The "Baggie" Desiccator Often a possible freshman chemistry experiment requires s, desiccator if good quantitative results are t o be obtained. The requirements are not so st,ringent ss those sometimes encountered in advanced work, but effective probectian against atmospheric moisture must be provided. Drying of crucibles and other small objects can be aecvmplinhed in a 40hml beaker, over ~ , h i c ha plastic sandwich bag (Baggie) hlls beer, iovert,ed.' The Baggie can be secured with a rubber band around the heakev near the bottom, or for short periods the opeu end may simply be tucked under the beaker. Crucibles and other small containers can be protected from desiccant placed in t h e bottom d t h e beaker io a number of ways: ( A ) A 2-in. evaporating dish will hold one crucible. ( B ) A p propriate small beaken will serve as holders for small b o t t l e or crucibles. ( C ) A 2-in. glass square may be placed on s. stand made by folding down the euds of a. wire triangle. ( D ) An a p propriate platform can be fashioned frum altnninum sheet or wire gauze. If calcium chloride is used as 8, desiccant.,~ rare should be txkeu that i t is not left to " ~ ~ l d d l e .since " t,he brine will corrode t h e metal used in supports. One caution m u t be obsewed in ~ i l l gthe Baggie dmiocator to cool very hot objects. A crucible heated t o red heat aver a burner should be allowed to cord for a t least 1 minute (preferably two) before placing it in t,he beaker. Otherwise, the plastic above t h e crucible softens, and the contracting gas pulls a hole through the Baggie. Berswe of the changing gas volume, a Baggie placed o v a a warm sample should not be pdled tight, bllt should be loose around the upper part of the beaker. Baggies may be used in other ways its conbrulled-envi~.o~~me~~t, chambers. Stndents preparing Ni(NH.).C12 experienced considerable difficulty with hydrolysis of t h e product i n t h e atmosphere. This was eliminated by placing their product on its filter paper in a. Baggie with a small beaker of desiccant. Baggies are not a fire hazard; they do not inflame in a burner flame. ~
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1 Other brands of sandwich bag will pmhahly work. author and his class.
Only Baggies have been tested by the
H. BRADFORD THOMPSON IOKASTATEUNIVERSITY Ames, Iowa
Volume 43, Number 9 , September 1966
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