Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: johndiver on 23/02/2005 03:41:16
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One night over a bunch of red wine, I and two other students decided we would investigate the possibility of writing a message onto our class flag. Once the semester is over, that flag will hang over an indoor swimming pool ... so I was wondering if anyone knew of an invisible ink that would appear after the flag was hanging over the pool where the chlorine fumes would make it visible again.
If not chlorine, then how about time or some other factor.
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Great question - I'll give it some thought - any ideas Ylide ?
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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I can't think of any specific product to recommend you buying but I think there are two approaches that can be investigated.
The first is to use a solution of a cation that forms a dark solute with chlorine but is colorless with whatever solution you initially have it in. This isn't really a good idea as most of the metals that make nice colored chloride salts are toxic and really shouldn't be used around a pool.
The second is to use an organic compound that will change color when chlorinated or perhaps just simple over time. Something like this probably already exists but a quick google search didn't turn up anything relevant. You might have better luck and I think this is probably your best avenue.
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Ylide: yes, a couple of good ideas. I was thinking about digging up a copy of Vogel's Analytical Chemistry to see if anything precipiates or changes colour in presence of chlorine or whatever other gas may be present in the swimming area.
Your comment made me think of an organic dye that works in reverse, instead of chlorine turning color into colorless, maybe I can find something.
- John
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Hey People,
I'm new to the forum and was wondering if there is a type of dye (preferably in the form of a marker or pen) that can only be seen with a pair of sunglasses? or special glass? I dont need a type of dye that requires a light I need it so I will be the only person who will see this dye. Please feel free to input any of your ideas.
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I'd be surprised if you found an organic dye which became coloured on reaction with chlorine... I believe coloured organic compounds tend (although I don't know how general this is) to get their colour from long chains of conjugated (basically neighbouring) carbon-carbon double bonds (google carotene or lycopene structures) which are broken open by the chlorine breaking the conjugated chain.
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How about a compound that changes colour in humid conditions? Cobalt compounds that change from blue to pink (or was it the reverse?) have been used in weather indicators to predict approaching rain. You may need a stronger colour change, but this could be fruitful avenue to explore. Let us know how you get on.
Barry
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red cabbage or an laxitive wit couple drops of viniger (the laxitive doesn't need viniger) is invisible then damp the paper wit ammona it will show up and when the ammona evaporats it will turn invisible again
or us lemon juice on paper then heat it the lemon will turn brown
Drew Rody
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we used to use onion juice, which when held near a source of heat it became visble as brown writing.
On driving recently with a pair of polaroid sunglasses (which work fine with my screen I might add) I notice some wierd colours in other screens. Some being bright purple and others metalic blue. So I guess if you can find out what they use as an additive to these types of tinted screens, you could use it on the flag, so that it can be read by people using polaroids. Sounds like it could be fun :)
"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
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i was wondering if you have found anything?
venckauskas@yahoo.com
quote:
Originally posted by Criddle12
Hey People,
I'm new to the forum and was wondering if there is a type of dye (preferably in the form of a marker or pen) that can only be seen with a pair of sunglasses? or special glass? I dont need a type of dye that requires a light I need it so I will be the only person who will see this dye. Please feel free to input any of your ideas.
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Sorry to be so late in replying, was on a long Caribean holiday studying the effect estrogen has on the transfer of ethyl alcohol across a male's epithelial tissues. :-).
I haven't nailed down a specific chemical yet, although there's some good basic information at http://www.chemguide.co.uk/. I was going to obtain some phenolphthalein to put in my beer (one of my room mate's friends is drinking my stuff, so I wanted to play a cruel but harmless trick on the culprit). Phenolphthalein turns pink at pH 8 and above, while methyl orange turns orange in acids of pH 3.7 and lower.
I have a more comprehensive list of indicators and their properties at my mother's house. But if anyone can suggest an indicator or dye from experience, that would be helpful.
Cheers.
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If I remember from my A-level chemistry lessons phenolphthalein is carcenogenic - so it may not be a very nice thing to do - use commercial laxatives from the chemists if you have to
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I've decided to use either a clear colourless substance (wax, acrylic compound, or egg white) to paint my name/logo onto the flag. In time, it becomes yellow or brown as the egg white decays, or the waxed portion remains brightly colored as the rest of the flag becomes dingy. More thoughts as the deadline day comes up.
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get some polerizing sun glasses and find some ink like substains that polerizies
Drew Rody
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If you want to write on a surface ,containing polysaccharides (paper,some sorts of clothes) you can use concentrated acetic acid. It causes hydrolisis of polymer chains. After writing on the material, just let it dry out and letters will disappear. Then, when material is put into water letters again appear as a "water signs".
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quote:
Originally posted by Barry37
How about a compound that changes colour in humid conditions? Cobalt compounds that change from blue to pink (or was it the reverse?) have been used in weather indicators to predict approaching rain. You may need a stronger colour change, but this could be fruitful avenue to explore. Let us know how you get on.
Barry
This sounds possible. Try to write on a similar colored background when in a dry atmosphere. As the atmosphere becomes humid, you may see the effect you want.
R A Beldin,
Improbable Statistician
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quote:
Originally posted by Barry37
How about a compound that changes colour in humid conditions? Cobalt compounds that change from blue to pink (or was it the reverse?) have been used in weather indicators to predict approaching rain.
Yes, you can do it, for example, with CoCl2 (cobaltum chloride). When it's wet, is pink coloured, when it's dry is light blue (In italian chemistry it's called "Madonna's mantle blue"!).
Another formula for an invisible ink: KI (potassium iodide) dissolved in water. The solution is colourless. Wetting the paper written with that solution with bleach, turns the writing yellow-brown, because the iodide (I-) is oxidized to iodine (I2) which is coloured. You should try with dilute solutions first.
The revelation is more sensitive if you add starch to KI. The writing becomes dark blue after reaction.
The same happens with gaseous chlorine in air, instead of bleach, but it's probably very long to happen, with the low levels of chlorine in a swimming pool's air. However, you can try!
Another one: a soluble salt of Cu(II), for example Cu(NO3)2 (copper (II) nitrate), CuSO4 (copper II sulphate), CuCl2 (copper II cholride) ecc.
To reveal it: put the paper over the opening of an ammonia's bottle and wait.
The writing becomes blue (it forms tetramminocopper (II) complex).
Another one: a soluble salt of Fe(III).
To reveal it: SCN-, for example NaSCN (sodium thiocianyde). It becomes red-orange.
With potassium ferrocianyde as revelator: K4[Fe(CN)6], it becomes dark blue (prussian blue).