Salt chemistry and the discovery of oxygen Roos is noted for her work in
Salt of the Earth demonstrating that the late 18th-century discovery of oxygen emerged from a 150-year English tradition of salt chemistry and iatrochemistry, reframing conventional narratives of the Chemical Revolution. In
The Salt of the Earth: Natural Philosophy, Medicine, and Chymistry in England, 1650–1750(Brill, 2007), she traced how English natural philosophers and physicians gradually shifted their focus from salts as fundamental principles of matter to acids as active chemical agents. Her research demonstrated that 17th-century figures including William Simpson, Isaac Newton, Bryan Robinson, and Stephen Hales developed theories about atmospheric acids and "saline spirits" as vital principles responsible for respiration, combustion, and material transformation. Roos argued that this intellectual tradition provided the conceptual framework for Antoine Lavoisier's identification of oxygen as the "acidifying principle" (principe acidifiant) in the 1770s–1780s. This work challenged conventional narratives that treat the Chemical Revolution primarily as a French development centered on the phlogiston debate, instead revealing its roots in earlier English iatrochemistry, Helmontian medicine, and Newtonian natural philosophy. Her analysis showed how the concept of a vital "volatile salt" was gradually modified into an understanding of atmospheric acids, which Lavoisier then identified as oxygen—a term meaning "acid-maker" that reflects this earlier tradition even though the theory of universal acidification was later disproven. Building on her work on salt chemistry, Roos has explored Isaac Newton's chemical investigations and their influence on 18th-century natural philosophy. She analyzed Newton's
De Natura Acidorum (1710) and its impact on physicians and chemists who developed theories about acids, fermentation, and atmospheric chemistry. Her research on figures like Bryan Robinson demonstrated how Newtonian ideas about acidic particles and the aether were applied to respiratory physiology and medical practice.
Martin Lister and natural history Roos has published extensively on the naturalist and physician Martin Lister (1639–1712), a fellow of the Royal Society. Her work includes the first comprehensive scholarly edition of Lister's correspondence, published in multiple volumes by Brill (2015–2025), for which she received the John C. Thackray Medal from the Society for the History of Natural History. In
Martin Lister and his Remarkable Daughters (
Bodleian Library, 2018; Chinese translation 2024), Roos documented how Lister's daughters Anna and Susanna created the scientific illustrations for
Historiae Conchyliorum, making them among the first women to use microscopes for scientific illustration. She showed that Lister employed his daughters because he considered professional illustrators insufficiently reliable for scientific precision. This work contributed to the emerging field of women's participation in early modern science and was featured in the
Guardian. Her
Web of Nature: Martin Lister (1639–1712), the First Arachnologist (Brill, 2011) established Lister's foundational contributions to the study of spiders and other arachnids and to the history of molluscs.
Martin Folkes and the 18th-century Royal Society Roos's
Martin Folkes (1690–1754): Newtonian, Antiquary, Connoisseur (
Oxford University Press, 2021) provided the first comprehensive biography of the only simultaneous president of the Royal Society and the Society of Antiquaries of London. The study examined Folkes's contributions to Newtonian science, numismatics, and antiquarianism, illuminating the intellectual culture of the early Georgian Royal Society in which antiquarianism and natural philosophy mutually influenced each other intellectually. Her edition of Folkes's Grand Tour travel diary,
Taking Newton On Tour (Boydell and Brewer with the Hakluyt Society, 2025), reveals how natural philosophical networks operated across Europe in the early eighteenth century, as well as the development of the ‘Scientific Grand Tour’ and scientific diplomacy.
Other Works Roos's early book
Luminaries in the Natural World: The Sun and Moon in England, 1400–1720 (Peter Lang, 2001) examined changing conceptions of celestial bodies from the late medieval through early modern periods. She has also written for general audiences, including
Goldfish (Reaktion Books, 2019), part of the publisher's Animal series exploring cultural and natural history. The book was the subject of an author interview for
National Geographic Roos has also made contributions to work on early taxonomy on the Asian Elephant which received press attention. She also was consulted to help resolve the protracted debates about the taxonomic naming of the Aldabra Tortoise. During the COVID-19 pandemic, she was interviewed by
National Geographic on historical plague outbreaks and quarantine practices in early modern Venice. Roos has edited several scholarly volumes on early modern knowledge-making and collecting practices, including
Collective Wisdom: Collecting in the Early Modern Academy (2022) and
Archival Afterlives: Life, Death, and Knowledge-Making in Early Modern British Scientific and Medical Archives (2018). ==Recognition and Impact==