Mannose polarimetry

Sowden and Schaffer [49] also detected what appeared to be a catalytic effect of calcium ions. They studied the reaction of mannose and found that it disappeared much faster in a solution of calcium hydroxide than it did in barium hydroxide and, in turn, in the latter medium faster than in sodium hydroxide. They followed the reaction by polarimetry and the results proved rather puzzling in sodium hydroxide solution the initial rotation was positive (as it should be for D-maimose) and declined over time but in calcium hydroxide the rotation was negative and increased as the reaction proceeded. The behavior in barium hydroxide was intermediate. Clearly, something more than mere catalysis was involved here. Incidentally, in LdB-AvE s original work [4], the greatest amount of mannose was produced in a concentrated solution of calcium hydroxide. 

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