Chemistry 101

[Gerald C Koch]

It is strange to have to post this on a site devoted to photography. I always thought photography was about taking pictures. (Yes, I know that there are those that still seek to find the grail.)

As a former graduate student and someone who has taught chemistry I have seen the results of some rather horrific accidents. The first thing that a person learns in chemistry 101 is never mix together two chemicals unless you know what is going to happen. Remember that plain water is also a chemical. Just because you can buy something in a local store does not means that it is safe. Such chemicals as lye (sodium hydroxide) can cause serious physical injury. Milder alkalis such as washing soda (sodium carbonate) can cause blindness. Then there are the strong acids; acetic acid 28% can cause burns. Oxidants like potassium dichromate or potassium permanganate can cause fires or even explosions. Solvents such as glycols and TEA are dangerous when heated (toxic vapors and fire hazard).

If you insist on experimenting at the very least read the Material Safety Data Sheets (MSDS) for everything you will be using. If you don't understand what you have read then seek advice. Invest in a pair of safety googles. A face shield would be even better. If you have no knowledge of chemistry then please just take pictures. I'm not saying this to be dramatic but I cringe when I read some of the posts.

 

[removed account4]

If you insist on experimenting at the very least read the Material Safety Data Sheets (MSDS) for everything you will be using. If you don't understand what you have read then seek advice. Invest in a pair of safety googles. A face shield would be even better. If you have no knowledge of chemistry then please just take pictures. I'm not saying this to be dramatic but I cringe when I read some of the posts.

i agree 100% jerry !

 

[Monito]

+1

Never pour water into acid when diluting. Pour acid into water, carefully in no hurry. Reason: the dilution is exothermic (gives out heat) and it is worse to have hot slightly diluted acid boiling up than to have hot slightly acidic water boiling up.

 

[Photo Engineer]

Right on Jerry!

PE

 

[Klainmeister]

Yes, this is important, and maybe we should devote some time for a sticky with basic info regarding the most common photo chemical components and what they do.

 

[michaelbsc]

Here is the trick I always used to remember to pour the acid into the water.

A sub's battery needs to be topped off regularly. And a sub is in the ocean - big pond of water. You can pour the acid into the ocean, but you cannot pour the ocean into the acid.

It's easier to remember the trick than do the thermal analysis of the reaction. Of course if you don't have my experiences that memory trick might not mean much to you.

 

[ChristopherCoy]

In a basic darkroom, what is the danger level? What could possibly happen?

For instance, I've got three chemicals - Dektol, Kodak indicator stop bath, and Fixer. How harmful are those chemicals really? (other than ingestion or eye splashes?)

Is Dektol going to eat through the skin? Countertop? Will the combo of Fixer and Dektol create a toxic gas?

Its awesome that you put out a public warning as a chemistry teacher, but for those of use who are absolutely NOT interested in studying chemistry, WHY is safety important? What kinds of accidents are possible with basic chemicals?

 

[Monito]

Here is the trick I always used to remember to pour the acid into the water.

It's even easier than that. Remember, hot/boiling water is less dangerous than hot/boiling acid.

 

[MattKing]

In a basic darkroom, what is the danger level? What could possibly happen?

For instance, I've got three chemicals - Dektol, Kodak indicator stop bath, and Fixer. How harmful are those chemicals really? (other than ingestion or eye splashes?)

Is Dektol going to eat through the skin? Countertop? Will the combo of Fixer and Dektol create a toxic gas?

Its awesome that you put out a public warning as a chemistry teacher, but for those of use who are absolutely NOT interested in studying chemistry, WHY is safety important? What kinds of accidents are possible with basic chemicals?

With working strength solutions:

Don't drink any of them, don't get any in your eyes and if you spill any of them, clean them up.

Dektol might lead to problems for some people in terms of contact allergies - it is never unwise to minimize contact with the skin. I say that despite the fact that I have essentially ignored my own good advice on this subject for 40+ years, without problem.

If you spill fixer on your clothes, it sometimes doesn't wash out well

Dektol, stop bath and fixer aren't going to interact in any potentially harmful way.

Concentrated stop bath is fairly strongly acidic, so a bit extra care is required with it. It is a bad idea to carelessly pour developer into it.

 

[Toffle]

Its awesome that you put out a public warning as a chemistry teacher, but for those of use who are absolutely NOT interested in studying chemistry, WHY is safety important?

Because you use chemistry in your darkroom. It is not necessary to have a full knowledge of chemical processes, but safety is always important. MSDS sheets are readily available and actually make for interesting reading. Short of a chemistry class, they are perhaps the quickest way to learn the safe use and disposal of darkroom chemicals.

Start here... they're not that bad.

 

[richard ide]

I completely agree with you Gerald. Another important item which seems to rear it's head here is: Never ever put a chemical in a bottle which could be mistaken for a beverage. Besides not tasting good; there is a real possibility of serious harm.

 

[Monito]

Do not dispose used fixer down the drain. It will kill necessary bacteria at the sewage plant and will deposit toxic heavy metal ions in the environment. Recover the silver or dispose of at a hazardous waste facility.

 

[Photo Engineer]

And remember, that all of this is used against analog photographers by digital photographers. Ho hum.

PE

 

[Roger Cole]

Do not dispose used fixer down the drain. It will kill necessary bacteria at the sewage plant and will deposit toxic heavy metal ions in the environment. Recover the silver or dispose of at a hazardous waste facility.

Are you so sure of that in normal hobbyist quantities? It contains silver ion but the ions won't stay ions for long in nature much less a sewage plant. Metallic silver is microbicidal but in hobbyist quantities is it really any worse than washing with antibacterial soap and washing it down the drain?

 

[OzJohn]

I congratulate Gerald for starting this thread. He has said what has needed to be said on this and several other forums. I am not a chemist but I studied, enjoyed and absorbed the subject in high school and at introductory college level. I probably know just enough to understand how little I really do know but certainly enough for it to have been useful in a 40 year photography career (I am totally out of my depth when guys like PE who are chemists discuss things like organic synthesis).
The lack of knowledge of chemistry displayed by people who propose mixing wierd and wonderful concoctions appalls me. People who don't seem to even understand the purpose of the components in a simple developer write seeking help as to the possible effect of adding some obscure chemical they have read about that is most likely unobtainable in any modest quantity.
I saw last year on another forum a suggestion that it was cheaper to make silver nitrate from scrap silver and nitric acid than to buy the substance. The guy who made the suggestion was under the impression that this reaction produced silver nitrate and water - as it does but he was unaware of the deadly nitric oxide also produced. There is also a video on YouTube that demonstrates this reaction but some good samaritan who cautions about the dangers also gets it wrong by saying that the gas produced is nitrogen dioxide (also dangerous but at least it is brown so you can see it).
As others have said, you can fully enjoy photography, including the darkroom, without knowing much about chemistry apart from general common sense safety precautions but if you want to start mixing chemicals together for any purpose you owe it to yourself and others to learn some chemistry. OzJohn

 

[Maris]

Are you so sure of that in normal hobbyist quantities? It contains silver ion but the ions won't stay ions for long in nature much less a sewage plant. Metallic silver is microbicidal but in hobbyist quantities is it really any worse than washing with antibacterial soap and washing it down the drain?

Roger Cole is right. In moderate quantities (pounds, not tons) silver tetrathionate and similar compounds which characterise used fixer don't harm sewerage treatment systems. The silver very quickly gets converted to silver sulphide in the presence of the free sulphide ion. Silver sulphide is geologically stable and inert and has one of the lowest solubility products known in chemistry. The stability and inertness of silver sulphide is the key to the remarkable archival properties of sepia toned photographs.

Before my darkroom was approved by my local council I had to calculate the silver concentration in my total household effluent. I'm pretty busy and use a few thousand sheets of film and paper per year but the result came to about 5 parts per billion. By the time this mixes with the output of the other 20 000 households that don't process photographic materials the silver concentration is below any conceivable detection limit down at the sewerage treatment plant.

 

[MattKing]

Do not dispose used fixer down the drain. It will kill necessary bacteria at the sewage plant and will deposit toxic heavy metal ions in the environment. Recover the silver or dispose of at a hazardous waste facility.

It is a good idea to recover silver, but used fixer doesn't contain enough silver to cause damage unless you produce relatively huge quantities.

If you are looking for a way to recover silver, check with jnanian here on APUG - he sells a unit that can do this for you.

 

[Monito]

It may be true that we can get away with disposing silver down the sewers with little environmental impact, but I still think it is not responsible unless it is really necessary. There is so little mercury in batteries, for example, yet we are strongly encouraged to keep them out of landfills. I have only just recently begun fixing (and developing) again after many years not doing it, during which environmental awareness and understanding has increased.

Perhaps the silver ions get bound up with sulfide but that material gets deposited somewhere. Environmental leaching is much harsher than what a gallery print experiences. Further, microbes and invertebrates eat it and digestion can free up the ions again in the food chain.

An added reason to recover silver is the value of the metal. It is likely that the quantities we can recover can hardly repay us for our time as an economic activity, but if nothing else it appeals to my hobbyist side. I have researched a little about the electrical requirements and would like to design and make a simple solar powered recovery system, which would require only a small cell area I think (rough estimate less than a square foot).

So, dump your silver if you insist, but I think we can do better. Doing better would either be the responsible thing to do or it would be good PR by appearing to be responsible.

 

[Steve Smith]

Before my darkroom was approved by my local council

You have a council approved darkroom?


Steve.

 

[ruilourosa]

a little explosion and some toxicity gives a adrenalin rush not possible with digital photography...

 

[removed account4]

silver is getting $31.90 / troy oz ...
dumping your spent fixer down the drain is the same as dumping
money down the drain, not to mention in some places it is illegal and punishable by a stiff fine.

if anyone is interested in a silver magnet
feel free to contact me for the details ...
i don't do the "hard-sell" but i will give you the facts
and help you get set up if you decide to make $$ from your spent fixer ...

thanks matt!

 

[Rudeofus]

Never pour water into acid when diluting. Pour acid into water, carefully in no hurry. Reason: the dilution is exothermic (gives out heat) and it is worse to have hot slightly diluted acid boiling up than to have hot slightly acidic water boiling up.

That's a nice rule but if you read what has been posted here just this week you'll realize that this is just a side issue. If you use KCN as fixer, as has been suggested by someone, just imagine what happens if you decide you also "need" an acidic stop bath.

It's a good thing that most of the really dangerous chemicals are not sold to ordinary people - otherwise the whole photographic community would have qualified for the Darwin awards many years in succession. I commend Gerald for bringing up this important issue here in this forum and call on all experts who post helpful recipes that they also include some information about the hazards their concoctions can bring with them or at least point out that people without experience and proper facilities should stay away from these mixtures.

 

[ChristopherCoy]

So basically,

-dont drink your fixer
-dont take a bubble bath with your developer
-and don't go mixing things in manners the instructions don't tell you to.

Isn't all of that known as common sense?

 

[artonpaper]

I tell my students that the standard black and white sink line chemicals are comparable to those found under the kitchen sink. Avoid skin contact, keep your face away from the tray and wash up after a darkroom session. Flush any areas that suffer contact with plenty of water. I then explain that mixing household products also have hazards, such as mixing bleach and ammonia which can be fatal and that certain chemicals used in advanced processes can have a similar reaction, such as ferric cyanide and acids. When working with chemicals always proceed with caution.

 

[K-G]

So basically,

-dont drink your fixer
-dont take a bubble bath with your developer
-and don't go mixing things in manners the instructions don't tell you to.

Isn't all of that known as common sense?

Correct , but the total amount of common sense seems to be shrinking at the same pace as the polar caps do.

Karl-Gustaf