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Filter paper and Sulphuric Acid


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#1 dan19_83

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Posted 22 March 2005 - 06:53 PM

Last week I was filtering a high concentration solution of H2SO4 solution with some standard filter paper. Once this was done, I placed it in a oven at around 110 degrees C to dry. When I took it out after about twenty minutes, I noticed that the filter paper had changed to a black colour and that it had degraded and of course I had lost my damn results! :mad:

Does anybody know what is happening here? I've also try this with Nitric acid and HCl and my results have worked out ok.
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#2 collector

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Posted 22 March 2005 - 07:36 PM

Sulfuric acid readilly absorbs water from organic material even at room temperature.
the absorbation is exothermic, as observed when mixing the acid with water.

At elevated temperatuers, the organic matter is simply destroyed by the acid.
Sugar is chemically decomposed when the acid absorbs water, and the residue is mainly carbon (coal). The same applies to paper (cellulose), and also in this case the residue is coal.
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#3 jdurg

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Posted 22 March 2005 - 08:04 PM

Yup. Concentrated H2SO4 will readily dehydrate a carbohydrate, and as collector has pointed out, paper is many cellulose which is technically a carbohydrate. The reaction of sucrose and concentrated sulfuric acid is a classic introductory chemistry demonstration. :D
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#4 dan19_83

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Posted 22 March 2005 - 08:58 PM

cheers folks. I guess good ole HCl will have to do!!
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#5 YT2095

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Posted 23 March 2005 - 08:43 AM

in future, use Rock Wool to filter sulphuric acid with, it`s not reactive and can`t cause a fire :)
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#6 budullewraagh

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Posted 23 March 2005 - 10:44 PM

i suggest you be careful with conc h2so4. if you aren't careful it will reduce to H2S
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#7 YT2095

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Posted 23 March 2005 - 11:06 PM

that`s never once happened to me, even in the days when I knew very little!

granted it CAN happen, but it`s not likely under ordinary circs :)
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#8 budullewraagh

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Posted 24 March 2005 - 12:10 AM

happened to me, and i wasnt doing too much of an oxidation reaction
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#9 dan19_83

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Posted 24 March 2005 - 08:37 PM

can't say it's ever happened to me either.

so what does H2S smell like?! any side effects?
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#10 jdurg

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Posted 24 March 2005 - 10:08 PM

H2S smells like rotting eggs and the side effects of inhalation are a numbness of your scent receptors followed by death. It's a poisonous gas just as hydrogen cyanide is. Thankfully, the human nose can detect hydrogen sulfide faaaaaaaaaaaaaaaaaar before it gets to toxic/lethal levels. The only problem is that it does numb your ability to smell so after a short while you can't smell it any more. (As a kind of gross side note, a bit of hydrogen sulfide is sometimes contained in human flatulence. As a result, when you pass gas you can usually smell it quite strongly right away, but after a while you can't notice it anymore. If a different person comes into the area, however, they'll probably smell it quite a bit. This just shows how sensitive our noses are to H2S since it's a pretty toxic gas but we can sense it before it even comes close to being bad).
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#11 budullewraagh

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Posted 24 March 2005 - 11:34 PM

you don't want to be near it. don't try to produce it at home
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#12 dan19_83

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Posted 25 March 2005 - 12:09 PM

According to jdurg, I produce it ever day!! :D
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#13 budullewraagh

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Posted 25 March 2005 - 12:32 PM

well, in minute quantities
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