[W.A.Hammond Drierite Co.] A registered trademark for a product composed of granular anhydrous calcium sulfate. Drierite® is an effective absorbent for both liquid and vapor-phase water. Drierite® may be regenerated numerous times by oven drying. One commercial form, Drierite® F-6, contains cobaltous chloride as a moisture indicator where the anhydrous form is blue and the hydrated form is pink.
W.A. Hammond Drierite: Website