专业英语课文翻译

Lesson 10 Derivatives of Carboxylic Acids

1.Chemistry of Esters

Esters are neutral compounds derived from reaction between a carboxylic acid and an alcohol. The esters of any individual carboxylic acid form a homologous series whose lower members are volatile liquids with pleasant, often fruit-like odours. As the relative molecular mass increases, volatility decreases and the esters gradually become viscous, oily liquids or waxy solids. They are immiscible with water and ethyl ethanoate is widely used as an organic solvent. They are polar compounds with boiling points well below those of carboxylic acids of corresponding relative molecular mass, since there is no intermolecular hydrogen bonding:

CH3CO2CH2CH3CH3CH2CO2CH3CH3CH2CH2CO2H Ethyl ethanoate (M r=88) methyl propanoate (M r=88) butanoic acid (M r=88) b.p.=77℃ b.p.=80℃ b.p.=163℃Esters occur naturally. Those derived from certain long-chain carboxylic acids (fatty acids) and the alcohol propane-1,2,3-triol(glycerol)are important constituents of vegetable oils and animal fats. Ester polymers, called polyesters, are very important synthetic materials; an example is the synthetic polyester fibre Terylene.

The following reactions are typical of esters.

1.1Hydrolysis

The hydrolysis of an ester to carboxylic acid and alcohol is the reverse of the esterification process and involves an equilibrium:

RCOOR’+H2O RCOOH+R’OH

The composition lf the equilibrium mixture is the same, no matter whether one has started from an equimolar mixture of acid and alcohol, or ester and water. Like esterification, the rate of hydrolysis is very slow but hydrolysis is catalysed by acid or alkali. Alkali hydrolysis is usually the more effective method because the salt of the carboxylic acid, rather than the free acid, is obtained, so that the equilibrium position is pushed so much towards the products that reaction is virtually complete. The hydrolysis is normally effected by heating the aster with sodium hydroxide solution under reflux. As hydrolysis proceeds, the separate ester and aqueous layers gradually merge into one. If the alcohol is wanted is can be distilled out of the alkaline mixture; acidification of the residue with sulphuric acid will liberate the free carboxylic acid, which may then be distilled from the solution. The alkaline hydrolysis of esters is sometimes referred to as saponification because the reaction is used in soap-making.

1.2 Reduction

Esters are reduced by lithium tetrahydridoaluminate to primary alcohols corresponding to the acid from which the ester is derived. The other organic product is the alcohol corresponding to the alcohol component of the ester:

RCOOR’→RCH2OH+R’OH

e.g.

CH3COOCH3→CH3CH2OH+CH3OH

Methyl ethanoate ethanol methanol

2.Chemistry of Acid Chlorides

Acid chlorides are very reaction compounds and hence are not found in nature. They

are conveniently prepared by the action of sulphur dichloride oxide ( thionyl chloride ) on a carboxylic acid, since the other product of the reaction are gases. The acid chlorides are generally volatile liquids and find applications, in many small-scale laboratory syntheses. The following reactions, in which the chlorine is replaced by other groups, are typical of acid chlorides.

2.1 Hydrolysis

Acid chlorides are vigorously hydrolyzed on contact with water, heat and fumes of hydrogen chloride being evolved. The acid chlorides even fume on contact with moist air, and hence must always be protected from moisture during storage. For the same reason reactions involving acid chlorides must be carried out with water-free reagents, and if a solvent is used, it must also be dry. Care must always be exercised when handling them.

RCOCL+H2O→RCOOH+HCL

The acid chlorides are named according to the corresponding carboxylic acid, the suffix-oic being replaced by –oyl; thus ethanoic acid forms the acid chloride, ethanoyl chloride.

2.2 Reaction with alcohols

Acid chlorides react with alcohols, although slightly less vigorously than with water, to form eaters;

RCOCl+R’OH→RCOOR’+HCl

This is a particularly useful method of making esters because the reaction goes to completion, and hence high yields may be expected.

2.3 Reaction with ammonia and amines \

When an acid chloride is added to a cold, concentrated ammonia solution, a vigorous reaction takes place and an acid amide is formed:

RCOCl+NH3→RCONH2+HCl

A similar reaction occurs with an amine and the reaction is often performed in a dry ether solvent to moderate its vigour. The product is an N-substituted amide, i.e. an amide in which hydrogen attached to the nitrogen atom has been replaced by an alkly group:

RCOCl+R’ NH2→RCONHR’+HCl

A secondary amine will also react in a similar fashion but a tertiary amine will not. The reaction of an acid chloride with an amine is used commercially in the manufacture of the very important range of semi-synthetic penicillins, first product by the Beecham Group in 1959. By varying the acid chloride, various groups can be introduced into the essential penicillin structure to produce new penicillin antibiotics with important pharmacological properties not possessed by natural penicillin.

2.4 Reduction

Acid chlorides can be reduced by catalytic hydrogenation or, more conveniently in the laboratory, by lithium tetrahydridoaluminate. The reduction product is a primary alcohol

RCOCl→RCH2OH

2.5 Friedel- Crafts reaction

Acid chloride enters into a substitution reaction with aromatic compounds to form

ketones. This reaction is known as the Friedel- Crafts reaction.

化学专业英语(修订版)翻译

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

汽车专业英语翻译综合

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大学英语精读1课文翻译

大学英语精读1课文翻译 Unit1 Some Strategies or Learning English 学习英语绝非易事。它需要刻苦和长期努力。 虽然不经过持续的刻苦努力便不能期望精通英语，然而还是有各种有用的学习策略可以用来使这一任务变得容易一些。以下便是其中的几种。 1. 不要以完全同样的方式对待所有的生词。你可曾因为简直无法记住所学的所有生词而抱怨自己的记忆力太差？其实，责任并不在你的记忆力。如果你一下子把太多的生词塞进头脑，必定有一些生词会被挤出来。你需要做的是根据生词日常使用的频率以不同的方式对待它们。积极词汇需要经常练习，有用的词汇必须牢记，而在日常情况下不常出现的词只需见到时认识即可。你会发现把注意力集中于积极有用的词上是扩大词汇量最有效的途径。 2．密切注意地道的表达方式。你可曾纳闷过，为什么我们说 "我对英语感兴趣"是"I'm interested in English"，而说"我精于法语"则是"I'm good at French"？你可曾问过自己，为什么以英语为母语的人说"获悉消息或秘密"是"learn the news or secret"，而"获悉某人的成功或到来"却是"learn of someone's success or arrival"？这些都是惯用法的例子。在学习英语时，你不仅必须注意词义，还必须注意以英语为母语的人在日常生活中如何使用它。 3．每天听英语。经常听英语不仅会提高你的听力，而且有助你培养说的技能。除了专为课程准备的语言磁带外，你还可以听英语广播，看英语电视和英语电影。第一次听录好音的英语对话或语段，你也许不能听懂很多。先试着听懂大意，然后再反复地听。你会发现每次重复都会听懂更多的东西。 4．抓住机会说。的确，在学校里必须用英语进行交流的场合并不多，但你还是可以找到练习讲英语的机会。例如，跟你的同班同学进行交谈可能就是得到一些练习的一种轻松愉快的方式。还可以找校园里以英语为母语的人跟他们随意交谈。或许练习讲英语最容易的方式是高声朗读，因为这在任何时间，任何地方，不需要搭档就可以做到。例如，你可以看着图片或身边的物件，试着对它们详加描述。你还可以复述日常情景。在商店里购物或在餐馆里吃完饭付过账后，假装这一切都发生在一个讲英语的国家，试着用英语把它表演出来。

《化学工程与工艺专业英语》课文翻译 完整版

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

汽车专业英语翻译

About car engine Of all automobile components,an automobile engie is the most complicated assembly with dominant effects on the function of an autombile.So, the engine is generally called the"heat"of an automobile. 在汽车的所有部件中，汽车发动机是最复杂的组件，其对整车性能有着决定性的作用。因而发动机往往被称作发动机的“心脏”。 There are actually various types of engines such as electric motors,stream engines,andinternal combustion engines.The internal combustion engines seem to have almost complete dominance of the automotive field.The internal combustion engine,as its name indicates,burns fuel within the cylinders and converts the expanding force of the combustion into rotary force used to propel the vehicle. 事实上，按动力来源分发动机有很多种，如电动机、蒸汽机、外燃机等。然而内燃机似乎在发动机领域有着绝对的统治地位。就像其字面意思一样，内燃机的染料在气缸内燃烧，通过将燃烧产生气体的膨胀力转换成转动力来驱动发动机前进。 Engine is the power source of the automobile.Power is produced by the linear motion of a piston in a cylinder.However,this linear motion must be changed into rotary motion to turn the wheels of cars or trucks.The puston attached to the top of a connecting rod by a pin,called a piston pin or wrist pin.The bottom of the connecting rod is attached to the crankshaft.The connecting rod transmits the up-and-down motion of the piston to the crankshaft,which changes it into rotary motion.The connecting rod is mounted on the crankshaft with large bearings called rod bearing.Similar bearings, called main bearings,are used to mount the crankshaft in the block. 发动机是整部车的动力来源。能量来自于活塞在气缸内的（往复）直线运动。然而这种（往复）直线运动必须要转换成旋转运动才能驱动车轮。活塞与连杆通过一个销来连接，这个销称为活塞销。连杆的下部连接于曲拐。连杆把活塞的上下往复运动传递给曲拐，从而将往复直线运动转变成旋转运动。连杆和曲拐的连接使用大的轴承，称之为连杆轴承，类似的轴承也用于将曲轴连接到机体，称之为主轴承。 They are generally two different types of cooling system:water-cooling system and air-cooling system.Water-cooling system is more common.The cooling medium, or coolant, in them is either water or some low-freezing liquid, called antifreeze.A water-cooling system consists of the engine water jacket, thermostat, water pump, radiator, radiator cap, fan, fan drive belt and neccessary hoses. 主要有两种类型的冷却系统：水冷和风冷。水冷系统更为普遍。系统所用冷却介质或是冷却液常委水或其他低凝固点液体，称为抗凝剂。一个完整的水冷系统包括机体水套，节温器，水泵，散热器，散热器罩，风扇，风扇驱动皮带和必需的水管。 A water-cooling system means that water is used as a cooling agent to circulate through the engine to absorb the heat and carry it to the radiator for disposal.The ebgine is cooled mainly through heat transfer and heat dissipation.The heat generated by the mixture burned in the engine must be transferred from the iron or aluminum cylinder to the waterin the water jacket.The outside of the water jacket dissipates some of the heat to the air surrounding it, but most of the heat is carried by the cooling water to the radiator for dissipation.When the coolant temperature in the system reaches 90°,the termostat valve open fully, its slanted edge shutting off

[实用参考]大学英语精读第三版第四册课文及课文翻译.doc

Unit1 Twocollege-ageboPs,unawarethatmakingmonePusuallPinvolveshardwork,aretemptedbPanadvertis ementthatpromisesthemaneasPwaPtoearnalotofmoneP.TheboPssoonlearnthatifsomethingseemstog oodtobetrue,itprobablPis. 一个大学男孩，不清楚赚钱需要付出艰苦的劳动，被一份许诺轻松赚大钱的广告吸引了。男孩们很快就明白，如果事情看起来好得不像真的，那多半确实不是真的。BIGBUCKSTHEEASPWAP轻轻松松赚大钱"Pououghttolookintothis,"Isuggestedtoourtwocollege-agesons."ItmightbeawaPtoavoidtheindignitP ofhavingtoaskformonePallthetime."Ihandedthemsomemagazinesinaplasticbagsomeonebadhungon ourdoorknob.AmessageprintedonthebagofferedleisurelP,lucrativework("BigBuckstheEasPWaP!")o fdeliveringmoresuchbags. “你们该看看这个，”我向我们的两个读大学的儿子建议道。“你们若想避免因为老是向人讨钱而有失尊严的话，这兴许是一种办法。”我将挂在我们门把手上的、装在一个塑料袋里的几本杂志拿给他们。塑料袋上印着一条信息说，需要招聘人投递这样的袋子，这活儿既轻松又赚钱。（“轻轻松松赚大钱!”） "Idon'tmindtheindignitP,"theolderoneanswered.“我不在乎失不失尊严，”大儿子回答说。"Icanlivewithit,"hisbrotheragreed.“我可以忍受，”他的弟弟附和道。"Butitpainsme,"Isaid，"tofindthatPoubothhavebeenpanhandlingsolongthatitnolongerembarrassesPou."“看到你们俩伸手讨钱讨惯了一点也不感到尴尬的样子，真使我痛心，”我说。TheboPssaidthePwouldlookintothemagazine-deliverPthing.Pleased,Ilefttownonabusinesstrip.BPmi dnightIwascomfortablPsettledinahotelroomfarfromhome.Thephonerang.ItwasmPwife.Shewantedt oknowhowmPdaPhadgone.孩子们说他们可以考虑考虑投递杂志的事。我听了很高兴，便离城出差去了。午夜时分，我已远离家门，在一家旅馆的房间里舒舒服服住了下来。电话铃响了，是妻子打来的。她想知道我这一天过得可好。 "Great!"Ienthused."HowwasPourdaP?"Iinquired.“好极了!”我兴高采烈地说。“你过得怎么样?”我问道。 "Super!"Shesnapped."Justsuper!Andit'sonlPgettingstarted.Anothertruckjustpulledupoutfront."“棒极了!”她大声挖苦道。“真棒!而且这还仅仅是个开始。又一辆卡车刚在门前停下。”"Anothertruck?"“又一辆卡车?” "Thethirdonethisevening.ThefirstdeliveredfourthousandMontgomerPWards.Thesecondbroughtfour thousandSears,Roebucks.Idon'tknowwhatthisonehas,butI'msureitwillbefourthousandofsomething.S incePouareresponsible,IthoughtPoumightliketoknowwhat'shappening.“今晚第三辆了。第一辆运来了四千份蒙哥马利-沃德百货公司的广告；第二辆运来四千份西尔斯-罗伯克百货公司的广告。我不知道这一辆装的啥，但我肯定又是四千份什么的。既然这事是你促成的，我想你或许想了解事情的进展。” WhatIwasbeingblamedfor,itturnedout,wasanewspaperstrikewhichmadeitnecessarPtohand-deliverth eadvertisinginsertsthatnormallPareincludedwiththeSundaPpaper.ThecompanPhadpromisedourboPs $600fordeliveringtheseinsertsto4,000housesbPSundaPmorning.我之所以受到指责，事情原来是这样：由于发生了一起报业工人罢工，通常夹在星期日报纸里的广告插页，必须派人直接投送出去。公司答应给我们的孩子六百美金，任务是将这些广告插页在星期天早晨之前投递到四千户人家去。 "Pieceofcake!"ouroldercollegesonhadshouted.“不费吹灰之力!”我们上大学的大儿子嚷道。"SiGhundredbucks!"Hisbrotherhadechoed,"Andwecandothejobintwohours!"“六百块!”他的弟弟应声道，“我们两个钟点就能干完!” "BoththeSearsandWardadsarefournewspaper-sizepages,"mPwifeinformedme."TherearethirtP-twot housandpagesofadvertisingonourporch.Evenaswespeak,twobigguPsarecarrPingarmloadsofpaperup thewalk.Whatdowedoaboutallthis?"“西尔斯和沃德的广告通常都是报纸那么大的四页，”妻子告诉我说，“现在我们门廊上堆着三万二千页广告。就在我们说话的当儿，两个大个子正各抱着一大捆广告走过来。这么多广告，我们可怎么办?”"JusttelltheboPstogetbusP,"Iinstructed."TheP'recollegemen.TheP'lldowhatthePhavetodo."“你让孩子们快干，”我指示说。“他们都是大学生了。他们自己的事得由他们自己去做。”AtnoonthefollowingdaPIreturnedtothehotelandfoundanurgentmessagetotelephonemPwife.Hervoic

汽车专业英语_单词表

unit1 body 车身chassis 底盘enclosure外壳、套hood车棚、车顶sway 摇摆frame车架steering转向、操作brake 制动weld焊接rivet铆钉bolt螺钉washer垫圈vibration 振动stabilizer稳定器ride乘坐舒适性handling操作稳定性linkages转向传动机构plier钳子distributor分电器alternator交流发电机regulator调节器carburetor化油器radiator散热器、水箱defroster除冰装置sludge金属碎屑transmission变速器differential 差速器power train 传动系unitized body 承载式车身suspension system 悬架系统steering system 转向系braking system 制动系shock absorbers减震器control arms控制臂steering wheel 转向盘steering column转向管柱steering gears 转向器tie rod 横拉杆idler arm随动臂brake shoe制动蹄disc brake 盘式制动器drum brakes 鼓式制动器ignition system 点火系统exhaust system 排气系统lubrication system 润滑系oil filters 机油滤清器drive（or propeller）shaft传动轴universal joints 万向节dynamo发电机horn喇叭swived 旋转steering box转向器timing gear 正时齿轮bevel gear 锥齿轮mesh with与啮合leaf spring 钢板弹簧stub axle 转向节 unit2 longitudinal纵向的transverse横向的reciprocate往复spin旋转piston活塞ignite点火rub摩擦quart夸脱reservoir油箱mechanical机械的enclosed被附上的gallon加仑stroke冲程camshaft凸轮轴combustion燃烧disengaged脱离啮合的flywheel飞轮internal-combustion engine内燃机diesel-fuel柴油LPG=Liquefied Petroleum Gas液化石油气体CNG=Compressed natural gas压缩天然气spark ignition火花点火compression ignition压缩点火spark plug火花塞gas-turbine engine蒸汽机Stirling engine斯特灵发动机lubricating system润滑系统oil pan油底壳oil pump机油泵exhaust system排气系统emission-control system排放控制系统energy conversion能量转换air/fuel ratio空燃比connecting rod连杆TDC=Top Dead Center上止点BDC=Bottom Dead Center 下止点intake stroke进气冲程compression stroke压缩冲程power stroke作功冲程exhaust stroke排气冲程compression ratio压缩比lifter挺柱rocker摇臂retainer弹簧座seal密封件tappet 推杆lobe凸起gasket垫圈valve train配气机构cam follower气门挺柱rocker arm摇臂combustion chamber燃烧室intake valve进气阀exhaust valve排气阀valve stem气门杆valve cover气门室盖valve port阀口valve guide气门导管 unit3

大学英语精读课文翻译

大学英语精读课文翻译 Unit 1 How to Improve Your Study Habits 你也许是个智力一般的普通学生。你在学校的学习成绩还不错，可你也许会觉得自己永远也成不了优等生。然而实际情况未必如此。你要是想取得更好的分数，也还是能做到的。是的，即使中等智力水平的学生，在不增加学习负担的情况下，也能成为优等生。其诀窍如下：1．仔细安排你的时间。把你每周要完成的任务一一列出来，然后制定一张时间表或时间分配图。先把用于吃饭、睡觉、开会、听课等这样一些非花不可的时间填上，然后再选定合适的固定时间用于学习。一定要留出足够的时间来完成正常的阅读和课外作业。当然，学习不应把作息表上的空余时间全都占去，还得给休息、业余爱好和娱乐活动留出一定的时间，这一点很重要。这张周作息表也许解决不了你所有的问题，但是它会使你比较清楚地了解你是怎样使用你的时间的。此外，它还能让你安排好各种活动，既有足够的时间工作，也有足够的时间娱乐。 2．寻找一个合适的地方学习。选定某个地方作为你的“学习区”。这可以是家里或者学校图书馆里的一张书桌或者一把椅子，但它应该是舒适的，而且不该有干扰。在你开始学习时，你应能够全神贯注于你的功课。 3．阅读之前先略读。这就是说，在你仔细阅读一篇文章之前，先把它从头至尾迅速浏览一遍。在预习材料时，你就对它的内容及其结构有了大致的了解。随后在你正式开始阅读时，你就能辨认出不太重要的材料，并且可以略去某些章节不读。略读不仅使你的阅读速度提高一倍，还有助于提高你的理解能力。< 4．充分利用课堂上的时间。上课时注意听讲意味着课后少花力气。要坐在能看得见、听得清的地方。要作笔记来帮助自己记住老师讲课的内容。 5．学习要有规律。课后要及早复习笔记。重温课堂上提到的要点，复习你仍然混淆不清的

应用化学专业英语翻译完整篇

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

汽车专业英语课文翻译4

Fuel Supply System of Gasoline Engine(UNIT SEVEN) All the gasoline engines have substantially identical fuel systems and run on a mixture consisting of fuel vapor and air. The fuel system comprises the units designed to store, clear and deliver fuel, the units intended to clean air and a unit for preparing a mixture from fuel vapor and air. In a fuel system different components are used to supply fuel from the fuel tank into the engine cylinder. Some of the important components are fuel tank, fuel pump, fuel filter, carburetor, intake manifold and fuellines or tubes connecting the tank, pump and the carburetor. The fuel tank is a fuel container used for storing fuel. It is made of sheet metal. It is attached to the vehicle frame with metal traps and is located at the rear of the vehicle. They are mounted in a boot or boot-floor pan in case of front-engined cars and small commercial vehicles. In order to strengthen the tank as well as to prevent surging of fuel when the vehicle rounds a curve of suddenly stops, baffle plates are attached to the inside of the tank. A cap is used to close the filler opening of the tank. The fuel line is attached at or near the bottom of the tank with a filtering element placed at the connection. The other components of the fuel tank are the fuel gauge sending unit, a vent pipe, receiving unit. To prevent the dirt and water from entering the luggage compartment, a sealing strip is fitted between the fuel tank and boot floor pan. Moreover to limit the transmission of frame distortion to the tank giving rise to squeaking as the metal parts get rubbed together, rubber or felt pads are often fitted between the mountings and the tank. Provision is also made against drumming of the tank by these mountings. The tank may be placed at the side of the chassis frame for convenience in case of large commercial vehicles. The length of the connecting lines or tubes from the tank to the carburetor is also restricted by this at the same time. A porous filter is attached to the outlet lines. By drawing fuel from the tank through the filter, any water in the bottom of the tank as well as any dirt into the fuel gathers on the surface of the filter. To keep the fuel always under atmospheric pressure, the filter pipe or tank is vented. In order to prevent dirt in the fuel from entering the fuel pump or carburetor, fuel filters and screens are used in the fuel system. If the dirt is not removed from the fuel, the normal operation of these units will be prevented. The engine performance will also be reduced.