I have prepared KClO3 by electrolyzing diet salt (2 parts KCl + 1 part NaCl) and then rinsed off the salts (Na+ and KCl) using ice-cold water in which KClO3 is barely soluble. I got rather pure KClO3 (flame test) but for upgrading it (about 50g) to KClO4 I used a platinized Ti anode and let it run fro 10 hours at 5 Amp and then I boiled off most water and let it cool off and put it into the fridge. I decanted off the remaining solution and again rinsed the crystals with ice-cold water, as KClO4 is far worse soluble than KClO3. I dried the crystals but how can I separate the (assuming there is still a considerable amount of it in) KClO3 from KClO4 ?