A Simple Method to Improve the Efficiency of Thermostatic Baths When working with open thermostatic baths, specially a t high temperatures, there i s a big loss of liquid and heat due t o evaporation. The classic way of avoiding this is to cover the liquid surface with an insulator, like liquid paraffin or plastic balls. Paraffin, although i t covers and isolates well, is inconvenient: i t stains everythingtaken from the bath. Plastic balls are cleaner but do not cover as well and are quite expensive. In our Department we have been using, for a few years, expanded polystyrene chips (Styrofoam) available in any laboratory from the packing of scientific material. These chips have great insulating power, provide better cover than plastic balls, and, above all, they are free. As a prwf of their efficiency we include heating curves for a cylindrical thermostatic bath with 25 1 of water, using a 1000-W electric resistance heater, without insulator (I); with expanded polystyrene chins 111). For the same bath. havine an even temprraturr d5W"', the heater operatrd 16 mmutps per hour without the insulator, bt only F, mmutes using the insulator, which 1s a filh saving of rnevy. ~~~
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Departamento d e Quimica ~ h c a Universidad d e Oviedo Oviedo-Espaiia
134 1 Journal of Chemical Education
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Cipriano Barrio Alon7o Jose Manuel J u a n c o U n a
