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The mass fraction and the properties of asphaltenes vary significantly with the n-alkane used to separate them from their parent oil and with the details of the separation procedure, such as washing steps. Measurement repeatability is challenging, with different error bounds reported within the American Society for Testing and Materials (ASTM) standards for a single operator using the same equipment and procedure vis-a-vis measurements performed by different operators in different laboratories. In this work, reversible interactions between Athabasca pentane asphaltenes and n-alkanes from pentane to hexadecane were observed using cross-polarized and visible light microscopy and were quantified using high-precision density measurements for mixtures ranging from 1000 to 8000 ppmw (from 0.8 to 6.5 g/L) and enthalpy of solution measurements for mixtures comprising from 1000 to 3500 ppmw (from 0.8 to 3 g/L) asphaltenes. The partial specific volumes of Athabasca pentane asphaltenes and the enthalpy of solution v...