VOL.9, NO.0 APPARATUS FOR ILLUSTRATING ARC METHOD
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APPARATUS FOR ILLUSTRATING THE ARC METHOD FOR THE FIXATION OF NITROGEN, AND ALSO FOR THE FORMATION OF OZONE In the JOURNAL OF CHEMICAL EDUCATION for March, 1931,* appeared an interesting article describing an apparatus for illustrating the fixation of atmospheric nitrogen, which makes use of dry cells with a Spark coil from a Ford automobile. The apparatus here described, and shown in the accompanying cut, uses current from the 120-volt lighting circuit with a transformer such as is used for neon tubes, a much more convenient method than the one which tnakcs nst of hatterics for the cnrrmt. T h e transformer is mounted on a wooden bast., with switvh and A double bindinp. - posts. three-neck Woulfe bottle is fitted with two quarter-inch brass rods passing through rnbber stoppers. Inside the bottle the rods are so bent that the somewhat sharpened ends are about one-half inch apart. The other ends are fitted with binding posts. The apparatus can be quickly connected, and is ready for use a t a moment's notice. After the current is turned on the brown color of nitrogen dioxide soon appears. To show the formation of ozone replace the cork in the center with a twohole stopper carrying two tubes, one of which extends nearly to the bottom of the bottle, and the other just through the stopper. The bottle is filled with oxygen by connecting the longer tube with a source of oxygen. A strip of starch potassium iodide paper is suspended in the bottle. The paper quickly becomes purple after the current is turned on. The transformer used gives 15,000 volts and will form a three-quarter inch spark. It costs about eight dollars. *WILLIAMS,"Fertilizer from the Air. A Project for Chemistry Students at thc Secondary-SchoolLevel," J. Cn~nr.E~uc.,8, 462-70 (Mar., 1931).
