Ammonium permanganate

Ammonium permanganate is an intriguing salt which at room temperature exists as slightly bronze-metallic purple crystals. It is a moderately strong primary explosive but has very rarely found much use in this field due to its high sensitivity, short shelf life and low power in comparison to the more widely used explosives. I don't really have any use for the compound and mainly just made some because of its interesting composition and to test out its explosive properties.

To make the ammonium permanganate, I followed this procedure (link) which seemed to give very satisfactory results.

To a 150ml beaker, I added 6.18g (0.0391 moles) of potassium permanganate and 17g (0.3178 moles) of ammonium chloride. I then added in 116ml of water using a graduated cylinder and stirred the mixture to dissolve everything. A dark purple solution was obtained and the beaker became intensely cold to the touch. Using a retort stand, I secured the beaker over a water bath heated by a hotplate. Medium heat was then applied and a thermometer was inserted into the mixture to monitor the temperature. Most of the time the temperature of the mixture stayed at around 80 C and care was taken not to let it go much higher then this. The liquid was occasionally stirred with the thermometer. Once the volume of the liquid had been reduced to 74ml, I took the mixture off heat and rapidly filtered it while hot into a 250ml conical flask to remove brown manganese dioxide. This is formed by some of the heat sensitive permanganate ions decomposing.

Anyway, I then chilled the flask containing the filtrate in an ice bath to 5 C whereupon a fair amount of ammonium permanganate precipitated as dark purple felted, short needle-like crystals. The mixture was then immediately filtered to collect the product, pressing it on the filter to remove as much liquid as possible. After drying, I obtained 1.68g (0.0123 moles) of ammonium permanganate which if pure, corresponds to a yield of 31%.

Left = dry ammonium permanganate  /  Right = mildly energetic decomposition of  ammonium permanganate (results in large cloud of manganese dioxide)

The reaction is a relatively simple double displacement with ammonium permanganate being forced out of solution by exploiting its radically reduced solubility in ammonium chloride solution at low temperatures. Hence the large excess of ammonium chloride.


KMnO4 + NH4Cl ==> NH4MnO4 + KCl