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1、粉笔灰的调查Thetypeofchalk:Now,thedomesticuseofchalkbasicallyhastwokinds,ordinarypieceofchalkanddust-freechalk(limestone)anditsmaincomponentsarecalciumcarbonatecalciumsulfate(gypsum),orcontainingasmallamountofcalciumoxide・Dustlesschalk:Dustlesschalkisanimpr
2、ovedproductofordinarychalk,designedtoeliminatedustfromclassroomchalk・Itjustaddgreaseclassinordinarychalkorpolyalcoholsasbinder,andaddtheproportionoflargepacking,suchasclay,marl,cement,etc.Thismakestheweightandvolumeofchalkdustincreases,noteasytofly,bu
3、tinpractice,itistochalkdustpollutionreductioneffectisnotveryobvious・Themainadvantagesofdustlesschalk:(1)tojoininthemainingredientoftracechemicalrawmaterials,increasedtheproportionofchalktowriteontheblackboard,dust-freeflyphenomenon,cleanhealth,avoided
4、becauseofchalkfoambybreathingintointernaloccupationaldisease.Asmallamountofpolishandadhesive,thechalkisnotinthehandsandclothes,andtheteacherhasnowhitemarksonhisfingers,nowashinghands・Addasma.11amountofmoisture-proofingagentandkeepitforalongtime・Regula
5、rchalkiseasytoabsorb,hardtobreak,andeasytowrite・TheblackboardthattheschoolUSESnowhasconcreteboard,plankandwoolglassboardetc・，becauseofthesmoothdegreeofthesurfaceoftheboardisdifferent,askforthehardnessdegreeofchalkisdifferentalso.Ihaveanewgenerationofd
6、ust-freechalkcanbearbitrarychangeitshardness,usedinallkindsoftheblackboardtherewillbenoskidorbrittlephenomenon,andwritingfluency,energysaving,feelisverygood.(5)inadditiontotheproductionofdust-freechalkwhiteoutside,stillcanproducebrightred,yellow,green
7、,blue,pinkandothercolors,andlongtimestorage,chromaticitywon'tdrop,alwaysprotectsthunder-and-1ightning,color・Thechemicalcompositionofchalk:Chalkismadefromcalciumsulfatehydrate(commonlyknownasgypsum)・Youcanalsoaddvariouspigmentstomakecoloredchalk.Inthep
8、rocessofmakingtheplasterstoneheatedtoacertaintemperature,thepartialdehydrationintoplasterofParis,thenhotplasterandwatermixintoapaste,frozenintothemode1.Themainreactionis:2CaS04times2H20Thehazardofchalk:Chalkdustcontainingsilicondioxide,drawnin
