Cooling-Trough Condenser for Sublimation Tubes E. J. ~isenbraun'and J. M. Lucas Oklahoma State University, Stillwater, OK 74078
The sketches (Side View and Top View) and the connecting plate A describe a versatile cooling trough for large (2.5-in. diameter), test-tube shaped, sublimation tubes. The cooling trough is easily fitted around a sublimation tube by connecting the two halves B and C using plate A and tightening two thumb screws S-2. Plate A is notched a t S-2 to allow quick disconnection. Because of its trough shape a variety of cooling agents (water, ice and water, Dry Ice, and Dry Ice with acetone or a n alcohol) may be used. A previously described water-cooled cylindrical cooling jacket(l), satisfactory for small (1-in. diameter or less) tubes, was found unsatisfactory for larger diameter sublimation tubes(2) because the tube must be withdrawn from the sublimation apparatus to remove the cooling jacket. This extra handling of the sublimation tube complicates removal of the sample from the tube because molten material can easily spill past the barier shown in F and thus spoil the separation. Handling sublimation tubes containing solid material also can be troublesome because some sublimed crystals are loosely attached to the wall of the sublimation tube and even slightjarring or rapid release of the vacuum can result in their breaking away and dropping back to the sublimation residue. As the diameter of the sublimation tube increases, these handling problems also increase and no sublimation or evaporative distillation is successful until the product is safely removed from the sublimation tube. The cooling trough shown in the sketches provides a solution to this problem because i t may be disassembled from the sublimation tube without disturbing the position of the latter. If water is used for cooling, the flow begins a t the entrance port P and passes out through either of the vertically stippled exit ports of chamber C (15132 in. diameter circles a t upper part of C Side View). I t then siphons into chamber B through a diagonally stippled hole (lower holes of B Side View) using silicone rubber tubing (10-12 in. of 0.5 in. diameter, 1116 in. wall) for the transfer. The silicone rubber tubing is easily forced through the holes and because i t i s 1132 in. oversize, a water-tight seal results. Water exits the cooling trough via the horizontally stippled holes a t the upper portion of chamber B. Again, silicone rubber tubing (0.5-in. diameter) is used. To ensure adequate flow of cooling water an extra set of holes is available in case of need. When not in use, these holes may be plugged with rubber stoppers. Alternatively, port P may be closed with a Pasteur pipet bulb or clamped rubber tubing, and the chambers of B and C are filled with ice and water. Ice is added as needed and the melt water is allowed to drain through the horizontally stippled holes of B. Dry Ice or Dry Ice and isopropyl alcohol also may be placed i n the trough chambers. The cooler is box-shaped to minimize construction cost. This shape is an advantage because the trough serves a s a cradle to support the front end of the sublimation tube. A laboratory jack, i n turn, is used to support the cooling trough a s shown i n sketch F. The cooler is drawn to onethird scale (overall assembled width is 8 in. and height i s 'Author to whom correspondence should be addressed
1056
Journal of Chemical Education
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Side View
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Construction diagram for the cooling trough condenser for sublimation tubes.
2.5 in.). It was constructed of 118-in. brass plate and a 3.25in. length of brass tubing (2.5-in. o.d x 1116-in. wall). The parts were joined with soft solder and the port P (standard 114-in. hose bib with 114-in. pipe threads) was tapped into the wall of C. If there is need for cooling smaller tubes (1 in. or smaller diameter for example) solid aluminum or copper inserts(l), to fill the void around the sublimation tube, may be machined and then split lengthwise a s shown for the half piece (D end view and E side view). A sketch (side view) of the assembled cooling trough, sublimation tube(21, and a lab jack is shown as F Literature Cited 1. Eisenbraun. E. J . J . Chem Educ. 1978.55. 806 2. Eisenbraun. E.J.;Cagle. M. D.; Lueas. J. M.;Denton. T.T J. Chem Educ 1995, 72, 476.
