A Rubber Reflux Condenser for a Test Tube An inexpensive and highly efficient condenser for a test tube may

easilv be constructed from a 3 1 0 rubber stoooer and 6 in. of %-in. soft

set a t low speed, and holding it againsta high speed grinding wheel. A center tip extending 31~6 in. is left on the rasp to position it midway be^ tween the top and bottom of the stopper while reaming out the latter. Two holes diametrically opposite each other are cut in the center of the edge of the stopper usinga #3 (%in.) cork borer. A convenientjig (diagram ( b ) ) for bending the copper tubing may be constructed from a 12-in. - length of 1-in. hardwood dowel by drilling two small holes '/&-in. apart diametrically through the center, pushing the ends of a loop of heavy iron wire through, bending them over and pounding them into the wood so as to securely anchor the loop. The soft copper tubing (5 in. length) is bent by catching its end in the wire loop and rolling the dowel and tubing on a block of wood. The tubes are cemented into the rubber stoooer with . . (b1 , .:' an epoxy or silicone cement. Rubber reflux condenser: a, construction; b, jig for

In use, the rubber condenser should be lubricated with a trace of bending copper tubing: c, reflux set-up. glycerine before inserting the test tube. This apparatus (diagram ( c ) ) was used with a drying tube for refluxing quantities of liquid as small as 1 ml in an elementary organic laboratory course. If 'I&. i.d. rubber tubing is used, the end of the tubing should be rolled back upon itself to provide a watertight connection to the copper tubing. In a test in which 10 ml of rnethylene chloride was boiled a t 40°C for two hours, the evaporation loss using the set-up shown in the diagram was only 0.2 ml.

Dwight Ray Mowery Southeastern Massachusetts University North Dartmouth, ME 02747

Volume 58 Number 4 April 1981 357