A Vacuum Sublimator for Student Use A convenient and inexpensive vacuum sublimator can easily he constructed from a side arm tube and polyester film. The impure sample is put at the bottom of a side arm test tube (Kimar #46225,25 X 200 mm) using a paper cylinder to prevent the sample from adhering to the walls of the tube. After the paper is removed, a sheet of transparent Mylar polyester film (0.07 X 130 X 160 mm), rolled into a cylinder, is placed in the tube with the lower edge held just shove the samole. The tendencv of the olsstic roll to uncoil keeos it nearlv flush aeainst the elass and above the crude material The tube is closed with a q 4 sol~drubber stopper and immersed in a heating bath to the top r,f the sample. Application of vacuum allows the ruhlrmate to collect on the plastic surface in thc cooler portion of the tuhe ahove the heating hath. After sublimation is complete, the heat and vacuum BOUrCeS are disconnected and the plastic cylinder is transferred to a 125-ml Erlenmyer flask, into which the sublimate is dislodged by bending the plastic. Alternatively, the cylinder is unrolled and the sublimate scraped onto a sheet of paper, although this caused naphthalene to become electrified and difficult to manipulate. The tendency of the sublimate to fall from the plastic into the crude appears to be minimal. A trace of sublimate mav collect on the side of the tuhe. The aooroach described here avoids oossible contamination hv stoneoek crease or bv condensed atmosoheric moisture.~,often encountered with a cold finger ~, " - condenser. ~ The mp of the pulyeswr is 210° C and n practical temperature limir is ?0OD C. which is also recommended for w o k in8 bags. N'here higher temperatures are needed. Teflon film can be used. The polyester survive. washing wirh neecone and is reusable. A 2 X 4-ft sheet was obtained in the art supply section of the local college store for $1 In this way the following substances have been sublimed. time wt. of sample(g) %recovered b a t h temp("C) pressure(torr) required(min) Compound henzoquinone 1.0 90 92-105 21 30 caffeine 0.090 66 168-197 14 15 camphor 1.05 95 152-160 12 5 naphthalene 0.220 70-80 12 75 21 This arrangement has heen used with Teflon sheet (1 X 305 X 305 mm) and a larger test tuhe (Corning #9800,50 X 400 mm), attached to a vacuum pump by a one hole #lo% rubber stopper, to sublime 5 g of acenaphthoquinone a t 1tom and a hath temoerature of 220' C. The work was supported, in part, by funds from the Sponsored Programs Grant Awards Program, the State University College at Buffalo. 7~~~
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State University College a t Buffalo Buffalo. New York 14222
720 / Journal of ChernicalEducation
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Fred H. Greenberg
