An improved method for the synthesis of four heterotrinuclearpolyacids of t
he type: H-x[EMy'M-z"O-40]. nH(2)O (E=P, Si; M'=Mo, W; M " =V, W) was elabo
rated. The studied compounds were characterized by elemental analysis, IR s
pectra and thermal behaviour over 20-800 degreesC temperature range.