Application to the diffusion of salts in solution

Fill a small cylindrical tube of unit sectional area with a solution of some salt (Fig. 164). Let the tube and contents be submerged in a vessel containing a great quantity of water, so that the open end of the cylindrical vessel, containing the salt solution, dips just beneath the surface of the water. Salt solution passes out of the diffusion vessel and sinks towards the bottom of the larger vessel. The upper brim of the diffusion vessel, therefore, is assumed to be always in contact with pure water. Let h denote the height of the liquid in the diffusion tube, reckoned from the bottom to the top. The salt diffuses according to Fourier s law, 

To find the concentration, V, of the dissolved substance at different levels, x, of the diffusion vessel after the elapse of any Stated interval of time, t. This is equivalent to finding a solution of Fick s equation, which will satisfy the conditions under which the experiment is conducted. These so-called limiting conditions ara (i) when 

The reader must be quite clear about this before going any further. 

What do F, x and t mean F0 evidently represents the concen--x=h ira on sa solution at the beginning 

First deduce particular solutions. Following the method of page 462, assume tentatively that 

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