Why Does Crystal Solute Residue Form And Grow ABOVE The ORIGINAL Solution Line As The Solvent Evaporates?

Let me venture my current hypothesis for consideration.

I stirred the hot solution in the container initially to help dissolve as much of the solute as possible. This probably left a thin film of solution on the sides of the container just above the solution line. Some of the hot solvent (water) may have evaporated from that film leaving a nearly invisible, unnoticed film of solute on the side of the container just above the solution line. Through a process of adsorption, the solution may have been drawn up into the solute film where more solvent evaporated leaving more solute crystals on the side of the container above the original solution line. That film had become "seed" crystals, but, more important, it exerted a sorptive attraction on the solution. This process of adsorption, drawing the solution up into the film of solute crystals on the side of the container continued throughout the evaporation process, continually adding to that film. That film became thicker and wider, even upward, farther above the original solution line through adsorption of the solution and evaporation of the solvent. The film below the original solvent line was not as thick or well developed because, while it was submerged, the deposited solute below the solution line would redissolve in the large body of solvent remaining available to it.

I would welcome comments on this hypothesis and ideas for simple tests to obtain good evidence to support, refute, or refine it.

Bob Jarvis--7/15/08--18:23 CDT

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