[Wheatfield]

You're right, you haven't. I'm juggling posting here with work in the lab, so sodium compounds on the brain.
It doesn't read as though you're not telling anyone to dump fixer down the drain, just fyi from an outsider's perspective.

My point stands that you've mentioned various silver complexes (amended above) interchangeably where it's not correct to.

Your point is taken, and a bit of research on my part points to only one silver compound in waste fixer, that being silver thiosulfate.
My apologies, working from memories of what one read 30-40 years ago can lead to inaccuracy.
If one is using a powdered fixer, the active compound will be sodium thiosulfate, if using a rapid fixer, the active ingredient will be ammonium thiosulfate. In either case, the resulting silver compound would be silver thiosulfate.

From: https://setac.onlinelibrary.wiley.com/doi/full/10.1002/etc.5620180112

"The highly soluble silver thiosulfate complex has low toxicity, which can be attributed to the silver complexed by thiosulfate."

That jives with my memory from Kodak's literature from when I was in the industry, that being the waste silver product was not especially toxic.
We did silver recovery because it was profitable to do it, not because we had any environmental laws telling us to, and the reason I don't actively discourage a small volume darkroom user to just dump used fixer is because of the low toxicity of the silver waste compound combined with the exceedingly small volume of compound that would be discarded.

Certainly one can take the product to a waste depot to let them deal with, though it will probably just be sewered anyway as silver recovery is no longer enough of a thing to make it worthwhile, or one could use any number of Rube Goldberg methods of recovering the silver oneself, though what will then be done with it remains a mystery as it can no longer be safely disposed of (the toxicity of pure silver is quite high).

I suppose one could warehouse it until they die and let their heirs deal with it, probably by dumping it in the trash......
I suspect it would take several lifetimes of processing a roll or two of film per month to recover enough silver to smelt down into anything useful such as a pair of earrings, and the smelting process itself is going to do environmental harm.
Electricity does come with an environmental price tag as well, after all.

Or, one could use a little bit of rationality, eschew the hysteria that seeps into everything we do, and just pour the stuff off, knowing that a bit of research has shown that what they are doing isn't exactly harmful to the environment, and is far less harmful than any other method available to them for disposal.

This is the key thing: what is the least harmful course of action?

Does one drive to the local hardware store (toxic gas released by their vehicle along with the background pollution from getting oil out of the ground, turning it into fuel and transporting it to the petrol station to be pumped via electricity into their gas tank, as well as microplastic pollution from their tires along with the pollution from manufacturing said tires and transporting them to market where more pollution is generated to install them on the user's vehicle) to buy a manufactured iron product (more toxicity from mining, smelting, manufacturing, packaging and transporting to the store) to recover a material that is now highly toxic by dint of being split off from the dissolved compound it was part of?
Even if one can combine the shopping trip with their weekly groceries and not have to drive anywhere special to buy their steel wool because the hardware store is right beside the grocery store, the processing of iron ore into steel wool is still an environmental issue.

Or does one bit the bullet and release their very small amount of relatively benign compound into the waste system to mix with all the other more toxic compounds that we pour down the drain every day of our lives?

I have always tried to do the least harm that I can, knowing that every decision I make has some potential to do harm, and that buying into environmental hysteria without doing proper background research and taking as much as possible into account can lead to virtue signaling decisions that have exactly the opposite effect of what we want to do.

As an aside, silver thiosulfate is available from Amazon if you want some of your own without bothering to process film......

---

Last edited by Wheatfield; 06-10-2022 at 07:52 AM.

[Benz3ne]

Your point is taken, and a bit of research on my part points to only one silver compound in waste fixer, that being silver thiosulfate.
My apologies, working from memories of what one read 30-40 years ago can lead to inaccuracy.
If one is using a powdered fixer, the active compound will be sodium thiosulfate, if using a rapid fixer, the active ingredient will be ammonium thiosulfate. In either case, the resulting silver compound would be silver thiosulfate.

From: https://setac.onlinelibrary.wiley.com/doi/full/10.1002/etc.5620180112

"The highly soluble silver thiosulfate complex has low toxicity, which can be attributed to the silver complexed by thiosulfate."

That jives with my memory from Kodak's literature from when I was in the industry, that being the waste silver product was not especially toxic.
We did silver recovery because it was profitable to do it, not because we had any environmental laws telling us to, and the reason I don't actively discourage a small volume darkroom user to just dump used fixer is because of the low toxicity of the silver waste compound combined with the exceedingly small volume of compound that would be discarded.

Certainly one can take the product to a waste depot to let them deal with, though it will probably just be sewered anyway as silver recovery is no longer enough of a thing to make it worthwhile, or one could use any number of Rube Goldberg methods of recovering the silver oneself, though what will then be done with it remains a mystery as it can no longer be safely disposed of (the toxicity of pure silver is quite high).

I suppose one could warehouse it until they die and let their heirs deal with it, probably by dumping it in the trash......
I suspect it would take several lifetimes of processing a roll or two of film per month to recover enough silver to smelt down into anything useful such as a pair of earrings, and the smelting process itself is going to do environmental harm.
Electricity does come with an environmental price tag as well, after all.

Or, one could use a little bit of rationality, eschew the hysteria that seeps into everything we do, and just pour the stuff off, knowing that a bit of research has shown that what they are doing isn't exactly harmful to the environment, and is far less harmful than any other method available to them for disposal.

This is the key thing: what is the least harmful course of action?

Does one drive to the local hardware store (toxic gas released by their vehicle along with the background pollution from getting oil out of the ground, turning it into fuel and transporting it to the petrol station to be pumped via electricity into their gas tank, as well as microplastic pollution from their tires along with the pollution from manufacturing said tires and transporting them to market where more pollution is generated to install them on the user's vehicle) to buy a manufactured iron product (more toxicity from mining, smelting, manufacturing, packaging and transporting to the store) to recover a material that is now highly toxic by dint of being split off from the dissolved compound it was part of?
Even if one can combine the shopping trip with their weekly groceries and not have to drive anywhere special to buy their steel wool because the hardware store is right beside the grocery store, the processing of iron ore into steel wool is still an environmental issue.

Or does one bit the bullet and release their very small amount of relatively benign compound into the waste system to mix with all the other more toxic compounds that we pour down the drain every day of our lives?

I have always tried to do the least harm that I can, knowing that every decision I make has some potential to do harm, and that buying into environmental hysteria without doing proper background research and taking as much as possible into account can lead to virtue signaling decisions that have exactly the opposite effect of what we want to do.

As an aside, silver thiosulfate is available from Amazon if you want some of your own without bothering to process film......

Understood.
What I don't think should be broadcast from the above is that pure silver is toxic.
The safety data sheet linked shows otherwise for pure silver - https://www.sigmaaldrich.com/GB/en/sds/aldrich/gf64080075
Antibacterial efficacy should not be confused with toxicity.
I'd personally try and take the less cynical approach, and that's with the knowing that a lot of recycling materials in the UK are shipped abroad for disposal, which means they typically end up in landfill. That's purely because the recycling industry here is saturated.
While it may also come across as environmental hysteria now, it might not in the future as has been proven in many previous instances relating to chemicals. E.g. diesel cars being promoted, washing hands with benzene in laboratories, industrial bakery workers breathing in flour, thalidomide.
I've noticed that silver thiosulfate is available on Amazon. A quick search for one of those sellers gives the following SDS at a concentration of only 20 mM (millimole for those who aren't familiar) - https://www.bio-world.com/site/accounts/masterfiles/MSDS/MS-41920008.pdf

I've noted H400 and H410 in the list of hazards, section 2.1 - Label elements. And precautionary statement P271 - avoid release into the environment.

[Alex645]

That jives with my memory from Kodak's literature from when I was in the industry, that being the waste silver product was not especially toxic.
We did silver recovery because it was profitable to do it, not because we had any environmental laws telling us to, and the reason I don't actively discourage a small volume darkroom user to just dump used fixer is because of the low toxicity of the silver waste compound combined with the exceedingly small volume of compound that would be discarded.

This is the key thing: what is the least harmful course of action?

Understood.
What I don't think should be broadcast from the above is that pure silver is toxic.
The safety data sheet linked shows otherwise for pure silver - https://www.sigmaaldrich.com/GB/en/sds/aldrich/gf64080075
Antibacterial efficacy should not be confused with toxicity.

I've noticed that silver thiosulfate is available on Amazon. A quick search for one of those sellers gives the following SDS at a concentration of only 20 mM (millimole for those who aren't familiar) - https://www.bio-world.com/site/accounts/masterfiles/MSDS/MS-41920008.pdf

I've noted H400 and H410 in the list of hazards, section 2.1 - Label elements. And precautionary statement P271 - avoid release into the environment.

In the 70's, in two school darkrooms and another at a university, there was no silver recovery. But by the 1980's when I worked in commercial labs under the Kodak ColorWatch system that later became a Fujifilm system, by law (California) we had electro static silver recovery systems for all exhausted fixer. The toxic formaldehyde used in the C41 stabilizer was a known carcinogen, but was still part of the process and not as regulated as silver waste.

As a manager of the lab, silver recovery was only done as legal requirement. The cost of the machine, the maintenance, the transport and processing of the sludge, and the final refining of the silver cost more than the recovery value of the silver. Yes, at one point there was a brief spike in silver prices, but for the most part, it was a good day when the silver recovered offset the cost of the whole process. Today our high school darkroom that I manage has a silver recovery system and the EPA does an annual inspection. If silver prices were like they were 20 years ago, it would pay for itself....but it doesn't and we are doing it for both legal and ethical reasons; not for profit.

What would I do if I had my own little home lab? I'd research to see who operates a silver recovery system in the area and befriend them to drop off my exhausted fixer. If they were too far away or refused to get my free silver, then I'd go the steel wool method.

[Wheatfield]

Understood.
What I don't think should be broadcast from the above is that pure silver is toxic.
The safety data sheet linked shows otherwise for pure silver - https://www.sigmaaldrich.com/GB/en/sds/aldrich/gf64080075
Antibacterial efficacy should not be confused with toxicity.
I'd personally try and take the less cynical approach, and that's with the knowing that a lot of recycling materials in the UK are shipped abroad for disposal, which means they typically end up in landfill. That's purely because the recycling industry here is saturated.
While it may also come across as environmental hysteria now, it might not in the future as has been proven in many previous instances relating to chemicals. E.g. diesel cars being promoted, washing hands with benzene in laboratories, industrial bakery workers breathing in flour, thalidomide.
I've noticed that silver thiosulfate is available on Amazon. A quick search for one of those sellers gives the following SDS at a concentration of only 20 mM (millimole for those who aren't familiar) - https://www.bio-world.com/site/accounts/masterfiles/MSDS/MS-41920008.pdf

I've noted H400 and H410 in the list of hazards, section 2.1 - Label elements. And precautionary statement P271 - avoid release into the environment.

Sure, but you are talking about millions of diesel cars, probably tens of thousands of people regarding washing hands with a petrochemical or inhaling flour dust, and doing this on a near continual basis over many years, not one guy in northern England trying to get rid of a few pints of solution per year.

As an aside, the methods that are being used to combat diesel pollution (DEF and DPF) are environmental theatre. Diesel exhaust in a "clean diesel" now contains nitric acid, and when the DPF burns off, it just creates smaller carbon particles. It also uses a significant amount of fuel. Approximately 10% of my fuel consuption goes to burning off the DPF.

We can add to your list common drinking water, which has been proven to be fatal if ingested in sufficient quantities.

When I was a young lad, there was a product on the market called Phisohex, an OTC wash yourself in Hexachlorophene product. Apparently it was pretty toxic. The way they discovered it was pretty toxic was by feeding huge quantities of it to lab rats until they eventually succumbed.
That was enough to have it taken off the market in Canada.

Using the same methodology, we should probably be banning drinking water...

MSDS sheets will always err on the side of extreme caution, and often have very little in common with the real world.
As an aside, the MSDS is for pure silver thiosulphate in it's powdered form, not the dissolved and much diluted chemical in solution.
Again, that makes a difference.

[BigMackCam]

This is a fascinating discussion, guys. Clearly I can't add anything to it, but I appreciate the different perspectives and reasonings. Thank you

Since I don't know enough about the various environmental factors, I'm going to stick with dropping my exhausted fixer off at the recycling centre as officially mandated. It's just a couple of miles from here, so the pollution from my oil-burner 4x4 is minimal, especially given the infrequency of my visits. Whether the diesel pollution from my journey is worse for the environment than fixer down the drain, I don't know, but whatever difference there is should be minimal, I'd hope. Plus, I can use those visits to drop off other recyclable waste that isn't routinely collected. By disposing of my fixer this way, I'm upholding my side of the bargain regarding waste disposal, even if my efforts aren't saving the planet What the local authority does with it is up to them...

[Benz3ne]

Sure, but you are talking about millions of diesel cars, probably tens of thousands of people regarding washing hands with a petrochemical or inhaling flour dust, and doing this on a near continual basis over many years, not one guy in northern England trying to get rid of a few pints of solution per year.

As an aside, the methods that are being used to combat diesel pollution (DEF and DPF) are environmental theatre. Diesel exhaust in a "clean diesel" now contains nitric acid, and when the DPF burns off, it just creates smaller carbon particles. It also uses a significant amount of fuel. Approximately 10% of my fuel consuption goes to burning off the DPF.

We can add to your list common drinking water, which has been proven to be fatal if ingested in sufficient quantities.

When I was a young lad, there was a product on the market called Phisohex, an OTC wash yourself in Hexachlorophene product. Apparently it was pretty toxic. The way they discovered it was pretty toxic was by feeding huge quantities of it to lab rats until they eventually succumbed.
That was enough to have it taken off the market in Canada.

Using the same methodology, we should probably be banning drinking water...

MSDS sheets will always err on the side of extreme caution, and often have very little in common with the real world.
As an aside, the MSDS is for pure silver thiosulphate in it's powdered form, not the dissolved and much diluted chemical in solution.
Again, that makes a difference.

That’s a seriously far stretch with your water analogy. Yes, “it’s the quantity that kills you” but that’s entirely irrelevant as the LD50 for ingestion/inhalation are outside the mL/kg categorisation.
My point is, if you cared to read carefully, that what was previously assumed safe is no longer assumed safe.
From my extensive experience of being a chemist, people “erring on the side of extreme caution” is simply untrue. There are categories and thresholds within those categories to generate H- and P-statements for SDS. For the example of aquatic toxicity, it will be based on the LD50 and LC50 values. There is significant safety data sheet regulations that aren’t a fun read, but do spell out all of these points.
The banning of a chlorinated aromatic, which are typically carcinogenic. That’s why that testing would have occurred. It would not have been banned if the rabbits required 20kg to be fatal. Either way, that is pretty well in line with my rationale, something previously thought to be harmless actually not being so. I’m actually struggling to find a safety data sheet for the silver thiosulfate solution (and on an aside, have seen some references to silver sulfide being generated), so if you have the source for one I’d love to have a look over it.

Referring back to my earlier comment, I see zero issue with BigMack being environmentally conscious yet you appear to have an issue with my opinion on it.

[Benz3ne]

This is a fascinating discussion, guys. Clearly I can't add anything to it, but I appreciate the different perspectives and reasonings. Thank you

Since I don't know enough about the various environmental factors, I'm going to stick with dropping my exhausted fixer off at the recycling centre as officially mandated. It's just a couple of miles from here, so the pollution from my oil-burner 4x4 is minimal, especially given the infrequency of my visits. Whether the diesel pollution is worse to the environment than fixer down the drain, I don't know, but whatever difference there is will be minimal I'm sure. Plus, I can use those visits to drop off other recyclable waste that isn't routinely collected. By disposing of my fixer this way, I'm keeping my side of the bargain regarding waste disposal, even if my efforts aren't saving the planet What the authorities do with it is up to them...

Very welcome BigMack - I think I’d go down your route for disposal. In work, we’re allowed to put very little down the drains which are often tested by Dwr Cymru. This includes heavy metals, including silver, at any concentration.

[Wheatfield]

That’s a seriously far stretch with your water analogy. Yes, “it’s the quantity that kills you” but that’s entirely irrelevant as the LD50 for ingestion/inhalation are outside the mL/kg categorisation.
My point is, if you cared to read carefully, that what was previously assumed safe is no longer assumed safe.
From my extensive experience of being a chemist, people “erring on the side of extreme caution” is simply untrue. There are categories and thresholds within those categories to generate H- and P-statements for SDS. For the example of aquatic toxicity, it will be based on the LD50 and LC50 values. There is significant safety data sheet regulations that aren’t a fun read, but do spell out all of these points.
The banning of a chlorinated aromatic, which are typically carcinogenic. That’s why that testing would have occurred. It would not have been banned if the rabbits required 20kg to be fatal. Either way, that is pretty well in line with my rationale, something previously thought to be harmless actually not being so. I’m actually struggling to find a safety data sheet for the silver thiosulfate solution (and on an aside, have seen some references to silver sulfide being generated), so if you have the source for one I’d love to have a look over it.

Referring back to my earlier comment, I see zero issue with BigMack being environmentally conscious yet you appear to have an issue with my opinion on it.

Hey, I don't have any issues with environmental consciousness, I just think the over the top hysteria that is so prevalent these days is counter productive.
Quite often the cure is worse than the disease.

And again, the MSDS is for pure powdered chemical, not dissolved in solution.
I'm sure that in its powdered form one probably doesn't want to inhale it any more than someone would want to drink saturated fixer.
My objection is this pretence that a few pints of fixer going down the drain in year is somehow comparable to industrial scale chemical dumping. I see that as hysteria.
As mentioned, it's available as a bottled product from Amazon. If it was that deadly it wouldn't be on the market at all.

[Benz3ne]

Hey, I don't have any issues with environmental consciousness, I just think the over the top hysteria that is so prevalent these days is counter productive.
Quite often the cure is worse than the disease.

And again, the MSDS is for pure powdered chemical, not dissolved in solution.
I'm sure that in its powdered form one probably doesn't want to inhale it any more than someone would want to drink saturated fixer.
My objection is this pretence that a few pints of fixer going down the drain in year is somehow comparable to industrial scale chemical dumping. I see that as hysteria.
As mentioned, it's available as a bottled product from Amazon. If it was that deadly it wouldn't be on the market at all.

My last comment here because it's apparent you're skim-reading my responses and we're going around in circles, resultantly.
I never once mentioned that a few pints of fixer going down the drain is comparable to industrial scale dumping.
I asked also whether you had a safety data sheet for the silver thiosulfate solution because it seems like they're few and far between for in-date SDS for liquid solutions.
You can get a lot from Amazon. Those things can certainly include environmentally hazardous materials. Environmentally hazardous does not equal banned. In fact, I'd bet some sellers don't understand dangerous goods transport regulations (ADR/IMDG/IATA) so package them wrongly (highlighting their lack of knowledge of the hazards)... in fact, I know some do, I've received insufficient packages/labels for chemicals before. Also interestingly, I can't actually find any silver thiosulfate on Amazon at all currently...

[slartibartfast01]

My last comment here because it's apparent you're skim-reading my responses and we're going around in circles, resultantly.
I never once mentioned that a few pints of fixer going down the drain is comparable to industrial scale dumping.
I asked also whether you had a safety data sheet for the silver thiosulfate solution because it seems like they're few and far between for in-date SDS for liquid solutions.
You can get a lot from Amazon. Those things can certainly include environmentally hazardous materials. Environmentally hazardous does not equal banned. In fact, I'd bet some sellers don't understand dangerous goods transport regulations (ADR/IMDG/IATA) so package them wrongly (highlighting their lack of knowledge of the hazards)... in fact, I know some do, I've received insufficient packages/labels for chemicals before. Also interestingly, I can't actually find any silver thiosulfate on Amazon at all currently...

Amazon UK have it
Sodium Thiosulphate 100g - Aquarium Dechlorinator Photographic Processing https://amzn.eu/d/huHtE4L

[Alex645]

I can't actually find any silver thiosulfate on Amazon at all currently...

Amazon UK have it
Sodium Thiosulphate 100g - Aquarium Dechlorinator Photographic Processing Sodium Thiosulphate 100g - Aquarium Dechlorinator Photographic Processing : Amazon.co.uk: Garden & Outdoors

Silver thiosulphate; not sodium thiosulphate.

[y0chang]

My local authority states that less than 20 pounds of regular photo chemicals a month can be mixed together to neutralized and then poured down the drain. They did this for X-ray film development at dentist offices (although most of them are doing digital x-rays now). You should check with your local authorities. Some chemicals are worse than others and you shouldn't dump them into the drain.

[Alex645]

My local authority states that less than 20 pounds of regular photo chemicals a month can be mixed together to neutralized and then poured down the drain. They did this for X-ray film development at dentist offices (although most of them are doing digital x-rays now). You should check with your local authorities. Some chemicals are worse than others and you shouldn't dump them into the drain.

Yes, the mixing together is to neutralize low and high ph so that nothing is too acidic or alkali to damage drain pipes over time. In our school darkroom we have two dilution tanks. One for the chem room where the films are process and one for the darkroom. The tanks are filled with limestone chips (calcium carbonate) and anything dumped in the sink will mix in it before leaving the building. The EPA inspects that we maintain those tanks by cleaning and replacing the limestone chips annually.

Back in the day when we used to have Cibachrome/Ilfochrome, P30 was very concentrated and much more of a concern than black and white chems. Now, the chems are fairly safe except the used fixer.

[Wheatfield]

Now, the chems are fairly safe except the used fixer.

Which is still perfectly safe in the quantities an occasional darkroom hobbyist is going to be pouring it off.
It's not like as if he is pumping scuba sized tanks of ricin into the atmosphere in the middle of London.

[y0chang]

I talked with a photographer who did his own darkroom prints for his photography business and he told me he touched too many prints in the development trays with his bare hands and now has permanent tinnitus in his ear. It all depends on your exposure level, your protection equipment, your skill using that equipment, and how much the chemical has been diluted.

It is better to be too safe than to find out you damaged your pipes in your home or even worse damaged your body.