SWENSON WA WALKER CRYSTALLI ZER
udy cr ys t al l i z at i on pr oc es s wi t h Swenson Wal ker AI M: To st Cr ys t al l i z er .
APPARATUS: • •
SwensonWal kerCrys t al l i zer . Fe edf orCr ys t al l i z at i on.
I NTRODUCTI ON Crystal l i zati on: Cry st al l i z at i on i s t he f orma mat i on of sol i d part i cl es wi t hi n a homo mog eneous phas e. I t may oc cur as t he f or mat i on of s ol i d par t i c l e si nav apor ,asi ns no w; w;assol i di fic at i onf r om al i qui dme l t , asi nt hemanuf ac t ur eofl ar g es i ngl ec r y s t al s ;orasc r y s t al l i z at i on f or ml i qui ds ol ut i on.
Cr yst al A cr ys t ali sa r egul arpol yhedr alf or m,bounded bysmoot hf aces, whi c hi sassumedbyac hemi calcompound,duet ot heact i onofi t s i nt e r at o mi mi cf o r c es ,whe n pas s i ng ,unde rs ui t abl ec o ndi t i o ns ,f r o m t hest at eofal i qui dorg ast ot hatofas ol i d.
s defined as a t hr ee di mensi onalne t wor k of Cr yst al Latt i ce i i magi naryl i nesconnect i ngt heat omsormol ecul es. The di s t ance be t ween t he cent eroft wo at oms ( ormol ecul es)i s cal l edl engt hofuni tcel landt heangl ebet weent heedgesofauni t cel li scal l edasl at t i ceangl e.
Cr yst alForms Cr y s t all at t i c ec anbec l as s i fie dac c or di ngt ot heang l e sbe t we e nt he f aces .Ther ei s onl y fini t e numberofsymme t r i calar r ange ment s pos si bl ef orac r ys t all at t i c e,t hi si st e r me dascr y st alf or ms . The abi l i t y ofa compound t o exi s ti n di ffer entcr ys t alf or ms i s knownaspol ymor phi sm. Ther ear esi xt ypesofcr ys t alf or ms,dependi ngont hear r angement oft hef acesexpr essedascrys t alaxesandangl esbet weent heaxes. 1.Cubi c-Thet hr eecrys t al l ogr aphi caxesar eal lequali nl engt h andi nt e r s e c tatr i g htang l e s( 90de g r e e s )t oe ac ho t he r .[ a=b= c] 2.Tet r agonal-Thr ee axes,al latri ghtangl es,t wo ofwhi ch ar e equali nl engt h( aandb)andone( c)whi chi sdi ffer enti nl engt h ( s hor t e ro rl ong e r ) .No t e :I fcwase quali nl e ng t ht oaorb,t he n wewoul dbei nt hecubi csys t em.
3.Or t hor hombi c-Thr eeaxes,al latr i ghtangl es,and al lt hr eeof di ffer entl engt hs.Not e:I fany axi s was ofequall engt ht o any o t he r ,t he nwewo ul dbei nt het e t r ag onals y s t e m 4.Hexagonal-Fouraxes,t hr eeoft heaxesf al li nt hesamepl ane andat600t oeach ot her .These3axes,l abel eda1,a2,anda3, ar et hesamel engt h.Thef our t haxi s,t er medc,maybel ongeror short ert han t he‘ a’axesset .Thecaxi sal sopassest hr ough t he i nt e r s e c t i o no ft he aax e ss e tatr i g htang l et ot hepl anef o r me d byt hease t . 5.Monocl i ni c-Thr eeaxes,al lunequali nl engt h,t woofwhi ch ( a and c )i nt e r s e c ta ta no bl i q ueang l e( no t90 de g r e e s ) ,t het hi r d ax i s( b)i spe r pe ndi c ul art ot heo t he rt woax e s .No t e :I fa andc cr os se d at90 degr ee s,t hen we woul d bei nt he or t hor hombi c sy s t em. 6.Tr i c l i ni c-Thet hr e eax e sar eal lune quali nl e ng t h andi nt e r s e c t att hr e edi ffe r e ntang l e s( anyang l ebut90de g r e e s ) .No t e :I fany t woaxescr oss edat90 degr ee s,t hen wewoul d bedes cr i bi nga monoc l i ni cc r y s t al .
THEORY OFCRYSTALLI ZATI ON I nt hef or mat i onofc r y s t al st wos t e psar er e qui r e d: ( i )Nuc l e at i on:i . e .t hebi r t hofane ws ol ut epar t i c l eand
( i i )Cr y s t alg r o wt h:i . e .t heg r o wt ho ft henuc l e ust o mac r o sc o pi c s i z e .
CLASSI FI CATI ON OFCRYSTALLI ZERS Cr ys t al l i z at i on equi pmenti s cl assi fied by t he me t hods by whi ch supersat ur at i oni sboughtabout .Thesear easf ol l ows: 1.Supersat ur at i onbycool i ngal one a.Bat chpr oce ss es i .T ankc r y s t al l i z e r s i i .Agi t at e dbat c hc r ys t al l i z e r s b.Cont i nuouspr ocesses i .SwensonWal ker i i .Ot her 2.Supersat ur at i onbyadi abat i ccool i ng a.Vacuum crys t al l i zer s i .wi t houte xt e r nalc l as s i f y i ngs e e dbe d i i .wi t he xt e r nalc l as s i f y i ngs ee dbe d 3.Supersat ur at i onbyev apor at i on a.Sal t i ngev apo r a t o r s b.Kr ys t alev apor at or s
THEORY: I tc onsi st s ofan open t r ough wi t h a semicyl i ndr i calbot t om.A wat erj ac ke ti swel ded t ot heout si desur f aceoft het r ough.I nsi de t het r oug h as l o ws pe e d,l ongpi t c h,s pi r alag i t at ori sfit t e dasc l os e aspossi bl et ot hebot t om oft het r ough.Theagi t at orr ot at esata l ow RPM.
Funct i onsoft hespi r alst i rr er : 1.I t pr ev ent st he accumul at i on of c ry st al s on t he cool i ng s ur f ac e . 2.I tl i f t st he cr ys t al st hat have al r eady been f or med and showert hem downt hr ought hesol ut i on. I nt hi smanner ,t hecr yst al sgr ow whi l et heyar ef r eel ysuspended i nt hel i qui dandt he r e f or et he yar e : 1.Fai r l ype r f e cti ndi v i dual s . 2.Uni f orm i nsi z e 3.Fr eef r om i ncl usi onsoraggr egat i ons.
Advant ages:
1.Lar ges avi ngi nfloorspace. 2.Lar gesavi ngi nmat er i ali npr ocess. 3.Savi ngi nl abor . 4.Uni f o r ms i z ec r y s t al s . 5.Fr eef r om i ncl usi onsandaggr egat i ons.
Procedure: Thi si s cont i nuous t ype cr ys t al l i z er . The hot super sat ur at ed sol ut i on i sf ed atoneend oft het r ough,and t hecool i ngwat eri s flowsi nt hej acket .Ast hehotsol ut i on flowsal ongt het r ough i ti s cool edandcrys t al sar ef ormed.Agi t at orpr event sanaccumul at i on o ft he c r y s t al so nt he c o ol i ng s ur f ac e and,l i f tt he c r y s t al s and shower t hem t hr ough t he sol ut i on. I n t hi s manner per f ec t l y i ndi v i dualc r y s t al sar ef or me d. Att heendoft hecr ys t al l i z at i on t hemot herl i quorandt hecr ys t al s ar eflowedi n adr ai ni ngt abl eordr ai n boxf r om whi c ht hemot her l i quori ss e par at e d and f e di nt hec r y s t al l i z e rag ai n.Thec r y s t al s ar ese ntt oc e nt r i f ug e .
