# What concentration is phenolphthalein indicator ? 1% or 0.1%

I read some information about phenolphthalein indicator, some websites suggested phenolphthalein indicator of 1%, others mentioned phenolphthalein indicator of 0.1%. What is the difference of both of these concentrations when we use them in titrations?

I assume that 1-2 drops of phenolphthalein indicator of 1% can be used as an indicator but for phenolphthalein indicator of 0.1%, it needs to drop more with 4-5 drops to obtain the same effeciency.

Look forward to hear from you all

• In my university, all our indicators are available at concentrations 0.1%. The students know they may need 3 - 4 drops for their titrations. Jan 18, 2021 at 15:35
• I remember the same, even from labs in my analytical chemistry focused high school. 1% is an unusual high concentration. Jan 18, 2021 at 15:40
• @Maurice Thank you for your answer. It is helpful to my experiments. Jan 24, 2021 at 14:46

During titration of small amounts of acids, the molar amount of the indicator in 1-2 drops of $$\pu{1 \%}$$ indicator solution may not be negligible compared to the acid molar amount, affecting the result.
So for that cases, $$\pu{0.1 \%}$$ solution is used, to be able to dose smaller indicator amounts.
As the phenolphalein molar mass is about $$M=\pu{318 g/mol}$$, 1 drop of $$\pu{1 \%}$$ solution is equivalent about 3 drops of $$\pu{0.01 M}\ \ce{NaOH}$$.