making litmus paper at home quick and cheap

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au-artifax

Well-known member
Joined
Jun 5, 2013
Messages
82
Hello.
While getting ready to re-precipitate some gold to purify it more, I took a break after finding I had no litmus paper to help in bringing down the gold with Oxalic acid. Everything is ready, but this side-track was good.


I decided to do a full blown how-to on making your own litmus paper, but the process of using the strips you'll make also uses some chromatography principles.

My three had to's were that it be cheap, quick, and easy. Here's all you need: I bought a small bottle of RED wine for $1.99, a notebook full of paper for $.25, and used a wide shallow casserole dish for $.00. How's that for cheap!!!

NOTE: use fresh unopened wine that has not had a chance to become acidic. It won't work right if your wine has started to become vinegar.

IMG_20150630_172613047.jpg

The How to MAKE: cut paper any size that fits in the dish. It is OK to stack as many layers as you want... the more the better. It only takes a little wine to make a lot of paper. Add the wine first, then lay in the paper and let soak. There is no need to heat it, and all it takes is 15 minutes to get satisfactory results. I like to let it soak longer though, 30-60 minutes.

IMG_20150630_173115615_HDR.jpg

What you will see is the paper becomes blue, (not red). That says it is ready.

IMG_20150630_173130086_HDR.jpg

Take the sheets of paper out and lay on a flat surface to dry. When dry it starts out as blue, but turns pink after a while which is OK.

IMG_20150630_192849935_HDR.jpg

Once dry it is ready for use!

The how to USE:

This paper has the ability to distinguish acid from base, and give a general idea of how close to neutral your solution is. Here is how it works: I did a series of tests while slowly adjusting the PH throughout the series. Look at the following pic...

IMG_20150630_191734.jpg

(The lower part of strips pictured shows results)

Notice that there will be some red on any solution that is somewhat acidic. But if you look close you will notice at some point a blue line starts to show up in the middle of the strip (starts at #10). The wider the strip, the closer to neutral you are. As the tests progressed, you can see finally the strip with no red and just blue (#18 in series). This solution is nuetral. Next the strips start showing a greenish tint as it progresses towards the yellow of base solution. Although I got sloppy in the end of the series, you can see the blue line getting smaller again as it nears base.

How does it work? As the PH goes up the solution experiences a loss of acidity as it soaks through the paper (like chromatography) and that is how the blue line starts to appear (the neutral color). And that is how we can get a feel for PH. When the red finally FAILS to show on the strip you are right around 7 on the PH scale.



In a test series with different acids the same results were found, with the blue line appearing and growing as PH got higher. Oxalic acid was cool though as it was a neat dark pink color (not red) during the series done on it.

So if you just need a general idea of where your solution is on the PH scale, then here is your way to have a lifetime supply of litmus chromatography paper for dirt cheap.

The only thing I couldn't price out earlier was a neat little storage bottle. An old pill bottle works too, so I guess you can add $.00 to the cost.



Hope this helps someone out.

Cheers!
 
Even the used wine is still consumable, provided the paper you use is fresh and it is not used paper from the bird cage or cat litter pan or something like that. I have already used yesterday's demo batch to do my Oxalic gold precip. Worked like a charm!
 
Very neat idea!
I wonder how long a batch will keep?
Please let us know if they go off quickly.
 
So far the original test batch kept in a bottle works the same. A piece I have kept out in the open air still works, although it is more pink/puple than blue before use. I don't know if it because of the light or some type of oxidation that makes the paper change color being stored in the open air. I will be periodically using the paper, and will make a forum note of when it becomes ineffective.
 
solar_plasma said:
Ever tried juice or alkoholic extract from red cabbage?

https://en.wikipedia.org/wiki/Anthocyanin#/media/File:Indicateur_chou_rouge.jpg

It's best used fresh.

I have heard of this procedure with red cabbage, and also have heard the same about rhubarb and grape skin juice. Someday I will try them all out, maybe, but I will have to be reeeaaally reeeeeally bored to put much effort into it.

If anyone else can make it work using other stuff then I would be interested. I think it important for it to work you would need to see blue as a reference to the test solution being in a neutral state, and see different colors for base and acid ranges.

OK, done playing, back to work. PS: re-refining my last batch of Au was such a success that I will forever opt for a second refining stage. What a HUGE difference in the end product. HUGE!
 
Here's a quick Instructable on red cabbage juice as your pH indicator: http://www.instructables.com/id/Easy-Science-Fair-Project/
 

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