makes it suitable for commercial-scale production. Sparging by inert gas Bubbling a solution with a high-purity (typically inert) gas can pull out undesired (typically reactive) dissolved gases such as oxygen and carbon dioxide. Nitrogen, argon, helium and other inert gases are commonly used. To maximize this process called sparging, the solution is stirred vigorously and bubbled for a long time. Because helium is not very soluble in most liquids, it is particularly useful to reduce the risk of bubbles in high-performance liquid chromatography (HPLC) systems. Addition of reductant If oxygen should be removed, the addition of reductants is sometimes effective. For example, especially in the field of electrochemistry, ammonium sulfite is frequently used as a reductant because it reacts with oxygen to form sulfate ions. Although this method can be applied only to oxygen and involves the risk of reduction of the solute, the dissolved oxygen is almost totally eliminated. The ketyl radical from sodium and benzophenone can also be used for removing both oxygen and water from inert solvents such as hydrocarbons and ethers; the degassed solvent can be separated by distillation. The latter method is particularly useful because a high concentration of ketyl radical generates a deep blue colour, indicating the solvent is fully degassed. Freeze-pump-thaw cycling In this laboratory-scale technique, the fluid to be degassed is placed in a Schlenk flask and flash-frozen, usually with liquid nitrogen. Next a vacuum is applied, perhaps to attain a vacuum of 1 mm Hg (for illustrative purposes). The flask is sealed from the vacuum source, and the frozen solvent is allowed to thaw. Often, bubbles appears upon melting. The process is typically repeated a total of three cycles. The degree of degassing is expressed by the equation (1/760)3 for the case of initial pressure being 760 mm Hg, the vacuum being 1 mm Hg, and the total number of cycles being three. Degassing wine Yeast uses sugar to produce alcohol and carbon dioxide. In winemaking, carbon dioxide is an undesired by-product for most wines. If the wine is bottled quickly after fermentation, it is important to degas the wine before bottling. Wineries can skip the degassing process if they age their wines prior to bottling. Storing the wines in steel or oak barrels for months and sometimes years allows gases to be released from the wine and escape into the air through air-locks. Oil degassing The most efficient method of