Scott
From: "Elson T. Elizaga" <elson@xxxxxx>
Organization: Nazca Graphic Design & Photography
Reply-To: photoforum@xxxxxxxxxxxxxxxxxxxxxx
Date: Sat, 10 Apr 2004 09:39:31 +0800
To: List for Photo/Imaging Educators - Professionals - Students <photoforum@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Torpical cabinet and cobalt chloride in silica gel
On a related topic, I just got information from a chemist that the blue thing in silica -- the silica that we use for our photographic equipment -- is cobalt chloride which, he claims, is highly toxic. It allegedly transfers to the skin during contact, and then to food, and then inside the body, where it accumulates. Here's a portion of his post yesterday in another list:
BUT cobalt chloride (which is the indicator compound found in silica gel) is highly toxic. the LD-50 of cobalt chloride in rats is 770 mg/kg, compare that with malathion with an LD-50 of 1375 mg/kg orally. of course, comparison like this is meaningless, but just to give you an idea. cobalt in pottery and earthenwares are most probably fused, cobalt chloride in silica gel is just mixed in. if you put the indicating silica gel in water, cobalt chloride will dissolve, and you'll get a very light pink color.Any comments from other chemists in the house?
cobalt in silica is not dust. you're right. but it's also not fused. and it is soluble in water (or the sweat of you hands). and that's how you get the cobalt into your system (if you touch the silica gel with your bare hands, hint hint...use gloves :).
Elson
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