Final answer:
The purple tube yields a purple gas that subsequently deposits as solid iodine on the colder part of the tube above.
Step-by-step explanation:
The purple tube yields a purple gas that subsequently deposits as solid iodine on the colder part of the tube above. This process is called sublimation of solid iodine. Figure 12.6.6 shows the sublimation of solid iodine in a test tube, where the dark substance at the bottom breaks up into a purple gas at the top.