Analytical Tests for Hydrophobicity

A further method is to place a drop of water on heap of silane treated hydrophobic filler. The time required for the water to sink into the filler is a quick indication of the hydrophobicity the treatment. 

I ncorporation of a suitable colorant in the silane solution can show the distribution of the silane on the treated mineral (e.g., Rhodamine B in isobutyltriethoxysilane). It is important to note that the colorant will not block any of the active sides on the mineral 

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