Abstract: The ther m al deco m position mechanism of a m m oniu m thiotungstate of the size of 63 ～75 μmin H2 has been investigated by D T A and X R D methods . The ther m al deco m position activationenergies and the orders of a m m oniu m thiotu ngstate were calculated by means of Kissinger , Freem an Carroll and Coast Redfern m ethods . It w as also obtained that therm al deco m posi tion is cond ucted according to four reaction equations :( N H4) 2 W S4· H2 O(s) ( N H4) 2 W S4(s) + H2 O(g) W S2(s) + 2 N H3(g) + H2(g) + 2 S(s) + H2 O(g) W S2(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) W S2(s) + W(s) + 2 N H3(g) + 2 H2 S(g) + H2 O(g) .

Key words: a m moniu m thiotungstate , ther m al deco m position , W S2 , H2