We describe results for the dynamic contact angle and transfer ratio for the deposition of docosanoic acid monolayers on to mica from CdCl2 subphases as a function of pH. The deposition changes from Z to Y type at approximately the pH corresponding to half ionisation. Deposition on OUT strokes occurs for dynamic contact angles < 90-degrees and on IN strokes for angles > 90-degrees and is consistent with a hypothesis of Bikerman.