Handling concentrated sulphuric acid (Reversal bleach)

timeUnit · Jan 25, 2006

Hello!

I'm embarking on a journey accompanied by very hazardous chemicals, as I'm trying to make enlarged negs with the "Negatives by reversal" method found on unblinkingyeye.com.

Unfortunately I'm not a chemist.

I would like some general advice on handling the sulphuric acid (disposing etc) and the potassium dichromate.

This I know. Never add water to an acid. Always add the acid to the water. Wear protective clothing, ie gloves, glasses, apron and face mask. The best would be a screen that covers my whole face, but I don't have one. Make sure all chemicals are stored away from kids, in tightly capped, labeled containers. Never eat, drink of smoke while handling chemicals.

Example: if I have a measuring cylinder (is it the right expression?) and want to measure the 50 ml of sulphuric acid in that, does the cylinder need to be BONE dry? Will any moisture in the cylinder start a chemical reaction and "boil" the acid? How do I clean the cylinder after having added the acid slowly to the distilled water? I'm thinking a bucket with say 10 liters of water, and slowly gently lowering the cylinder into the bucket to wash of most of the acid, then picking it up and washing it carefully in the sink.

The sulphuric acid isn't harmful to the environment once diluted and/or neutralised, right? I mean, the small amounts of acid washed down the drain should not be a problem?

When the reversal bath is used and is to be stored before disposal at an appropriate place, is there something the bath / baths cannot come in contact with? Developer, fix, etc. I've heard one should add the clearing bath to the reversal bleach as these would be slightly neutralised by this. True?

I know Ole does not like sulphuric acid, but is it worse than NaOH (sodium hydroxide), which is readily available at department stores?

Thanks for all advice, and please don't tell me to stay away from all this because I'm not a chemist.

Cheerio,
henning

avandesande · Jan 25, 2006

Many people don't realize this, but caustic burns (NaOH) are more damaging to tissue than acid burns. It is harder to wash off or out of your eyes. The scarring is worse, and they never seem to heal. In any case you want to handle with care!
I wouldn't pour acid into a graduate if there are any visible water droplets inside. A slight residue wont do anything. When you are done, just rinse the graduate in the sink really well. That is too small amount to worry about.

Sodium sulphate is used as fertilizer, a little bit down the drain wont hurt anything.

Sulphuric acid is available at department stores too. They sell bags of the stuff at sears for car batteries.

Robert Budding · Jan 25, 2006

Well, I was educated as a chemist, though I work in finance now.

The most important advice that I can give is always protect your eyes. Goggles are the best and they usually fit over prescription glasses. And be sure to wash your hands if you need to remove your goggles to scratch. Also wear rubber gloves - the heavy duty black ones that are sold in hardware stores. A rubber apron will protect your clothes to protect your body is good, too (I skipped this when working in labs as I wore a lab coat and we had safety showers).

Don't worry about adding water to the traces of acid left in your graduate cylinder when cleaning. It won't be a problem. And clean with plain water - it's cheaper than distilled.

You can handle sulphuric acid safely if your careful. But really take care to keep it away from children. A locked cabinet is best.

This reminds me of a reaction I had to run one in hydrofluoric acid - I used plastic because it was so acidic that it would dissolve glass. Now that was very nasty stuff.

timeUnit · Jan 25, 2006

avandesande said:
Sulphuric acid is available at department stores too. They sell bags of the stuff at sears for car batteries.

In the US, yes. NOT in Sweden or EU. We can't even get battery acid (diluted sulph. acid) here anymore. Which is fine by me, I might add. With the difficulties in getting these chemicals, it seems less likely that these chemicals end up in the hands of uneducated, inexperienced bozos. Like me...

Philippe-Georges · Jan 25, 2006

Henning,

Do not use Sulpheric acid if it is not needed, try this AGFA-GEVAERT formulla:

bleach :
K2Cr2O7 5 g./1l. (= Kaliumbichromaat)
NaHSO4 20 g./1l. (= Natriumbisulfaat)
3 min @ 24°c

claering bath :
K2S2O5 christals 65 g./1l. (= Kaliummetabisulfiet krist.)
5 min @ 24°C
The clearing bath is not the same as for the Sulpheric acid based bleach!

Good luck,
Philippe

P.S. i do not know the right names in English, sorry.

eumenius · Jan 25, 2006

Henning,
I can only say that all the directions above are quite correct. But we should not forget about the bichromate, that is more dangerous than the acid. Never touch its dry powder or a bleach bath with bare hands, especially if you have hangnails/scratches on skin. If it come in contact with your skin somehow, wash it of quick with plenty of water, and perhaps rub some baking soda over the spot. Keep it well locked, so no one could inadvertenly drink it (storing reagents in food containers, e. g. soda water - always bad idea). Yes, I also recommend bichromate bleach instead of permanganate - it works cleaner, on my opinion. I always mix 5l jug of the bleach, and take from it as much as I need for single development, then I pour the used bath away (we don't have here any service for proper disposal, alas).

Regards, Zhenya

Gerald Koch · Jan 25, 2006

Sulfuric acid, even dilute, can have a serious effect on your wardrobe. Wear a rubber or plastic apron when working with it. Small splatters which may not be evident when they occur will become holes after the clothing is washed.

Sodium bisulfate (sodium acid sulfite, sodium hydrogen sulfate) which is a solid, and easier to handle, can be substituted in most applications calling for sulfuric acid . Sodium bisulfate comes in two forms; anhydrous and the monohydrate. You can substitute 4.4 grams of the anhydrous or 5.1 grams of the monohydrate for every ml of conc sulfuric acid. Sodium bisulfate, monohydrate is sold to lower the pH in swimming pools. One brand is pH Minus.

Struan Gray · Jan 25, 2006

Henning, do you have any contacts at Chalmers or HFF? Signing up for a course there, or at Folkuniversitet if they have photo options, would be one way of getting supplies from the Nordic Laboratory suppliers.

Sulphuric Acid you can send down the drain, although in large amounts it can corrode some pipework or attack the caulking at junctions.

Potassium Dichromate you absolutely must not flush down the drain. Talk to whoever handles domestic waste in Göteborg to see how they recommend you drop it off to them once you have used it. Alternately, contact a skyddsombud at one of the educational institutions and see what they do. Here at Lund there is a central university disposal unit for such chemicals and I would be very surprised if Chalmers didn't have something similar. If you are only using small amounts they may let you piggy back off their system.

NaOH burns are worse than Sulphuric Acid ones, and strong alkalis will attack glass bottles (or weld the stopper on) faster than you think. On the other hand, Sulphuric acid is usually sold in concentrated form, and then you have the fumes and the hydrophilia to cope with. Not a big deal if you treat it with respect, but I wouldn't have it anywhere that young kids can get at.

eumenius · Jan 25, 2006

Pardon me, but the concentrated sulphuric acid does not give off any fumes - you've probably mistaken it for nitric or hydrochloric acid. In chemistry labs, the large dessication jars are filled with H2SO4 in their lower part, so it takes water from, say, filters being dried.

Struan Gray said:
On the other hand, Sulphuric acid is usually sold in concentrated form, and then you have the fumes and the hydrophilia to cope with. Not a big deal if you treat it with respect, but I wouldn't have it anywhere that young kids can get at.

Struan Gray · Jan 25, 2006

eumenius said:
Pardon me, but the concentrated sulphuric acid does not give off any fumes

It does if you put it in a wet beaker

I agree that it is not as bad as other inorganic acids. However, take a deep sniff near an open beaker of the stuff and you'll know all about it. Do the same near even a saturated solution of NaOH and you won't notice a thing.

I have spent a fair bit of my working life dipping bits of silicon into sulphuric acid and bits of tungsten into 2M NaOH. I know which I prefer to be around.

Jordan · Jan 25, 2006

The vapours from concentrated H2SO4 will chemically damage certain materials placed nearby -- I'm pretty sure of that.

The main danger with H2SO4, besides the burns, is its highly exothermic dissolution in water (which is why we add it to water -- which absorbs the heat and prevents spattering -- and not vice-versa). Your mixing container could become literally too hot to hold. Same goes for when you clean out your measuring containers.

For my B&W reversal needs I've been using a bleach composed of 65 g/L sodium bisulfate (pH Minus swimming-pool additive) and 10 g/L potassium dichromate. This is an efficient, stable bleach that (when fresh) does its work in well under two minutes.

I am a practicing chemist and wouldn't want to handle concentrated sulfuric acid outside of a fume hood (i.e. at home). Dichromates are nasty too, but since they are crystalline, inhalation/ingestion is not much of a risk (when they are handled carefully).

Your clearing bath should be composed of sodium sulfite (I use a 5% aqueous sodium sulfite solution). Metabisulfite clearing baths are used after permanganate bleaches and are not recommended for use after dichromate bleaches (I'm not 100% sure why, I have to review the chemistry of them.) After it's been used once, I find that the metabisulfite clearing baths develop a rather nasty sharp SO2 odour -- another reason to avoid them.

Any small spills of dichromate bleach can be neutralized before clean-up by treating them with a little bit of your clearing bath, which will reduce the Cr(VI) to the much less toxic Cr(III) and Cr(II).

Struan Gray · Jan 25, 2006

Just to be clear: my comment in the dichromate was motivated by Swedish environmental laws. Discharging Chromium ions in any oxidation state is illegal. Any large town will have a place you can send your collected waste, usually for free, but I don't know where that is in Göteborg. You just need to find the right 'gubbe' to ask.

FWIW, I am a physicist, was a Docent at Lund University and for many years was the Safety Officer for my Department.

timeUnit · Jan 25, 2006

Thank you everyone. It seems there are different views on the sulphuric acid.

Jordan,
have you checked out the Negatives by reversal article on unblinkingeye? Would you say I'm at risk of getting hot containers when mixing 50 ml of sulphric acid into 700 ml of distilled water? Should I start with very cold water? I can easily lower the temperature to 5°C or so, as it's winter here.

Some posters said I could wash the graduate in running water. From what Jordan writes I think it sounds like a bad idea. Can anyone clear this up?

All in all, do you recommend me NOT making this reversal bleach, trying something else instead? I have already ordered the chemicals.

Of course, if I had a lab and a fume hood I would use it. I will do this by the sink in my darkroom, not at home. I will try to be as careful as I possibly can, and not being alone while handling the chemicals. If I mess up someone will be able to help me and/or call the ambulance, but let's not hope for that happening.

timeUnit · Jan 25, 2006

Struan Gray said:
Just to be clear: my comment in the dichromate was motivated by Swedish environmental laws. Discharging Chromium ions in any oxidation state is illegal. Any large town will have a place you can send your collected waste, usually for free, but I don't know where that is in Göteborg. You just need to find the right 'gubbe' to ask.

FWIW, I am a physicist, was a Docent at Lund University and for many years was the Safety Officer for my Department.

I will leave the waste CLEARLY LABELED, at my local miljöstation, where I leave spent fixer etc. To be honest, I will not contact the environmental authorities in this matter as I'm already doing this illegally. I don't have a degree in chemistry, I don't have a lab that follows the very strict regulations of swedish environmental law. Getting a permit for this would most probably be impossible. If I knew someone at Chalmers college I would contact them, but I don't. Or maybe I do... will check out.

Aggie · Jan 25, 2006

A really cheap source of sulfuric acid is at pool supply stores. It's the acid they use to balance the ph in swimming pools. In other words if you swim in a pool you are swimming in some very dilute acid. In California the last time I bought the acid, it cost me $5 for 2 one gallon jugs. That was in 1999. All you have to do if you want to make sure that it is nuetralized before you dump it is put baking soda in it until it stops fizzing. That was all that was required by law in California before we dumped our acid solutions down the drain after using them in the pickling process for jewelry.

Claire Senft · Jan 25, 2006

Others have given you much better advice than could I. I would add only one thought. If you have Potassium Ferricyanide in your darkroom make very certain that they can not come in contact with each other because the effects could be deadly and the dead would not necessarily include you.

avandesande · Jan 25, 2006

It's all a matter of degree. It will probably fizzle and spatter a bit, but the quicker you get the water in there the better. I have rinsed graduates in a sink with sulphuric acid on them before. Since the amount is small, and you are wearing goggles and apron, you dont have much to worry about.

The classic case is when someone adds water to acid, it spatters all over and they drop the container they are working with out of suprise, creating a bigger mess.

Also in the unlikely event you get conc sulfuric on yourself, DO NOT wash it off. The exotherm will burn you, and when the acid is hot/diluted it will react with your skin more readily. remove contaminated clothing immediatly, and wipe as much of it off of your skin as possible. Then you can rinse with water.

Once I was working in a plant with a lithium amide salt dissolved in tetrahydrofuran. This stuff would spontaniously inflame. One of my thoughtful coworkers forgot to clear a hose and when I picked it up, a couple cups of this stuff went down the front of my pants.
I stripped down to my underwear and got under a safety shower in about two seconds. Not fun having to walk back to the locker room naked in the middle of the winter.

On another occasion one of my coworkers had dumped a barrel of caustic soda beads into a tank to neutralize something. The water was hot and when he tossed them in it boiled and he was soaked, the entire front of his body is covered with ugly scars now.

It is important to understand the properties of what you are working with and be prepared to deal with situations that come up.

timeUnit said:
Some posters said I could wash the graduate in running water. From what Jordan writes I think it sounds like a bad idea. Can anyone clear this up?

Tammyk · Jan 25, 2006

I would suggest looking on-line at the MSDS (Material Safety Data Sheets) for more safety information on the chemicals you will be using.

There are certain reactions that can happen during storage, or if a spill should occur, between some of the chemicals that you are handling. The MSDS can advise safe storage and handling, disposal, and what to do in case of spills, exposure, etc.

Whenever handling larger quantities of more conc. NaOH or acids PLEASE wear eye protection in the form of goggles. I knew a man working with a face shield with NaOH preparation and somehow a droplet flew up and over his shield and into his eye. The eye was permanently damaged, even with access to an eye wash.

I would also recommend purchasing a bottle (they come in 500mL for example) of buffered eyewash solution and have it on hand. It's amazing how a little acid or base in the eye can render one completely useless, and if your sink is already occupying an ice-bath, you should have ready access to another clean and buffered water source.

~Tammy

Struan Gray · Jan 25, 2006

Henning, I was surprised at how helpful and ready to be flexible the various environmental health people I came across were. Perhaps it's just Lund, but I would turn to them again if I were doing what you were doing.

There is no reason you shouldn't use dichromates and strong acids for your own hobbies. I hope I didn't give the impresssion that they should be reserved for august institutions. I wanted more to let you know that there are people who are willing and able to help the serious enthusiast on an informal basis, if only with information.

FWIW, on the sulphuric acid front, I would happily wash glasswear with a few drops remaining in it under running water. The acid-into-water rule, and recommendations for fume cupboards is for beakers with a reasonable amount of liquid that might be dropped. If you are wearing eye protection, gloves and an apron/labcoat there is no reason not to wash off a few residual drops directly.

Jordan · Jan 25, 2006

Henning, as the others have mentioned, the running water isn't a problem. The heat of mixing is really only a big deal when you add water slowly to acid -- if you quickly flood the container with water, the exotherm won't be a big problem. (Don't splash it in your eyes!)

I agree with avandesande that the best thing is to imagine anything that could go wrong, and to prepare ahead for it (make a plan)... and that lithium amide story is pretty sad. I can't imagine working with it on a plant scale. A few grams at a time is fine.

Once I was doing a trans-metalation reaction at -78C using tert-butyllithium. It ended up precipitating during the addition, and the re-dissolution as the reaction warmed up was VERY EXOTHERMIC... not a pretty sight.

Don't be too scared of sulfuric acid -- use your head and you'll be fine -- but if you can find "pH Minus" or another swimming-pool-supply source of sodium bisulfate, it'll be much more convenient.

timeUnit · Jan 25, 2006

Claire Senft said:
Others have given you much better advice than could I. I would add only one thought. If you have Potassium Ferricyanide in your darkroom make very certain that they can not come in contact with each other because the effects could be deadly and the dead would not necessarily include you.

Thanks for the thought, it has entered my mind. I'm thinking right now of a good way to keep these chemicals safe from eachother and other people. Potassium ferricyanide, or as I think it's called in Sweden kaliumhexacyanoferrat (III), can turn into cyanide gas if exposed to heat or an acid. The Pot. ferri. will probably be stored at my friends darkroom. Safe enough?

timeUnit · Jan 25, 2006

And thank you everyone for your tips! I feel a little more prepared for the task now. I'm also glad I'm not dealing with barrelfuls of these things...

nworth · Jan 25, 2006

Back to the original topic. You are right to be concerned about handling concentrated sulfuric acid. It is a heavy, viscous liquid that can be quite difficult. The measuring container should be dry, although a speck of moisture will not be a problem. Concentrated sulfuric acid does emit noxious fumes (sulfur dioxide) in a moist or even high humidity situation. They are not usually a problem unless you really get your nose in them. If you spill any of the acid, immediately (_immediately_!!!) flood the area of the spill with plenty of water, and keep the water going for several minutes. If you spill it on your clothing, strip off the clothing immediately and flood any area that may even possibly touched the acid with water. Then wash out the clothing, which will be ruined. This sort of thing happens all the time in the lab, which is why lab workers wear safety glasses and all sorts of protective gear. At the very least, wear glasses and an apron. Rubber gloves help too, if you can handle the glassware decently with them.

The substitute bleach using sodium bisulfate is probably a good idea. The bisulfate forms (dilute) sulfuric acid when it is dissolved in water. Dichromate is a possible carcinogen, but it is OK to handle small quantities (and even dispose of them down the drain in most places) without any significant danger. Permanganate has been used as a substitute bleach, but I don't have a formula handy. You might check the Kodak website under motion picture processing. (I think the document is H-34, but I'm not sure.)

timeUnit · Jan 26, 2006

nworth said:
Back to the original topic. You are right to be concerned about handling concentrated sulfuric acid. It is a heavy, viscous liquid that can be quite difficult.

Yes, I have read it's quite viscous. The advantage to that is that it "moves" slowly, and is less likely to splash everywhere if my hands are a bit unsteady.

Handling concentrated sulphuric acid (Reversal bleach)

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