Silica gel has been used as a desicant for many years to protect sensitive materials form damage due to excess humidity.
In our Country lik many others , silica gel which contains a moisture indicator is currently produced by impregnating silica gel or silica hydro gel with cobalt chloride solution to produce adry granular end-product. European union has recently classified cobalt chlorid as a category 2 carcinogen (According to Directive 67/54/EEc and Directive 98/98/EEC).
In its project silica gel impregnated with an iron (III)salt functions as a safe humidity indicator turning from adeep amber color when dry to colorless or nearly colorless upon exposure to moisture, has successfully produced in a laboratoary and bench scales.
This indicator silica gel produced by two impregnating techniques, in the first silica gel and in the seconded hydrogel were successfully impegnatal to the end product.
In accordance to the studies and searching done, the impregnation of hydrogel with the indicator is done successfully for the first time in the word.
The indicator silica gel produced color over arange of 20-40% relative humidity, this is similar to the traditional cobalt-based indicating gel. It is thermally stable allowing it to be regenrated and reused for many times .It has the advantage over the cobalt chloride system of being non carcinogenic.