TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: pH range, which is changed for 2 times, is more than 0.8 and less than 1.2, and more than 1.2 and less than 1.8. Alternately, extraction is performed using the extracting agent containing cyclic phenol sulfide derivative of formula (1), and subsequently extraction is performed using extracting agent containing cyclic phenol sulfide derivative excluding cyclic phenol sulfide derivative of formula (1), preferably extracting agent containing cyclic phenol sulfide derivative of formula (2). Platinum is selectively extracted by one of the extraction processes.R5=H or 1-10C hydrocarbyl. Preferred Definitions:    R1,R3,R4=H or 1-10C alkyl;and    R2=0-10C alkylene.    EXAMPLE - Diphenylether (64 ml), p-tert-butyl phenol (in g) (300), and ethylene glycol (56 ml) were heat-stirred at 60 degrees C, in presence of nitrogen. Calcium oxide (28) was added, heated to 120 degrees C and reacted for 2 hours and 20 minutes. The solution was distilled. Sulfur (95.9) was added and reacted at 230 degrees C for 3 hours. Subsequently, toluene (250 ml) was added and reacted to obtain cyclic phenol sulfide intermediate oligomer (A). The obtained oligomer (A) (30), diphenylether (64 ml), sodium hydroxide (3.99) and acetic acid (1.62) were heat-stirred and reacted with sulfur (2.14) at 230 degrees C for 4 hours. After completion of reaction, the solution was washed, distilled and precipitated, to obtain crude crystals of cyclic phenol sulfide. Sodium iodide (1.66), ( alpha )-chloro-N,N-diethyl acetamide (1.66) and acetone (30 ml) were stirred at room temperature for 2 hours. The obtained cyclic phenol sulfide (1), cesium carbonate (2.6), acetone (65 ml) and water (5 ml) were heat-stirred at 64 degrees C for 120 hours. After completion of reaction, acetone was distilled off and residue was dissolved in chloroform, distilled and washed. The obtained organic layer was washed, filtered and dried to obtain cyclic phenol sulfide derivative of formula (1-1) at a yield of 78.1%. The obtained derivative had excellent extraction efficiency of rare metals.