Oxygen: Potassium Chlorate Heated with Manganese Dioxide at about 240 °C

The convenient laboratory way, from Thorpe's Dictionary (1913): potassium chlorate mixed with about an eighth of its weight of manganese dioxide gives off oxygen steadily at about 240 °C, well below its melting point. 100 parts of chlorate give 39.16 parts of oxygen. Test the dioxide first: pyrolusite adulterated with coal dust has exploded with chlorate and killed. Face shield. The picture: our diagram.