DEMONSTRATING the OXIDATION of AMMONIA THOMAS H. HAZLEHURST, JR. Lehigh University, Bethlehem, Pennsylvania
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COMMON method of demonstrating the oxida- flask and serve as supports for a spiral of platinum wire. tion of ammonia to nitric acid is to insert a glow- The tungsten-to-platinum connection is made by means ing spiral of platinum wire in the vapor above a of a small bit of tungsten wire wound into a spiral boiling solution of ammonium hydroxide through which which will just slip along the rod and must be sprung a air or oxygen is bubbling. The platinum continues to little in order to admit the end of the platinum wire. glow brightly because of the heat of the reaction taking The device is operated by starting the flow of gases place on its surface, and occasional small explosions and heating the platinum spiral initially by means of an add interest to the demonstration. electrical current drawn through a lamp bank. A rheoThis experiment has the disadvantage that a large stat might be used in place of the lamp bank, but the quantity of unoxidized ammonia escapes into the atmos- latter has the advantage that, when the reaction has phere. Furthermore, the demonstration is somewhat commenced and the current is turned off, the lamps are very obviously extinguished whereas the platinum conlacking in visibility tinues to glow. The composition of the incoming because everything ocmixture may be controlled by means of bubble tubes curs within the beaker. A new device avoiding or flowmeters, containing mercury. Of course, the outthese difficulties was flowing gases are led, via a trap, through water. The demonstration is quite striking. A few seconds developed in connecafter the platinum has commenced glowing under the tion with the "Open iduence of the current, its brightness suddenly inHouse" a t Lehigh creases. At this point the current is turned off, the University. wire continues to glow brightly, and a white smoke or As indicated in the figure, the essential cloud appears near it and passes through the outlet train. The presence of nitrate can he demonstrated in piece of apparatus is the water through which the escaping vapors pass. a three-necked, thick.It is obvious that no ammonia can reach the atmoswalled, pyrex balloon phere. flask. The flask acThe one drawback of this set-up is the danger of too tually used was of half-liter capacity, but rapid reaction which is followed by explosion. The d o u b t l e s s larger or danger is not large when air is used. The device was smaller ones would tried with oxygen instead of air, but,it-was practically work about as well. The one side-neck serves as an inlet impossible to adjust the gas flow to keep the wire glowtube for ammonia gas (supplied from a desk cylinder) ing and yet avoid explosion. Even with air the reacand air (from the compressed air line). It is fitted with tion becomes at times quite vigorous and caution should a two-hole stopper bearing two lengths of small-bore be used. The danger can be minimized by taking care glass tubing extending well into the flask. The other to set the large central stopper loosely. in the flask. side-neck furnishes an outlet tube, being fitted with a With this precaution, not a single explosion injured the stopper and a section of wide glass tubing. T!+e central flask in any way, and since the tungsten rods and platineck is closed by a two-hole stopper carrying two pieces num spiral represent a rugged set-up they were uninof tungsten rod, which extend into the center of the jured and could he replaced at once.
I t is by no means necessary to have just views and a true hypothesis, n +ri, in order to make real discoveries. Very lame and imperfect theories are sufficient to suggest useful experiments which serve to connect those theories, and give birth to others more perfect. These then occasion further experiments, which bring us still nearer to the truth, and in this method of appmximation, we must be content to proceed, and we ought to think ourselves happy if, in this slow method, wemalceany real progress.-Joseph Priesflcy.
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