It is desired to dry $10 \mathrm{~kg}$ of soap from $20 \%$ moisture by weight to no more than $6 \%$ moisture by contact with hot air. The wet soap is placed in a vessel containing $8.06 \mathrm{~m}^{3}$ of air at $350 \mathrm{~K}$ and $1 \mathrm{~atm}$, and a water-vapor partial pressure of $1.6 \mathrm{kPa}$. The system is allowed to reach equilibrium, and then the air in the vessel is entirely replaced by fresh air of the original moisture content and temperature. How many times must the process be repeated in order to reach the specified soap moisture content of no more than $6 \%$ ? When this soap is exposed to air at $350 \mathrm{~K}$ and $1 \mathrm{~atm}$, the equilibrium distribution of moisture between the air and the soap is as follows:

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Wt% moisture in soap Partial pressure of 2.40 water, kPa 1.29 3.76 2.56 4.76 3.79 6.10 4.96 7.83 6.19 9.90 7.33 12.63 8.42 15.40 9.58 19.02 10.60