This essay argues that categories of corruption and reform, so often used by historians to assess the Gilded Age, are themselves the ideological products of the period's struggles for political, economic, and social power. It does so by exploring fierce disputes over how to value sugar, a crucial commodity in the political economy of the late nineteenth-century United States. Confronted with evidence of massive fraud, the Treasury hoped that chemical techniques would rationalize the collection of sugar tariffs. Instead their introduction enabled the rise of the notorious Sugar Trust, by making it more difficult to distinguish corrupt influence from the legitimate exercise of expert judgment.Sugar exemplifies how Gilded Age battles over corruption should be seen in the broader and longer context of the history of capitalism, in which self-proclaimed reformers have used charges of fraud and adulteration to discredit the knowledge of artisans and workers while mantling themselves in claims to objectivity and reason. Scientific knowledge, far from being the inevitable ally of accountability and good governance, could just as easily be deployed to obfuscate and confuse, and thereby to wrest control of social and economic power.