A CONVENIENT LABORATORY STILL EDWARD RIETZ1 Howard College, Birmingham, Alabama
THE still described in this article was constructed as a makeshift when the commercial still in the laboratory broke. I t was found to have such ease of operation and such reliability of performance, however, that it was retained for the production of distilled water for research students. A diagram of the still is shown. The reader will observe that it is essentially a Florence flask equipped with a constant leveling d e ~ i c e . ~ Water is supplied to cup B by a tube A a t a rate slightly greater than the rate of distillation, the excess passing through the overflow and into the drain through C. As water is distilled in flask F, the level momentarily drops below the level of the water in cup B, but syphoning restores the levels. Tube E is provided to permit removal of the air bubbles which come out of solution of the water and which would "break" the syphon should they be permitted to accumulate. They are removed when necessary (about once a week) by sucking a t G, a tube which is clamped with a pincb-clamp while the still is in operation. Since the union of the tube to the flask requires moderate skill in glassblowing, the preparation of the joint will be described. A six-inch section of 14-mm. pyrex tubing is constricted to 4 mm. a t one end and is joined to a six-inch section of 8-mm. pyrex a t the other end. A bulb about 20 mm. in diameter is blown about one inch from the constricted end. A 15-17-mm. hole is then blown into a one-liter Florence flask about twoinchesfrom the bottom. The 14-mm. tube is then inserted into the hole a t about a 45' angle and is clamped into position. The seal is made with a hand torch. The bends are made as indicated. 1 Present address: The University of Chicago, Chicago, IUinois. FINDLAY, "Practical physical chemistry." 6th edition. Longmans, Green & Co., New York City. 1936, page 31.
It will be noted that the seal is introduced a t some distance from the base of the flask. This avoids strains near the bottom-the most vulnerable section. The still, once in operation, operates without attention and consistently produces one and one-half to two liters per hour when adequate heat is applied. The author acknowledges the helpful suggestions of Mr. Norman H. Horton, a student a t Howard College.
