Hood-Size Sand Bath Many procedures in qualitative and quantitative analysis require evaporation of aqueous solutions. With large groups, it is safer t o perform such evaporations inside fume hoods. In our experimental chemistry lahoratory, we use a sand hath custom-made for fume hoods. The sand hath is made of an aluminum box (2.5 mm thick) lined on five faces with glass wool (2 cm thick) which is simply held in place hy the sand. A heating coil of Kantal(50 mohmlcm), resting on porcelain blocks on the bottom, provides 650 W (110 V) to heat the sand which covers the coil and fills the box to about 3 em from the top. An aluminum plate with holes the size of a 50-ml oorcelain crucible rests on the elass wool. ahout 1cm above the S"M0 sand surface. G L A S S WOOL ALUM,^^^ The temperature on the surface reaches llO°C, while in the upper 2 cm of sand i t ranges between 150 and 250"C, and mayreach400°C a t a depth of 4 em. T o keep the temperature constant, the sand hath SAND BATH is heated continuously. The sand hath occupies only a fraction of the space in the fume hood, as it is set over the gas, air, and water outlets a t the rear of the hood. For qualitative analysis, preparation of carbonate or acid solutions is performed in porcelain crucibles which are keot . upright . . and a t the correct depth in the sand bv.. orooer s the alukinum o l a t e . ~ o auantitative r analvsis, evaoaration mav he conducted in healkrs . o.~ e n i n e in or porcelain dishes by removing the aluminum piate and positioning the veisel a t a correct depth in sand. With an enrollment of about 150 students, we have used 12 such units (one per fume hood) without any accident or failure during the last four years. UniversitC Laval QuCbec, Canada
136 1 Journal of Chemical Education
Claude Barbeau Gaston Marquis
