Lawrence Berkeley National Laboratory Recent Work Title PRINCIPLES OF HIGH TEMPERATURE CHEMISTRY Permalink https://escholarship.org/uc/item/4z7550gk Author Broker, Leo. Publication Date 1963-06-01 eScholarship.org Powered by the California Digital Library University of California UCRL-10619 University of California Ernest 0. lawrence Radiation Laboratory PRINCIPLES OF HIGH TEMPERATURE CHEMISTRY TWO-WEEK LOAN COPY This is a library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. 5545 Berkeley, California DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain coiTect information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any waiTanty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. .·.. , r~:~~~;:;;-,e e~.:;:f Robert -~::--1 ! '• · Welsh Foundation Con(•. , ~ousto~; :·UCRL-10619. 'i •. fl Texas ~ Nov~ 26, 1962 (and to ft be published in the Proceedings)~ ··;.._ ·.~lm ,. ,· .. ' ; - •'· j ~ t•l ' '• II ... .... ., .:· .. : ,, ' .. '';:' •t., ·-.~ -~ .-~ ~- ·J -" ,. ,. f ,• ;,.· . j ; ~ ,•.,c·::·.. · ~-· ~.' ,. ' j, :. ; '~~'I :. ' ~: .. ·, ·{ ;" :. ; ;UNIVERSITY .OF CALIFORNIA . \ .• . ·, -::~ ( ,. l'. ' ~-) . ~ ~ ,· ' .... L~wrence .·Radiation Laboratory i. "l :'io' ·.Berkeley,. California . ~ ~ ' ,, ,· j ,. 't'" C6ntrad't No. ·w ~7405 ~eng-4S · - -~- -:·. .? . \ ''·;'· . ~ i} _::( : . ~.; .. ,. ~ . ·, .... :_j~ ~\ ~ .. ... .'I ·, . ·'•t ' ' -~ ..; . :_(. ' '·,' t·. -~·j! •. ~ ;. : ) ~~ '',. ~ .. '.·· .~.· •.!.-i l, J_ ~ ·: <. ;, .; .. ;.' ·,·'IJ ·'· ·L.'· ' ~ . ' .._· .: .. '.t L-t ' . ~· . ~ . ' . i' .. -: ~- .· .. ·.... ) T;_ ~ ,. .,: . ~:· ; · .... ~- . '.,-·... · .;, .... ,;_ ....... {'·' : ~ .i ·.. ··~ • ' .·j .•'' J· . i ·~: . < ·., '· . .~ ' ( PRINC"t:PLES •oF HIGH TEMPERATURE. CHEMIS1',RY · i·. ,. ·-:: -~ ' ·.. -·~·· ·.~· \ 1_.: _, :.· ~--·. .'· ~t .. ; i,.j'• 't· ' .: i,· ·;,, ;·· .. ' ;· • ' ...~ .':. • "•-"f~ . \. h ~ June 1963 ~--.. j: !. ··,\ '. ..· ._· ..... ~t . :.: ··.· \"'' ·::,· ,: '~- f . ~- . ; i. (:· ·., ......,.,(>' :~ . ;: ,•" ··.. :~;; ., ....... t, ·:· ft ''· 1'-~ ::_ ... , I~ I; ., . ; . '· . ·.~ t~ !·. ·; :1 ;t; ,, ' . ..; . ~·- ! . .. \. ·.·: .· .~ ' '.. i- ~ . ..... ' ~· ·' ' -:-~·- •,· ::, f~-~ \.:;.~~!... ·., ;' •• e .f .·, ,r,. -, . •._·,, ., ·, '' . fj, ·.~· ·~ .. ~;·· ·r ··.j ·..• -.t.i I, ... '! ' ..,_. '·.,;' '- : 1.·.• l.·. !':·····;·:··· ,I -~ '~..?-. ~ I. :t:. ''l '' .~ ~.: . ~~- ): ~' ~~ ~ l' ·.' } ;, -1- UCRL..,l0619 . ;. ;; .. i ·. ' ( " : (-' •; PRI:DTCIPLES OF EIGH .TElv!PERAT"URE CHEMISTRY '··J. ; ' ·.·: ."i .....l ...... ·~ ~ • ~- ............ ___ -1.,..:..... •• ~-- •. t. i. ,. ' . ' I ,. ' . ~ ,. ' · · Department of Chemistry, and Inorganic V~terials Research Division '' of the Lawrence Radiation Laboratory, University of California·~ ,, ,'..., . ~ Berkeley, California ;: . , . .... ---------- . ·- ... ., .... ·~ .. -· ·-··--··· ··- ........·-·:--··-·----~----·-· .. ·--·-------------__..,-·---------·-··-··-· 7nank you, Glenn. 'It is a real pleasure to be here in Houston today and to participate . in this Conference.· , I . ' '' The developments in high temperature chemistry have been much too . .; ·extensive to hope to present a complete revie~or of this field this after­ ', noon. ~lhat I propose to do instead is to present two thin cross-sections of' the field. Fir-st I ~orish to take a cross-section in breadth to examne .... so~e of the general principles which characterize chemical behavior at , high temperature, and, in fact, disting~ish it from the normal type of ··chemistry to 't·rhich we are accustomed. Then I 11ould like to take a cross- section in depth. by taking one particular relatively :r4rroi-l' field and ' ' ' carrying ·it throuen to the present frontiers. In this manner I hope to·. point out tr.e n:.ajor problems· of high temperature che~stcy' and to indicate ·fi.. I I ':: "--......·' :. , . so:x.e of· the tecbnig:,ues th8. t are· needed to resolve these problems. ,,.· . '' • !• r, ···;: Often 11hen I encoUnter people i-l'hO are not famili~r i-l'ith high te:znporature · . '' '•_!. .. ' ,., ·cne:nistry, the usUa.l comrn.ent is,:. "Oh,· it must be very· :difficult to produce . }: .· ' :: . · ; · t:nese hiz,."l. temperatures, but,·.'~t least once you get them, the cltell).istry ,1,' '"' . 1 -, ' < must be verysimple~"·o:r course, it's. just the opposite •. It is very ·' ) .easy to get high teni.peratures., but high tempera"~U:re chemis-try can be ', ' . ·.' ' .... :. •, .·. ·. ,-:-' .. ; .. ·: ' . ' . e:ftremely complex/ The :f'act that rat.her complex ga.seo~s mOlecules 'eXist . ~ . ~ :· . .· • •, I. .' in high temperature· systems and that the complexity o:f' saturated vapors '·· .' ·! 1. ; . ::: -2- ~. (, .. · i·rith respect to the number of different species actually .increas.es vrith :· ',.~· ' : '. increasing temperature seems to pose a paradox to most people. ~lhat I .<~ ' i·Iould like to do is to present some simple thermodynamic reasoning to " '. resolve this paradox. and to illustrate l·rhy it is that high temperature .. :; • chemistry is so complex, and essentially establish some of the'basic i' principles which fix the chemical behavio~ at high temperatures. ' Now, to simplify _our discussion I 't·Tould like to l;"estrict my examples·. to a specific type of problem. I would like to discuss the problem of equilibriumbetweeri a condensed phase and·a gaseous phase athiBh temperatures. ··. • •..... i,,2 3/" . Actu·a-lly ali. of the co:rnments I will make can be generalized '\_ ~, · to a ivide . ·,;:.. range of situations, e.g., completely·condensed systems and a variety of ; . ' other systenis. I thin.'1): it might simplify the discussion· if YTe just restrict . .i ourselves to a specific situation . I think Ylhat misleads most people ivhen they expect chemical behavior in high temperature g~seous systems to be simple is that they are thinking in terms·of heatinga gas·at constant pressure in an inert container. ~{hen one heat~-\~terials one most. always has t6 contain the gases in some t:rpe of material and there is thus almost alvmys a condensed phase present . ., ' . ·' l' W".nen one heats a gaseous system in contact uith a cond~nsedphase the partial pressures of the various species i·!ill not ·remain constant. · And ·. as•·r i\-'ill ·shmv. shortly the _pressures· t;,.ill increase fa~t enough to offset. ·· .. ·.. f . ·.any simplifying effect of increase in temperature that might be expected .. ";· !,.··, ' . ., . ' ' . · -in 1 a· system at constant pressure; so that, in fa~t, high temperature ' .. ·~· . ·' . g~se'ous systems in contact with condensed phases \·rill :become more complex . l ~ . :.. ~ the higher the temperature.· ·.. ' ., : . !' ·•' f ) .. :, . ·.;.. High ·temperature syste~ become· more . comptex in three principal WJ.ys. ,· First, the oxidation numbers and formulas of the_ compoUnds become unfamiliar . ; .. ; ' -3- 'r at high. tem,Peratures. \·le are accustomed to the alkali· metals having an. ~:~'\. .... ' :'i.-. ' oxid?-tion number.of 1,· the alkaline ,earth metals having an .. oxidation number of 2, aluminum and the third group' elements having anoxidation number .of ~~-: 3, and any deviations from those oxidation numbers at room temperature ··would be considered quite unusual. At high. temperatures these arc no"c the -~- co:mrnon oxidation states at all. One finds a variety of unusual oxidation ·states. Compound~ lilte LiO, for example·, are quite. stable and compounds· ~ . ' \,t;;l' of bariuni< in both the l and 3 oxidation sta<:;es are observed. Alur.a.inum ,. ~ t occuri'P-!J>'i~ the. l and 2 oxidation state~. At high temperatures one can ·: . ' ' just forget about the octet rule and all the other valence. rules that ".·le . have been taught. Anything goes. That's the first complication that a:dses. You won't recognize some of the compounds you will see listed· in the figures or some of the compounds I idll talk about if you are ·' ·' accustomed to thinlting of chemistry at room temperatures. We •rill discuss ·. ,'·t in a moment why that might be. ·.The second respect in which. gaseous sJrstems become more· complex at ' ' · high temperatur:es ~s that the molecules becom,e very complex. There are ·I no.t only diatomic and .. triatomic molecules but also gaSeous molecules w·ith 5, · .!..·.: 10, and more atoms per molecule . 1 ,i The third vray in w·hich these gaseous systems become more complex is '' . :·.! , , : tp.at, in ~ontrast to low temperature systems ".-There one ;maY hive one .or • ' ' • • • j • ". two principal spec·ies, one may have many different species of roughly. ' ' ·•· :-co~parable' importance. at high temperatures~. '' :: .. ,.j Now, •.I · vrouid ·like •to •exUmine some