This is one of several bottles of solutions used in protein crystal growth experiments on the Space Shuttle. Its handwritten label PPT indicates that it held a precipitant to activate the crystal growth process. Protein crystal growth experiments involved mixing proteins in different solutions to learn which combinations and conditions produced the best crystals for analysis.
Researchers from the University of Alabama at Birmingham, actively involved in experiments for Shuttle flights, gave this item and a large set of protein crystal growth equipment to the Museum in 2012.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.