Improved Kugelrohr Distillation Accessories Distillation using a Kugelrohr apparatus has not been described in undergraduate laboratory manuals but it has become a permanent and valuable laboratory practice in organic h hem is try.'.^ A Kugelrohr apparatus, suitable for a broad range of sample sizes, is commercially available and a selection of glassware and accessories is offered.3 A highly sophisticated distillation oven (Brinkmann Instruments Inc., Westbury, NY 11590; BR 298B) for small samples also is available. Items A, B, and C represent accessories that are an improvement over currently available apparatus.
0lT$lJp 1
b ] ,
c
In use, flask A, receiver B or multiples of B (3), and extension tube C are connected and C is threaded through the opening f of the f plastic cooling container D. The latter is constructed from a plastic milk carton. It encloses receiver B and the neck of flask A fits into notch d. If opening f is too restrictive it may he cut open to form a notch. A drain line, 3Is-in. rubber tubing e, is inserted through a hole in the bottom wall of D, and the height of e is adjusted to serve as a stand-pipe in D for maintaining the water level when water or icewater coolants are used. Receiver B also may he cooled with dry ice. Medium-length outer joints (Ace Glass Iuc., Vineland, NJ 08360.7568, T 14/20,19/22,24/25, or 29/26) are used at a (A and B) whereas full length, o-ring joints (Ace Glass Inc., 7648, T 14135,19138. 2414001 29/42) are used a t h (B and C). This combination ofjoints is advantageous in that o-ring joint h does not require lubrication, and joint b protrudes into A providing a drip tip that reduces flooding of distillate into B. The baffle c is included to prevent return of distilled material from Bas it oscillates in the Kugelrohr apparatus. Having baffle c permits inclining the assembled glassware (A, B, C) duringdistillation, which in turn improves reflux. Another important function of baffle c is to direct hot vapor toward the wall of receiver B. This greatly increases the efficiency of condensation and reduces the possibility of distillate being carried to the vacuum trap. Baffle c prevents emptying receiver B through joint h. Solid material in receiver B, resistant to scraping, may be removed by inverting B and attaching it to a round-bottomed flask containing refluxing solvent. This is accomplished through use of double-ended adapters having appropriate T joints. Receiver B is a modified recovery flask or Kjeldahl flask (Ace Glass Inc., 6892 or 6969). Its shape facilitates removal of solids by scraping. The added length of B, in comparison to one of a spherical shape, improves condensation, and the shape of B alsolends itself to use of an ice pack, around and above B, during distillation. The selection of joint size (a and h) is critical. Small dismeterjaints, T 14 and 19, cannot be avoided for small samples. However, larger samples >I00 mL, are best distilled using T 29 joints. The wider bore of this joint size is less likely to pass residual material to B since the gas velocity is less; Bernoulli principle.
' Graeve, R.; Wahl, G. H., Jr. J. Chem. Edue. 1964,41,279.
Harding, K. E.; Kinnel, R. B. Org. R e p . R o e . Int. 1970,2,313. Tech. Bull. AL-139 and Aldrieh Catalog Handbook of Fine Chemicals, 198E-1989, pp 2032-2033 and 1958; Aldrich Chemical Co.: Milwaukee, WI. "orreaponding author. K. W. Payne, T. Denton, and E. J. Elrenbraun4
Oklahoma State University Stillwater. OK 74078
Volume 66
Number 12
December 1989
1059
