1. The problem statement, all variables and given/known data What is the mass transfer coefficient for natural convection from rock salt (assume flow is over a horizontal cylinder (salt crystal) of length 2cm, diameter 0.5cm). Given: Temperature = 24degrees Density of salt 2165kg/m^3 Density of mixture when salt concentration is saturated = 1310kg/m^3 2. Relevant equations Sh = C2 (Gr.Sc)^p Sc = Kinematic viscosity/Diffusivity 3. The attempt at a solution I am having trouble finding the correct diffusivity to use for the Sc number. I have previously calculated the maximium concentration of the salt in the water. Which is 6kmol/m^3 and i also a table of values for the diffusivity for different solute concentrations. So the qn is do i use the maximium concentration of salt to find my diffusivity or do I have to use the actual concentration? Thats because I am not given the volume of the solvent even though i am able to find the mass of the solute by finding the volume of solute x the density. A great big load of thanks in advance.