Phenolphthalein Agar

and any other non-chem subjects.
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Narelle01
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Re: Phenolphthalein Agar

Post by Narelle01 » 19 May 2011, 14:24

i will also not be sad to see the end of this prac!!!

curie
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Re: Phenolphthalein Agar

Post by curie » 23 May 2012, 11:37

Made some yesterday, should have checked this thread first. It was originally quite pink but has faded considerably. I will try the layer of phenolphthalein on the top trick, if that doesn't work its back to the drawing board.

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Narelle01
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Re: Phenolphthalein Agar

Post by Narelle01 » 23 May 2012, 11:39

paint it with Na Oh - that should turn it pink quick!

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DavidPeterson
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Re: Phenolphthalein Agar

Post by DavidPeterson » 23 May 2012, 12:27

I love this prac - one of the few Biology pracs that actually works (probably because it relies on Chemistry - which always works!)...spoken by a true chemist........
DCP 8-)
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bindibadgi
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Re: Phenolphthalein Agar

Post by bindibadgi » 23 May 2012, 13:34

Oh David, I say that just means Chemistry's not as much fun as Biology coz it's too predictable :giggle:

I reckon the more organic & less predictable biology pracs are cool....even if they don't always work as expected :crazy: .....& do Chem classes get to play with anything living? Nup.....but we biologists get to have lessons with stick insects, bearded dragons, bunnies, all sorts of plant life, gorgeous microscopic critters....& we get to make capsicum soup & blow lungs up with a bicycle pump! :w00t: ....spoken by a true biologist :wink2:
bindibadgi

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sunray18
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Re: Phenolphthalein Agar

Post by sunray18 » 23 May 2012, 13:50

and we get to wash up all those goey messes that students make and teachers put out of sight so they go right 'off' before we find them!

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DavidPeterson
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Re: Phenolphthalein Agar

Post by DavidPeterson » 23 May 2012, 14:15

I keep no living things in my labs....
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Graham Kemp
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Re: Phenolphthalein Agar

Post by Graham Kemp » 23 May 2012, 14:56

Narelle01 wrote:paint it with Na Oh - that should turn it pink quick!
Well, unless the indicator is fading from being in a pH too far above 9. "Add more" won't cure "too much"!

I always prepare by adding NaOH slowly in small portions, until just passed the color change; rather like a crude titration. The excess in the fridge hasn't faded in the months since the last time.

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Narelle01
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Re: Phenolphthalein Agar

Post by Narelle01 » 24 May 2012, 08:41

are you a chemist too Graham? ;)
I'm a bucket chemist taught by a master bucket chemist, Noona :p

I'm more a biologist - i love 'my guys' love my LIVING Euglena!

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lada
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Re: Phenolphthalein Agar

Post by lada » 24 May 2012, 09:23

I have adopted a recipe from this website a long time ago and it is fool proof.
20g of agar, boil in 1L of water. Cool to about 50oC, add 4g NaOH and enough phenolphthalein powder to colout the solution. I use a tip of spatula.Always works,
Happy days
Lada

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carolmay
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Re: Phenolphthalein Agar

Post by carolmay » 04 Sep 2012, 15:20

You all have some wonderful ideas of making Phenolphthalein Agar, will have to give it a try, I use a large tray at 3cm depth, but the kids have to do the rest.

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melsid
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Re: Phenolphthalein Agar

Post by melsid » 03 Jun 2013, 11:56

Hi all,

wish me luck, I'm about to make my 1st batch... thanks for all the hints & tips, I'm sure it will be fine :D

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macca
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Re: Phenolphthalein Agar

Post by macca » 03 Jun 2013, 13:06

I put mine in ice cube trays, then the kids cut up. :crazy:

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melsid
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Re: Phenolphthalein Agar

Post by melsid » 03 Jun 2013, 14:56

So far, so good - it went a beautiful colour! :clap3:

Now to wait and see if it sets...

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melsid
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Re: Phenolphthalein Agar

Post by melsid » 04 Jun 2013, 09:25

Bugger!! It didn't set. Will it set if I heat & add more agar? Or should I cut my losses & start from scratch??

Mel

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