterotoxigenic Escherichia coli (ETEC)leads to in?ammation,diarrhea and intestinal damage.In this study,we investigated whether the yeast strains Saccharomyces cerevisiae (Sc ,strain CNCM I-3856)and S.cerevisiae variety boulardii (Sb ,strain CNCM I-3799)decreased the expression of pro-in?ammatory cytokines and chemokines in intestinal epithelial IPI-2I cells cultured with F4+ETEC.Results showed that viable Sc inhibited the ETEC-induced TNF-?gene expression whereas Sb did not.In contrast,killed Sc failed to inhibit the expression of pro-in?ammatory genes.This inhibition was dependent on secreted soluble factors.Sc culture supernatant decreased the TNF-?,IL-1?,IL-6,IL-8,CXCL2and CCL20ETEC-induced mRNA.Furthermore,Sc culture supernatant ?ltrated fraction <10kDa displayed the same effects excepted for TNF-?.Thus,our results extended to Sc (strain CNCM I-3856)the inhibitory effects of some probiotic yeast strains onto in?ammation. ? 2011 Elsevier B.V. All rights reserved. 1.Introduction Enterotoxigenic Escherichia coli (ETEC)are pathogenic gram negative bacteria which infect humans and sev-eral species of farm animals such as calves and pigs.ETEC interacts with intestinal epithelial cells,colonizes the small intestine and secretes enterotoxins such as the heat-labile enterotoxins (LT),the heat-stable enterotox-ins (STa and/or STb),and the enteroaggregative E .coli heat-stable enterotoxin 1(EAST1)(Nagy and Fekete,2005).In pigs,ETEC infection and enterotoxin secretions can induce intestinal in?ammation and diarrhea resulting in reduced growth rate,increased mortality and economic ?Corresponding author.Tel.:+33247427331;fax:+33247427779.E-mail addresses:salmon@tours.inra.fr ,henri.salmon@tours.inra.fr (H.Salmon).1 These authors contributed equally to this work.loss (Fairbrother et al.,2005).Moreover,F4+ETEC strain induce pro-in?ammatory response in intestinal epithe-lial cells (Devriendt et al.,2010).Administration of the yeast Saccharomyces cerevisiae variety boulardii (Sb )has been shown to protect pigs in reducing ETEC transloca-tion (Lessard et al.,2009).In vitro studies showed that Sb secretes soluble factors that decrease the expression of pro-in?ammatory cytokines induced by enteric pathogens (Zanello et al.,2009).However,to our knowledge,there is no in vitro data regarding the anti-in?ammatory effects of S.cerevisiae (Sc )secreted soluble factors.Sc and Sb are members of the same species but they differ geneti-cally,metabolically and physiologically (Edwards-Ingram et al.,2007;Hennequin et al.,2001).Thus,in this study,we assessed if the non-commensal and non-pathogenic yeasts Sc (strain CNCM I-3856)and Sb (strain CNCM I-3799)secreted factors allowing the down-regulation of pro-in?ammatory gene expression in intestinal epithe-lial cells cultured with F4+ETEC.Sc (strain CNCM I-3856) 0165-2427/$–see front matter ? 2011 Elsevier B.V. All rights reserved.doi:10.1016/j.vetimm.2011.01.018
01.THE ELEMENTS AND THE PERIODIC TABLE 01元素和元素周期 表。 The number of protons in the nucleus of an atom is referred to as the atomic number, or proton number, Z. The number of electrons in an electrically neutral atom is also equal to the atomic number, Z. The total mass of an atom is determined very nearly by the total number of protons and neutrons in its nucleus. This total is called the mass number, A. The number of neutrons in an atom, the neutron number, is given by the quantity A-Z. 原子核中的质子数的原子称为原子序数，或质子数，卓电子数的电中性的原子也等于原子序数Z，总质量的原子是非常接近的总数量的质子和中子在原子核。这被称为质量数，这个数的原子中的中子，中子数，给出了所有的数量 The term element refers to, a pure substance with atoms all of a single kind. To the chemist the "kind" of atom is specified by its atomic number, since this is the property that determines its chemical behavior. At present all the atoms from Z = 1 to Z = 107 are known; there are 107 chemical elements. Each chemical element has been given a name and a distinctive symbol. For most elements the symbol is simply the abbreviated form of
Unit 1 Chemical Industry 化学工业 1.Origins of the Chemical Industry Although the use of chemicals dates back to the ancient civilizations, the evolution of what we know as the modern chemical industry started much more recently. It may be considered to have begun during the Industrial Revolution, about 1800, and developed to provide chemicals roe use by other industries. Examples are alkali for soapmaking, bleaching powder for cotton, and silica and sodium carbonate for glassmaking. It will be noted that these are all inorganic chemicals. The organic chemicals industry started in the 1860s with the exploitation of William Henry Perkin‘s discovery if the first synthetic dyestuff—mauve. At the start of the twentieth century the emphasis on research on the applied aspects of chemistry in Germany had paid off handsomely, and by 1914 had resulted in the German chemical industry having 75% of the world market in chemicals. This was based on the discovery of new dyestuffs plus the development of both the contact process for sulphuric acid and the Haber process for ammonia. The later required a major technological breakthrough that of being able to carry out chemical reactions under conditions of very high pressure for the first time. The experience gained with this was to stand Germany in good stead, particularly with the rapidly increased demand for nitrogen-based compounds (ammonium salts for fertilizers and nitric acid for explosives manufacture) with the outbreak of world warⅠin 1914. This initiated profound changes which continued during the inter-war years (1918-1939). 1．化学工业的起源 尽管化学品的使用可以追溯到古代文明时代，我们所谓的现代化学工业的发展却是非常近代（才开始的）。可以认为它起源于工业革命其间，大约在1800年，并发展成为为其它工业部门提供化学原料的产业。比如制肥皂所用的碱，棉布生产所用的漂白粉，玻璃制造业所用的硅及Na2CO3. 我们会注意到所有这些都是无机物。有机化学工业的开始是在十九世纪六十年代以William Henry Perkin 发现第一种合成染料—苯胺紫并加以开发利用为标志的。20世纪初，德国花费大量资金用于实用化学方面的重点研究，到1914年，德国的化学工业在世界化学产品市场上占有75%的份额。这要归因于新染料的发现以及硫酸的接触法生产和氨的哈伯生产工艺的发展。而后者需要较大的技术突破使得化学反应第一次可以在非常高的压力条件下进行。这方面所取得的成绩对德国很有帮助。特别是由于1914年第一次世界大仗的爆发，对以氮为基础的化合物的需求飞速增长。这种深刻的改变一直持续到战后（1918-1939）。 date bake to/from: 回溯到 dated: 过时的，陈旧的 stand sb. in good stead: 对。。。很有帮助
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中国教育在线考研频道提供考研全方面信息指导及咨询服务，为您成功考研提供一切帮助。 哲学Philosophy 马克思主义哲学Philosophy of Marxism 中国哲学Chinese Philosophy 外国哲学Foreign Philosophies 逻辑学Logic 伦理学Ethics 美学Aesthetics 宗教学Science of Religion 科学技术哲学Philosophy of Science and Technology 经济学Economics 理论经济学Theoretical Economics 政治经济学Political Economy 经济思想史History of Economic Thought 经济史History of Economic 西方经济学Western Economics 世界经济World Economics 人口、资源与环境经济学Population, Resources and Environmental Economics 应用经济学Applied Economics 国民经济学National Economics 区域经济学Regional Economics 财政学（含税收学）Public Finance (including Taxation) 金融学（含保险学）Finance (including Insurance) 产业经济学Industrial Economics 国际贸易学International Trade 劳动经济学Labor Economics 统计学Statistics 数量经济学Quantitative Economics 中文学科、专业名称英文学科、专业名称 国防经济学National Defense Economics 法学Law 法学Science of Law 法学理论Jurisprudence 法律史Legal History 宪法学与行政法学Constitutional Law and Administrative Law 刑法学Criminal Jurisprudence
Unit 2 Research and Development 研究和开发 Research and development, or R&D as it is commonly referred to, is an activity which is carried out by all sectors of manufacturing industry but its extent varies considerably, as we will see shortly. Let us first understand, or at least get a feel for, what the terms mean. Although the distinction between research and development is not always clear-cut, and there is often considerable overlap, we will attempt to separate them. In simple terms research can be thought of as the activity which produces new ideas and knowledge whereas development is putting those ideas into practice as new process and products. To illustrate this with an example, predicting the structure of a new molecule which would have a specific biological activity and synthesizing it could be seen as research whereas testing it and developing it to the point where it could be marketed as a new drug could be described as the development part. 研究和开发，或通常所称R&D是制造业各个部门都要进行的一项活动。我们马上可以看到，它的内容变化很大。我们首先了解或先感觉一下这个词的含义。尽管研究和开发的定义总是分得不很清楚，而且有许多重叠的部分，我们还是要试着把它们区分开来。简单说来，研究是产生新思想和新知识的活动，而开发则是把这些思想贯彻到实践中得到新工艺和新产品的行为。可以用一个例子来描述这一点，预测一个有特殊生物活性的分子结构并合成它可以看成是研究而测试它并把它发展到可以作为一种新药推向市场这一阶段则看作开发部分。 1.Fundamental Research and Applied Research In industry the primary reason for carting out R&D is economic and is to strengthen and improve the company?s position and profitability. The purpose of R&D is to generate and provide information and knowledge to reduce uncertainty, solve problems and to provide better data on which management can base decisions. Specific projects cover a wide range of activities and time scales, from a few months to 20 years. 1．基础研究和应用研究 在工业上进行研究和开发最主要的原因是经济利益方面，是为了加强公司的地位，提高公司的利润。R&D的目的是做出并提供信息和知识以减低不确定性，解决问题，以及向管理层提供更好的数据以便他们能据此做出决定。特别的项目涵盖很大的活动范围和时间范围，从几个月到20年。 We can pick out a number of areas of R&D activity in the following paragraphs but if we were to start with those which were to spring to the mind of the academic, rather than the industrial, chemist then these would be basic, fundamental (background) or exploratory research and the synthesis of new compounds. This is also labeled “blue skies” research. 我们可以在后面的段落里举出大量的R&D活动。但是如果我们举出的点子来源于研究院而不是工业化学家的头脑，这就是基础的或探索性的研究 Fundamental research is typically associated with university research. It may be carried out for its own intrinsic interest and it will add to the total knowledge base but no immediate applications of it in the “real world” well be apparent. Note that it will provide a valuable
1 Unit5元素周期表 As our picture of the atom becomes more detailed 随着我们对原子的描述越来越详尽，我们发现我们陷入了进退两难之境。有超过100多中元素要处理，我们怎么能记的住所有的信息？有一种方法就是使用元素周期表。这个周期表包含元素的所有信息。它记录了元素中所含的质子数和电子数，它能让我们算出大多数元素的同位素的中子数。它甚至有各个元素原子的电子怎么排列。最神奇的是，周期表是在人们不知道原子中存在质子、中子和电子的情况下发明的。Not long after Dalton presented his model for atom( )在道尔顿提出他的原子模型（原子是是一个不可分割的粒子，其质量决定了它的身份）不久，化学家门开始根据原子的质量将原子列表。在制定像这些元素表时候，他们观察到在元素中的格局分布。例如，人们可以清楚的看到在具体间隔的元素有着相似的性质。在当时知道的大约60种元素中，第二个和第九个表现出相似的性质，第三个和第十个，第四个和第十一个等都具有相似的性质。 In 1869,Dmitri Ivanovich Mendeleev,a Russian chemist, 在1869年，Dmitri Ivanovich Mendeleev ,一个俄罗斯的化学家，发表了他的元素周期表。Mendeleev通过考虑原子重量和元素的某些特性的周期性准备了他的周期表。这些元素的排列顺序先是按原子质量的增加,,一些情况中, Mendeleev把稍微重写的元素放在轻的那个前面.他这样做只是为了同一列中的元素能具有相似的性质.例如,他把碲(原子质量为128)防在碘(原子质量为127)前面因为碲性质上和硫磺和硒相似, 而碘和氯和溴相似. Mendeleev left a number of gaps in his table.Instead of Mendeleev在他的周期表中留下了一些空白。他非但没有将那些空白看成是缺憾，反而大胆的预测还存在着仍未被发现的元素。更进一步，他甚至预测出那些一些缺失元素的性质出来。在接下来的几年里，随着新元素的发现，里面的许多空格都被填满。这些性质也和Mendeleev所预测的极为接近。这巨大创新的预计值导致了Mendeleev的周期表为人们所接受。 It is known that properties of an element depend mainly on the number of electrons in the outermost energy level of the atoms of the element. 我们现在所知道的元素的性质主要取决于元素原子最外层能量能级的电子数。钠原子最外层能量能级（第三层）有一个电子，锂原子最外层能量能级（第二层）有一个电子。钠和锂的化学性质相似。氦原子和氖原子外层能级上是满的，这两种都是惰性气体，也就是他们不容易进行化学反应。很明显，有着相同电子结构（电子分布）的元素的不仅有着相似的化学性质，而且某些结构也表现比其他元素稳定（不那么活泼） In Mendeleev’s table,the elements were arranged by atomic weights for 在Mendeleev的表中，元素大部分是按照原子数来排列的，这个排列揭示了化学性质的周期性。因为电子数决定元素的化学性质，电子数也应该（现在也确实）决定周期表的顺序。在现代的周期表中，元素是根据原子质量来排列的。记住，这个数字表示了在元素的中性原子中的质子数和电子数。现在的周期表是按照原子数的递增排列，Mendeleev的周期表是按照原子质量的递增排列，彼此平行是由于原子量的增加。只有在一些情况下（Mendeleev注释的那样）重量和顺序不符合。因为原子质量是质子和中子质量的加和，故原子量并不完全随原子序数的增加而增加。原子序数低的原子的中子数有可能比原子序数高的原
Basic Control Actions and Industrial Automatic Control An automatic controller compares the actual value of the plant output with the desired value, determines the deviation, and produces a control signal which will reduce the deviation to zero or to a small value.The manner in which the automatic conroller produces the control signal is called the control action. Classifications of industrial automatic controllers Induetrial automatic controllers may be classified according to their control action as: ·two-position or on-off controllers; ·proportional controllers; ·integral controllers; ·proportional-plus-integral controllers; ·proportional-plus-derivative controllers; ·proportional-plus-derivative-plus-integral controllers. Most industrial automatic controllers use eletricity or pressurized fluid such as oil or air as power sources. Automatic controllers may also be classified according to the kind of power employed in the operation, such as pneumatic controllers, hydraulic controllers, or electronic controllers.What kind of controller to use must be decided by the nature of the plant and the operating conditions,including such considerations as safety, availability, reliability, accuracy, weight, and size? Elements of industrial automatic controllers An automatic controller must detect the actuating error signal, which is usually at a very low power level, and amplify it to a sufficiently high level. Thus, an amplifier is necessary. The output of an automatic controller is fed to a power device, such as a pneumatic motor or valve, a hydraulic motor, or an electric motor. The controller usually consists of an error detector and amplifier. The measuring element is a device that converts the output variable into another suitable variable, such as a displacement, pressure, or electric signal, which can be used for comparing the output to the reference input signal. This element is in the feedback path of the closed-loop system. The set point of the controller must be converted to a reference input of the same units as the feedback signal from the measuring element. The amplifier amplifies the power of the actuating error signal, which in turn operates the actuator. The actuator is an element which alters the input to the plant according to the control signal so that the feedback signal may be brought into correspondence with the reference input signal. Self-operated controllers In most industrial automatic controllers, separate units are used for the measuring element and for the actuator. In a very simple one, however, such as a self-operated controller, these elements are assembled in one unit. Self-operated controllers utilize power developed by the measuring element and are very simple and inexpensive. The set point is determined by the adjustment of the spring force. The controlled pressure is measured by the diaphragm. The actuating error signal is the net force acting on the diaphragm. Its position determines the valve opening. The operation of self-operated controller is as follows: Suppose that the output pressure is lower than the reference pressure, as determined by the set point. Then the downward spring force is greater than the upward pressure force, resulting in a downward movement of the diaphragm. This increases the flow rate and raises the output pressure.
Uｎit 1 The RｏotｓoｆCｈemisｔry Ｉ．Ｃoｍpreｈensioｎ. 1。Ｃ 2. Ｂ3．D 4. C 5. B ＩI。Ｍａｋe ａsenｔeｎｃe ｏut of ｅach ｉｔem ｂy reaｒranging ｔhe wordｓin ｂracｋets. 1.Tｈｅｐuｒiｆｉcation of aｎorganｉc compounｄis usually a matter of consｉｄerａｂlｅdｉfｆicｕｌtｙ, and iｔis nｅcｅｓsaｒy to eｍploy vａrious methoｄs fｏr thｉｓpurpｏse。 2.Science is an ｅｖeｒ－iｎcｒｅasing boｄy ofａccｕｍｕlａｔed anｄ ｓｙsｔｅmatiｚed knowledｇe ａnd iｓalsｏan activｉty bｙwｈic ｈｋnowledge iｓｇenerated。 3.Lifｅ，aftｅr all, is onｌy cｈeｍistry,in faｃｔ, a sｍall example of ｃ hｅｍistry ｏbsｅｒved oｎａsｉngle munｄane pｌａnet。 4.Peoplｅaｒe made of molｅculｅｓ; sｏmｅｏf ｔhｅmｏleculｅs in p ｅople aｒe rａｔher ｓimple whｅreas otｈerｓａｒｅhｉghly compｌex。 5.Chｅｍistry ｉｓever preseｎｔin ｏｕｒｌｉves frｏm ｂｉｒtｈ tｏｄeａthｂeｃａｕse withoｕt chｅmｉｓtrｙｔhere iｓneither life nor deａth. 6.Maｔhｅｍaｔics apｐeａｒs ｔo be almost as humaｎkiｎｄand ａｌ ｓo ｐermeaｔeｓall aspeｃts of ｈuman life, aｌthough ｍａｎｙof us are ｎｏｔfuｌly ａwａrｅoｆtｈis. III。Tｒanｓlatioｎ. 1.（a)chｅmicaｌprｏcess (b) natuｒal scienｃe（c）the teｃhｎｉ ｑｕe of distｉllaｔioｎ 2.Iｔｉs theａtｏｍs that ｍａkｅuｐｉron, waｔeｒ，oｘygen and the lｉke/anｄso on／aｎｄsｏfortｈ/aｎd otherｗiｓe. 3.Cheｍisｔｒy haｓa very long hｉｓtorｙ, ｉnｆaｃｔ，human a ｃtivity in chｅｍｉstrｙgｏes bａｃk ｔo ｐreｒecｏrｄed tｉmｅｓ/pｒedatiｎg reｃｏrded times． 4.Aｃcoｒdｉng to/Froｍthe eｖapoｒaｔion oｆwaｔeｒ，pｅople know ／reaｌized ｔｈat ｌiquidｓcａn ｔurn/bｅ/changeｉｎto gases ｕndeｒcertain conditions/circｕmsｔance／enｖironment。 5.Yoｕｍusｔknow ｔhe propｅｒtieｓｏfｔｈe materiaｌbeｆore y ｏu use it. IＶ．Ｔrａnslation 化学是三种基础自然科学之一,另外两种是物理和生物.自从宇宙大爆炸以来，化学过程持续进行,甚至地球上生命的出现可能也是化学过程的结果。人们也许认为生命是三步进化的最终结果,第一步非常快，其余两步相当慢.这三步