silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
Contaminated silver nitrate solution
Hello everyone, glad to be on the forums.
I am a wet-plate photographer from the US. I recently contaminated a 1200 ml bath of 10% silver nitrate (solution in distilled water) with I'd say,
maybe 6 grams of potassium iodide also in a distilled water solution. As would be expected, when I added the KI it immediately precipitated AgI, and,
I assume, the KNO3 dissolved into the solution.
So, I am wondering if there is a way to remove the KNO3. If there is no cost effective way to do so, I would be interested to know if the KNO3 might
interfere with metallic silver recovery using copper.
Thank you!
Alex
|
|
|
tetrahedron
Hazard to Others
Posts: 210
Registered: 28-9-2012
Member Is Offline
Mood: No Mood
|
|
hi alex
any chemical method to precipitate the K would probably introduce even more impurities. maybe fractional crystallization could work, but this sounds
impractical. how did you plan on using this solution anyway? you don't necessarily need to remove it.
certainly not, the little K present won't even be noticed. for photographic applications it might be relevant, but i'm no expert.
[Edited on 19-10-2012 by tetrahedron]
|
|
|
silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
The bath is being used to sensitize a collodion plate. Nitrocellulose suspended in ether and ethanol, with a small amount of KI and KBr is poured onto
an aluminum plate. After the solvents evaporate a bit the plate is submerged into the bath of silver nitrate and the plate becomes coated in silver
halides. Then in the dark it's transferred to the camera, etc etc.
I have heard that a "pinch" of KNO3 helps to whiten highlights. But this was way more than a pinch.
Thank you though your response was very helpful. I think I'll be back on this forum because I have always wanted to understand (conceptually, at
least) more about the photo chemistry involved in wet plate, but it seems no one has any idea on the photo forums.
|
|
|
tetrahedron
Hazard to Others
Posts: 210
Registered: 28-9-2012
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by silvergrahm  | | Nitrocellulose suspended in ether and ethanol, with a small amount of KI and KBr is poured onto an aluminum plate. After the solvents evaporate a bit
the plate is submerged into the bath of silver nitrate and the plate becomes coated in silver halides. |
thanks for explaining the process. it seems that the bath becomes naturally contaminated with K as part of it's normal operation. there must be an
upper limit to the concentration of K after which the quality of the plates starts suffering, check your literature. btw 6g KI corresponds to 1.4g K
or 3.6g KNO3.
how would you regenerate the AgNO3 solution normally? precipitate with copper and then redissolve in HNO3?
|
|
|
silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
Most of the literature is written by photographers. So, people tend to be very vague, and even describe the inconsistencies in the process in terms of
a necessary and even desirable "unpredictability." I certainly do not have a big enough brain to understand chemistry in depth but recently I have
been on a hunt to track down more info, because one really does run into a lot of problems with this process.
People calculate the % of AgNO3 initially and then maintain it with a standard gravity meter. So, currently my bath is reading 1.06. But, I understand
now that probably some of that is from other contaminants like KNO3.
I have never heard of anyone trying to reclaim silver from a bath. Although undoubtedly it has been done. Some people keep these baths in operation
more than a year doing nothing more than adding a pinch of AgNO3 after every dozen plates or so and, from time to time, putting the AgNO3 out to
"sun," which does indeed remove the silver halides floating around after filtration.
There may also be questions of cost effectiveness. This current 1200ml bath came to around $120. I have considered reclaiming the metallic silver off
of developed glass plates with nitric acid, but it would take many hundreds of plates I imagine before I would get a payback.
|
|
|
tetrahedron
Hazard to Others
Posts: 210
Registered: 28-9-2012
Member Is Offline
Mood: No Mood
|
|
you're probably right. photographic techniques developed over two centuries and only recently reached an acceptable level of predictability. the old
techniques are interesting mostly from an artistic standpoint. the $120 invested (it's not lost as long as you don't throw away anything) doesn't
sound too big an expense given the time and effort you're putting in. of course, from a commercial point of view the recovery of the silver is not a
competitive process at anything but large scale/cheap labor.
may i ask how you obtained the nitrocellulose suspension?
|
|
|
silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
It's called Collodion, USP. I got it direct from a company called mavidon. It's used to attach sensors to people's scalps for EEGs, or something. I
just dilute it with more ether and 95% ethanol.
I don't know what country you're in but in the US you can order diethyl ether right to your doorstep.
|
|
|
tetrahedron
Hazard to Others
Posts: 210
Registered: 28-9-2012
Member Is Offline
Mood: No Mood
|
|
interesting seller..i just checked their prices and they're predictably extortionate..if you wanna try a more ghetto method, get the nitrocellulose
from some ping pong balls ;p
|
|
|
Endimion17
International Hazard
Posts: 1468
Registered: 17-7-2011
Location: shores of a solar sea
Member Is Offline
Mood: speeding through time at the rate of 1 second per second
|
|
Hey, I think some sorf of "collodion" is used for making artificial scars. Like the one Ledger used in Dark Knight. You might want to check on that...
|
|
|
silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Endimion17 | | Hey, I think some sorf of "collodion" is used for making artificial scars. Like the one Ledger used in Dark Knight. You might want to check on that...
|
Yes, I've heard of that. I believe it is also sell an ether less type I. Drugs stores called "liquid band aid"
|
|
|
CHRIS25
National Hazard
Posts: 951
Registered: 6-4-2012
Location: Ireland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by silvergrahm | The bath is being used to sensitize a collodion plate. Nitrocellulose suspended in ether and ethanol, with a small amount of KI and KBr is poured onto
an aluminum plate. After the solvents evaporate a bit the plate is submerged into the bath of silver nitrate and the plate becomes coated in silver
halides. Then in the dark it's transferred to the camera, etc etc.
I have heard that a "pinch" of KNO3 helps to whiten highlights. But this was way more than a pinch.
Thank you though your response was very helpful. I think I'll be back on this forum because I have always wanted to understand (conceptually, at
least) more about the photo chemistry involved in wet plate, but it seems no one has any idea on the photo forums. |
Hi, I am a photographer also and was wondering which photo forums you refer to. Just in case, Photo.net has a very large darkroom photography member
list. Alternative photography forum is also very specialised. I know what you mean though about the lack of knowledge about the nitty gritty of
chemistry, I too like chemistry for its own sake and want to understand the engine behind every molecule, so although these people are very
knowledgeable about chemicals and processes, they naturally confine it to their immediate needs, which is understandable.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
|
|
|
silvergrahm
Harmless
Posts: 36
Registered: 19-10-2012
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by CHRIS25 | | Quote: Originally posted by silvergrahm | The bath is being used to sensitize a collodion plate. Nitrocellulose suspended in ether and ethanol, with a small amount of KI and KBr is poured onto
an aluminum plate. After the solvents evaporate a bit the plate is submerged into the bath of silver nitrate and the plate becomes coated in silver
halides. Then in the dark it's transferred to the camera, etc etc.
I have heard that a "pinch" of KNO3 helps to whiten highlights. But this was way more than a pinch.
Thank you though your response was very helpful. I think I'll be back on this forum because I have always wanted to understand (conceptually, at
least) more about the photo chemistry involved in wet plate, but it seems no one has any idea on the photo forums. |
Hi, I am a photographer also and was wondering which photo forums you refer to. Just in case, Photo.net has a very large darkroom photography member
list. Alternative photography forum is also very specialised. I know what you mean though about the lack of knowledge about the nitty gritty of
chemistry, I too like chemistry for its own sake and want to understand the engine behind every molecule, so although these people are very
knowledgeable about chemicals and processes, they naturally confine it to their immediate needs, which is understandable. |
I'd rather not say where precisely it was on the Internet. Let me assure you it was extremely specialized. Though I certainly respect the valid
experience of those members I wouldn't want them thinking I'm bad mouthing them.
Let me say that it is entirely possible to get great film based photographs by keeping a clean workspace and a consistent workflow. One does not need
even the slightest bit of knowledge about chemistry, you literally just follow the box. To get truly exceptional technical photos I would argue that
you only need the sparest of info on what is happening with the chemistry, namely the relationship between exposure time, development time and
temperture, and silver density on the negative.
For wet plate, though, there's a lot more involved, there are no manufacturer directions to follow, and a lot more goes wrong. Im sure that there are
people out there who know who re photographers, if I were to search a little harder.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
