Freeze-pump-thaw degassing

Preparation of a Typical Au-Acetone Colloid. The metal atom reactor has been described previously. (39,59, 60) As a typical example, a W-A1 0 crucible was charged with 0.5Qg Au metal (one piece). Acetone (300 mL, dried over K2C0 ) was placed in a ligand inlet tube and freeze-pump-thaw degassed with several cycles. The reactor was pumped down to 1 x 10 Torr while the crucible was warmed to red heat. A liquid N2 filled Dewar was placed around the vessel and Au (0.2g) and acetone (80g) were codeposited over a 1.0 hr period. The matrix was a dark purple color at the end of the deposition. The matrix was allowed to warm slowly under vacuum by removal of the liquid N2 from the Dewar and placing the cold Dewar around the reactor. 

This chapter describes the removal of water and atmospheric gases from some common solvents and the purification of some common laboratory reagents which are susceptible to contamination by moisture and oxygen. Equipment designs and procedures are introduced here as needed, but most of this material is described in other sections of this book general inert-gas techniques (1.1, 1.3-1.5), conventional distillation (1.2), desiccants (3.2.B), freeze-pump-thaw degassing (5.3.A), and trap-to-trap distillation (5.3.D,E). 

Bulk photolyses were carried out using a Kratos 1000-W, variable power, high pressure, Xe lamp. This radiation was filtered first with a CuSO S O aqueous solution and then an ultraviolet bandpass filter with maximum transmittance at 3A5 nm. For purposes of calibration and evaluation of power, 20 mW of power at 3A5 nm is produced at the sample surface of the test tube cell. This corresponds to 3.A x lO1 photons/second. Iron carbonyl zeolite samples were loaded into ampoules with a magnetic stir bar and freeze-pump-thaw degassed three times before sealing off the pyrex tube. Sample tubes were opened just before the chromatographic analysis. 

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