Air-free technique

Air-free techniques refer to a range of manipulations in the chemistry <a href="/facts/Laboratory/kqR3Vtx9">laboratory</a> for the handling of <a href="/facts/Compound_(chemistry)/37FXqqtv">compounds</a> that are <a href="/facts/Air-sensitive/4KqwjkKr">air-sensitive</a>. These techniques prevent the compounds from reacting with components of <a href="/facts/Air/hQ95Jznz">air</a>, usually <a href="/facts/Water/0lkXnJPK">water</a> and <a href="/facts/Oxygen/acyn6o8r">oxygen</a>; less commonly <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> and <a href="/facts/Nitrogen/Nf1QpGDz">nitrogen</a>. A common theme among these techniques is the use of a fine (100–10−3 Torr) or high (10−3–10−6 Torr) <a href="/facts/Vacuum/BTk3goyV">vacuum</a> to remove air, and the use of an <a href="/facts/Inert_gas/3EkBEoYh">inert gas</a>: preferably <a href="/facts/Argon/QX6NRH6d">argon</a>, but often <a href="/facts/Nitrogen/Nf1QpGDz">nitrogen</a>.
The two most common types of air-free technique involve the use of a <a href="/facts/Glovebox/NnR37n6E">glovebox</a> and a <a href="/facts/Schlenk_line/Bl52qujq">Schlenk line</a>, although some rigorous applications use a high-vacuum line. In both methods, glassware (often <a href="/facts/Schlenk_tube/nAJ7W1I9">Schlenk tubes</a>) are pre-dried in ovens prior to use. They may be flame-dried to remove adsorbed water. Prior to coming into an inert atmosphere, vessels are further dried by purge-and-refill — the vessel is subjected to a vacuum to remove gases and water, and then refilled with inert gas. This cycle is usually repeated three times or the vacuum is applied for an extended period of time. One of the differences between the use of a glovebox and a Schlenk line is where the purge-and-refill cycle is applied. When using a glovebox the purge-and-refill is applied to an <a href="/facts/Airlock/0W9ruNBq">airlock</a> attached to the glovebox, commonly called the "port" or "ante-chamber". In contrast when using a Schlenk line the purge-and-refill is applied directly to the reaction vessel through a hose or ground glass joint that is connected to the manifold.

Air-free technique open-in-new

Air-free technique