bromothymol blue solution - Page 2 - The Planted Tank Forum
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post #16 of 22 (permalink) Old 08-09-2011, 08:58 AM Thread Starter
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Hello

jeffww i was feeling very hopeless but now i have hope

Quote:
3',3" - Dibromothymolsulfonephthalein (Bromothymol Blue) 6.0 - 7.6 yel to bl 0.1 g in 16 ml 0.01 M NaOH + 234 ml water
looks simple only need a high precision scale or can convert it to lets say 2 liter to make the values larger. 16 ml 0.01 M <--(is this mole) NaOH


jasonpatterson
Quote:
It appears that some versions of the indicator are water soluble (sold as the sodium salt of bromothymol blue) and all of them should be alcohol soluble to some degree. You might try simply dissolving a bit of the indicator in ethanol (even something like vodka ought to work.) It should be much easier to get a color change in that case.
OK if i make 4kh solution and add btb powder and if it disolves then does that mean i am good to go...

does alcohol changes ph because yesterday i added good amount of pure alcohol in my solution in a test tube but the colour did not change the test tube just got cold lol i guess due to alcohol evaporation

Thanks and Regards.
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post #17 of 22 (permalink) Old 08-09-2011, 09:11 PM
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Alcohol is generally neutral. It may be slightly basic it may also be slightly acid depending on your alcohol but you can count on it being close enough to 7. That M is molar solution so it's mol/L. And since NaOH has a molar mass of 40. A 40g/1L solution is 1M. .1M is 4g/L and .01M is .4g/L.
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post #18 of 22 (permalink) Old 08-10-2011, 04:02 AM Thread Starter
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Thanks Guys
I think i am in the right direction this time. I will let you know my results.

Regards
Masud.
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post #19 of 22 (permalink) Old 08-11-2011, 01:30 AM
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So how runs the stream?
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post #20 of 22 (permalink) Old 08-22-2011, 02:45 AM Thread Starter
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Hello
I am about to make my solution using using 4 times the original to keep this more accurate.
So here it goes...
original formula --> 0.1 g in 16 ml 0.01 M NaOH + 234 ml water

4 times the original formula --> 0.4 g in 64 ml 0.04 M NaOH + 936 ml water

or

4 times the original formula --> 0.4 g in 64 ml 0.01 M NaOH + 936 ml water

which 4 times the original formula is correct? I have a feeling that 0.01 M NaOH is correct.
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post #21 of 22 (permalink) Old 04-26-2019, 03:36 PM
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Sorry for ressurecting a dead thread, but it never had a definite anserw, and might help others googling the same. Anywho, I'm studying to become a chemist, and just happen to have aquariums as my hobby too. So I wanted to make some Bromothymol blue (BTB) indicator, as I have it readily available and it was for a school project.

The issue that OP was having, is that he is making a BTB solution. For our use we need a BTB indicator. There is a difference. Comercial pH test is usually 0.04% BTB indicator, but I want 0.1%. As it makes no difference in readings, just make the color stronger.

When making a indicator you just use a solvent and the BTB, no NaOH. And since BTB is not very soluable in water, we have to use alcohol. 50% v/w or higher ethanol or isopropyl alcohol will work. This will make a dark green indicator that will work just as API pH test.

The reason API and some others are yellow/orange in the bottle is that they use Sodium Bromothymol Blue, which is soluable in water. This is for shipping reasons, alcohol is flammable and there is a ton of regulations when transporting flammable products. And I'm guessing they use some acid to inhibit bacterial/fungal growth in the bottle, lowering the pH. Hence the yellow. Since we use alcohol, we don't need perservatives. As a side note, you can use alcohol with Sodium BTB too without perservatives.

So say you want to mix 0.1% BTB indicator, 100ml:
0.1g BTB in a measuring container, add solvent (alcohol) to 100ml mark.

Or if you want just like commercial 0.04%:
0.04g in 100ml.


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post #22 of 22 (permalink) Old 04-26-2019, 06:22 PM Thread Starter
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Thanks. It been a while since I have been into aquarium. I am planning to start planned tank soon and hopefully I will make it this time perfectly using your formula.


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