Silica Gel

<p>I have been using Blue Silica Gel for my lenses for last several years. When it turns purple, I heat it and it turns blue and becomes active again. Recently I have received 2/3 big pouches of Silica Gel along with some computer equipments. It is in the form of very tiny clear glass like balls-which is normally found in small pouches in medicine bottles. How do I ascertain whether it is active or not and can it be activated from timt to time like the blue variety ?</p>

<p>Pure silica gel is white. The blue variety is doped with cobalt chloride to indicate when the silica gel requires regeneration. You can mix the white with the blue type. Cobalt chloride is toxic and a carcinogen.</p>

<p>Thanks, Peter. I wanted to know as to when white silika gel needs to be regenerated and how.</p>

<p>http://demec.ufpr.br/reterm/ed_ant/08/artigo/technol01.pdf</p>

<p>Page 5 of the pdf shows that 4.454 Kg of silica gel can absorb 1.363 Kg of water and thus the spent silica gel package weighs 5.817 Kg. This is a weight gain of 30.6%.</p>

<p>Therefore, dry your dessicant and weigh it. Periodically weigh each 'pack'. When the weight winds up being some 30% more, consider the 'pack' at the end of useful cycle and in need of regeneration.</p>

<p>The non-indicating gel cannot be simply looked at and determined if it is 'dry' or 'wet'. Too bad the cobalt chloride is a suspected carcinogen, that takes away a real easy to use option. The EU is purportedly banning the indicating gel.</p>

<p>Jim</p>

<p>A few granules of indicating silica gel in a bag of non-indicating gel would be sufficient to know when if needs regeneration.<br>

The MSDS for indicating silica gel is here: http://www.jtbaker.com/msds/englishhtml/s1622.htm<br>

for non-indicating gel here: http://www.jtbaker.com/msds/englishhtml/s1610.htm<br>

Note that the indicating silica gel should be disposed off as hazardous waste because the cobalt chloride may leach out when in contact with water.</p>

<p>Thanks, Peter and Jim for the valuable info.</p>