Making Potassium Perchlorate

Safety first

Potassium perchlorate (KClO₄) is a strong oxidizer, albeit less than chlorate (KClO₃), but safety measures still apply. Do not heat or rub it with combustibles, like carbon, sugar, etc.

Molecular formula:	KClO₄
Formula weight:	138.55
CAS number:	7778-74-7
Melting point:	400^oC (decomposing)

Introduction

Potassium perchlorate KClO₄ (also called Potassii Perchloras or Kalii Perchloras or Perchloras Kalicus/Potassicus) is the potassium salt of perchloric acid and is an oxidizer, used in chemistry to produce oxygen, but also used in fireworks. It is more stable than chlorate (KClO₃), unlike chlorate, it can be mixed with sulfur so it is preferred over chlorate in fireworks. It is obtainable at chemicals supply shops, such as Merck or other large suppliers. It used to be available at the local chemist but this is getting harder and harder. With rather simple means you can make this yourself by electrolysis. Due to its very poor solubility in cold water, compared to sodium (per-)chlorate and chlorides, it is to prepare rather purely.

Experiment Febuary 2025 (video)

Making Potassium Perchlorate Feb 2012

Making Potassium Perchlorate by electrolyzing ordinary table salt using an MMO anode and then a PbO₂ anode, converting to NaClO₄, and then precipitating KClO₄ by pouring a concentrated KCl solution into it.

Video taken with the Sony RX100M6.

Last update: 2025 February 24