A rapid, simple and virtually universal technique is described for decomposing a wide range of materials such as ores, sinters, slags, ferro-alloys and other reagents and additives used in the steel industry, as well as environmental dusts and particulate matter. The procedure involves fusion with sodium peroxide, alone or with sodium carbonate (mixed flux) in a zirconium or vitreous carbon crucible. Treatment of the fused melt with water and acid results in complete dissolution. It avoids the tedious operations involved in dissolving residues left by other dissolution techniques. Losses of normally volatile elements such as arsenic, phosphorus, lead and zinc do not occur. Application of this technique is described, particularly for the photometric methods developed for determining arsenic, phosphorus, titanium and vanadium in iron ores in the ranges 0.0002-0.1% As, 0.002-0.6% P, 0.01-0.6% Ti, and 0.001-0.5% V. Both the precision and accuracy are excellent.