Most methods measure changes in the mass of a sample due to adsorption, condensation, or reaction in high-pressure, high-temperature vessels by balancing or directly sensing its weight. In a recently published study , we presented a method to determine mass through the objectâs inertia under high pressure conditions using vibration. The natural frequency of a sample suspended by a spring was measured using a solenoid and an oscilloscope. The effect of the surrounding fluid on the frequency of oscillation was characterized and accounted for in mass determination. In this study, we verify that this method can also be used at high temperature conditions after the effect of temperature on gas density and spring moduli is considered. Then, we tested Berea sandstone as a representative sample of a macroporous solid, and a Niobrara shale (crushed) as a representative sample of a mesoporous solid. The additional mass sensed by the spring, for the case of Berea sandstone, is due to the mass of dense gas that saturates the pores of the porous solid. For the case of Niobrara shale, addition to the frequency of oscillation is dominated by capillary condensation. The change in mass due to capillary condensation is analyzed using the Kelvin equation.
 Z. Larson, Y. Cho and X. Yin, Experimental technique to measure mass change under high pressure conditions using oscillatory motions of a spring-mass system, Meas. Sci. Tech. 28:065902, 2017.