項(xiàng)目八：常規(guī)物理常數(shù)與性能分析任務(wù)二：熔點(diǎn)的測(cè)定熔點(diǎn)概念及測(cè)定方法課程：工業(yè)分析中文Scenario8:PhysicalconstantsandperformancetestingTask2:DeterminationofmeltingpointTheconceptandmeasurementmethodofmeltingpointCourse:IndustrialAnalysisEglish熔點(diǎn)：指一種物質(zhì)由固體熔化成液體的溫度，用Tmp表示。熔程：初熔溫度與全熔溫度的間距純凈的固體有機(jī)物熔程一般不超過(guò)0.5～1℃一、熔點(diǎn)的基本知識(shí)物質(zhì)熔化過(guò)程中文Meltingpoint:referstothetemperatureatwhichasubstancemeltsfromasolidtoaliquid,expressedinTmp.Meltingprocess:thedistancebetweentheinitialmeltingtemperatureandthefullmeltingtemperatureThemeltingrangeofpuresolidorganicmattergenerallydoesnotexceed0.5-1℃一、BasicknowledgeofmeltingpointTheprocessofmaterialmeltingbescaredsamplecontractdropletsappearclearEglish注意：在鑒定某未知物時(shí)，如測(cè)得其熔點(diǎn)和已知物的熔點(diǎn)相同或相近時(shí)，不能認(rèn)為它們?yōu)橥晃镔|(zhì)。還需把它們混合，測(cè)該混合物的熔點(diǎn)，若熔點(diǎn)仍不變，才能認(rèn)為它們?yōu)橥晃镔|(zhì)。1、測(cè)定熔點(diǎn)的意義熔點(diǎn)是固體化合物在1個(gè)標(biāo)準(zhǔn)大氣壓下固—液兩相處于平衡時(shí)的溫度。含有雜質(zhì)時(shí)，會(huì)使其熔點(diǎn)下降，熔程延長(zhǎng)。中文payattentionto：Whenidentifyinganunknownsubstance,ifthemeltingpointoftheunknownsubstanceisthesameorsimilartothatoftheknownsubstance,theycannotbeconsideredasthesamesubstance.Itisnecessarytomixthemandmeasurethemeltingpointofthemixture.Ifthemeltingpointremainsunchanged,theycanbeconsideredasthesamesubstance.1、ThesignificanceofmeasuringmeltingpointThemeltingpointisthetemperatureatwhichasolidcompoundisinequilibriumbetweenthesolidandliquidphases(atstandardatmosphericpressure).Whenasolidcontainsimpurities,theimpuritieswillloweritsmeltingpointandprolongitsmeltingrange.Eglish2、熔點(diǎn)與物質(zhì)本質(zhì)的關(guān)系同系物中熔點(diǎn)隨相對(duì)分子質(zhì)量的增大而增高。分子中引入能形成氫鍵的官能團(tuán)后，熔點(diǎn)也會(huì)升高，形成氫鍵的機(jī)會(huì)越多，熔點(diǎn)越高。

m.p=-83℃m.p=-117℃

中文2、TherelationshipbetweenmeltingpointandtheessenceofmatterThemeltingpointinhomologouscompoundsincreaseswiththeincreaseofrelativemolecularweight.Afterintroducingfunctionalgroupsthatcanformhydrogenbondsintothemolecule,themeltingpointalsoincreases,andthemoreopportunitiesforhydrogenbonding,thehigherthemeltingpoint.

m.p=-83℃m.p=-117℃

Eglish分子結(jié)構(gòu)越對(duì)稱，越有利排成規(guī)則的晶格，有更大的晶格力，所以熔點(diǎn)越高。m.p=-56℃m.p=104℃中文Themoresymmetricalthemolecularstructureis,themorefavorableitistoformaregularlatticewithgreaterlatticeforce,resultinginahighermeltingpoint.m.p=-56℃m.p=104℃Eglish二、熔點(diǎn)的測(cè)定方法中文二、DeterminationmethodofmeltingpointCapillarytubemethod(Tillertubehotbath)Capillarytube

method(dualbathhotbath)Microscopicmeltingpointdeterminationmethod.ObservingthedissolutionofthesamplewiththehumaneyeandreadingthethermometerEquippedwithamagnifyingglassobservationwindow,capableofdisplayingtemperaturedigitallyEglish1、毛細(xì)管法測(cè)定裝置提勒管法中文1、CapillarymethodmeasuringdeviceTillertubemethodWoodenstopperswithnotchesLiquidlevelofheatcarrierat200℃LiquidlevelofheatcarrieratroomtemperaturecapillaryRubberbandRubberbandcapillaryheatcarrierthermometersamplelampEglish1-圓底燒瓶，2-試管，3、4-膠塞，5-溫度計(jì)，6-輔助溫度計(jì)，7-熔點(diǎn)管雙浴式熱浴法中文1-Roundbottomflask;2-Testtube;3,4-Rubberstopper;5-Thermometer;6-Auxiliarythermometer;7-MeltingpointtubeDoublebathhotbathmethodEglish2、顯微熔點(diǎn)測(cè)定裝置原理圖中文原理:加熱毛細(xì)管中的樣品，觀查其相變過(guò)程或相變時(shí)透光率的變化以確定熔點(diǎn)。優(yōu)點(diǎn):使用數(shù)字熔點(diǎn)儀進(jìn)行測(cè)定，方便、準(zhǔn)確、易于操作。熔點(diǎn)儀采用光電檢測(cè)，數(shù)字溫度顯示等技術(shù)，具有初熔、全熔自動(dòng)顯示，可與記錄儀配合使用，可進(jìn)行熔化曲線自動(dòng)記錄。通過(guò)設(shè)定升溫程序達(dá)到不同階段升溫速率不同。中文2、MicroscopicmeltingpointdeterminationmethodPrinciple:Heatthesampleinthecapillarytube,observeitsphasetransitionprocessorthechangeintransmittanceduringphasetransitiontodeterminethemeltingpoint.Advantages:Theuseofadigitalmeltingpointmeterformeasurementisconvenient,accurate,andeasytooperate.Themeltingpointmeteradoptstechnologiessuchasphotoelectricdetectionanddigitaltemperaturedisplay,withautomaticdisplayofiniti