Abstract: In order to decrease arsenic, which is a harmful substance, in a copper concentrate, provided is a method for selectively recovering an arsenic-containing copper mineral from a mixture including the arsenic-containing copper mineral and a non-arsenic-containing copper mineral, and a flotation agent used in the same. For a collecting agent, which is a component of the flotation agent used in a flotation step for selectively recovering the arsenic-containing copper mineral from the mixture including the arsenic-containing copper mineral and the non-arsenic-containing copper mineral, a sulfide compound having an R1—S—R2 (in this expression, R1 is a C5-10 alkyl group, and R2 is a C1-10 alkyl group) structure such as methyl n-octyl sulfide or di-n-octyl sulfide is used.

Abstract: A method and apparatus for determining the stability of arc welding between a base metal and a welding electrode. A welding current for the arc period and a welding current for the short-circuit period fed from a welding power source are sampled every cycle of the repetition of arc and short-circuit, in accordance with a predetermined sampling frequency. The welding current for the arc period is integrated, and a standard deviation of the integrated welding current for the arc period is calculated. The standard deviation of the integrated welding current for the short-circuit period is calculated, as well. These standard deviations are multiplied together to produce a product, so that a welding stability parameter is calculated on the basis of the product. Then, the welding stability parameter is compared with a predetermined reference value. In response to the result of comparison, the welding stability between the base metal and the welding electrode is determined.