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1、Low-temperaturenucleationofmagnesiteanddolomiteByJ.C.Deelman,EindhovenWith4figuresinthetextDEELMAN,J.C.:Low-temperaturenucleationofmagnesiteanddolomite-N.Jb.Miner.Mh.,1999(7):289-302,Stuttgart1999.Abstract:BywayofduplicatinganexperimentdescribedbyLieberm
2、ann(1967)nucleationofmagnesite,huntiteand/ordolomitehasbeenattainedattemperaturesbetween313Kand333Kandunderatmosphericpressure.EssentialtotheseexperimentsarefluctuationsinpHvalue.Afterinterruptinganexperimentafter1,3,5,or8ofsuchfluctuations,thechangefrom
3、oneormoremetastablephasesintothestablephase(magnesiteordolomite)couldbefollowed.Atheoreticalexplanationfortheselow-temperaturesynthesescanbefoundinstabilityrelations.Ostwald'sRulestipulatesthenucleationofametastablephasebeforethatofthestablephase.However
4、fluctuationsofsufficientamplitudeanddurationarecapableofcrossingtheborderbetweenthemetastableandthestablefields.Asaresultthestablephasewillnucleatetogetherwiththemetastablephase.Conditionsopposingthesubsequentgrowthofthemetastablephase(suchastheslightlya
5、cidicconditionsresultingfromperiodicallyintroducingCO2intothesolution)willfavourthecontinuedgrowthofthestablephase.Keywords:Magnesite,dolomite,huntite,low-temperaturesyntheses.MagnesiteThefirsttimeIobservedtheformationofmagnesitewasuponduplicatingofExp.N
6、o.57ofLiebermann(1967).InmyexperimentM-2110.918MolNaCl,0.0316MolMgCl2.6H2O,0.018MolMgSO4.7H2Oand0.020MolKCl(allchemicalsarereagentgrade)weredissolvedin3330cmdistilledwaterand2mMolCaCO3addedlater,wasdissolvedbywayofbubblingCO2(industrialgrade)throughthesu
7、spensionduring12hours.TitrationtopH=8.00tookplacewithdiluteammonia.Thenextphase,thegradualescapeofCO2fromthesolution,involvedheating3the500cmErlenmeyerflaskonanelectricplateto(inthiscase)333Kduring60hours.AsdescribedbyLiebermann(1967),thetotalexperimentc
8、onsistsofrepeating14timesthedissolutionphase,thetitrationandthephaseofheatingandgradualescapeofCO2.ThepHofthesolutionwasmeasuredeverytimeafterbubblingCO2throughit(pH=5,30to6,10inthisparticulartest),upontitration,andattheen
