Silica gel, at the time of publishing this brief summary, was discovered just under a hundred years ago. Coincidentally, the one-hundred-year anniversary of the Great War or the First World War was commemorated. Sadly, there was to be another world war not more than twenty years later. Thankfully, and again, at the time of writing, there has been no third world war. Historians believe that this has something to do with what the victors of that last great war achieved around the round table. And today, silica gel desiccant regeneration is believed to be a safer and less toxic alternative to the use of cobalt chloride.
It is a chemically safe desiccant. During the first World War, silica gel was used to absorb vapors and gases in gas mask canisters. During the second World War, silica gel was used to keep penicillin dry. It could protect military equipment from moisture damage, acting as fluid cracking catalysts for the production of high octane gasoline. It acted as a catalyst support mechanism for the manufacture of butadiene from ethanol. Today, it is still used in the production of feedstock for the synthetic rubber program. Silica gel is safe to use because its doping agents that act as moisture indicators are derived from an inorganic iron compound. The compound is not dangerous and can be utilized safely in a wide range of applications.
Silica gel that utilizes cobalt (II) chloride needs to carry the warning skull and crossbones icon in terms of existing US and EEC legislation. It is easy to identify when silica gel has expired. It is blue when it is active and dry. But it turns to pink when exhausted or hydrated. And it loses its color completely when saturated with moisture.