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Homemade indicators


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#1 vrus

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Posted 28 October 2005 - 12:19 PM

Can someone instruct me on how you could possibly make an indicator at home and what colour could be observed in different media of varying pH ? I have hardly any chemica supplies, so this might be a good start!

A did a practical at school 2 years ago on making indicator with red cabbage, but I forgot the procedures and requirements. Also can anyone tell me the steps required to make and indicator in order ?

What's Universal Indicator made from ?

Thnx in advance!
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#2 RyanJ

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Posted 28 October 2005 - 12:33 PM

Can someone instruct me on how you could possibly make an indicator at home and what colour could be observed in different media of varying pH ? I have hardly any chemica supplies, so this might be a good start!

A did a practical at school 2 years ago on making indicator with red cabbage, but I forgot the procedures and requirements. Also can anyone tell me the steps required to make and indicator in order ?

What's Universal Indicator made from ?

Thnx in advance!


As far as I remember when you boil red cabbage you get a reddish juice - that works as a basic indicator I think :)

You may alos be interested to know that Geranium Petals also tell you the Ph of the soin - cool!

For more information have a look here (Shows you the composition of the indicator) :-)

Cheers,

Ryan Jones
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#3 YT2095

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Posted 28 October 2005 - 02:25 PM

Turmeric is also good for Higher PH indication as is a tincture made from the petals of a Hydrangea plant.
beetroot juice works too, but that`s again, only for a high ph.

here`s a bit on these plants: http://www.hydrangea...olorchange.html
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#4 akcapr

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Posted 28 October 2005 - 09:44 PM

I also heard that exlax has indicator in it- although it never worked.
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:)

#5 NeonBlack

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Posted 28 October 2005 - 10:12 PM

yeah phenolphthalein is a laxative. I'm not sure which brands contain it though.
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#6 woelen

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Posted 29 October 2005 - 04:32 PM

you get a reddish juice - that works as a basic indicator I think :)

I actually tried this one and it really is great. Boil some red cabbage for several minutes, such that you get a pruple liquid.

At low pH it is beautifully red/pink.
At neutrality it is purple.
Slightly alkaline makes it blue.
More alkaline (e.g. ammonia, dilute sodium carbonate) makes it deep green.
Very alkaline (NaOH and very concentrated Na2CO3) makes it yellow.

Unfortunately I have no number chart for this, but with some effort you can make your own.
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#7 RyanJ

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Posted 29 October 2005 - 05:24 PM

I actually tried this one and it really is great. Boil some red cabbage for several minutes, such that you get a pruple liquid.

At low pH it is beautifully red/pink.
At neutrality it is purple.
Slightly alkaline makes it blue.
More alkaline (e.g. ammonia, dilute sodium carbonate) makes it deep green.
Very alkaline (NaOH and very concentrated Na2CO3) makes it yellow.

Unfortunately I have no number chart for this, but with some effort you can make your own.


I tried it too - only because my mother made some cabbage and had some of the juice left over - it was pretty fun (And the cabbage was nice too :D)

I suppose you could make one - I'll have to try that one day too (Make a number chart for the alkilnity or acidity :-)

Cheers,

Ryan Jones
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#8 insane_alien

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Posted 30 October 2005 - 09:34 AM

i remember someone in my chemistry class spilt some phenolphthalien on his hand and didn't notice. he then wiped his mouth with his hand and ingested some of the phenolphthalien and he didn't even make it to the toilet. bad for him funny as hell for the rest of us. poor guy. i think he works in a mcdonalds now.
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#9 xeluc

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Posted 30 October 2005 - 02:53 PM

i remember someone in my chemistry class spilt some phenolphthalien on his hand and didn't notice. he then wiped his mouth with his hand and ingested some of the phenolphthalien and he didn't even make it to the toilet. bad for him funny as hell for the rest of us. poor guy. i think he works in a mcdonalds now.

I work at Mcdonalds. RRRR I mean I did yesterday I work at Dairy queen now. HA. Anyhow, your saying that he licked his hand and spontaniously pooed?....
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#10 vrus

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Posted 30 October 2005 - 08:34 PM

Very alkaline (NaOH and very concentrated Na2CO3) makes it yellow.


That must look awesome! How can you get concentrated Sodium Carbonate ? I heard heating the same's bicarbonate gives the carbonate. How alkaline would it be then ?
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#11 woelen

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Posted 30 October 2005 - 09:43 PM

That must look awesome! How can you get concentrated Sodium Carbonate ? I heard heating the same's bicarbonate gives the carbonate. How alkaline would it be then ?

You can buy it at a supermarket as washing soda. Heating sodium bicarbonate also works. After it has decomposed, dissolve it in a small amount of water.
You can also mix NaOH and NaHCO3.

As far as I remember, a concentrated solution of Na2CO3 has a pH somewhere near 11, which is quite alkaline already. If you want really strong alkalinity, use NaOH. NaOH however is quite corrosive and exceedingly dangerous for the eyes. Be careful!
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#12 vrus

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Posted 31 October 2005 - 11:31 AM

You can buy it at a supermarket as washing soda. Heating sodium bicarbonate also works. After it has decomposed, dissolve it in a small amount of water.
You can also mix NaOH and NaHCO3.

As far as I remember, a concentrated solution of Na2CO3 has a pH somewhere near 11, which is quite alkaline already. If you want really strong alkalinity, use NaOH. NaOH however is quite corrosive and exceedingly dangerous for the eyes. Be careful!


I didn't know that washing soda was alkaline! Do you have to dissolve it in water and then drive off some water or what ? Where I live, you only get the bare necessities required for a happy life without any scienctific stuff. So I have learnt to make do.... :D
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#13 woelen

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Posted 31 October 2005 - 12:04 PM

Washing soda is Na2CO3.10H2O. Simply dissolve it in water and you have an alkaline solution. No heating, driving off something, etc. required.
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#14 vrus

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Posted 31 October 2005 - 12:41 PM

I finally got an alkaline solution!
I heated Baking Soda until it turned to a black looking powder. Then I added small quantities of water. The solution was brownish. After the tube had cooled down, well.... I was trying to keep it somewhere and a little spilt on my fingers and it felt sopy and a bit strange!
Thanks for the help woelen!
I'll get some red cabbage for the indicator and test it out on Friday probably!
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#15 YT2095

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Posted 31 October 2005 - 01:05 PM

it shouldn`t have gone brown or blackish at all?

are you 100% it wasn`t baking powder you used?
as that often contains wheat flour and potassium bitartarate (cream of tartar), as well as the sodium bicarbonate (the bit you want).
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#16 woelen

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Posted 31 October 2005 - 02:07 PM

I finally got an alkaline solution!
I heated Baking Soda until it turned to a black looking powder.

As YT2095 stated, it indeed should not get black. The flour in the baking powder chars when heated. That causes the black color.

Can't you buy pure sodium bicarbonate or sodium carbonate?

Sodium bicarbonate is sold as baking soda. This is a snow-white powder.
Sodium carbonate is sold as washing soda. This consists of transparent crystals.

But, the brownish solution you have right now may also work for you. Let the brown stuff settle at the bottom and I think you'll be left with a pale yellow/brown solution. The problem with this, however, is that the brown color interferes with the really nice and bright colors of the red cabbage indicator.
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#17 vrus

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Posted 1 November 2005 - 11:36 AM

But, the brownish solution you have right now may also work for you. Let the brown stuff settle at the bottom and I think you'll be left with a pale yellow/brown solution. The problem with this, however, is that the brown color interferes with the really nice and bright colors of the red cabbage indicator.


Yeah. I kept decanting until i didn't have any solid left at the bottom and my solution is brown. Its eid here so ive got a short holiday. I'll get the indicator ready soon.... :-)
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#18 vrus

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Posted 3 November 2005 - 10:30 AM

I gave some of the sample to my friend who had obtained some universal indicator paper. He tested it and told me the pH was 8... :-(
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#19 pearl1994

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Posted 28 July 2011 - 03:28 PM

wow, thank you everyone . this is exactly what i was looking for.
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