What is the purpose of the aluminum block in Microscale simple distillation? Sol

Question

What is the purpose of the aluminum block in Microscale simple distillation?

Explanation / Answer

A distillation is one of the most commonly used techniques to purify liquids. For instance, it is used to refine alcohol from the fermatation process or to purify water (=distilled water). In general, there are two important processes involved in this technique. 1. Vaporization = phase transfer from liquid to vapor (gas) 2. Condensation = phase transfer from vapor to liquid The vaporization process requires heat, hence is endothermic (DH>0), while the condensation process releases heat (=exothermic, DH300 oC) if a setting of “10” is used. It will be very difficult to control the distillation since the liquid will foam much more. An appropriate temperature setting has to be used. Often times, a water or oil bath is used for better temperature control. If a heating mantle is used as heat source, it has to be plugged into a variable power control. 5. A liquid boils when a reflux ring is going up the neck of the Hickman head or three-way adapter, and not when it starts to bubble! Often times, liquids dissolve gases that are released prior reaching the boiling point because their solubility decreases. For example, a coke can expands when you store it in a warm/hot place because the CO2 dissolved in the liquid is desorbed!

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