impregnating desiccant with cobalt chloride?

Cobalt chloride as indicator:

For example, the compositions may also comprise a chemical substance that changes color upon absorption of water, such as cobalt chloride or other salt. Such a chemical substance may indicate whether or not the desiccant needs replacement and/or recharging. As is appreciated by those skilled in the art, cobalt chloride (i.e., CoCl2) is normally blue when desiccated and red or pink when hydrated. Stated somewhat differently, a color change associated with such novel compositions may be used to indicate the degree to which the desiccant composition has absorbed water because cobalt chloride will slowly turn pink upon absorbing water due to the formation of various colored hydrates, finally leading to the pink hexahydrate, CoCl2.6H.sub.2 O. In a preferred embodiment, the amount of cobalt chloride added is about 1%-2% by weight of the total composition. The cobalt chloride may be directly added to the aqueous solution of PVOH and CaCl2 or CH3 COOK during the cook and stir process as described above.

In addition to cobalt chloride, the compositions of the present invention may also include other materials to maintain its physical integrity (i.e., desired shape and form), where such solid support materials include (but are not limited to): paper product, wood products, natural or synthetic sponges, cotton, synthetic fibers, charcoal, pumice, porous rock, and the like. In general, the above-identified novel compositions are coupled to such other materials by an impregnation technique. More specifically, one or more of the hygroscopic materials of the present invention may be mixed with a suitable solvent to yield a solution, and the solution may then be used to impregnate the solid support by, for example, immersing the solid support into the solution until it is saturated (the solid support may then be dried). In a preferred embodiment, the hygroscopic material consists essentially of polyvinyl alcohol, the solvent consists essentially of water, and the solid support consists essentially of a paper product like cardboard. However, it is to be understood that other techniques may be employed to couple the hygroscopic material with the solid support, such as through the use of a suitable coupling agent like, for example, an adhesi

I don't know about silica desiccant but I know that anhydrous calcium chloride (a solution drying agent) often uses that method so we know if the stock bottle is too old and has absorbed water from the air so we don't use it in our labs.