Archived posting to the Leica Users Group, 2000/09/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]And how many old cameras and lenses have been scrapped by their owners as too devalued to be worth selling because of the lack of batteries? Where are the hundreds of thousands of fixed lens popular rangefinders of the sixties and seventies? I think their sheer volume was bigger than that of all the mercury camera batteries ever manufactured. Amilcar John Coan wrote: > William, > Do you happen to know what mercury compound is in fluorescent tubes? I > wonder how much is in one industrial size light, vs. one PX-625? > Anybody else? > John > > William Gower wrote: > > > > With regards to the recent postings on Hg, batteries and Minamata: > > > > > From: "Raimo Korhonen" <raimo.korhonen@pp2.inet.fi> > > > > > Metallic mercury is not particularly harmful - but some organic compounds > > > that contain mercury are lethal and thatīs what caused Minamata, not > > > mercury batteries. > > > > Partly true: Metallic (elemental Hg) is not "harmless" per se, but the rate > > of absorption into the bloodstream via the skin slow. Slow enough, that you > > would have to be in direct contact for long periods of time for any > > significant symptoms to manifest themselves. Not that it wouldn't or > > couldn't happen, mind you - it's just that the likelihood is small. > > > > Remember handling the stuff as a kid when you broke a thermometer or old > > thermostat ? How about good old dental fillings (amalgams of Mercury and > > Tin). Although I wouldn't recommend it, accidental swallowing some Hg is > > generally considered harmless (save for a tummy ache). > > > > My point - exposure by handling or occasional ingestion of elemental Hg (the > > good old silver liquid) is, for all intensive purposes, benign. The skin is > > a pretty good barrier to uptake of Hg. > > > > However, increase the rate of absorption of Hg into the bloodstream, and > > trouble begins. > > > > How to you increase the absorption ? Via the respiratory tract is one. > > Exposure to Hg dust (mining of sulphide ores rich in cinnabar) or vapour > > (heating Hg in the presence of oxygen, forming HgO) are the two most common > > and toxic occupational exposure routes. > > > > Dimethyl Mercury (CH3)2Hg is the real bugger in the environment. This is an > > organic mercury compound that is readily absorbed into the bloodstream. In > > nature, certain aquatic organisms will break down elemental Mercury into > > this organic form. If the level of Mercury in natural waters is high, the > > concentration of of Dimethyl Mercury will be high as well. This translates > > into accumulation of Hg in marine life (i.e. fish). > > > > Minamata is a prime example. It was the high concentrations of Hg in the bay > > from industrial processes that caused an elevated level of Dimethyl Hg in > > the aquatic life. This, combined with a diet rich in seafood that caused the > > high incidence of Hg poisoning in the areas surrounding Minamata Bay, Japan. > > > > There have been other cases of widespread Hg poisoning due to eating > > contaminated grains that had been treated with organic Mercury pesticides. I > > believe it was in somewhere in the middle east (Iraq or ?) > > > > No, I'm no "expert", but I took enough toxicology and biochemistry courses > > to know that Hg is bad news. And yes, I have a Rollei 35s that needs to be > > recalibrated to the '625 alkaline cells. > > > > Kind regards > > > > William Gower