Imagine a superstitious novel in which the main character, Pam, finds a keychain talisman alleged to bring good luck; perfect for her school exam that day. As she turns her car's ignition to leave her house, the new weight of the talisman in her hand draws her attention, and she looks down to notice the low fuel gauge on her car's instrument panel. Arriving early at the filling station, she thwarts a robbery in progress. Police arrive, and she gives her account, whereupon a bystander who happens to be a jeweller notices the talisman and offers to appraise it if she brings it to his shop before his tent sale that afternoon. More eager for money than for luck, Pam agrees, knowing that the appraisal will curtail her last-minute study time. But lo! The talisman turns out to be an heirloom of Ben Franklin's, a long-lost emblem of Freemasonry. Pam spends the rest of the day speaking into television cameras and scheduling interviews with museum curators, and contra her original intention in carrying the talisman, flunks her exam.

Serendipity from wayward goals similarly characterizes the development of the eudiometer and the fate of its scientists, in Pere Grapí’s Inspiring Air. For while a eudiometer, etymologically speaking, detects and measures ‘good’ as in ‘salubrious’ air, Grapí’s account of this functionality from the late eighteenth century to the late nineteenth proves remarkably sparse. He focuses instead on scientists’ reasons for modifying the instrument, such as improving its portability and durability, chasing consistent results from bad theories, and confirming new chemical theories that bear only indirectly on the alleged salubriousness of air in hospitals, farms, fermentation houses, mines, ships and mountaintops. Hence one could infer from Grapí’s account that before a robust and repeatable measure of salubrity could be attained, the chemical revolution of oxygen over phlogiston undermined the view that air itself could be health-giving. But Grapí does not analyse this revolution, which he references in only a few paragraphs of his concluding tenth chapter. Inspiring Air instead exhaustively documents the eudiometer's use, discussion and design changes by Volta, Priestley, Lavoisier, Gay-Lussac, Humbolt, Laplace, Dalton, Cavendish, Fontana, Ingenhousz, Ben Franklin and many others.

Granted, salubrity as a concept motivated the construction of the first eudiometers, since they visually demonstrated the differential reaction of ‘nitrous air’ (nitric oxide gas designated NO) with breathable and unbreathable air, roughly construed. That is, the more breathable or healthy the air, the greater its reduction in volume when it mixes with nitrous air, and the eudiometer contains this reaction in a tube inverted over water, drawing a volume of water up the graduated tube equal in volume to the volume reduction of the mixed air. The theory of how nitrous air (attainable by a variety of means) renders breathable air unhealthy developed in tandem with the eudiometer, but Grapí’s more immediate point is that the invention expedited and economized air salubrity research by eliminating the need to suffocate mice under glass.

Nitrous air tests have their challenges, however, including a precise determination of when the reaction starts and stops. Alessandro Volta remedied this problem somewhat inadvertently. Interested more in the composition of swamp gas than in eudiometry per se, Volta showed that an electric discharge within a compound volume of common air and swamp gas also yields a volumetric reduction. While this reduction can measure salubrity by revealing how many parts of common air (or air under test) are required to combust a given volume of swamp gas, the historico-technical point is the considerable staying power of Volta's invention, as it appears decades later in the work of Robert Bunsen, and in Humbolt's and Guy-Lussac's measurement of hydrogen gas compositionality. Further design variants, which Grapí recounts in unremitting detail, but which I can here only mention, include fast and slow phosphorous eudiometers, alkaline sulphide eudiometers, inventions in the mechanical methods of bubbling the reactants together, and changes in glass geometry that resist thermal shock and spark-combustion explosions. Six short appendices supplement descriptions in the main text.

Thus Inspiring Air reads as an incredibly well-sourced catalogue of design changes for an instrument that even persons with an undergraduate science background are unlikely to recognize. It is unfortunate, then, that the publisher did not select a slightly larger page size, because the annotations in a majority of the diagrams are illegibly small, despite such annotations incurring explicit citation in the main text. Hence too much of the book consists of annotated descriptions of unreadable figures, a result that may not impede historicity, but certainly impedes a mechanical appreciation for the very mechanical improvements in question. Inspiring Air also could have benefited from a glossary, such as Victor D. Boantza provides in the fifth chapter of his Matter and Method in the Long Chemical Revolution (2013, p. 151 n. 20), since discerning the eighteenth-century versus twenty-first-century meanings of fixed air, common air, inflammable air, breathable air, phlogisticated and dephlogisticated air and nitrous air can be confusing. On the other hand, Grapí’s provisions of chemical equations in footnotes prove uniquely helpful in this regard, complementing main-text descriptions of chemical reactions, and keeping the reader oriented. I recommend Inspiring Air for inspired readers of chemical history, but anticipate frustration from those who enjoy deciphering patents and studying blueprints.