WINNERS IN SEVENTH "WHAT IS WRONG?" CONTEST

The seventh contest called forth the largest number of contributions yet received. We are happy to report that many of the papers and drawings were good.

The criticism of Elmer C. Montania of Milwaukee, Wisconsin, winner of the five-dollar award, follows:

The ring stand, as was shown in the drawing, was not drawn in proportion with the rest of the apparatus. There were also Lines drawn through the gas hose, thistle tube, flask, and the mouth of the bottle containing sulfuric acid. The delivery tube of thc second bottle was also shown closed, thereby preventingany air from escaping.

PREPARATION .f SULPHUR DIOXIDE. A- SULPHURIC x.

The drawinx did not show a rubber stopper in the flask; therefore, all of the sulfur ~ ~

clioxide grncratccl would paas otT into tllr ntrnospllerc. Reeatase sulfur d~oxidr pruduccs a choking, irritntiu~ scncatior~ in the thrmt, it is undrsirnblr to have it ~ras~ut l in to the room where one is working.

There was no opening showu in the second bottle to permit the air to escape; therefore, if there were a stopper in the flask the apparatus would be air-bound.

The drawing had shown both delivery and outlet tubes extending quite far into the bottle; since sulfur dioxide is heavier than air i t settles to the bottom of the bottle. The only air forced out will be the small amount between the bottom of the bottle and the bottom of the tubes; this makes i t impossible for one to get a full bottle of pure sulfur dioxide. The bottle should be connected in this manner: the delivery tube is to ex- tend fairly well into the bottle, while the outlet tube extends just beyond the stopper. This permits the sulfur dioxide to displace the air.

1402

VOL. 7, No. 8 THE CHEMISTRY STUDENT 1403

The thistle tube shown in the drawing played no part in the experiment, since the demonstrator was pouring the acid into the flask by means of a glass stirring rod. The sulfuric acid should be administered through the thistle tube. The end of this tube must be submerged in the solution; if the tube is not, the sulfiir dioxide generated will pass out through it.

In the drawing the flask with a round bottom was shown placcd in a bowl of water; therefore, it wouldtend to tip easily, because i t was not suppo&d by a clamp.

When capper reacts with hot concentrated sulfuric acid: copper sulfate, water, and sulfur dioxide are formed. The rate a t which sulfur dioxide is generated depends greatly upon the temperature of the reacting solution. A fairly good reaction is ob- tained above the boiling point of water. It is impossible to obtain a temperature higher than 10O0C., as long as the flask is indirectly heated through a bowl of water. When water boils the action is vigorous. If this temperature is retained the flask, which was not shown clamped, would be broken by the constant bobbing up and down produced by the violent action of the water. Should the flask be broken, the hot concentrated sulfuric acid coming in contact with the hot water, would spatter. The howl of water, therefore, is impractical in this experiment. There should also have been a piece of asbestos gauze beneath the howl to prevent the %me from coming in direct contact with the glass, thus preventing any possibility of its cracking. For the reasons stated above . . . one concludes that a flask resting on asbestos gauze would prove to be a better method than the one shown in the drawing. In the sugzested method a low flame should be - -

applied to the reacting solution to prevent the sulfuric acid from reaching its boiling point. When sulfuric acid boils it decomposes into water and sulfur trioxide, which is not desired.

There should be three battles used in performing this experiment, the first to collect all water vapor which passes over into i t from the generator, the second to collect pure sulfur dioxide, and the third, containing water, as a medium for eliminating the air and preventing the sulfur dioxide from passing into the atmosphere. In each case the bottles should be connected thus; the delivery tube is to extend fairly well into the bottle, while the outlet tube is to extend just beyond the stopper.

In the first bottle ample room should be provided between the bottom of the bottle and the bottom of the delivery tube, to prevent the condensed water from being drawn back into the generator, while i t is cooling. The delivery tube of the third bottle is to extend into the water, while the outlet tube of this bottle is merely an opening into the atmosphere, to permit the air to escape.

At standard conditions 79.789 volumes of sulfur dioxide will dissolve in one volume of water; therefore, as the air ceases to bubble through the water in the third bottle one knows that the sulfur dioxide has forced out all of the air, and the excess sulfur dioxide is being dissolved in the water.

The set-up depicted by Mr. Montania might be somewhat improved, we believe, by providing for flexibility and ease of disconnection in the connecting tubing.

Wimers of one-dollar awards were: Francis Kinkel, Kirkwood, Mis- souri; 0. J. wenburg, Oberlin, Ohio; R. M. Lewis, New Canaan, Con- necticut; Letitia Yoakam, Providence, Rhode Island; Elvira HernLndez, El Paso, Texas.

The world is daily increasing in experimental howledge, and let no man flatter the age with pretending we have arrived a t a perfection of our discoveries.-BENJAMIN FEANKLIN