Australia's Science Forum

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've only ever used distilled water - pH 2.8 to 4.6

sorry to add to the confusion, but I follow the book.

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.

Only ever used the distilled water.

I have used 20% alcohol pH about 3-4.5.
Don't throw it out, Curie

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.

My labels for methyl orange indicator carry the flammable warning. I have always used ethanol in preparing this indicator.