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  1. #1

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    Handling concentrated sulphuric acid (Reversal bleach)

    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

  2. #2

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    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.
    art is about managing compromise

  3. #3

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    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.

  4. #4

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    Quote Originally Posted by avandesande
    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...

  5. #5
    Philippe-Georges's Avatar
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    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.

  6. #6

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    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

  7. #7

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    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.

  8. #8
    Struan Gray's Avatar
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    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.

  9. #9

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    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.

    Quote Originally Posted by Struan Gray
    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.

  10. #10
    Struan Gray's Avatar
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    Quote Originally Posted by eumenius
    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.

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