The NinaBottle Experiment Revisited Students have been delighted, challenged, and enlightened far the past 43 years by the famous nine-bottle experiment1 The original description of the experiment states, "Nine bottles, each containing a colorless water solution of a pure chemical, are issued to each student. The bottles are labeled with numbers from 1to 9, and along with the set is given a list of the nine chemicals contained in the bottles, hut the order of arrangement is not given. The student's problem is to mix portions of the contents of the various hottles. o h s e ~ n the e results. and to deduce from these the identitv of the chemicals." This basic scheme ran be easily modifled hyany i n s t r k u r to vary thp level of difficulty, to limit the kfndsoireagencs to be studied, to change the number ofiulutions, etc. This flerihility has been an important factvr in the long life of this approarh. We changed it by involving our students in the design of the experiment as well as its execution. In our introductoryehemistrycourse we have a 3-wk period at the end in which student pairs are assigned oneof anumber of open-ended projects. Last year we suggested that several teams try to devise a set of solutions suitable for a nine-bottle experiment. They were encouraged to develop a thought-provoking, but not impassible, set. They were also required to devise and test a stratew that would lead toan unambieuous identification of the contents of eachof their solutions. Then earh team exchanged ics nine bottle set with that of another team, and each attempted to solve the
