Chemistry 101

Gerald C Koch · Sep 30, 2011

RPippin said:
I now always wear nitrale gloves when woking with developers, but sometimes they get into the glove on one hand

You might try using a barrier cream on your hands before putting on the gloves. There are two types, one for working with water and the other for oil based products. You want the former type. I got mine at the local pharmacy.

I am allergic to phenylenediamine and some color developing agents. Once you become sensitized to one developing agent you often become cross-sensitized for other ones. This is why I always discourage people from using ppd based developers. IMO, this developing agent is not necessary for todays finer grained emulsions.

A researcher in organic mercury compounds died a few years ago. She thought that her gloves would protect her and didn't immediately remove them after a sihgle drop of methyl mercury contacted one of them.

Roger Cole · Sep 30, 2011

How many people make their own emulsion? Clearly some do, and some of those have little knowledge and even less sense. How many people are working with methyl mercury, or even mercury salts for intensifiers nowadays?

That, I guess, was my point. Things like not adding water to acid we should know, granted, and using gloves for some stuff. Mask for mixing some powders. Other than that my darkroom chemistry is limited to "open a can of XXX developer...add to Y amount of water while stirring until dissolved, then add water to make Z.." or, at most, well tested published formula using the usual ingredients. I might use more or less sulphite or Kbr or benzotriazole than called for to tweak the results a bit but that's about it. For people doing no more than this it's no more hazardous than working with the stuff under the kitchen sink, as someone said - maybe less so. That requires care but should be a level of care we are all used to.

If you're messing with some of this other stuff without thoroughly researching what you're doing then, yeah, you're a Darwin award waiting to happen and these warnings are justified.

RPippin · Sep 30, 2011

Who was this guy Darwin? And how do I get one of those awards?

Athiril · Sep 30, 2011

Photo Engineer said:
There are several emulsion formulas floating around on the internet that were compiled by amateurs who know no chemistry. These in particular refer to making an acidified emulsion which uses citric acid during the make, and then which calls for ethyl alcohol to reduce bubbles or to aid in coating the emulsion. Well, this combination of Silver Nitrate, Citric Acid and either Methyl or Ethyl Alcohol is a route to disaster. Under the right conditions, it can form an explosive mixture! That is why I do not use acid in unwashed emulsions and why I use i-Propyl Alcohol.

Now, how many knew that one? Of course I am not aware of any explosions by this route, but then why take the chance. OTOH, maybe we have not heard from people who have had explosions from this reaction as they cannot report their experience to us!

PE

I knew about citrates and explosives... it's anhydrous form in the baking section is had for very cheap at the supermarket.

Athiril · Sep 30, 2011

Photo Engineer said:
I think that due to some recent posts and threads here on APUG, it became obvious that people are doing a lot of "experimenting" who have no knowledge of chemistry at all and Jerry has jumped in to help save them from possible grief.

I myself, have tried to prevent accidents when people were advised to heat chemicals in cook pots on the stove and etc..... Or, even heating chemicals in the microwave. All of these are dangerous practices that should not be done, especially for the average unprepared person. After years in the lab and seeing many accidents happen even to trained professionals, I advise caution of you are going into the "unknown" and ask the experts for advice.

PE

I hope people don't copy some of the things I do!

Bromine Gas Bleaching #2 by athiril, on Flickr

Rudeofus · Oct 1, 2011

Athiril said:
I hope people don't copy some of the things I do!

flickr supports your stance and threw a safe browsing warning when I wanted to see your pic

Roger Cole · Oct 1, 2011

RPippin said:
Who was this guy Darwin? And how do I get one of those awards?

http://www.darwinawards.com/

Athiril · Oct 1, 2011

Rudeofus said:
flickr supports your stance and threw a safe browsing warning when I wanted to see your pic

Actually flickr reviewed my account as safe, then marked it as restricted the next day, I complained and referred them to the previous review, they took it back, but then did it again the next day. Now they've ignored all my inquiries so far.

Gerald C Koch · Oct 3, 2011

Roger Cole said:
How many people make their own emulsion? Clearly some do, and some of those have little knowledge and even less sense. How many people are working with methyl mercury, or even mercury salts for intensifiers nowadays?

That, I guess, was my point. Things like not adding water to acid we should know, granted, and using gloves for some stuff. Mask for mixing some powders. Other than that my darkroom chemistry is limited to "open a can of XXX developer...add to Y amount of water while stirring until dissolved, then add water to make Z.." or, at most, well tested published formula using the usual ingredients. I might use more or less sulphite or Kbr or benzotriazole than called for to tweak the results a bit but that's about it. For people doing no more than this it's no more hazardous than working with the stuff under the kitchen sink, as someone said - maybe less so. That requires care but should be a level of care we are all used to.

If you're messing with some of this other stuff without thoroughly researching what you're doing then, yeah, you're a Darwin award waiting to happen and these warnings are justified.

I agree with your post particularly the last paragraph,

The point about the rubber gloves was to warn people who think that they are protected against all dangerous chemicals when wearing them is a false assumption. What's safe, what's not? I don't know. It appears that certain organic liquids readily penetrate them.

Photo Engineer · Oct 3, 2011

The chemicals commonly used in darkroom work do not easily penetrate either latex or vinyl gloves. It can happen, but it is quite uncommon with the things we usually use.

PE

brianmquinn · Oct 3, 2011

Just an FYI. Elemental Bromide will go right through a rubber glove in seconds (see post #55). I worked in lab with someone that was using it in a proper vented chemical hood. She was wearing rubber gloves and their left hand felt “itchy”. When she finished her work she peeled her gloves off and the skin of her left hand came off with the glove.

Photo Engineer · Oct 3, 2011

In photography, there is no need to use elemental Bromine. Any use of it is FAR outside the limits of photographic systems use or design.

So, what is the point?

PE

peeniwali · Oct 3, 2011

Mark your bottles so you and everyone else knows whats in that container.

A few years back I used to do wet bench work in a lab. There was a well worn container which had been marked years ago but the bitches brew it contained had long since been cooked off. if you worked in the lab you absolutely knew it was a vicious mix of nitric acid, hydrofluoric acid and glacial acetic. The mix was designed to cook metals quickly and effectively.
One day the boss came by to get a bottle of alcohol and go blow the frost off his windscreen. He mistakenly grabbed this brew of acid and walked out to his car. with no gloves he washed the windscreen using his bare hands. When the HF etched the glass he knew he was in trouble and ran for the snowbank to wash his hands. Were it not for the chilly winter night his fingers would have been gone, if the HF got into his bones possibly far worse. At the end of the day was it his fault for reaching for the wrong bottle in the lab or was it our fault for not clearly labeling the bottles we cooked with? As funny as we thought it was at the time it was of course our fault.

Kirk Keyes · Oct 4, 2011

Gerald C Koch said:
Then there are the strong acids; acetic acid 28% can cause burns.

Technically speaking, acetic acid is what's called a "weak acid".

Dispite that classification, concentrated acetic acid is corrosive, and attacks the skin.

Athiril · Oct 4, 2011

brianmquinn said:
Just an FYI. Elemental Bromide will go right through a rubber glove in seconds (see post #55). I worked in lab with someone that was using it in a proper vented chemical hood. She was wearing rubber gloves and their left hand felt itchy. When she finished her work she peeled her gloves off and the skin of her left hand came off with the glove.

It's not a problem with the amounts I use, I only 'fumigate' the film in a closed environment from a very small amount, which then I let air out.

Photo Engineer said:
In photography, there is no need to use elemental Bromine. Any use of it is FAR outside the limits of photographic systems use or design.

So, what is the point?

PE

I was 'dry' bleaching old film with very small amounts.

Kirk Keyes said:
Technically speaking, acetic acid is what's called a "weak acid".

Dispite that classification, concentrated acetic acid is corrosive, and attacks the skin.

Glacial acetic acid is a bit of a hazzard if you check out he MSDS, it's also an acid that literally burns.. as in combusts, and has a low flash point.

Bob-D659 · Oct 4, 2011

Here is a good read on "advanced chemistry". Dead Link Removed

Enjoy.

Gerald C Koch · Oct 4, 2011

Kirk Keyes said:
Technically speaking, acetic acid is what's called a "weak acid".

Dispite that classification, concentrated acetic acid is corrosive, and attacks the skin.

You're right, I should have phrased the sentence better. I did put a semicolon before the "acetic acid" to separate it from the first part of the sentence. What I wanted to express was that even a weak acid found in many darkrooms can cause burns.

peeniwali · Oct 4, 2011

When i used to cook with HF/Nitric/Acetic the acetic was the least of our worries even if the acetic was 99% pure. it was after all a semiconductor and optics lab so in theory we knew what we were doing. That said, I did watch a fellow burn himself quite badly with acetic. i was at a large, well known optics facility and had some prototype lens blanks used for IR lenses. There was a bit of mounting material left on the blank after I cut the metallic crystal to shape. I suggested the optician remove the material with some acetic which he did. However, he literally stuck his fingers into glacial acetic and promptly burned himself badly. I should have known he was unfamiliar with the material when he said: "you mean like vinegar?" His fingers swelled to 4x the nornmal size and were rock lobster red. I felt badly for him.

Photo Engineer · Oct 4, 2011

I'm wondering what you stored that HF solution in. Not a glass bottle for sure!!!

I knew of a guy who mistook HF for cleaning solution and put some on his pants. He flew across the Pacific! He started as Charlie and ended up as Charlene. No pain, no notice of loss with HF!!!!!! Just a bit of an itch!

PE

OzJohn · Oct 5, 2011

Didn't old time chemists call a mixture of nitric and hydrofluoric acids Aqua Regis because it reputedly was the only thing that could dissolve the noble metals? Not being a chemist I'm unsure what glacial acetic acid contributes to the power of this combination but I can certainly vouch for its corrosive powers on skin. I was not aware that it is flammable - you live and learn. OzJohn

K-G · Oct 5, 2011

OzJohn said:
Didn't old time chemists call a mixture of nitric and hydrofluoric acids Aqua Regis because it reputedly was the only thing that could dissolve the noble metals? Not being a chemist I'm unsure what glacial acetic acid contributes to the power of this combination but I can certainly vouch for its corrosive powers on skin. I was not aware that it is flammable - you live and learn. OzJohn

I think what you refer to is a mixture of nitric acid and hydrochloric acid or just sodium chloride ( normal cooking salt ) added to nitric acid. As long as you get the chloride ions into the nitric acid it works.

Karl-Gustaf

Athiril · Oct 5, 2011

OzJohn said:
Didn't old time chemists call a mixture of nitric and hydrofluoric acids Aqua Regis because it reputedly was the only thing that could dissolve the noble metals? Not being a chemist I'm unsure what glacial acetic acid contributes to the power of this combination but I can certainly vouch for its corrosive powers on skin. I was not aware that it is flammable - you live and learn. OzJohn

That's nitric acid and hydrochloric acid. Nice combination.

There is this one awesome example of it, being used to dissolve physcicist's gold nobel prizes, sparing it from a nazi raid during the war, the gold was precipitated out later and recast and presented to the physicists again.

Jim Chinn · Oct 5, 2011

As others have pointed out, the basic chemistry for B&W is pretty safe when common sense is used. But some photographers eventually begin to delve into the "dark arts" of mixing their own chemistry which involves working with raw compounds that can cause problems if not treated with respect. if one reads the MSDS for catechol (http://fscimage.fishersci.com/msds/04360.htm) you might just run, not walk away even though it is a compound in one of the best film developers you can make from scratch or from a kit.

As you move into the various realms of alternative processes, you begin to work with various carcinogenic compounds and heavy metals. Wet plate collodion uses a bunch of potentially harmful chemicals from cadmium, to silver nitrate to KCN yet it is one of the most rewarding of all photographic processes. The key is to treat all chemistry with respect and research any new process thoroughly with regards to the handling of chemicals.

nworth · Oct 5, 2011

ChristopherCoy said:
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?

Even the simple darkroom can be dangerous if you are careless. Packaged chemicals, used as directed, are reasonably safe. But even they can react with other things around the house to cause trouble. If you brew you own, you need to be more careful. There are several chemical incompatibilities that you need to be aware of because they can cause serious safety problems. Anschell and Troop's "The Film Developing Cookbook" gives some good guidelines and lists the more common chemical incompatibilities, as do several other photo darkroom books. Even something as simple as pouring developer into fixer can release a cloud of choking, dangerous ammonia gas. Concentrated or solid chemicals are usually more hazardous and generally more troublesome than the diluted solutions. Clean up spills thoroughly and promptly.

peeniwali · Oct 5, 2011

PE: HF is kept in an HDPE bottle. Sorry to hear about your she-friend's itch

Chemistry 101

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