Measuring low silver concentrations (in fixer)

PeterB · Jan 31, 2010

Hi folks.
I've searched APUG and the 'net but to little avail. Can folks please list me a few different inexpensive and relatively easy methods to measure/test when the silver in my (yet to be processed/reclaimed) fixer. Then my local government/water authority will permit it to be discarded down the drain.

Some ideas include measuring the conductivity of the sol'n (assuming I am testing for dissolved silver). Also perhaps Colorimetry. No test strips will test such low levels of silver.

Please steer away from suggesting ideas like "once no more steel wool/aluminium foil disentegrates then it will be <50ppm" as I would like a quicker method please.

rgds
Peter

dancqu · Jan 31, 2010

How low must you go? Dan

Neal · Jan 31, 2010

Dear Peter,

This company claims to have a test strip that will measure to 5ppm.

http://silverprofitphoto.com/products/SilverEstimatingTest/images/stf-50.pdf

Neal Wydra

Photo Engineer · Jan 31, 2010

Some of these do not work in hypo itself, just in the wash water. This advert. only shows that it works in the wash water.

PE

Neal · Jan 31, 2010

Dear PE,

I do not doubt that some products do not work in fixer, nor do I know for a fact that this product does, but the quote from the ad is "A simple reliable test for the silver content of Photo Graphic and X-Ray chemical & wash water effluent solutions below 5 parts per million (the E.P.A. threshold limit).". The phrase "chemical & wash water" leads me to believe the product might be appropriate.

Neal Wydra

Photo Engineer · Jan 31, 2010

"Might be appropriate" is the operative phrase here. Due to the wording, the effective working conditions are not clear. I am just setting out a warning, not an absolute. I agree with you but stress my previous precaution.

Hypo can be strong enough that it can dissolve the test material from the paper in some cases.

PE

PeterB · Jan 31, 2010

Thanks Neal and PE, I'm contacting the seller of the STF-50 to see if it works in fixer before it is diluted.

Dan, I need to ensure the silver is <50ppm. The STF-50 product claims to measure between 5ppm to 50ppm

rgds
Peter

dancqu · Jan 31, 2010

Way Below Fixer Limits

PeterB said:
Dan, I need to ensure the silver is <50ppm. Peter

That is equal to 0.05 grams per liter. That compares with
recommended silver levels of 0.5 to 2.0 grams for paper
fixers and as much as 8 to 10 grams for film. Those are
Ilford suggested limits. Dan

ras351 · Jan 31, 2010

Hi Peter,

This might not help but are you able to get away with working with known dilutions? ie if you know your litre of fixer contains a certain amount (using test strips) then you can dilute it with a calculated volume of water to reduce the level to below that needed. I'm pretty sure (but don't quote me) that the X-Ray guys here at work do this as there's a mark on their sink and signs saying to fill the sink with water to this level before it goes down the drain.

Roger.

PeterB · Jan 31, 2010

Hi Roger,
this sounds like a good idea. This was suggested to me with the phrase "The solution to pollution is dilution" !

I am contacting a representative from Dead Link Removed (Photographic Uniform Regulations for the Environment) to ask if this is a permissible way to achieve 50ppm. The only limitation might be that the TOTAL mass of silver one puts down the drain might be limited over a particular frame of time. Not that I would ever be capable of exceeding such a limit with my small volumes.

regards
Peter

ras351 said:
Hi Peter,

This might not help but are you able to get away with working with known dilutions? ie if you know your litre of fixer contains a certain amount (using test strips) then you can dilute it with a calculated volume of water to reduce the level to below that needed. I'm pretty sure (but don't quote me) that the X-Ray guys here at work do this as there's a mark on their sink and signs saying to fill the sink with water to this level before it goes down the drain.

Roger.

removed account4 · Jan 31, 2010

hi peter

why don't you ask the folks who regulate you what they suggest you do
to test your effluent, and if necessary how to reduce your silver tailings ?

it might be easier to buy a device or make one that will desilver your water to an acceptable level
trying to find a product that will cost a lot of money after you buy it 3 or 4 or 5 times.
after you use "it " your you just need to bring a sample down 1 time to assure yourself and the regulators that your method
removes enough silver and is doing a sufficient job ... and it will be the end of it. you won't be stressed if they do a surprise effluence check,
and you won't have to keep buying test strips.

you might also consider speaking with a high school or college science teacher to find out
if you can make a salt solution ( using table salt and water ) of a certain concentration
that will indicate that you have more or less than 50ppm.
hypo-check does the same sort of thing ...
it would be easy to make, and work every time ...

good luck!
john

PeterB · Feb 1, 2010

A question to all the chemists out there, If I made my own hypo-check and put in a sufficient conc. of potassium iodide, could I then make it so that a milky white precipitate forms in the silver poor fixer only when the silver conc is >50ppm ? Would this idea also work with Sodium Chloride solution instead of the potassium iodide ?

Peter

jnanian said:
find out if you can make a salt solution ( using table salt and water ) of a certain concentration that will indicate that you have more or less than 50ppm. hypo-check does the same sort of thing ...
it would be easy to make, and work every time ...
good luck!
john

removed account4 · Feb 1, 2010

peter

contact stephen frizza
who used to or still does run a custom lab in australia ...
(there was a url link here which no longer exists)

he might be able to tell you an easy way to do these things
since he is probably doing them himself ...

good luck!
john

Mr Bill · Feb 1, 2010

PeterB said:
Hi folks.
please list me a few different inexpensive and relatively easy methods to measure/test when the silver ... will permit it to be discarded down the drain.

Sorry to say, but I don't think there are such methods. If you are trying to convince a regulatory body, you'll probably need to use an independent analytical lab. The most common method is to run samples on an AA unit (Atomic Absorption Spectrophotometer) equipped to measure silver. I think if you check for "Testing Laboratories" in your local area, you'll probably find something (assuming you are near a decent sized city).

If you're just trying to screen results of your desilvering, there's a decent alternative. This was described in Kodak literature quite a few years back, I am not aware of a current publication. Basically, you use the standard "silver test papers", such as Kodak sold a few years back. Normally, these papers are to check for much higher silver concentration from roughly 1 to about 6 grams/liter. However, by doing an extended immersion time, motionless, in a small beaker of the fixer, for about 30 seconds, you could probably get in the range you are looking for. But.... you won't know what the results mean until you run a set of calibration samples which are also sent out to your local testing lab. So again, no cheap and easy method.

Most definitely, there are a handful of "wet lab" test methods in literature, but I think they are mostly iffy about the results.

Kirk Keyes · Feb 1, 2010

AA - Atomic Absorption is one way of measuring silver. But most labs nowadays use an ICP or ICP-MS (inductively Coupled Plasma without or with a Mass Spectrometer) to do metals analysis. The AA can only measure one metal at a time, whereas the ICP can measure 20 or more at a time.

Anyway, if this is for commercial effluent regulation, you will most likely have to submit effluent samples to an approved lab. If it is home use, and you are just curious - then the test papers should suffice.

So which is it - home or business use?

dancqu · Feb 2, 2010

Silver Iodide - Extremely Insoluble

PeterB said:
If I made my own ...hypo-check and put in a sufficient conc. of
potassium iodide, could I then make it so that a milky white
precipitate forms in the silver poor fixer only when the
silver conc is >50ppm? Peter

I've tested very silver poor fixer with the iodide. The method
could be quantified with the use of standard solutions. The
problem though is the formation of the precipitate. With
little silver an extremely fine precipitate forms. So
fine as to make it very difficult to determine the
end point of the titration.

A titration with H2O2, hydrogen peroxide, will produce
a very visible brown flocculent precipitate of silver
hydroxide. The H2O2 test could be quantified for
good eyeball estimating. Dan

PeterB · Feb 3, 2010

Thanks Dan,
that's a good idea.
rgds
Peter

PeterB · Feb 3, 2010

Hi Kirk,
it is for home use, but I am querying my water authority, because I was only allowed to have my DR sink plumbed to the sewer after filling in an application form and getting permission from them. It didn't include discarding silver poor fixer (diluted or not) down the drain - only photographic wash water. So I'm waiting to hear back from them if they'll accept fixer (dilted or just with silver reclaimed) with up to 50ppm of silver in it in line with the Dead Link Removed.

rgds
Peter

Kirk Keyes said:
AA - Atomic Absorption is one way of measuring silver. But most labs nowadays use an ICP or ICP-MS (inductively Coupled Plasma without or with a Mass Spectrometer) to do metals analysis. The AA can only measure one metal at a time, whereas the ICP can measure 20 or more at a time.

Anyway, if this is for commercial effluent regulation, you will most likely have to submit effluent samples to an approved lab. If it is home use, and you are just curious - then the test papers should suffice.

So which is it - home or business use?

Doremus Scudder · Feb 3, 2010

Peter,

This may seem off-topic, but it seems to me that you are not seeking to determine the state of your fixer exhaustion, but rather if your fix contains little enough silver to dump it down the drain into the municipal sewer system.

If so, it might be easier for you simply to collect it and dispose of it at your local HazMat collection center. This is what I do. A years worth of fairly intensive work (for me) only leaves me with 15-20 gallons of used fixer. I collect the fix in 5-gallon jugs and take a couple of trips a year to the collection center.

Another alternative is to find a working film lab in your area. They normally have silver recovery units and are often happy to take your used fixer (since they get the silver out of the deal). This is what I did before all the labs in my area went out of business.

Now, more on-topic: I would really be interested in a test-strip system for measuring the silver content of fixer for the purpose of determining fixer exhaustion. If something like that exists, I would be interested. It seems from the above replies, however, that a practical system of this type is not available. In the meantime, I'll just keep using photographic strip-tests.

Best,

Doremus Scudder
www.DoremusScudder.com

PeterB · Feb 3, 2010

Doremus Scudder said:
Peter,
This may seem off-topic, but it seems to me that you are not seeking to determine the state of your fixer exhaustion, but rather if your fix contains little enough silver to dump it down the drain into the municipal sewer system.

Hi Doremus, that is correct. And you offer reasonable alternative suggestions, I was exploring the idea of diluting it and dumping it - my water authorities are getting back to me on that.

Doremus Scudder said:
Now, more on-topic: I would really be interested in a test-strip system for measuring the silver content of fixer for the purpose of determining fixer exhaustion. If something like that exists, I would be interested. It seems from the above replies, however, that a practical system of this type is not available.

These strips do exist and are sold by Tetenal. They measure from 1g/L to 10g/L of silver. See this Google search for the product.

rgds
Peter

Measuring low silver concentrations (in fixer)

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