The professional perc process is to take sodium chloride (salt -food grade is OK) electrolyse it to sodium chlorate, then boil it down to about half volume and harvest the crystals of chlorate that form on cooling. These crystals are then dissolved in hot water and electrolysed a second time against a platinum electrode to turn the chlorate into perc. Then you add a saturated solution of K (or other) chloride. This forms sodium chloride which you reuse, and your desired perchlorate as a precipitate.
Actually, I avoid food grade salt as most have additives which become contaminants in the final product.
I've had better luck with water softener grades of salt (either sodium or potassium), but even then I recommend purifying the brine before electrolyzing it, so that the end product will be purer.
The typical commercial method of purification involves treating the raw brine (NaCl in this case) with a mixture of sodium carbonate and sodium hydroxide solutions, which drops out many contaminants (calcium, magnesium and iron, for example) as flocculant precipitates, which can be filtered out, leaving a more pure brine.
I've found the best filtration method to be vacuum filtration using a slow grade of laboratory filter paper (hardened is a good idea, also) since the precipitates are very fine.
Also, any excess alkalinity in the purified brine can be neutralized with dilute HCl to leave a neutral to slightly acid solution, ideal for electrolyzing into oxidizers. Neutral brine is best for conversion to other salts, as is the case of converting sodium perchlorate into potassium perchlorate.
NaClO4(aq) + KCl(aq) -> NaCl(aq) + KClO4(s)v
By taking the extra steps to purify all the materials used, I believe better-than-commercial grade oxidizers can be produced.
Edited by WSM, 27 May 2019 - 05:39 AM.