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aga
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Starch-Iodide Test Papers
One of the remaining items needed to follow magpie's Congo Red synth is some starch-iodide test paper.
Apparently it is a good test for strong oxidisers, such as H2O2, Cl2 etc.
Incredibly simple to make from starch, KI and some filter paper :
https://www.youtube.com/watch?v=ztXFWo0DyWk
Add about 150ml water to a beaker, 1g starch, 1 spatula of KI, heat up with stirring, dunk in some filter paper, hang it up to dry, then cut into
strips. Done !
Works too. Slightly damp, this strip instantly changed colour when exposed to the slightest whiff of chlorine :
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Velzee
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(Yay! One of my favorite dudes is back!!)
Yep! I've heard of this before, but I don't think I've seen it done. Thank you, aga, for the video and post!
Check out the ScienceMadness Wiki: http://www.sciencemadness.org/smwiki/index.php/Main_Page
"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."
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—Saint José Sánchez del Río |
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aga
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Thanks for the thanks !
It is always good to know how to make all the stuff you need, so this seemed like a good (and easy) thing to make.
Basically ScienceMadness is the Best chemistry forum ever.
It's also very much like a drug : once hooked, there is no way out.
Whilst wandering in the Wilderness for the past few weeks, i encountered a few other SM exiles.
Likely some will return one day, hopefully soon.
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Magpie
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You can also make lead acetate paper for the detection of H2S.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Wha !
I think my nose will pick it up sooner !
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aga
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Normal Saturday afternoon, neutralising some conc sulphuric acid that is laden with dissolved Cl2 as usual, and the gas pours out of the
beaker, so i thought i'd try out those test papers versus universal pH papers.
 
The home-made one at least shows something (clearly unevenly coated) and amazingly the gas just bleaches the bejeesus out of the pH paper !
A shiny new nut-n-bolt was put in a beaker and had a little gas poured over it, then was left covered for 20 mins.
Definitely not nice stuff that chlorine !
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NEMO-Chemistry
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No thread would be complete without a stupid question, so i feel its my duty to ask it.
I take it starch is starch? What i mean is you can get corn starch, tapioca starch, potato starch and so on. So does it matter what starch?
I think making them is a much better idea, saves buying in booklets that degrade in the back of the cupboard.
As for chlorine, it makes you wonder what that last sniff you had did to the lungs! I think generally the population as a whole dont think chlorine
thats bad, we are so used to it in bleach and swimming pools etc.
I dont think too many people (general population not people messing with chemicals) take chlorine that seriously, shocking when you see what it can
do.
Cool experiment BTW, i have some KI so i will give this a go.
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j_sum1
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Chlorine is colloquial for any chemical containing chlorine atoms. I have come across many people who think that chlorine is a solid white substance
-- after all, pool chlorine is a white powder.
So we (again) get a chemical term that has entered common parlance with people having no idea of its properties.
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aga
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I used potato starch.
https://www.youtube.com/watch?v=PgKR6EsKl5I
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Metacelsus
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Anything with amylose will work, so corn, potato, and tapioca starch will all be good.
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NEMO-Chemistry
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At last i have something i can do with 2kg of tapioca starch!
You have me thinking what other test strips can be made at home?
I really like the idea of these ones.
Aga you sure thats sulphuric acid with chlorine? Looks alot like recycled beer in a cup TBH  .
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aga
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100% certain.
I've made Both and know that recycled beer is a <b>much</b> lighter yellow, and tends not to smell of chlorine, depending on where you
take a pee.
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NEMO-Chemistry
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I tried this today and failed (kind of). Would bleached paper make a difference? I soaked mine and before it had dried properly it had gone dark.
I used tapioca starch and cheapo filter paper, i also tried some on acid free butchers paper, its too thin to use but it didnt change colour.
So i am wondering if maybe the filter paper is bleached?? Then again surely if it affects this then its not going to any good for filtering anything.
Maybe i just fucked it up, i will give it another go tomorrow.
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S.C. Wack
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What filter paper isn't bleached, maybe some coffee filter...unbleached paper will not help one see the iodine complex...doubled-up coffee filters
will work and so will Chinese filter paper even, when prepared according to the directions of Norris...using corn starch and at least nearly approx.
around 50 mgs KI: Grind about 1 g of starch with a few ml of water and pour the mixture into 200 ml of boiling water. Cool the solution and
dissolve in it a crystal of potassium iodide. Insert pieces of filter-paper into the solution, and hang them up to dry in a place free from acid
vapors.
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aga
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Yep S.C. , that's the secret formula.
I skipped the cooling part, reasoning that they'd dry quicker.
I just used some of the round filter papers i have, undoubtedly bleached.
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Magpie
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I think any kind of paper will work, obviously white will be better for seeing the color change to blue/purple. Cooking the starch is the secret IMO.
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Please explain.
All i got left is to make benzene in order to copy your Congo Red synth from napthalene mothballs, which are nowhere near as easy to acquire (here) as
Klein found, wherever he was.
If my Starch papers are crap, Please state Why, and how they should be prepared, as following your synth is not uncomplicated.
It would be a real PITA if it all went tits up at the last step.
Edit:
Lab ambient has now reduced to 34 C, so Summer (48+ C) has passed.
In a week or two i can stop venting the acetone/ethanol/HNO3/etc bottles and maybe Do some actual chemsitry again.
[Edited on 12-9-2016 by aga]
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Magpie
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Quote: Originally posted by aga  | Please explain.
All i got left is to make benzene in order to copy your Congo Red synth from napthalene mothballs....
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Do you mean benzidine?
| Quote: Originally posted by aga |
If my Starch papers are crap, Please state Why, and how they should be prepared, as following your synth is not uncomplicated. |
I make my starch papers for iodine testing using the procedure in Brewster, p.124 (forum library). I cut up strips of lab grade filter paper and soak
them in the solution, then air dry.
yes!
The single most important condition for a successful synthesis is good mixing - Nicodem
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NEMO-Chemistry
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| Quote: Originally posted by aga | Please explain.
All i got left is to make benzene in order to copy your Congo Red synth from napthalene mothballs, which are nowhere near as easy to acquire (here) as
Klein found, wherever he was.
If my Starch papers are crap, Please state Why, and how they should be prepared, as following your synth is not uncomplicated.
It would be a real PITA if it all went tits up at the last step.
Edit:
Lab ambient has now reduced to 34 C, so Summer (48+ C) has passed.
In a week or two i can stop venting the acetone/ethanol/HNO3/etc bottles and maybe Do some actual chemsitry again.
[Edited on 12-9-2016 by aga] |
Got the other problem here! normal temp in garage ~7C, so everything needs heating lol
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Magpie
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| Quote: Originally posted by aga |
If my Starch papers are crap, Please state Why, and how they should be prepared, as following your synth is not uncomplicated.
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What we may have here is "a failure to communicate." I never said your starch papers are crap: the picture you show looks good to me.
Edit: I recommend that you test your paper on a nitrite solution. That's what you need it for.
[Edited on 13-9-2016 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Sorry, text is such a narrow bandwidth media.
All i meant to convey was concern that i'd missed something, and that my Congo Red attempt would go all fubar (right at the end) due to a botched bit
of test paper.
Thanks - i'll try out the papers with some nitrite solution.
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aga
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Well, glad i tested the papers with the sodium nitrite as suggested.
They react rapidly to NOx and 3% H2O2 yet not to a solution of what i imagined was sodium nitrite.
The papers are fine, but the nitrite is shitrite.
I guess i chickened out too quick when the lead/sodium nitrate reaction went all vesuvius.
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Magpie
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Before you throw out your nitrite make a dilute aqueous solution, then add a few drops of HCl or H2SO4, then test it with your starch-iodide paper.
I just did this: no color change until the HCl was added, then an intense blue. My paper was made in 2007.
You should also see a lot of bubbles formed when the HCl is added. This would be NO which I think is the actual oxidant.
6NO2- + 4H+ ---> 4NO(g) + 2H2O + 2NO3-
The single most important condition for a successful synthesis is good mixing - Nicodem
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aga
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Life saver ! Thanks.
The nitrite certainly makes loads of NOx when HCl is added, and the papers react instantly to that.
Wasn't looking forward to re-doing the molten lead thing again.
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Magpie
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You're welcome aga. I also did another interesting test for nitrite:
Prepare a small ice bath using, say, a 250mL beaker. Add a gram or so of table salt on top of the ice to get things really cold. Fill a small test
tube half full of DI water and place a 1/4" chunk of your nitrite in it and dissolve. Place the test tube in the ice bath and wait until the solution
is cooled. Then add 5-10 drops of HCl or H2SO4. You should see the beautiful blue color of nitrous acid, HNO2.
NO2- + H+ --> HNO2 (unstable)
I'm using lab grade NaNO2 so your results may vary, depending on the quality of your nitrite salt.
The single most important condition for a successful synthesis is good mixing - Nicodem
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