A metallic material with its basic components similar to the metal to be tested is made into an external sleeve. The diameter of inscribed circle of its bottom periphery is greater than the top aperture of spark chamber in optical spectrum analyzer by at least 1mm. At first, the one end of the external metal sleeve, which has a smaller diameter of inscribed circle, is put on steel or glass plate and a small specimen to be tested is put in the center of the bottom of external metal sleeve. Then, one of three alloys (Sn-Pb, Sn-Pb-Bi, or Sn-Bi) is heated until it is molten, filled into the external metal sleeve, and cooled. |