The crystallization of K,SO, from aqueous solutions of glaserite (a double salt of sodium and potassium sulphate) was investigated in an MISMPR cooling apparatus at 35 "C. The precipitation of K,SO, at an average purity of 93 wt.% was obtained and the crystallization kinetics were derived from the experimental data. The nucleation and growth rates here obtained were, respectively, remarkably higher and slightly lower than those relevant to pure K,SO, : this behaviour may be explained by a faster nucleation and a slower growth of crystals containing also Na,SO,. The effect of small (0.05%) calcium additions t o the feed was also tested, which caused an increase of supersaturation and a depression of the growth kinetics, whereas the nucleation one was not appreciably modified.
On a realis6 la cristallization de K,SO, i% partir de solutions aqueuses de glaserite (sulfate double de Na et K), par refroidissement i% 35 "C dans un appareil MSMPR. On a obtenu la prhcipitation de K,SO, h une purete moyenne de 93% en poids et on a en correspondance determine les cinetiques de cristallization. Les cinetiques de nucleation et d'accroissement ainsi obtenues rksultent, resphctivement, considhrablement plus Blevee et legkrment plus basse que celles correspondantes h solutions de K,SO, pur; ce phhnom8ne peut btre explique avec un nucleation plus rapide et un accroissement plus lent des cristaux contenant Na,SO,. L'effet de petites additions de calcium (0.05%) augmente la supersaturation et diminue I'accroissement, tandis que la nucleation ne parait appreciablement modifiCe.