Harry Morrison Purdue University W. Lafayette, Indiana 97404
A New Short-Path Distillation Apparatus
Even in this age of vapor phase ehromatography (VPC), there is a need for additional equipment' whieh can he used for the rapid and quantitative distillation of small amounts of material, especially in the ease of high-boiling mixtures. A piece of apparatus is now described whieh has been suceessfully used in our laboratoriesfor several years. The design is basically a modification of the kugelrohr method but was specifically created to surmount two disadvantages inherent in that technique, i.e., difficulty in eooling the receiver and removing the distilland. The apparatus as illustrated consists of a pot of varying length, A , and a pear-shaped reeeiver with three necks, B, C, and D. Pots with A between 10-70 mm have been used, their capacities ranging from 1-6 ml.; the receiver as shown will hold about 5 ml. The pot is attached through a 5/20 + joint to neck D of the receiver with the aid of a small spring connecting the glass nipples. Neck B is connected to an outer 5/20 + joint and thence to a vacuum pump. Neck C is capped during the distillation with a small rubber serum stopple whieh is adequate for vacuums to ahout 0.5 mm. Kg. After it is connected to the receiver, the pot is inserted up lo the nipple of the receiver into a glass tube, 9 in. in length and 37 mm od. This tube, when wrapped with electric heating tape, serves as the oven. The back of this tube has appended to it a smaller tube, 3 in. long and 10 mm od, whieh allows for the insertion of a thermometer into the oven. 'GRAEVE,R., AND WAHL,JR., G. H., J. CHEM.ED. 41, 279 (1964). HICKMAN, K. C. D., Chem. Revs. 34.51 (1944); WIBER~, K., "Laboratory Technique in Organic Chemistry,'' McGrawITill Co., New York, 1960, p. 66.
As mentioned above, this assembly was developed to provide ready access to the distilland and to allow for maximum eooling of the reeeiver. Thus, the dimensions of C are such that a syringe may be inserted to the bottom of the receiver and a small sample withdrawn for VPC analysis; larger quantities are readily removed with a 4-in. needle and a 5-ml syringe. The use of the stopple allows for the sampling of the distilland while a distillation is in progress. The reeeiver can he immersed in a 1/2+ dewar flask well above the point of attachment of the necks; in this fashion, essentially quantitative distillation of ether a t about 40 mm Hg pressure has been achieved using dry ice slurry as the coolant. The quantity to be distilled will of course determine dimension A but the capability of this apparatus for semi-micro distillation is illustrated by its ability to handle the distillation of 30 mg of n-decaue; 19 mg of distilland could be easily removed from the reeeiver in the manner described.
Receiver and still-pot of
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short-pa* distillation apparatus
Volume 44, Number 3, Morch 1967
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