Problem $4.$

The diffusivity of toluene in air was determined experimentally by allowing liquid toluene to

vaporize isothermally into air from a partially filled, $3-$mm diameter, vertical tube. At a temperature

of $39\mathrm{.}4$ C$,$ it took $96$ x $104$ s for the level of the toluene to drop from $1\mathrm{.}9$ cm below the top of the

open tube to a level of $7\mathrm{.}9$ cm below the top. The density of toluene is $0\mathrm{.}852$ g$/$cm$3,$ and the vapor

pressure is $57\mathrm{.}3$ torr at $39\mathrm{.}4$ C$.$ The barometer reading was $1$ atm. Calculate the diffusivity and

compare it with the value predicted from $(3-36).$ Neglect the counter diffusion of air. $(8$ pts$)$