thanks for the information.Donald Qualls said:The only use I've made of potassium dichromate is as a contrast enhancer in cyanotype; I use one or two drops of 2% solution in the sensitizer for a 5x7 print (much of which subsequently is washed down the drain in developing the print), haven't yet gone through the first 50 g.
Your laws must be very strict indeed -- how much dichromate are you trying to buy? I know it's an oxidizer, a carcinogen, and pretty acutely toxic as well, but still, 100 g will go a long way and unless you dump it in a pretty short time or it accumulates without any means of removal, can't possibly present a major pollution problem. Have you tried ammonium dichromate? I've heard it's interchangeable in some or most processes, though typically faster (that is, more sensitive to exposure) than potassium dichromate (bad news is, you may have to use more of it, and it's really no different in the waste stream).
For my ordinary chemicals, B&W developer and and depleted stop bath just go down the drain after use -- developer working solution, diluted with additional water, will be oxidized to harmless tannin-like materials before it even reaches the treatment plant. Recently, I've been similarly dumping my print fixer (diluted at 1+7 from an automatic processor concentrate that was very affordable) after a single session (10-20 8x10 inch RC prints in a quart, should be about half capacity), on the expectation that any silver will be converted to the insoluble sulfide and precipitate in the pipes before it can do any harm in the city sewer system. The last batch of film fixer I used up, I treated with steel wool, then promptly forgot for a couple months; eventually, I poured off the liquid on the lawn and disposed of the precipitate and very rusty steel wool to the landfill, but the next batch I may just evaporate after a much shorter silver precipitation.
Given the relative rarity of B&W processing in this digital age (insufficient to keep even one local store carrying paper or chemicals, in a combined community of close to a quarter million), I doubt there's enough going into the drains to cause a problem, even if all of us here dumped everything that way.
However -- America hasn't anything like the population density of Europe; in between cities, this country is damned near empty, even with 280 million people (some pretty large areas have less than one person per square mile, which is just under 26000 hectares). Denmark has as many people for its area as our denser regions, places like New Jersey or Connecticut, and a lot fewer places to put nasty stuff.
FWIW, its actually possible to recover silver from exhausted fixer in enough quantity to pay for the process, if you use enough fixer, and almost all commercial labs are now required to do this.
gandolfi said:thanks for the information.
(I once saw a TV show about the ORWO plant (east Germany) which made so cheap photo stuff...
but we saw the area outside the plant... in a HUGE area, ALL was dead. no plants - white trees; dead, and frankly it was scary...)
I know in these digital ages the photographic "problem" is going down, but that said; shouldn't we care about out inviroment?
gandolfi said:I think it is annoying with theese restrictions, but in the same time I am proud of my goverment, as it actually take the inviroment issue serious..
Kirk Keyes said:Dichromates have chromium in the Cr6+ state - also known as hexavalent chromium. It is toxic and carcinogenic. However, chromium in the Cr3+ state, trivalent chromium, is not.
hehe...laz127 said:And you should be proud! Europe is far far ahead of the US in environmental awareness. Much of europe has well considered and scientificly rigorous regulation. Part of the explaination of course is that the countries of the European union know from hard experience how their neighbors environmental actions or inactions impact them; the waste one county dumps in the Rhine on Monday becomes another country's problem on Tuesday.
Americans worship their freedoms, even those that will eventually kill them.
-Bob
gandolfi said:hehe...
I once read about a guy, that developed his Tri-x in "plain" water from the Rhine...
sounds scary, or?
laz127 said:In the late '60s early '70s the Cayoga River near Clevland Ohio would occassionally catch fire! Can you imagine that call to the fire department. "help our river is on fire!"
laz127 said:And you should be proud! Europe is far far ahead of the US in environmental awareness. Much of europe has well considered and scientificly rigorous regulation. Part of the explaination of course is that the countries of the European union know from hard experience how their neighbors environmental actions or inactions impact them; the waste one county dumps in the Rhine on Monday becomes another country's problem on Tuesday.
Americans worship their freedoms, even those that will eventually kill them.
-Bob
laz127 said:5. Trivalent chromium may be the ultimate carcinogen responsible for the effect of hexavalent chromium since it is able to bind DNA directly. However, it is unclear whether the reduction of hexavalent to trivalent chromium and the subsequent oxidative damage, or the direct binding of trivalent chromium to DNA, or both is responsible.
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