Molecular Structure of Potassium manganate (CAS NO. 10294-64-1):

IUPAC Name: Dipotassium dioxido(dioxo)manganese 
Molecular Formula: K₂MnO₄
Molecular Weight: 197.132249 g/mol
Melting Point: 190 °C(lit.)
Polar Surface Area: 74.6 Å²
EINECS: 233-665-2
Product Categories: Catalysis and Inorganic Chemistry; Chemical Synthesis; ManganeseMetal and Ceramic Science; Potassium Salts; Salts

There are some ways to synthesis Potassium manganate:

1. The industrial ways:

MnO₂ + 2 KOH + ½ O₂ → K₂MnO₄ + H₂O

2. In laboratory, it can be synthesized by heating a solution of KMnO₄ in concentrated KOH solution
followed by cooling to give green crystals:

4 KMnO₄ + 4 KOH → 4 K₂MnO₄ + O₂ + 2 H₂O

3.  It can also be made by using iodide as the reducing agent:

KMnO₄ + KI → K₂MnO₄ + ½ I₂

Safety Information of Potassium manganate (CAS NO. 10294-64-1):
Hazard Codes: O , Xi 
Risk Statements: 8-36/37/38
R8: Contact with combustible material may cause fire
R36/37/38: Irritating to eyes, respiratory system and skin
Safety Statements: 17-26
S17: Keep away from combustible material
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice
RIDADR: UN 1479 5.1/PG 3
WGK Germany: 2
HazardClass: 5.1
PackingGroup: III

  Potassium manganate with cas registry number of 10294-64-1 is a common chemical used as an intermediate in the industrial synthesis of Potassium permanganate, KMnO₄. It is also known as Potassium manganate(VI) ; Manganic acid (H₂MnO₄), dipotassium salt ; Manganic acid (H₂MnO₄), potassium salt (1:2) .