Americium oxides. Keller [K2, КЗ] reports three stoichiometric’binary oxides of americium: AmO, Am2 03, Am02. The dioxide Am02 is the most stable of the americium oxides. It crystal­lizes with the cubic fluorite structure of all the actinide dioxides. It can be formed as a dark brown powder, stable up to 1000°C, by heating trivalent americium nitrate, hydroxide, or oxalate in oxygen to 700 to 800°C. Americium dioxide is readily soluble in mineral acids. Hydrogen reduction of the dioxide yields Am2 03.

Americium monoxide AmO is observed as a surface layer on americium metal if oxygen is present during preparation.

Americium halides. Americium forms binary halides in the oxidation states of III and IV. The trifluoride is prepared by hydrofluorination of Am02 with HF at 400 to 500°C and by precipita-

tion from aqueous solutions. Fluorimtion of AmF3 or Am02 with F2 at 400 to 500°C yields AmF4. Similar compounds are formed with chlorine, bromine, and iodine.