SEATTLE (Bloomberg) — Gold may rise for a third week on speculation the US dollar will weaken, boosting the appeal of the precious metal as an alternative investment. Nineteen of the 30 traders, investors and analysts surveyed by Bloomberg News from Sydney to Chicago on January 18 and 19 advised buying gold, which rose $9.50, or 1.5 percent, to $636.40 an ounce last week on the Comex division of the New York Mercantile Exchange. Four respondents said to sell, and seven were neutral. Respondents have forecast prices accurately in 86 of 143 weeks, or 60 percent of the time.This week’s survey results: Bullish 19; bearish 4, neutral 7.