Ammonia can be absorbed by copper sulfate forming the [Cu(NH 3 ) 4 ] 2+ complex and acetone or alcohols are absorbed by CaCl 2 forming adducts. The formed compounds may not be hygroscopic anymore. So a higher amount of desiccant has to be used. 33 % 2.299 %RH ≙ 0.469 gm -3 acid (3.271 +/-0.093) %RH h -1 Not possible Potassiu m carbonat e deliquescence humidity: 43.1 %RH 7 The second point to be considered for desiccants is the capacity for absorbing water. For water free substances that form hydratres the capacity can be calculated as follows, for the example copper sulfate: