Fresenius’ wash bottle

Qualitative analysis is one of the rituals that contribute to the education of a chemist. The older you are, the longer you will have spent in a lab doing a practical that pits you directly against a battery of test tubes. While some students love it, for many the sessions leave scars from stress, frustration and uncertainty. It is a lab class that emphasises method, attention to detail and technique, and is unforgiving of the hasty and the slapdash. Yet it is also one of the few practicals that approaches the epistemic uncertainty of research, or indeed of real life, where the conclusion to be drawn and best course of action to be taken are not listed in a model answer. But if today we see it as a useful practical experiment in thinking and inference, its origins were much more serious. It is to qualitative analysis that we owe a piece of kit as ubiquitous today as it is fundamental: the wash- or squirt-bottle.