So, let's move to homemade Uranyl oxide (UO3); U3O8; uranyl salts ! is produced by heating dry UO4·nH2O in an open-air container at about 300 °C. During the process of heating, volatile contaminants (water, oxygen, ammonia, halogens, hydrogen peroxide) are driven off. During preparation, keep stirring the yellow peroxide as it turns orange. If the temperature is managed properly, the product will be a clean orange color. If allowed to overheat, U3O8 begins forming and the orange color fades to darker shades of brown-green