Thorium forms two nitrides, ThN and Th3N4. Th3N4 loses nitrogen at temperatures above 1500eC. At low pressures and temperatures above 2200 K, ThN also dissociates, into thorium and nitrogen. The Na pressure over solid ThN in equilibrium with liquid Th-N alloy is [II]

log10 p(atm) = 8.086 — 33,224 + 0.958 X 10*17Г5 2689 < T < 3063 К (6.5)

At a nitrogen partial pressure around 2 atm, ThN melts at 2820eC without dissociation [B4]. The density of ThN is 11.9 g/cm3.

Th3N4 is made by reacting thorium hydride with nitrogen at temperatures increasing from 200 to 900°C. ThN is made by pressing Th3N4 in vacuo at 1500°C, The nitrides react rapidly with water or moist air.