. Practical methods of organic chemistry . lass withits convex side uppermost is placed on it, andthe two are held together by a watch-glassclamp. If the lower glass is now heated veryslowly on a sand-bath with a free flame, thevaporised substance condenses on the cold sur-face of the upper watch-glass in crystals; thefilter-paper prevents the very small, light crys-tals from falling back on the hot surface of thelower glass. To keep the upper glass cool, it iscovered with several layers of wet filter-paperor with a small piece of wet cloth. If largequantities of a substance are to be sublimed
. Practical methods of organic chemistry . lass withits convex side uppermost is placed on it, andthe two are held together by a watch-glassclamp. If the lower glass is now heated veryslowly on a sand-bath with a free flame, thevaporised substance condenses on the cold sur-face of the upper watch-glass in crystals; thefilter-paper prevents the very small, light crys-tals from falling back on the hot surface of thelower glass. To keep the upper glass cool, it iscovered with several layers of wet filter-paperor with a small piece of wet cloth. If largequantities of a substance are to be sublimed,the upper watch-glass in the apparatus just described is replacedby a funnel somewhat smaller than the lower glass (Fig. 9). Toprevent the escape of vapours, the stem of the funnel is closed bya plug of cotton or is covered with a small cap of apparatus for sublimation designed by Briihl is admirablyadapted to the purpose for which it is intended (Fig. 10). Itconsists of a hollow metal plate through which water flows. In. Fig. 9.
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