PNEUMATICTROUGHFORTHEGENERALLABORATORY WILLIAM H. POWERS AND JOHN WACLAWIK Alliance College, Cambridge Springs, Pennsylvania
IN HIGH-SCHOOL and elementary college work, gases are usually collected in ordinary wide-mouthed 8-oz. bottles. In spite of the fact that this is one of the most common laboratory operations no improvements have been made in the pneumatic trough in years, as shown by perusal of the catalogs of the apparatus companies. The old-style trough is hard to operate, the bottles tip over easily, and removal of one bottle often causes loss of gas from another. The writers have been experimenting with various devices to overcome these difficulties and have found the device shown to be very satisfactory. A circular plate of copper is cut from sheet copper to fit an ordinary two-quart stew pan at the bottom. On the disc are soldered four curved strips of copper with openings to accommodate the delivery tube from the generator. All dimensions are shown on the accompanying drawing. The strips may also be welded
or crimped on. The edges of the disc may be crimped up or left flat. Advantages are that the bottles cannot tip over, they can he left in the trough, and that both hands of the student are free for other manipulations. If the edges are bent up the entire tray can be lifted out of the pan without losing gas. The piece can be made by any tinsmith or handyman and the cost is very small. The pans can be used for many other laboratory purposes and ten discs can be stored in a space 18 cm. by 13 cm. square. All dimensions are shown in drawing. The copper is 16-oz. plate. Material cost is eleven cents each. Gases form a slight oxide film only.
