newerthannew
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Chlorine Dioxide bleaching of paper
I'm a paper conservator in private practice and so I don't have access to all the equipment and supplies I should have. I am interested in making
small quantities of chlorine dioxide to bleach paper documents as I work with some fragile documents that cannot be bleached through aqueous methods
but only by vapour/gas treatments and I am only aware of chlorine dioxide as the only form of a gaseous bleach. I can build a safe plexiglass housing
so I don't poison myself (or others) but I was thinking of doing some "kitchen chemistry" and mixing sodium hypochlorite and vinegar to produce the
chlorine gas I am after. My question(s) are: what is the potential for explosive hazards (i.e at what concentration does chlorine dioxide gas
explode), what quantities of each constituent do I need to produce enough chlorine gas to bleach a document that is 8 1/2 X 10 1/4 in a chamber of
roughly 20X24X4? How do I neutralize the mixture after I'm done (add water?) I'm not 100% committed to the idea of using chlorine dioxide, but it
would make bleaching (and treatment) of certain objects a lot easier....
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Texium
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Well first of all, chlorine dioxide and chlorine are two different things. Second of all, most of the information that you need can be found by simply
going to Wikipedia and looking at the safety information on chlorine and chlorine dioxide. We have a policy here that before posting a new thread you
should try and do some basic research yourself. Also, this belongs in Beginnings rather than Organic Chemistry.
All that aside, welcome to the forum.
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Texium
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Thread Moved
16-1-2016 at 09:12 |
TheAlchemistPirate
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After reading the Wikipedia article on ClO2 I strongly suggest to stay far away from it. The risk alone is so unnecessary, not to mention the
difficulty you might have obtaining the chlorates or chlorites to generate it. IIRC from my chemistry kit book (Thames and Kosmos Chem 2000) dry
elemental chlorine gas can bleach papers too, without the risk of explosion when light is shown upon it. It was either chlorine gas or HCl gas that I
used.
If you use chlorine gas the setup should be like this:
Sealed chlorine gas generator ----> sealed container holding papers ---> NaOH solution (scrubs the chlorine gas to form NaClO and NaCl). This
apparatus would have some pressure inside it so you would have to build accordingly. You may also want to have different sizes of containers to hold
the various paper loads. Otherwise, when you open the apparatus, you may be met with a somewhat pressurized halogen in your face.
"Is this even science anymore?!"
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woelen
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Chlorine dioxide can easily be made from so-called MMS. This is sodium chlorite. A good affordable source (I have had good personal experience with
this source a few times) is
http://tulucechemicals.com/SODIUM-CHLORITE-WATER-PURIFICATIO...
From this chemical you can make ClO2 by adding hydrochloric acid. This operation is not without risk! ClO2 is fairly toxic (not as toxic as chlorine,
but still it is quite nasty and you should avoid inhaling the gas). The main risk, however, is that the gas is EXTREMELY explosive when concentrated.
If you want to use it for bleaching purposes, then you need to dilute the gas to less than 10%. Just to be absolutely safe, keep it below 5%.
You need to fill appr. 30 liters with a 5% mix of the gas. This requires appr. 10 grams of the product, sold by tulucechemicals to which you should
add 20 ml or so of conc. HCl. Safer is to mix the HCl with 1 part of water and then slowly add the NaClO2 to this. With air (e.g. from an aquarium
pump) bubbled through the liquid you could drive off the ClO2 and pass it into you container with the paper. You will need quite some apparatus and
some construction skills to make a safe bleaching chamber. At any cost avoid having more than 10% of ClO2 in your chamber. Otherwise you could have a
MASSIVE explosion!! I personally would not feel comfortable with more than 5% in the chamber.
The gas has a very strong yellow color, even at low concentration it is perfectly visible. The web page below shows the gas and some of its
properties. It is very different from chlorine and cannot be made from hypochlorite.
http://woelen.homescience.net/science/chem/exps/ClO2_propert...
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argyrium
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I am an objects conservator and don't deal w/ paper but am pretty sure ClO2 is old technology and better more benign treatments are presently being
used. I do occasionally work with a paper person here and could ask if you would provide more information.
You state that aqueous treatments are out - what is the nature of the staining and what type of paper is it?
You can U2U me off list if you like.
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papaya
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If I'm not mistaken there's one more gaseous agent to do that - SO2. Have no references, sorry, but just burning sulfur can easily prove me right or
wrong.
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woelen
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SO2 indeed can bleach certain substances, but it is a reductive bleach, while ClO2 is an oxidative bleach. This of course can make quite a big
difference. I am no expert in paper conservation and I would be very careful with whatever kind of bleach you intend to use. If the object is really
delicate and has large value, then I first would ask an expert in the field of (paper) conservation before I would start exposing it to all kinds of
potentially damaging chemicals.
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