Pharmaceutical houses that produce Tc-99m/Tc-99 generators have on occasion received product solutions of Mo-99 produced from U-235 fission that contained a black precipitate. Addition of sodium hypochlorite to product bottles prior to shipment prevents precipitate formation, which is evidence that the precipitate is most likely a reduced farm of Mo. The radiation effects of the dose from Mo-99 on the product and product bottle have been determined by irradiating simulated Mo-99 product solutions with the Co-60 source at Sandia National Laboratories' Gamma Irradiation Facility (GIF). The GIF experiment successfully generated a black precipitate in amounts sufficient for isolation and analysis by infrared and Raman spectroscopy. Changes in the pH of the basic Mo-99 product solution during irradiation were monitored by titration. Results of these analyses and the nature of the process that generates the precipitate, a mixture of molybdenum oxides that forms in plastic bottles but not in glass containers, are discussed.