Demonstration notes: Delivering a gas under pressure

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ALUMINUM: OXIDATION-REDUCTION Submztted by: Joseph F. Castka, C. W. Post College of Long Island University, Brookville, N. Y Checked by: George Ferris, Michigan State University, East Lansing, Michigan

PREPARATION

DEMONSTRATION

Polish the outside of an aluminum cigar container with steel wool. Fit the cylinder with a one-hole stopper. Insert a 5-ft length of glass tubing so that one end reaches the bottom of the aluminum cylinder. Pour 3-5 ml of colored water (red ink) into the cylinder. Provide a solution of Hg2(NO&, cotton, ringstand and clamp, 8-in. test tube, and a small basin.

Set up the aluminum cylinder with clamp. Amalgamate the outside by vigorous rubbingwith the solution of Hga(NO& Students observe the oxidation of Al, the formation of the oxide, and the steady rise of the ink in the glass tube. On occasion, the action will be so vigorous that the column of ink is shot out of the glass tubing.

REMARKS

Then remove tubing and insert the aluminum cylinder into the 8-in. test tube. Place underneath the water in the basin so that air is completely displaced. Raise the test tube to vertical position. The aluminum slowly displaces the hydrogen (action is visible) and the test tube may be filled with gas. Make the burning splint test for hydrogen

The air thermometer experiment was a favorite of Ross Baker, formerly of City College of New York. The necessary expense of purchasing and smoking a fairly expensive cigar in an aluminum container (I recommend Bering-just the right size) is compensated for by making use of the cylinder.

Journal of Chemical hdwat-iw

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June 1962

DEMONSTRATION NOTES

RELATIVE WEIGHT OF ATOMS ANALOGY Dale Drcisbach of Hiram College, Hiram, Ohio, uses samples of seeds such as poppy, broccoli, radish, corn, and lima beans, and a triple beam balance. One of the poppy seeds is placed on the pan of the balance to shov the impossibility of weighing a single seed with this equipment. To obtain relative weights, an arbitrary scale is developed, using enough poppy seeds to make one pound (810,000), an equal number of each of the larger seeds could be weighed for comparison Typical data are 6 8 lbs of broccoli seeds; 20 6 Ibs of radish seeds and 210 Ibs of corn. In this way, a scale of seed weights based on the poppy unit (P. U ) = 1.0 is developed. The analogy to atomic weights with hydrogen equal to 1 0 is then made and the Avagadro number concept is introduced.

DELIVERING A GAS UNDER PRESSURE

C H. Breedlove, Jr., and Lewis R. Sanford suggest a method of delivering a gas under pressure which was common in the older books on demonstrations, but does not appear frequently in current materials. The gas, which must not be water-soluble, is collected in a container such as a one-gallon jug by displacement of water The jug is then fitted with a two-hole stopper and two tubes One tube is for delivery, perhaps to a rubber balloon, and the other is connected to the water faucet. Water pressure is used to displace the gas from the container.