This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Q: Passage: Zinc(I) compounds are rare, and require bulky ligands to stabilize the low oxidation state. Most zinc(I) compounds contain formally the [Zn2]2+ core, which is analogous to the [Hg2]2+ dimeric cation present in mercury(I) compounds. The diamagnetic nature of the ion confirms its dimeric structure. The first zinc(I) compound containing the Zn—Zn bond, (η5-C5Me5)2Zn2, is also the first dimetallocene. The [Zn2]2+ ion rapidly disproportionates into zinc metal and zinc(II), and has only been obtained as a yellow glass formed by cooling a solution of metallic zinc in molten ZnCl2. Question: When a solution of metallic zinc is cooled in molten ZnCl2, what is formed?
A: 
yellow glass