This study develops a tool to identify errors in the presentation of natural laws based on the epistemology and ontology of the Scientific Realism of Mario Bunge. The tool is able to identify errors of different types: (1) epistemological, in which the law is incorrectly presented as data correlation instead of as a pattern of causality; (2) semantic, in which natural law is presented as a mathematical statement that relates variables but with an absence of ambiguous material reference; (3) deterministic, in which the relationship of natural variables is presented but with no causality statement; and (4) mechanistic, in which a causality statement is presented with the absence of an explanatory mechanism. In this work, Boyle's law was used as an example of the applicability of the instrument. In this case, we found errors in most of the university textbooks that we analyzed. Most of the errors arose from the disconnection between the symbolic and microscopic levels. The presentations of Boyle's law in general chemistry are given in textbooks that include illustrations based in a macroscopic perspective, in which the macroscopic compression mechanism is completely disconnected from the microscopic collision mechanism. This disconnection results in the incorrect presentation of gas pressure as the cause and gas volume as the effect.