Dendritic aggregates of ice and brine formed upon freezing of aqueous solutions have been studied. Chlorides of sodium, potassium, lithium and hydrogen were used as solutes; structures produced on freezing of binary, ternary and quaternary solutions were examined. Effects of freezing rate, solute concentration, solute diffusivity, mixing of solutions and magnetic fields are reported.The spacing between ice platelets or dendrites was found experimentally to be proportional to the square root of the freezing time when the freezing rate was constant from beginning to end of solidification. During unidirectional freezing from a constant temperature chill, the solution at each location is subjected to a spectrum of freezing rates; dendrite spacing increases linearly with distance from the chill surface and it is inversely proportional to the square root of the maximum freezing rate.In binary solutions dendrite spacing increases linearly with solute concentration; above a critical solute concentration ice platelets develop side branches. Application of an external magnetic field has an effect similar to increasing concentration. At a given solute concentration, spacing between ice dendrites increases linearly with solute diffusivity.In ternary and quaternary solutions dendrite spacing is a function of the concentrations and diffusivities of each of the constituent solutes.

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A BSTRACT. D endriti c aggrega tes of ice and brine formed upon fr eezing of a queous solutions have been studied . Chlorides of sodium, po tassium, lithium a nd h ydrogen were used as solutes; structures produced on fr eez ing of binary, terna r y a nd qua terna ry solutions were exa mined . Effects of freez ing ra te, solute con centration, solute diffusivity, mixing of so lutions and magn e ti c fields a re reported.The spacing be tween ice platelets o r d endrites was found experimentall y to be proporti onal to the squa re root of the freezing tim e wh en the freez ing ra te was consta nt from beg inning to end of solidifi ca ti on . During unidirection a l freez ing from a consta nt tempera ture chill , th e solution a t each loca ti on is subj ected to a spectrum of freezing ra tes; d endrite spacing increases linea rl y with d istance fro m th e chill surface a nd it is in versel y proportiona l to the squa re root of the m aximum freezin g ra te.In bina ry solutions d endrite spacing increases lin ea rl y with solu te concentratio n; above a critical solute concentra tion ice pla telets d evel op sid e branches . Applica tion of a n extern a l m agnetic field has an effect simil a r to incr easing concentrati on. At a given solute concen tra tion , spacing between ice d endrites in creases linea rly with solute diffusivity.In tern a ry a nd quaterna r y so lutions d endrite spac ing is a fun cti on of the con cen tra ti ons a nd diffusiviti es of each of the constituent solutes . R ESUME. Aggregat derzdritiqlle de glace et de saumllre.!orme par le gel de solutions a quellses. D es a ggrega ts d endritiques de g lace e t d e sa umure, formes lors du ge l d e soluti ons aqu euses , o nt ete etudi es. D es chlorures d e sodium, potassium, lithium et hyd rogene on t ete utilises comme sels; les structures, produites pa r le gel d e solu t ions bina ires, terti a ires et qua tern a ires, ont e te exa minees . Les effets de la vitesse de congelation, de la con centration d e la solution, d e la vitesse d e diffusion du sel , du mela nge d es solutions et d es cha mps m a gnetiques, sont donn es .L'es pacem ent entre les pl aqu ettes d e g lace ou les d endrites s'est revele experimen ta lem en t etre proportionn e l a la racin e carree du te mps d e conge la ti on lorsque la vitesse d e congela tion e ta it consta nte du d eb ut a la fin d e la so lidificat ion. Pend a nt un e congela tion unidi rectionn e ll e pa r un a ba issem ent d e te mpera ture consta nt, la soluti on en chaque point es t suj e tte a un spectre de vitesses d e conge la tion ; I'es pacem ent entre les d endrites a ug mente lin ea ire m ent avec la dista nce d e la surface d e refro idissement et il es t in versement proporti onnel a la racin e ca rree d u m a ximum d e la v itesse d e conge lation.D a ns les soluti ons bina ires, l'espacem ent en tre les d endrites a ug mente lin ea ire ment avec la concentra tion ; a u-dess us d ' un e co ncentration critique, les pl aque ttes d e g lace d evel oppen t d es a rbo rescences. L 'a pplica...

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