Methyl Orange Indicator
- Kathryn
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Methyl Orange Indicator
Hi all
I have been working slowly through my new GHS labelling and have found a slight discrepancy with methyl orange indicator. In our Labbie Bible ie "the Laboratory" the recipe adds 1g methyl orange to 200ml ethanol and 800ml water. This has a colour range of pH2.8-4.6. However on Chemwatch all the SDS's for the indicator do not use ethanol and the colour range is pH3.1-4.4 and also has Nil hazard (except the screened version which is different).
My question is: should I make it up the way in the book and therefore will need some kind of hazard grading or should I just use water?
Does anyone have any idea??
Thanks in advance
Kathryn
I have been working slowly through my new GHS labelling and have found a slight discrepancy with methyl orange indicator. In our Labbie Bible ie "the Laboratory" the recipe adds 1g methyl orange to 200ml ethanol and 800ml water. This has a colour range of pH2.8-4.6. However on Chemwatch all the SDS's for the indicator do not use ethanol and the colour range is pH3.1-4.4 and also has Nil hazard (except the screened version which is different).
My question is: should I make it up the way in the book and therefore will need some kind of hazard grading or should I just use water?
Does anyone have any idea??
Thanks in advance
Kathryn
Re: Methyl Orange Indicator
I've only ever used distilled water - pH 2.8 to 4.6
Re: Methyl Orange Indicator
sorry to add to the confusion, but I follow the book.
Re: Methyl Orange Indicator
I've found that as well. I have found that there is a supplier MSDS /label that has it made up in 20% ethanol, so that is what I have used . I have a few litres of the stuff in stock and dropper bottles, so I don't really want to throw it all out. I would also like to hear other's ideas.
Re: Methyl Orange Indicator
Only ever used the distilled water.
Re: Methyl Orange Indicator
I have used 20% alcohol pH about 3-4.5.
Don't throw it out, Curie
Don't throw it out, Curie
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Re: Methyl Orange Indicator
Hmmm interesting. My old "Handbook of Laboratory Solutions" is 200ml ethanol up to 1 litre as well, but the Methyl Orange/Bromocresol green ind is just water? so I don't get it. Maybe the alcohol dissolves it better or alternatively preserves it longer??? I make mine up with ethanol and water through habit though.
- Lyn
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Re: Methyl Orange Indicator
My labels for methyl orange indicator carry the flammable warning. I have always used ethanol in preparing this indicator.
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Re: Methyl Orange Indicator
Jumping into a very old thread here... But I have a request for methyl orange indicator for a titration. It's CaCo3 and HCl. Should I be recommending a different indicator? This one only does from pH 3.2-4.4 according to google, but the bottle (screened methyl orange) says Alkaline green, acid magenta with transition grey at pH 3.8. I don't see how that's going to give an accurate result! I've always used phenolphthalein in the past from memory. The teacher is just going by what the textbook says.
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Re: Methyl Orange Indicator
My initial understanding of the titration prac is for the students to titrate a base into an acid until a basic/neutral solution is reached. If this is the case for your situation, i'd agree that their results wont be very accurate as Methyl Orange's 'transition colour' occurs at pH 3.0-to-pH 4.8 and 'neutral' pH is reached at a reading of pH 7. However, if they arent necessarily trying to get a basic/neutral solution, rather just practicing their titration technique by ensuring a solution reads a certain pH, I dont see there being a problem. The teachers here have always asked for multiple types of indicators (i.e. phenolphthalein, methyl orange, bromothymol blue, etc) when doing this prac.
Furthermore, i could be wrong so please dont take my word for gospel xD
Furthermore, i could be wrong so please dont take my word for gospel xD
Regards, Labbie Seth
Lab Tech NSW Sydney
Lab Tech NSW Sydney
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Re: Methyl Orange Indicator
They are trying to calculate the concentration of acid.
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Re: Methyl Orange Indicator
Im of no help but for Titration we have always used Phenolphthalein.