Schlenk line

The Schlenk technique is a chemical operating procedures, can be processed in the absence of atmospheric oxygen and humidity to the air-or moisture -sensitive substances. It is named after the German chemist Wilhelm Schlenk ( 1879-1943 ).

Method

There are glassware used with ground-glass joints, which have an additional tap connector provided with vented through which the apparatus can be supplied if necessary and dried with inert gas. Most carried the degassing ( evacuation ) through a rotary vane pump with upstream cold traps. Protective gases nitrogen or argon are used. Nitrogen compared to argon -cost, but reacts with some highly sensitive reagents (including Titanorganylen ).

The Schlenk equipment are usually connected via tubing to a glass apparatus ( Schlenk line, vacuum - inert gas line, nitrogen distributor rake ), depending on a particular valve position ( two-way stopcock, or separate valves) vents the connected apparatus or with a protective gas crowded. In general, these apparatuses have a plurality of glass valves such that with a plurality of apparatuses can be used simultaneously or in parallel. The apparatus is empty, that is, built without chemicals. All ground connections are secured, for example by means of springs and ligatures. Then the hoses are connected.

One or more cold traps before the rotary vane pump are usually with liquid nitrogen filled in Dewar flasks, cooled, opened the Inertgasflasche and turned on the vacuum pump. There is the so-called " Sekurieren ": The air and traces of water in a glass vessel, by alternately evacuating and flow of the inert gas can be removed. Residual humidity are very effectively removed by the equipment in the evacuated state from the outside are heated, for example with a heat gun or by flaming with a burner flame. Alternatively, glassware can be baked in an oven and assembled hot. Then allowed the inert gas flow. After appropriate preparation of the apparatus, the reagents are introduced.

During the entire experimental procedure must be taken to ensure that no air enters the apparatus, if a plug or a sekuriertes vessel is opened. Do you have to open the apparatus for the laboratory environment, a slight overpressure of inert gas can be given to the open vessel. The opening of the vessel outward flow of inert gas prevents the ingress of ambient air.

For higher demands or very complex problems to work under inert gas in a so-called glove box ( glove box ) can be performed. In particular, very toxic, radioactive or very oxygen sensitive substances are handled in a glove box. However, this has the particular disadvantage compared to the Schlenk technique, that the work is very time consuming and must be very well prepared, as all equipment and substances via gates to the glove box must be brought out and into it. An advantage of the Schlenk technique is that it can operate in a high vacuum in this.