Talk:Rotary evaporator
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Wrong
[edit]Ask yourself: why do all rotary evaporators work at an angle?
The entire purpose behind rotary evaporators is the production of a thin film of the solution on the surface of the flask as it rotates above the surface of the solution. This thin film evaporates more easily than solvent right at the surface at the bulk of the solution. thus the angle and the rotation are necessary to create this thin film.
A common misconception among undergraduates is that the rotation is used to prevent bumping. this is not true. indeed, faster rotation can even REDUCE the speed of distillation in most cases. undergraduates will often, frustratedly, crank the rotation speed up to full, expecting things to evaporate faster... This is not the case, and it never will be.
the key to the perfect rotovap technique is finding the perfect speed of rotation, using a properly sized flask (never fill >50%), proper bath temp, and maintaining the flask level in the bath (if the solvent gets too low in the bath, it will bump more easily). —Preceding unsigned comment added by 68.6.52.200 (talk) 01:45, 27 January 2010 (UTC)
- It's not only the thickness of the film, with thin films allowing the heat to transfer from the glass to the solvent surface faster, but also the increased surface area for evaporation to occur through.
- Correction: It does actually reduce bumping by preventing a localised build-up of heat. The rotation speed though is important to maintain a think film of solvent on the inside of the flask. — Preceding unsigned comment added by Camope999 (talk • contribs) 09:12, 16 March 2023 (UTC)