Purification - distillation

Rapid purification Distil, discarding the first 10% of distillate or until the distillate is clear. The distilled CCI4 is then stored over 5A molecular sieves. 

Rapid purification Distil, discarding the forerun. Stand distillate over Grade I alumina (5% w/v) or 4A molecular sieves. 

Rapid purification Distil, dry over K2CO3, distil again and store over 4A molecular sieves. 

Norbomadiene as supplied by Shell Chemical Co. is used without further purification. Distillation of the norbomadiene immediately before use gives no change in yield of 7-/-butoxy-norbomadiene. 

Methylene iodide was obtained from Lancaster Synthesis, Inc., and used without further purification. Distillation of the methylene iodide from copper prior to use does not lead to increased product yield or purity. 

Reagent-grade methanol and salts manufactured by Nakarai Chemicals, Ltd. (Tokyo) were used without further purifications distilled water was used. The physical properties of methanol and water were compared with the published data (3). Carbon dioxide was supplied from a commercial cylinder and the purity was confirmed by gas chromatogram to be greater than 99.8%. 

B is correct. Distillation will not completely separate two compounds which form an azeotrope. Crystallization is a very inefficient method of purification. Distillation is more effective when done slowly. 

UF6 Purification. Distillation of the UFfi is required for purification when the yellow cake does not go through solvent extraction. At Metropolis, the molybdenum, vanadium, and other impurities are removed in a pair of columns, one a 120-foot, 100-plate column operating at 200°F and 85 psia to remove the... 

Purification distilled under reduced pressure immediately prior to use. Partially polymerized material may be cracked by distillation under reduced pressure at 100 °C. ... 

---