[gentlekboy]

Please how can methyl orange and phenolphthalein be prepared in the laboratory?

[Borek]

Google "phenolphthalein synthesis".

Unless you mean preparing solutions to be used as indicators, when you already have the substance. Then it is just a matter of finding what concentration is suggested (any good analytical textbook with practical section should have this information) and preparing solutions.

[Arkcon]

The simple answer is, this way:

https://en.wikipedia.org/wiki/Phenolphthalein#Synthesis

The longer, more involved answer is -- that's not as easy as it looks, so it isn't done, but instead purchased.

[gentlekboy]

I meant "preparing solutions to be used as indicators". I don't have a textbook that's why I need your help

[Arkcon]

If you have the solid, the USP specifies 1 gram in 100 mL alcohol.  That's a nominally correct 1% concentration, because you're using a few drops anyway, and a more accurate solution concentration isn't needed.

[Borek]

Googling for "how to prepare methyl orange indicator solution" yields plenty of hits.

[gentlekboy]

Okay... Thanks, Borek and Arkon!