A method of operating circuitry in communication with a Coriolis flowmeter , the method comprising the step of: receiving pickoff signals and a temperature signal from the Coriolis flowmeter responsive to a fluid being flowed through the Coriolis flowmeter; the method being characterized by the step of: processing the pickoff signals and the temperature signal to determine the purity of the fluid, including the steps of: providing a reference density (ρ ref ) of the fluid flowing through the Coriolis flowmeter , wherein the reference density represents the density of a majority component of the fluid at a reference temperature; processing the pickoff signals and determining a measured density of the fluid flowing through the Coriolis flowmeter therefrom; processing the temperature signal and determining a temperature-varying density (ρ temp ) therefrom, the temperature signal representing the temperature of the fluid flowing through the Coriolis flowmeter; determining the fluid is substantially pure if the measured density equals the temperature-varying density; and determining the fluid contains a minority component in addition to the majority component if the measured density does not equal the temperature varying density. receiving pickoff signals and a temperature signal from the Coriolis flowmeter responsive to a fluid being flowed through the Coriolis flowmeter; the method being characterized by the step of: processing the pickoff signals and the temperature signal to determine the purity of the fluid, including the steps of: providing a reference density (ρ ref ) of the fluid flowing through the Coriolis flowmeter , wherein the reference density represents the density of a majority component of the fluid at a reference temperature; processing the pickoff signals and determining a measured density of the fluid flowing through the Coriolis flowmeter therefrom; processing the temperature signal and determining a temperature-varying density (ρ temp ) therefrom, the temperature signal representing the temperature of the fluid flowing through the Coriolis flowmeter; determining the fluid is substantially pure if the measured density equals the temperature-varying density; and determining the fluid contains a minority component in addition to the majority component if the measured density does not equal the temperature varying density. providing a reference density (ρ ref ) of the fluid flowing through the Coriolis flowmeter , wherein the reference density represents the density of a majority component of the fluid at a reference temperature; processing the pickoff signals and determining a measured density of the fluid flowing through the Coriolis flowmeter therefrom; processing the temperature signal and determining a temperature-varying density (ρ temp ) therefrom, the temperature signal representing the temperature of the fluid flowing through the Coriolis flowmeter; determining the fluid is substantially pure if the measured density equals the temperature-varying density; and determining the fluid contains a minority component in addition to the majority component if the measured density does not equal the temperature varying density. <EOS>