Submined by: Frank P. Cassarct.to,Loyola University, Chicago, Illinois Checked bu: Wayne Taylor, Science and Mathematics Teaching Center, Michigan State Universit,y. East Lansing
PREPARATION
Obtain two or more square-meshed molded plastic berry baskets (such as arc used to hold berries and small veget~iiblrsin t,he markets), two large trays or glass jars filled with t,ap water, and a litt,le powdered or liquid detergent. DEMONSTRATION
Place each hasket in a tray or jar on the wat,er surface where it will float. Add a few milligrams (or a drop or two) of det,ergent adjacent to one of the baskets. The basket will sink within a few s e e
onds. Allow the second basket to float duriug the remainder of the class period and then sink it by similar procedures to convince the most skeptical. REMARKS
Film pressure may be demonstrated by this device. A very small quantity of the detergent is sprinkled on the water surface to one side of the floating basket. It will cause the basket to move suddenly in t,he opposite direction. Before the baskets can be used again, they must be thoroughly rinsed to free them From detergent.
DEMONSTRATION NOTES From time to time, items such as the following which do not require a full half page will be listed foe/ethrr. &me of them will be modifications o f previously published demonstrations, in which case it i s suggested that they be clipped and attached to the pertinent experiment. GENERATING COMMON GASES
Walter Ainsworth of the State Vniversity of&ett York, College at Buffalo, submitted a simple method of generating common gases which appeared on page A117 of the February, 1962, issue of THIS JOL'B-\AL He has since reported that the single bottle method lends itself well to the production of pure (colorless) nitric oxide The hottle is filled with a 25% solution of HNOi and a small wad of copper turnings are added and the bottle inverted A bottle of clear colorless nitric oxide is obtained. If it is not to be used immediately, the bottle should be transferred to another dish, since nitric oxide is apparently quite soluble in the copper nitrate solution. The bottle may be held horizontally vith the month exposed t o the air and the formation of brown nitrogen dioxide is easily seen If the bottle is then placed in a dish containing water, the solubility of nitrogen dioxide is shown as the nater level rises in the bottle. Obviously, it isdesirable
to keep one's fingers out of the n i t r ~ ca'cjd aolntion. LIQUEFACTION OF IODINE
I n i n g IIolstein of Bay Side High School, S e n 1 ork, points out that the sublimation of iodine is frequently shown students but they rarely have an opportunity to observe iodine in the liquid state He points out that this ran readily be shown t o a class by placing about 15 g of iodine crystals in an %in. Pyrex test tube closed with a stopper which carries a piece of glass tubing extending about 6 inches above the test tube. The iodine is easily melted by placing it in an oil bath along with a thermon~eter When the temperature of the oil bath reaches lGO,the iodine will melt (mp 113.5'C). The glass tubing in the mouth of the test tube serves to condense and collect any iodine vapor produced in the experiment Raising the iodine to the boiling point (184 3'C) ran he easily a \ aided.
