Bromothymol blue

[CC]

Help.....i've done a search and it doesn't answer my question.

When I make up my Bromothymol blue it is going red.
When I had a base it goes blue, but when I had acid it just gets a deeper red. I can get it to neutral with a bit of fiddling but when I add acid it still goes red.

WHAT AM I DOING WRONG? AHHHHHHHH

[Judy R]

Are you doing the following
dissolve 0.4g bromothymol blue in 200ml of ethanol and make up to 1 litre with distilled water?

[CC]

Yes Judy exactly that twice the second time with the chem teachers assistance No good at all I am beginning to think that there is something wrong with my bromothymol blue because it is acting like litmus solution. I am really stumped

[lada]

Check your distilled water, but pink colour indicates pH less than 5, so unlikely to be water.
Lada

[SGG]

Hi
I sympathise CC. I have knocked my head against the wall with this every time I go to refill/ make some more. The previous labbie bought Bromothymol Blue 0.04% in Ethanol which is a reddish/ yellow colour and I was having your problems. I have since opened a newer bottle and it seems better - I can even dilute it with water to obtain the "blue" colour for some tests of solutions. The ethanol will bias it towards the low pH but could your ethanol be old? Also Distilled water can be pH of 6 - 6.5. I tried making up the powder (bought 2006) but the results were off. I have bought more powder (2009) and just today made up a batch but at 0.1g in distilled water (it was a yellow colour so had to add drops 0.1M NaOH to make green/blue) it was weak on the acid. So threw caution to the winds and put in 0.3g more of the powder. Seems to work ok. The solution seems to go off with keeping though so......I don't know!
So confused
Regards
Sue G

[CC]

New bromothymol blue ordered this morning because I went through everything else.
Wish me luck

[Lyn]

I have bromothymol blue made up with ethanol and the solution is a reddish orange colour. Several drops of this solution added to a base will give blue. Several drops added to acid will give a yellow orange colour. If I do the reverse and add acid to the bromothymol blue I get a reddish colour. (There is more indicator than acid in the test tube.) If I make up bromothymol blue with water I get a greenish solution. Add this to a base and it goes blue. Add to an acid and the result is yellow. Is it possible that the name of the indicator gives us the wrong idea as to the colour we should expect when we make up the solution? I never questioned the colour of the solution. I just thought it was one of those quirky things that happens with chemicals.
Lyn.

[Mother]

Hi all
When the blue colour disappears from my Bromothymol Blue,I just add drops of NaOH until the blue colour appears.
Cheers
Mother

[Rowyrow]

I just check my bromothmol blue powder and it is pink, is that normal. I have nevr used it befor so I dont know what to expect. Only got the bottle end of last year.

[Ocean Breeze]

Can anyone assist please? I dont have a colour chart for bromothymol blue.

Any one have one, or a link, or anything please?

[dime]

The powder I've had for quite a few years, is and has always been orange. When you make it up, as Mother says, just add NaOH(2M) by drops till it turns blue. I have added a note on the receipe to say it dissolves better in alcohol. So I would guess that I dissolved it in some and made it up to the litre with distilled water. (been a long time since I made it up). Turns yellow in the presence of carbon dioxide, and pH range 6.0 to 7.6.

[fibreweb]

I have just found this colour chart for common indicators which may be of benefit.

http://mmchscchem2011.wikispaces.com/Acidic+Environment

Wendy

[Ocean Breeze]

thanks Wendy

Perfect

[Ocker]

Did you say Purrrrrr fect

[Robdean]

The posts on the bromothymol blue remind me of a “problem” we were having while back with our universal indicator. Despite my having checked the reaction, and finding that the results were the same despit the colour of the reagent, my teachers were throwing away bottles of universal which were red. I contacted Chemsupply who supplied the universal and this was the reply:

“We are happy to advise that the starting colour of our universal indicator solution does not affect its performance in any way.

We manufacture the product by dissolving a series of dyes in a mixture of ethanol and water. Once the dyes are added, the mixture is actually red (possibly because the ethanol has a small amount of residual acidity). In the last step of manufacturing the product, we add a very small amount of sodium hydroxide to our mixture so that the pH is 7 (giving a green colour).

The tests you performed with the HCl and NaOH solutions proved that the indicator solutions gave the same colour, regardless of the starting colour, when added to an excess of sample. When we manufacture the product, we carry out a similar test using pH buffer solutions so you can be assured that our product will be accurate.

Finally, you may be aware that water left standing in air actually becomes slightly acidic due to the absorption of carbon dioxide, forming a dilute carbonic acid solution; this may account for the colour change in your bottles.

Best regards,

Josh Krieg
Chemist
Chem-Supply Pty Ltd”

Does the bromothymol blue still give the desired result?? Maybe the problem is similar to the one I had and the actual starting colour doesn’t matter.

[Rita]

Hi All

I need to order more bromothymol blue powder and I am not sure which to buy. There is the "free acid" and sodium "salt" versions. Do I assume it is the free acid for both indicator solutions as the formula on the chemical bottle I have does not contain Na (Sodium)?

The two solutions I make are in the book "The Laboratory".

For the use of indicator in CO2 in air prac, the solution is 0.1g bromothymol blue made with distilled water to one litre.
This solution is red and seems to work fine for blowing bubbles in water. Method mentions if green (nothing about red) add NaOH until blue.

For the use of indicator for volumetric work, dissolve 0.4g bromothymol blue in 200ml ethanol and make up to one litre with distilled water. Filter.

Appreciate your advice.

[rae]

Sorry I can't help, However I have always bought the premade solutions and never made it from a solid! We use this for everything you just mentioned. Because you only use a drop or 2 every time its not overly expensive! I have bought it once in 10years!

[mtg]

Ask the supplier, mine doesn't have that information on it, but it's been here longer than me! From May and Baker Ltd Dagenham England!!!