Citizen Scientists in the Laboratory: Accuracy of Titrimetric Analysis of the Hardness of Water

The overarching scientific goal of this study was to evaluate the implementation and validation of a quantitative laboratory method for analyzing drinking water in a citizen science project. By comparing the data of complexometric titrations performed by a group of citizens (n = 122) with those performed by a group of experts (n = 18) using the same method, we showed that the water hardness obtained by the citizens was similar to that obtained by the experts. In this semiexperimental study, the citizens, despite working less precisely than experts, achieved measurements that were comparably true to those made by experts when they repeated their individual measurements. An alternative method utilizing a visual marker was successfully introduced to support the citizens in reading the burette. The data of a second group of citizens (n = 79) indicated minor improvements in overall accuracy. The presented findings outline a useful procedure for implementing and validating chemical laboratory methods in citizen science projects that could also be used in educational contexts. Furthermore, this study underlines the importance of multiple measurements when working with citizens in a science project, especially when chemical laboratory methods are used.